Organizing Committee
Abstract

Combinatorial algebraic geometry comprises the parts of algebraic geometry where basic geometric phenomena can be described with combinatorial data, and where combinatorial methods are essential for further progress.

Research in combinatorial algebraic geometry utilizes combinatorial techniques to answer questions about geometry. Typical examples include predictions about singularities, construction of degenerations, and computation of geometric invariants such as Gromov-Witten invariants, Euler characteristics, the number of points in intersections, multiplicities, genera, and many more. The study of positivity properties of geometric invariants is one of the driving forces behind the interplay between geometry and combinatorics. Flag manifolds and Schubert calculus are particularly rich sources of invariants with positivity properties.

In the opposite direction, geometric methods provide powerful tools for studying combinatorial objects. For example, many deep properties of polytopes are consequences of geometric theorems applied to associated toric varieties. In other cases geometry is a source of inspiration. For instance, long-standing conjectures about matroids have recently been resolved by proving that associated algebraic structures behave as if they are cohomology rings of smooth algebraic varieties.

Much research in combinatorial algebraic geometry relies on mathematical software to explore and enumerate combinatorial structures and compute geometric invariants. Writing the required programs is a considerable part of many research projects. The development of new mathematics software is therefore prioritized in the program.

The program will bring together experts in both pure and applied parts of mathematics as well mathematical programmers, all working at the confluence of discrete mathematics and algebraic geometry, with the aim of creating an environment conducive to interdisciplinary collaboration. The semester will include four week-long workshops, briefly described as follows.

  • A 'boot-camp' aimed at introducing graduate students and early-career researchers to the main directions of research in the program.
  • A research workshop dedicated to geometry arising from flag manifolds, classical and quantum Schubert calculus, combinatorial Hodge theory, and geometric representation theory.
  • A research workshop dedicated to polyhedral spaces and tropical geometry, toric varieties, Newton-Okounkov bodies, cluster algebras and varieties, and moduli spaces and their tropicalizations.
  • A Sage/Oscar Days workshop dedicated to development of programs and software libraries useful for research in combinatorial algebraic geometry. This workshop will also feature a series of lectures by experts in polynomial computations.

Image for "Combinatorial Algebraic Geometry"

Confirmed Speakers & Participants

  • Speaker
  • Poster Presenter
  • Attendee
  • Virtual Attendee
  • Abdulafeez Abdulkareem
    University of Africa Toru Orua
    Feb 1-5, 2021
  • Adnan Abdulwahid
    University of Iowa
    Mar 22-26, 2021
  • Simonetta Abenda
    Università di Bologna
    Feb 1-5, 2021; Feb 15-19, 2021
  • Guillermo Aboumrad
    Stanford University
    Feb 15-19, 2021
  • Dan Abramovich
    Brown University
    Feb 1-May 7, 2021
  • Ashleigh Adams
    UC Davis
    Feb 1-May 7, 2021
  • Adam Afandi
    Colorado State University
    Feb 1-May 7, 2021
  • Rizal Afgani
    Institut Teknologi Bandung
    Apr 12-16, 2021
  • Daniele Agostini
    Max Planck Institute for Mathematics in the Sciences
    Feb 1-5, 2021
  • Daniele Agostini
    Max Planck Institute for Mathematics in the Sciences
    Feb 1-5, 2021
  • Huda Ahmed
    New York University
    Feb 1-5, 2021
  • Florian Aigner
    Université du Québec à Montréal
    Feb 1-5, 2021
  • Tair Akhmejanov
    University of California-Davis
    Feb 1-May 7, 2021
  • Edvard Aksnes
    University of Oslo
    Apr 12-16, 2021
  • Doriann Albertin
    Université Gustave Eiffel
    Feb 1-5, 2021; Apr 12-16, 2021
  • Elie Alhajjar
    US Military Academy
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Ayah Almousa
    Cornell University
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Kamyar Amini
    Sharif University of Technology
    Feb 24-May 7, 2021
  • David Anderson
    Ohio State University
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Mar 31-May 5, 2021; Apr 12-16, 2021
  • Nicholas Anderson
    Queen Mary University of London
    Apr 12-16, 2021
  • Federico Ardila
    San Francisco State University
    Feb 1-May 31, 2021
  • Muhammad Ardiyansyah
    Aalto University
    Apr 12-16, 2021
  • Veronica Arena
    Brown University
    Feb 1-5, 2021
  • Xerxes Arsiwalla
    Pompeu Fabra University & Wolfram Research
    Feb 1-5, 2021; Apr 12-16, 2021
  • Ahmed Umer Ashraf
    University of Western Ontario
    Feb 1-May 7, 2021
  • Faqruddin Azam
    Oklahoma State University
    Feb 1-5, 2021
  • Olga Azenhas
    University of Coimbra
    Mar 10-May 5, 2021; Mar 22-26, 2021
  • Christoph Baerligea
    Beijing International Center for Mathematical Research
    Feb 1-5, 2021
  • Matthew Baker
    Georgia Institute of Technology
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Esther Banaian
    University of Minnesota
    Feb 1-5, 2021
  • Grant Barkley
    Harvard University
    Feb 3-5, 2021
  • Gonzalo Barranco Mendoza
    Universidad Nacional Autonoma de Mexico
    Apr 12-16, 2021
  • Victor Batyrev
    Universität Tübingnen
    Apr 12-16, 2021
  • Alexander Bauman
    Brown University
    Feb 1-5, 2021
  • Dori Bejleri
    Harvard University
    Feb 1-5, 2021
  • Prakash Belkale
    University of North Carolina at Chapel Hill
    Mar 22-26, 2021
  • Mara Belotti
    Technische Universität
    Feb 1-5, 2021; Feb 15-19, 2021
  • Carolina Benedetti V.
    Universidad de los Andes
    Feb 3-5, 2021
  • Marko Berghoff
    University of Oxford
    Apr 12-16, 2021
  • Joe Bernstein
    North Dakota State University
    Feb 1-5, 2021
  • Marc Besson
    University of North Carolina at Chapel Hill
    Feb 1-5, 2021; Mar 22-26, 2021
  • Nivedita Bhaskhar
    University of Southern California
    Feb 3-5, 2021
  • Dhruv Bhatia
    Brown University
    Feb 1-5, 2021
  • Shivam Bhatt
    University of Toronto
    Apr 12-16, 2021
  • Christin Bibby
    Louisiana State University
    Feb 1-May 7, 2021
  • Sara Billey
    University of Washington
    Feb 1-May 7, 2021
  • Simone Billi
    University of Bologna
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Aram Bingham
    Tulane University
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 17-May 5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Rekha Biswal
    Universite Laval
    Mar 22-26, 2021
  • Alex Black
    UC Davis
    Feb 1-5, 2021; Apr 12-16, 2021
  • Kenneth Blakey
    Brown University
    Feb 1-5, 2021
  • Andreas Blatter
    University of Bern
    Feb 1-5, 2021
  • Lev Blechman
    Tel Aviv university
    Feb 1-5, 2021
  • Thomas Blomme
    Université de Neuchâtel
    Feb 1-5, 2021
  • Janko Boehm
    TU Kaiserslautern
    Feb 15-19, 2021
  • Narasimha Chary Bonala
    Ruhr University of Bochum
    Apr 12-16, 2021
  • Jonathan Boretsky
    Harvard University
    Feb 1-5, 2021
  • Alessio Borzì
    University of Warwick
    Feb 1-5, 2021
  • Lara Bossinger
    Mathematics Institute UNAM, Oaxaca
    Feb 1-5, 2021; Apr 12-16, 2021
  • Alin Bostan
    INRIA
    Feb 15-19, 2021
  • Tom Braden
    University of Massachusetts Amherst
    Mar 22-26, 2021; Apr 12-16, 2021
  • Madeline Brandt
    Brown University
    Feb 1-May 7, 2021; Apr 11-17, 2021
  • Sarah Brauner
    University of Minnesota
    Feb 1-5, 2021
  • Paul Breiding
    Technische Universität Berlin
    Feb 3-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Michel Brion
    Université Grenoble Alpes
    Feb 1-May 8, 2021
  • Jennifer Brown
    UC Davis
    Feb 1-5, 2021
  • Jose Brox
    Centre for Mathematics of the University of Coimbra
    Feb 1-5, 2021; Feb 15-19, 2021
  • Juliette Bruce
    University of California, Berkeley / MSRI
    Feb 1-May 7, 2021
  • Laura Brustenga i Moncusi
    University of Copenhagen
    Feb 15-19, 2021
  • Taylor Brysiewicz
    Max Planck Institute for Mathematics in the Sciences
    Feb 1-5, 2021; Feb 15-19, 2021
  • Anders Buch
    Rutgers University
    Feb 1-May 8, 2021
  • Daniel Bump
    Stanford University
    Feb 15-19, 2021
  • Amanda Burcroff
    Durham University
    Feb 1-May 7, 2021
  • Hannah Burson
    University of Minnesota
    Feb 1-5, 2021
  • Mahir Bilen Can
    Tulane University
    Feb 1-May 7, 2021
  • Erik Carlsson
    UC Davis
    Apr 7, 2021
  • Federico Castillo
    University of Kansas
    Apr 12-16, 2021
  • Federico Castillo
    Max Planck Institute for Mathematics in the Sciences (MiS) in Leipzig.
    Feb 1-5, 2021
  • Eduardo Cattani
    University of Massachusetts Amherst
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Renzo Cavalieri
    Colorado State University
    Apr 12-16, 2021
  • Ian Cavey
    The Ohio State University
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Seth Chaiken
    University at Albany
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Teressa Chambers
    Brown University
    Feb 1-5, 2021
  • Melody Chan
    Brown University
    Feb 1-May 7, 2021
  • Megan Chang-Lee
    Brown University
    Feb 1-5, 2021
  • Pierre-Emmanuel Chaput
    université de Lorraine
    Feb 15-19, 2021
  • Rajarshi Chatterjee
    Kazi Nazrul University
    Apr 12-16, 2021
  • Anastasia Chavez
    University of California, Davis
    Feb 1-May 7, 2021
  • Enrique Chávez Martínez
    Universidad Nacional Autónoma de México
    Apr 12-16, 2021
  • Yifan Chen
    UC Berkeley
    Feb 3-5, 2021
  • Chongyao Chen
    Duke University
    Feb 1-5, 2021
  • Linda Chen
    Swarthmore College
    Feb 1-5, 2021; Mar 22-26, 2021; Mar 31-May 5, 2021; Apr 12-16, 2021
  • Ke Chen
    Nanjing University
    Feb 1-5, 2021
  • Sunita Chepuri
    University of Michigan
    Feb 1-May 31, 2021
  • Man-Wai Cheung
    Harvard University
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Daniel Corey
    University of Wisconsin, Madison
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Alvaro Cornejo
    San Francisco State University
    Apr 12-16, 2021
  • Ethan Cotterill
    Federal Fluminense University
    Apr 12-16, 2021
  • Steven Creech
    Brown University
    Feb 1-5, 2021
  • María Angélica Cueto
    Ohio State University
    Feb 1-5, 2021; Feb 14-20, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Mark Curiel
    University of Hawaii at Manoa
    Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Xinle Dai
    Harvard University
    Feb 1-May 7, 2021
  • Xinle Dai
    University of Waterloo
    Feb 24-May 5, 2021
  • Chiara Damiolini
    Rutgers University
    Mar 22-26, 2021
  • Alessandro Danelon
    University of Technology Eindhove
    Feb 1-5, 2021
  • Hailong Dao
    University of Kansas
    Feb 1-5, 2021
  • Quang Dao
    University of Michigan
    Mar 24-26, 2021
  • Frances Dean
    University of Washington
    Feb 1-5, 2021
  • Wolfram Decker
    Technische Universität Kaiserslautern
    Feb 15-19, 2021
  • Colin Defant
    Princeton University
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Graham Denham
    University of Western Ontario
    Apr 12-16, 2021
  • Hamdi Dervodeli
    Kyoto University
    Feb 15-19, 2021
  • Papri Dey
    University of Missouri
    Feb 15-May 7, 2021
  • Alexander Diaz-Lopez
    Villanova Universiry
    Mar 22-26, 2021
  • Hunter Dinkins
    University of North Carolina-Chapel Hill
    Feb 1-5, 2021
  • Anton Dochtermann
    Texas State University
    Feb 3-5, 2021
  • Galen Dorpalen-Barry
    University of Minnesota
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Theo Douvropoulos
    University of Massachusetts, Amherst
    Feb 1-May 7, 2021
  • Jan Draisma
    Universität Bern
    Feb 1-5, 2021
  • Anne Dranowski
    Institute for Advanced Study
    Feb 1-May 7, 2021
  • Nicholas Early
    Institute for Advanced Study
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Holger Eble
    TU Berlin
    Feb 15-19, 2021
  • Christian Eder
    University of Kaiserslautern
    Feb 15-19, 2021
  • Griffin Edwards
    Brown University
    Feb 1-5, 2021
  • Richard Ehrenborg
    University of Kentucky
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Balazs Elek
    Cornell University
    Feb 3-5, 2021; Mar 3-May 5, 2021; Mar 22-26, 2021
  • Ben Elias
    University of Oregon
    Mar 22-26, 2021
  • Matthew Emerson
    Brown University
    Feb 1-5, 2021
  • Laura Escobar
    Washington University- St. Louis
    Feb 1-May 7, 2021
  • Alexander Esterov
    National Research University Higher School of Economics
    Feb 1-5, 2021
  • Sen-Peng Eu
    National Taiwan Normal University
    Feb 1-5, 2021
  • Christopher Eur
    Stanford University
    Feb 1-May 7, 2021
  • Eleonore Faber
    University of Leeds
    Apr 12-16, 2021
  • Lorenzo Fantini
    Goethe University Frankfurt
    Feb 1-5, 2021; Apr 12-16, 2021
  • Jeová Farias Sales Rocha Neto
    Brown university
    Feb 1-5, 2021
  • Matthew Faust
    Texas A&M University
    Feb 1-May 7, 2021
  • Elisenda Feliu
    University of Copenhagen
    Feb 1-5, 2021; Apr 12-16, 2021
  • Luis Ferroni
    University of Bologna
    Feb 2-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Claudia Fevola
    Max Planck Institute for Mathematics in the Sciences (Leipzig)
    Feb 1-5, 2021
  • Claus Fieker
    University of Kaiserslautern
    Feb 15-19, 2021
  • Tara Fife
    Max Planck Institute for mathematics in the Sciences
    Feb 1-5, 2021; Apr 12-16, 2021
  • Alex Fink
    Apr 12-16, 2021
  • Sergey Fomin
    University of Michigan
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Garrett Fowler
    Virginia Tech
    Feb 1-5, 2021
  • Netanel Friedenberg
    Yale University
    Feb 1-May 31, 2021
  • Carrie Frizzell
    Kansas State University
    Feb 1-5, 2021
  • Anne Frühbis-Krüger
    University of Oldenburg
    Feb 15-19, 2021
  • William Fulton
    University of Michigan
    Feb 1-May 7, 2021
  • Nir Gadish
    MIT
    Feb 1-May 7, 2021
  • Christian Gaetz
    MIT
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Pavel Galashin
    University of California, Los Angeles
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Yibo Gao
    Massachusetts Institute of Technology
    Feb 1-5, 2021; Mar 22-26, 2021
  • Shiliang Gao
    University of Illinois at Urbana-Champaign
    Feb 1-5, 2021; Mar 22-26, 2021
  • Dichuan Gao
    Brown University
    Feb 1-5, 2021
  • Samuel-Louis Gardiner
    Queen Mary University of London
    Feb 3-5, 2021
  • Marina Garrote-López
    Universitat Politècnica de Catalunya
    Feb 15-19, 2021
  • Jack Garzella
    University of California, San Diego
    Feb 15-19, 2021
  • Alheydis Geiger
    Eberhard Karls University Tübingen
    Feb 15-19, 2021
  • Deniz Genlik
    The Ohio State University
    Feb 1-5, 2021; Mar 22-26, 2021
  • Angela Gibney
    Rutgers University, New Brunswick
    Mar 22-26, 2021
  • Julius Giesler
    University of Tuebingen
    Apr 12-16, 2021
  • Maria Gillespie
    Colorado State University
    Mar 17-May 5, 2021
  • Andrey Glubokov
    Ave Maria University
    Feb 1-5, 2021; Feb 15-19, 2021; Feb 24-May 6, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Rebecca Goldin
    George Mason University
    Feb 1-5, 2021; Apr 12-16, 2021
  • Sergio Gómez
    CINVESTAV
    Feb 1-5, 2021; Apr 12-16, 2021
  • José González
    University of California, Riverside
    Apr 12-16, 2021
  • Vassily Gorbounov
    Higher School of Economics, Russia
    Mar 7-Apr 30, 2021
  • Brent Gorbutt
    George Mason University
    Apr 12-16, 2021
  • Elisa Gorla
    University of Neuchatel
    Feb 24-May 5, 2021; Apr 12-16, 2021
  • Eugene Gorsky
    UC Davis
    Feb 1-May 7, 2021
  • Torin Greenwood
    North Dakota State University
    Feb 1-5, 2021
  • Sean Griffin
    Brown University
    Jan 27-May 31, 2021
  • Sarah Griffith
    Brown University
    Feb 1-5, 2021; Apr 12-16, 2021
  • Darij Grinberg
    Drexel University
    Feb 1-5, 2021; Feb 15-19, 2021
  • Helen Grundman
    Bryn Mawr College
    Feb 1-5, 2021
  • Samuel Grushevsky
    Stony Brook University
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Aziz Burak Guelen
    The Ohio State University
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Emily Gunawan
    University of Oklahoma
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021
  • Trevor Gunn
    Georgia Institute of Technology
    Feb 1-5, 2021; Apr 12-16, 2021
  • Ajeeth Gunna
    The University of Melbourne
    Feb 1-5, 2021; Apr 12-16, 2021
  • Sabir Gusein-Zade
    Lomonosov Moscow State University
    Feb 1-5, 2021
  • Christian Haase
    Freie Universität Berlin
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Marvin Hahn
    Max Planck Institute for Mathematics in the Sciences
    Feb 1-5, 2021
  • Iva Halacheva
    Northeastern University
    Feb 3-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Zachary Hamaker
    University of Florida
    Feb 1-5, 2021
  • Wesley Hamilton
    University of North Carolina, Chapel Hill
    Feb 1-5, 2021
  • Sang Geun Han
    KAIST
    Feb 1-5, 2021
  • Kangjin Han
    Daegu-Gyeongbuk Institute of Sciences and Technology (DGIST)
    Feb 1-May 7, 2021
  • Megumi Harada
    MCMASTER UNIVERSITY
    Feb 1-May 7, 2021
  • Pamela E. Harris
    Williams College
    Mar 22-26, 2021; Apr 12-16, 2021
  • Jonathan Hauenstein
    University of Notre Dame
    Feb 15-19, 2021
  • Xiang He
    Hebrew University
    Feb 1-5, 2021
  • Lauren Heller
    University of California, Berkeley
    Feb 1-5, 2021
  • Paul Helminck
    Swansea University
    Apr 12-16, 2021
  • Oskar Henriksson
    University of Copenhagen
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Milena Hering
    The University of Edinburgh
    Feb 1-May 7, 2021
  • María Herrero
    University of Buenos Aires - CONICET
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Dylan Heuer
    North Dakota State University
    Feb 1-5, 2021
  • Cvetelina Hill
    Georgia Institute of Technology
    Feb 2-5, 2021
  • Joseph Hlavinka
    Brown University
    Feb 1-5, 2021
  • Do Kien Hoang
    Yale University
    Feb 1-5, 2021
  • Reuven Hodges
    University of Illinois at Urbana-Champaign
    Feb 1-5, 2021
  • Tommy Hofmann
    TU Kaiserslautern
    Feb 15-19, 2021
  • Roser Homs Pons
    Technical University of Munich
    Feb 1-5, 2021
  • Neha Hooda
    Fairfield University
    Apr 12-16, 2021
  • Eric Hopper
    Duke University
    Feb 1-5, 2021
  • Max Horn
    Technische Universität Kaiserslautern
    Feb 15-19, 2021
  • Serkan Hosten
    San Francisco State University
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Daoji Huang
    Brown University
    Sep 1, 2020-May 31, 2021
  • Yifeng Huang
    University of Michigan
    Feb 1-May 7, 2021
  • Suzanne Huaringa Mosquera
    PUCP
    Feb 1-5, 2021
  • June Huh
    Stanford University
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Benjamin Hutz
    Saint Louis University
    Feb 15-19, 2021
  • Brian Hwang
    Cornell University
    Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Anthony Iarrobino
    Northeastern University
    Feb 1-May 7, 2021
  • Muhammad Imran
    United Arab Emirates University
    Apr 12-16, 2021
  • Bogdan Ion
    University of Pittsburgh
    Feb 1-May 7, 2021
  • Alexey Izmailov
    Brown University
    Feb 1-5, 2021; Feb 15-19, 2021
  • Shashank Jaiswal
    Purdue University
    Apr 12-16, 2021
  • Delio Jaramillo
    Cinvestav-IPN (MEXICO)
    Apr 12-16, 2021
  • Manoel Jarra
    IMPA
    Feb 1-5, 2021; Apr 12-16, 2021
  • David Jensen
    University of Kentucky
    Feb 1-May 7, 2021; Mar 3-May 5, 2021
  • Minyoung Jeon
    The Ohio State University
    Mar 22-26, 2021; Apr 12-16, 2021
  • Sam Jeralds
    University of North Carolina at Chapel Hill
    Feb 1-5, 2021; Mar 22-26, 2021
  • Shuai Jiang
    Virginia Tech
    Feb 1-May 7, 2021
  • Tong Jin
    Georgia Institute of Technology
    Apr 12-16, 2021
  • Michael Joswig
    TU Berlin & MPI Leipzig
    Feb 1-May 7, 2021
  • Nidhi Kaihnsa
    Brown University
    Feb 1-May 7, 2021
  • Elana Kalashnikov
    Harvard University
    Feb 1-5, 2021; Apr 28, 2021
  • Marek Kaluba
    Technische Universität Berlin
    Feb 15-19, 2021
  • Siddarth Kannan
    Brown University
    Feb 1-May 7, 2021
  • Daniel Kaplan
    University of Birmingham
    Feb 1-5, 2021
  • Selvi Kara
    University of South Alabama
    Feb 1-5, 2021
  • Lars Kastner
    Institute of Mathematics of the Technical University
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Syu Kato
    Kyoto University
    Mar 17-May 7, 2021
  • Eric Katz
    The Ohio State University
    Apr 12-16, 2021
  • Kiumars Kaveh
    University of Pittsburgh
    Apr 12-16, 2021
  • Kiran Kedlaya
    University of California, San Diego
    Feb 15-19, 2021
  • Hannah Keese
    Cornell University
    Mar 3-May 5, 2021; Mar 22-26, 2021
  • Elizabeth Kelley
    University of MInnesota
    Feb 1-5, 2021; Apr 12-16, 2021
  • Gary Kennedy
    Ohio State University
    Feb 1-May 7, 2021
  • Nguyen Khanh
    Institut Camille Jordan
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 3-May 5, 2021; Apr 12-16, 2021
  • Joshua Kiers
    Ohio State University
    Feb 1-5, 2021; Mar 22-26, 2021
  • Shinyoung Kim
    Institute for Basic Science Center for Geometry and Physics
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Young Rock Kim
    Hankuk University of Foreign Studies
    Mar 22-26, 2021; Apr 12-16, 2021
  • Donghyun Kim
    UC Berkeley
    Feb 1-5, 2021
  • Jaehyung Kim
    University of Illinois - Urbana Champaign
    Feb 1-5, 2021
  • Patricia Klein
    University of Minnesota
    Feb 1-May 7, 2021
  • Allen Knutson
    Cornell University
    Feb 1-5, 2021; Feb 15-May 7, 2021
  • Kathlén Kohn
    KTH Royal Institute of Technology
    Apr 12-16, 2021
  • Aleksandr Kolpakov
    University of Neuchâtel
    Mar 22-26, 2021; Apr 12-16, 2021
  • Jakub Koncki
    Institute of Mathematics, Polish Academy of Sciences
    Feb 1-May 7, 2021
  • Matthias Köppe
    UC Davis
    Feb 15-19, 2021
  • Korkeat Korkeathikhun
    University of North Carolina at Chapel Hill
    Feb 1-5, 2021; Mar 22-26, 2021
  • Gaurish Korpal
    University of Arizona
    Feb 15-19, 2021
  • Lukas Kühne
    Max Planck Institute for Mathematics in the Sciences
    Feb 1-May 7, 2021
  • Tri Lai
    University of Nebraska, Lincoln
    Feb 1-5, 2021
  • Pierre Lairez
    INRIA
    Feb 15-19, 2021
  • Thomas Lam
    University of Michigan
    Feb 1-May 7, 2021
  • Tyler Lane
    Brown University
    Feb 1-5, 2021
  • Matthew Larson
    Stanford University
    Feb 1-May 7, 2021
  • Cédric Le Texier
    Universitetet i Oslo
    Apr 12-16, 2021
  • Kang-Ju Lee
    Seoul National University
    Feb 1-5, 2021; Feb 24-May 5, 2021
  • Eunjeong Lee
    IBS-CGP
    Apr 12-16, 2021
  • Samuel Lelièvre
    Université Paris-Saclay
    Feb 15-19, 2021
  • Yoav Len
    University of St Andrews
    Feb 1-5, 2021; Apr 12-16, 2021
  • Cristian Lenart
    University at Albany
    Feb 1-5, 2021; Mar 22-26, 2021
  • Anton Leykin
    Georgia Tech
    Feb 15-19, 2021
  • Chen Li
    Brown University
    Feb 1-5, 2021
  • Shiyue Li
    Brown University
    Feb 1-May 7, 2021
  • Daniel Li
    Brown University
    Feb 1-5, 2021
  • Amy Li
    University of Texas at Austin
    Feb 3-5, 2021
  • Yen-Kheng Lim
    Xiamen University Malaysia
    Apr 12-16, 2021
  • Kuei-Nuan Lin
    Penn State University, Greater Allegheny
    Feb 1-5, 2021; Mar 22-26, 2021
  • Feiyang Lin
    Harvey Mudd College
    Feb 1-5, 2021
  • Davis Lister
    Brown University
    Feb 1-5, 2021
  • Bingyan Liu
    university of illinois (UIUC)
    Feb 1-5, 2021
  • Yuqing Liu
    University of Michigan
    Feb 1-5, 2021
  • David Lowry-Duda
    ICERM & Brown University
    Feb 1-May 7, 2021
  • Yuze Luan
    UC Davis
    Feb 1-5, 2021
  • Trent Lucas
    Brown University
    Feb 1-5, 2021
  • Antonio Macchia
    Freie Universität Berlin
    Feb 1-May 7, 2021
  • Diane Maclagan
    University of Warwick
    Apr 12-16, 2021
  • Timothy Magee
    University of Birmingham
    Feb 1-5, 2021; Apr 12-16, 2021
  • Saikat Maity
    University of Calcutta
    Apr 12-16, 2021
  • Firdous Mala
    GDC Sopore, Bla
    Feb 1-5, 2021
  • Aimeric Malter
    University of Birmingham
    Feb 3-5, 2021
  • Kelly Maluccio
    Texas A&M University
    Feb 15-19, 2021
  • Travis Mandel
    University of Oklahoma
    Apr 12-16, 2021
  • Yelena Mandelshtam
    University of California, Berkeley
    Feb 1-5, 2021
  • Olya Mandelshtam
    University of Waterloo
    Mar 10-May 5, 2021
  • Madhusudan Manjunath
    INDIAN INSTITUTE OF TECHNOLOGY BOMBAY
    Feb 1-May 7, 2021
  • Hannah Markwig
    Eberhard Karls University of Tübingen
    Feb 1-May 7, 2021
  • Jesus Martinez-Garcia
    University of Essex
    Feb 1-5, 2021; Feb 15-19, 2021
  • Lily Mayo
    Brown University
    Feb 1-5, 2021
  • Mikhail Mazin
    Kansas State University
    Feb 1-May 7, 2021
  • Jason McCullough
    Iowa State University
    Apr 12-16, 2021
  • Alex McDonough
    Brown University
    Feb 1-May 7, 2021
  • Jodi McWhirter
    Washington University in St. Louis
    Apr 12-16, 2021
  • Hana Melánová
    University of Vienna
    Feb 15-19, 2021
  • Margarida Melo
    Universita Roma Tre
    Feb 1-5, 2021
  • Karola Meszaros
    Cornell University
    Apr 12-16, 2021
  • Mike Michailidis
    The MathWorks Inc.
    Mar 22-26, 2021
  • Leonardo Mihalcea
    Virginia Polytechnic Institute and State University
    Feb 1-May 7, 2021
  • Elizabeth Milićević
    Haverford College
    Mar 3-May 5, 2021; Mar 15-Apr 16, 2021; Mar 22-26, 2021
  • Kalina Mincheva
    Yale University
    Feb 15-19, 2021; Apr 12-16, 2021
  • Luca Moci
    Universita' di Bologna
    Feb 1-5, 2021
  • Ali Mohammad Nezhad
    Purdue University
    Feb 1-5, 2021; Apr 12-16, 2021
  • Fatemeh Mohammadi
    University of Bristol
    Feb 24-May 5, 2021
  • Fatemeh Mohammadi
    Ghent University
    Feb 1-May 7, 2021
  • Jonathan Montaño
    New Mexico State University
    Feb 1-5, 2021; Apr 12-16, 2021
  • Héctor Montiel
    UNAM
    Feb 3-5, 2021; Apr 12-16, 2021
  • Han-Bom Moon
    Fordham University
    Feb 1-5, 2021
  • Alejandro Morales
    University of Massachusetts, Amherst
    Feb 1-5, 2021; Apr 12-16, 2021
  • Sophie Morel
    CNRS/ENS Lyon
    Feb 3-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Marc Moreno
    University of Western Ontario
    Feb 15-19, 2021
  • Ralph Morrison
    Williams College
    Feb 1-5, 2021; Apr 12-16, 2021
  • Jennifer Morse
    University of Virginia
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 21-27, 2021; Apr 12-16, 2021
  • Chenqi Mou
    Beihang University, China
    Mar 22-26, 2021
  • Hanna Mularczyk
    Harvard University
    Feb 3-5, 2021
  • Tommi Muller
    University Of British Columbia
    Apr 12-16, 2021
  • Reshma Munbodh
    Alpert Medical School of Brown University
    Apr 12-16, 2021
  • Gregg Musiker
    University of Minnesota
    Feb 1-5, 2021
  • Robert Muth
    Washington & Jefferson College
    Mar 22-26, 2021
  • Philippe Nadeau
    Institut Camille Jordan
    Feb 1-5, 2021; Feb 15-19, 2021; Feb 24-May 5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Uwe Nagel
    University of Kentucky
    Feb 1-5, 2021
  • Alfredo Nájera Chávez
    Mathematics Institute UNAM, Oaxaca
    Apr 12-16, 2021
  • Hiroshi Naruse
    University of Yamanashi
    Feb 1-May 7, 2021
  • Evangelos Nastas
    SUNY
    Feb 15-19, 2021
  • Abhiram Natarajan
    Purdue University
    Feb 3-5, 2021
  • Benjamin Nativi
    The University of Texas at Austin
    Feb 3-5, 2021; Apr 12-16, 2021
  • Gleb Nenashev
    Brown University
    Feb 1-May 31, 2021
  • Xianglong Ni
    University of California, Berkeley
    Feb 1-5, 2021
  • Nathan Nichols
    University Of Minnesota Twin Cities
    Feb 1-5, 2021
  • Ivan Nikitin
    NRU HSE
    Feb 1-5, 2021
  • Benjamin Nill
    University of Magdeburg
    Apr 12-16, 2021
  • Mounir Nisse
    Xiamen University Malaysia
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Augustine O'Keefe
    Connecticut College
    Feb 1-5, 2021
  • Damián Ochoa
    Universidad Nacional Autónoma de México
    Apr 12-16, 2021
  • David Oetjen
    Virginia Tech
    Feb 1-5, 2021; Mar 3-May 5, 2021; Mar 22-26, 2021
  • Jaeseong Oh
    Seoul National University
    Feb 1-5, 2021
  • Gidon Orelowitz
    University of Illinois, Urbana-Champaign
    Feb 1-5, 2021
  • Daniel Orr
    Virginia Tech
    Mar 22-26, 2021; Mar 31-May 5, 2021
  • Alperen Ozdemir
    Georgia Tech
    Feb 1-5, 2021
  • Roberto Pagaria
    Alma Mater Studiorum Università di Bologna
    Feb 1-5, 2021; Feb 15-19, 2021
  • Jianping Pan
    University of California, Davis
    Feb 1-May 7, 2021
  • Marta Panizzut
    TU Berlin
    Feb 1-5, 2021; Feb 15-19, 2021
  • Theodoros Stylianos Papazachariou
    University of Essex
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Joseph Pappe
    UC Davis
    Feb 1-5, 2021
  • Matteo Parisi
    University of Oxford
    Feb 3-5, 2021; Apr 12-16, 2021
  • Beatriz Pascual Escudero
    Universidad Carlos III de Madrid
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Brendan Pawlowski
    University of Southern California
    Feb 1-5, 2021; Mar 22-26, 2021
  • Sam Payne
    University of Texas at Austin
    Jan 31-May 8, 2021
  • Oliver Pechenik
    University of Michigan
    Feb 1-5, 2021; Mar 22-26, 2021
  • Raul Penaguiao
    San Francisco State University
    Feb 2-5, 2021
  • Michael Perlman
    Queen's University
    Mar 22-26, 2021
  • Nicolas Perrin
    Versailles Saint-Quentin-en-Yvelines University
    Feb 1-May 7, 2021
  • Nathan Pflueger
    Amherst College
    Feb 1-May 7, 2021
  • Viviane Pons
    Université Paris Sud
    Feb 15-19, 2021
  • Irem Portakal
    Otto-von-Guericke-Universitaet Magdeburg
    Feb 15-19, 2021; Apr 12-16, 2021
  • Martha Precup
    Washington University in St. Louis
    Mar 22-26, 2021
  • Ying Anna Pun
    University of Virginia
    Feb 1-5, 2021; Mar 22-26, 2021
  • Jiayue Qi
    University of Linz
    Feb 1-5, 2021
  • Zhijun (George) Qiao
    University of Texas Rio Grande Valley
    Apr 12-16, 2021; Apr 21-May 5, 2021
  • Jenna Rajchgot
    McMaster University
    Mar 22-26, 2021; Apr 12-16, 2021
  • Rohini Ramadas
    Brown University
    Feb 1-5, 2021; Feb 24-May 5, 2021; Apr 12-16, 2021
  • Arvind Ramaswami
    Georgia Institute of Technology
    Feb 1-5, 2021
  • Alondra Ramírez Sandoval
    Universidad Nacional Autónoma de México
    Apr 12-16, 2021
  • Dhruv Ranganathan
    University of Cambridge
    Apr 12-16, 2021
  • Margaret Readdy
    University of Kentucky
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Yue Ren
    Swansea University
    Apr 12-16, 2021
  • William Reynolds
    University of Edinburgh
    Feb 1-5, 2021; Apr 12-16, 2021
  • Brendon Rhoades
    University of California, San Diego
    Feb 1-5, 2021
  • Harry Richman
    University of Washington
    Apr 12-16, 2021
  • Edward Richmond
    Oklahoma State University
    Feb 1-5, 2021; Mar 30-May 5, 2021
  • Konstanze Rietsch
    King's College London
    Feb 1-May 7, 2021
  • Richard Rimanyi
    University of North Carolina at Chapel Hill
    Feb 1-5, 2021; Mar 3-May 5, 2021; Mar 22-26, 2021
  • Jesus Rivera Ramirez
    CINVESTAV
    Feb 1-5, 2021
  • Diego Robayo Bargans
    Universidad de los Andes
    Feb 1-5, 2021
  • Colleen Robichaux
    University of Illinois at Urbana-Champaign
    Feb 1-May 7, 2021
  • Colleen Robles
    Duke University
    Feb 1-5, 2021
  • Alejandro Rodriguez Matta
    Universidad Nacional Autónoma de México
    Apr 12-16, 2021
  • David Roe
    Massachusetts Institute of Technology
    Feb 15-19, 2021
  • Felix Röhrle
    Goethe University Frankfurt
    Feb 1-5, 2021; Apr 12-16, 2021
  • Piotr Rudnicki
    University of Warsaw
    Feb 1-5, 2021
  • Oliver Ruff
    Kent State University
    Mar 22-26, 2021
  • Julian Rüth
    none
    Feb 15-19, 2021
  • Felix Rydell
    KTH
    Apr 12-16, 2021
  • María Sabando Alvarez
    Washington University in St. Louis
    Apr 12-16, 2021
  • Adriana Salerno
    Bates College
    Feb 15-19, 2021
  • Francisco Santos
    University of Cantabria
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Anna-Laura Sattelberger
    Max Planck Institute for Mathematics in the Sciences
    Feb 15-19, 2021
  • Justin Sawon
    University of North Carolina - Chapel Hill
    Feb 1-5, 2021
  • Mahrud Sayrafi
    University of Minnesota
    Feb 1-May 7, 2021
  • Hal Schenck
    Auburn University
    Feb 1-May 7, 2021
  • Hal Schenck
    Iowa State University
    Feb 24-May 5, 2021
  • Anne Schilling
    UC Davis
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 24-26, 2021
  • Bernd Schober
    Carl von Ossietzky Universität Oldenburg
    Apr 12-16, 2021
  • Nolan Schock
    University of Georgia
    Apr 12-16, 2021
  • Georgy Scholten
    North Carolina State University
    Feb 3-5, 2021
  • Daniel Schultz
    Technische Universität Kaiserslautern
    Feb 15-19, 2021
  • Adam Schultze
    State University of New York, University at Albany
    Feb 3-5, 2021
  • Alexandra Seceleanu
    University of Nebraska-Lincoln
    Apr 12-16, 2021
  • George Seelinger
    University of Virginia
    Feb 1-5, 2021; Mar 22-26, 2021
  • Maiko Serizawa
    University of Ottawa
    Mar 31-May 5, 2021
  • Stefano Serpente
    Università degli Studi Roma 3
    Feb 1-5, 2021
  • Oswaldo Sevilla
    Centro de Investigación en Matemáticas, Guanajuato Mexico
    Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Tim Seynnaeve
    University of Bern
    Feb 1-5, 2021
  • Aniket Shah
    The Ohio State University
    Feb 3-5, 2021; Apr 12-16, 2021
  • Kristin Shaw
    University of Oslo
    Feb 1-5, 2021; Apr 12-16, 2021
  • Melissa Sherman-Bennett
    UC Berkeley/Harvard
    Feb 1-May 7, 2021; Mar 3-May 5, 2021
  • Ryan Shifler
    Salisbury University
    Feb 1-5, 2021; Feb 24-May 5, 2021
  • Mark Shimozono
    Virginia Tech
    Feb 1-5, 2021; Mar 21-27, 2021
  • Farbod Shokrieh
    University of Washington
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Yiyan Shou
    UNC - Chapel Hill
    Feb 1-5, 2021; Apr 22, 2021
  • Kevin Shu
    Georgia Institute of Technology
    Apr 12-16, 2021
  • Eugenii Shustin
    Tel Aviv University
    Apr 12-16, 2021
  • Sergio Silva
    Universidad Distrital Francisco Jose de Caldas
    Apr 12-16, 2021
  • Rob Silversmith
    Northeastern University
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Jose Simental Rodriguez
    Max-Planck Institute for Mathematics
    Mar 22-26, 2021
  • Connor Simpson
    University of Wisconsin -- Madison
    Feb 1-May 7, 2021
  • Rahul Singh
    Virginia Polytechnic Institute and State University
    Feb 1-5, 2021; Feb 24-May 5, 2021
  • Uriel Sinichkin
    Tel Aviv University
    Feb 1-5, 2021; Apr 12-16, 2021
  • Gregory Smith
    Queen's University
    Apr 12-16, 2021
  • Jason Snyder
    University of California, Los Angeles
    Feb 3-5, 2021
  • Ivan So
    Michigan State University
    Apr 12-16, 2021
  • Eric Sommers
    University of Massachusetts
    Mar 22-26, 2021
  • Miruna-Stefana Sorea
    SISSA, Trieste
    Feb 1-May 7, 2021
  • Frank Sottile
    Texas A&M University
    Feb 1-5, 2021; Feb 14-20, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Pedro Souza
    Goethe Universität Frankfurt am Main
    Feb 1-5, 2021; Apr 12-16, 2021
  • David Speyer
    University of Michigan
    Feb 1-5, 2021; Apr 11-17, 2021
  • Sylvain Spitz
    TU Berlin
    Feb 15-19, 2021
  • Avery St. Dizier
    Univeristy of Illinois at Urbana-Champaign
    Feb 1-May 7, 2021
  • Evgeny Statnik
    Higher School of Economics
    Feb 1-5, 2021
  • Jessica Striker
    North Dakota State University
    Feb 1-5, 2021; Mar 22-26, 2021
  • Eric Stucky
    University of Minnesota-Twin Cities
    Feb 1-5, 2021; Feb 24-May 5, 2021
  • Bernd Sturmfels
    MPI Leipzig
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Changjian Su
    University of Toronto
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 3-May 5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Nawaz Sultani
    University of Michigan
    Feb 1-5, 2021; Feb 15-19, 2021
  • Yuri Sulyma
    Brown University
    Feb 1-May 7, 2021
  • Kevin Summers
    Virginia Polytechnic Institute and State University
    Feb 1-5, 2021
  • Mariel Supina
    University of California, Berkeley
    Feb 1-May 7, 2021
  • Joshua Swanson
    University of California, San Diego
    Mar 22-26, 2021
  • Nafie Tairi
    University of Bern
    Feb 1-5, 2021
  • Henry Talbott
    Brown University
    Feb 1-5, 2021
  • Pedro Tamaroff
    Trinity College Dublin
    Feb 15-19, 2021
  • Daniel Tamayo Jiménez
    Université Paris-Saclay
    Mar 22-26, 2021
  • Anna Tao
    Brown University
    Feb 1-May 7, 2021
  • Nicola Tarasca
    Virginia Commonwealth University
    Feb 1-May 7, 2021
  • Mojdeh Tarighat
    University of Virginia
    Mar 22-26, 2021
  • Mihail Tarigradschi
    Rutgers University
    Feb 1-5, 2021; Mar 3-May 5, 2021
  • Andrew Tawfeek
    Amherst College
    Feb 1-5, 2021; Apr 21-May 5, 2021
  • Máté Telek
    University of Copenhagen
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Ayush Tewari
    TU Berlin
    Feb 1-May 7, 2021
  • Ayush Tewari
    Eberhard Karls Universitat Tubingen
    Feb 24-May 5, 2021
  • Vasu Tewari
    University of Hawaii
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Warut Thawinrak
    University of California Davis
    Feb 1-5, 2021
  • Nicolas Thiéry
    Université Paris Sud
    Feb 15-19, 2021
  • Zonglin Tian
    Texas A & M University
    Feb 1-5, 2021
  • Angelica Torres
    KTH Royal Institute of Technology
    Feb 1-5, 2021
  • Joaquin Torres Henestroza
    Universidad Nacional Autónoma de México, UNAM
    Apr 12-16, 2021
  • Trang Tran
    Ucsc
    Feb 1-5, 2021; Apr 12-16, 2021
  • Nathaniel Trask
    Sandia National Laboratory
    Feb 1-5, 2021
  • Ling Hei Tsang
    The Ohio State University
    Feb 1-5, 2021; Feb 15-19, 2021; Apr 12-16, 2021
  • Daniele Turchetti
    Durham University
    Feb 1-5, 2021
  • Martin Ulirsch
    Goethe University Frankfurt
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Jeremy Usatine
    Brown University
    Feb 1-May 7, 2021
  • Ravi Vakil
    Stanford University
    Feb 1-May 7, 2021
  • Bart Van Steirteghem
    CUNY and FAU Erlangen-Nuernberg
    Apr 12-16, 2021
  • Alejandro Vargas
    University of Bern
    Feb 1-5, 2021
  • Paul Vater
    Max Planck Institute for Mathematics in the Sciences
    Feb 15-19, 2021
  • Lorenzo Vecchi
    Alma Mater Studiorum - Università di Bologna
    Feb 1-5, 2021; Feb 15-19, 2021; Feb 24-May 5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Emanuele Ventura
    University of Bern
    Feb 1-May 7, 2021
  • Diego Villamizar
    Tulane University
    Mar 22-26, 2021
  • Filippo Viviani
    Roma Tre University
    Feb 1-5, 2021
  • Duc Vo
    Harvard University
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Arina Voorhaar
    Université de Genève
    Feb 1-5, 2021
  • Daniel Wang
    Brown University
    Feb 1-5, 2021
  • Chengyang Wang
    UC Davis
    Feb 1-5, 2021
  • Jeremy Wang
    Brown University
    Feb 1-5, 2021
  • Charles Wang
    Harvard University
    Feb 1-5, 2021
  • Ying Wang
    Colorado College
    Feb 1-5, 2021
  • Weikun Wang
    Southern University of Science and Technology
    Feb 1-5, 2021; Feb 15-19, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Jidong Wang
    University of Oregon
    Feb 3-5, 2021
  • Andrzej Weber
    Uniwersity of Warsaw
    Feb 1-May 7, 2021
  • Ivy Wei
    University of Minnesota
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Anna Weigandt
    University of Michigan
    Feb 1-May 7, 2021; Mar 22-26, 2021
  • Max Weinreich
    Brown University
    Feb 1-5, 2021
  • Nathaniel Welty
    Texas A&M University
    Feb 1-5, 2021
  • Daping Weng
    Michigan State University
    Apr 12-16, 2021
  • Ian Whitehead
    Swarthmore College
    Mar 22-26, 2021
  • Rebecca Whitman
    UC Berkeley
    Feb 1-5, 2021
  • Amy Wiebe
    Freie Universität Berlin
    Feb 1-5, 2021
  • Harold Williams
    University of Southern California
    Mar 22-26, 2021
  • Lauren Williams
    Harvard University
    Feb 1-May 7, 2021
  • Kaelyn Willingham
    The Ohio State University
    Feb 3-5, 2021; Apr 12-16, 2021
  • Rosa Winter
    Max Planck Institute for Mathematics in the Sciences, Leipzig
    Feb 15-19, 2021
  • Camron Withrow
    Virginia Tech
    Feb 1-5, 2021
  • Corey Wolfe
    Tulane University
    Feb 1-May 7, 2021
  • Tian An Wong
    University of Michigan-Dearborn
    Mar 22-26, 2021
  • Russ Woodroofe
    University of Primorska
    Feb 1-5, 2021
  • Cameron Wright
    University of Washington
    Feb 1-May 7, 2021
  • Kayla Wright
    University of Minnesota
    Feb 1-5, 2021
  • Chenxi Wu
    university of wisconsin at madison
    Feb 1-5, 2021
  • Ralph Xu
    Syracuse University
    Feb 15-19, 2021
  • Weihong Xu
    Rutgers
    Feb 1-May 7, 2021
  • Damir Yeliussizov
    Kazakh-British Technical University
    Feb 1-May 7, 2021
  • Alexander Yong
    University of Illinois at Urbana-Champaign
    Feb 1-May 7, 2021
  • Semin Yoo
    University of Rochester
    Feb 1-5, 2021; Feb 24-May 5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Benjamin Young
    University of Oregon
    Feb 15-19, 2021
  • Tianyi Yu
    University of California, San Diego
    Feb 1-5, 2021
  • Josephine Yu
    Georgia Institute of Technology
    Feb 1-5, 2021
  • Chi Ho Yuen
    Brown University
    Feb 1-May 7, 2021
  • Claudia Yun
    Brown University
    Feb 1-May 7, 2021
  • Oguzhan Yürük
    TU Berlin
    Feb 15-19, 2021
  • Dmitry Zakharov
    Central Michigan University
    Feb 1-5, 2021; Apr 12-16, 2021
  • Mohammad Zaman Fashami
    Amirkabir University of Technology
    Apr 12-16, 2021
  • Yuanning Zhang
    UC Berkeley
    Feb 1-5, 2021; Apr 12-16, 2021
  • Xiping Zhang
    Fudan University
    Feb 1-5, 2021
  • Zehong Zhao
    University of California, San Diego
    Feb 1-5, 2021
  • Changlong Zhong
    State University of New York Albany
    Feb 1-5, 2021; Mar 22-26, 2021; Apr 12-16, 2021
  • Xu Zhuang
    Jilin University
    Feb 1-5, 2021
  • Paul Zinn-Justin
    The University of Melbourne
    Feb 1-May 7, 2021

Visit dates listed on the participant list may be tentative and subject to change without notice.

Semester Schedule

Monday, February 1, 2021
  • 9:50 - 10:00 am EST
    Welcome
    Virtual
    • Brendan Hassett, ICERM/Brown University
  • 10:00 - 10:45 am EST
    Short Introduction to Hodge Structures Part 1
    Virtual
    • Colleen Robles, Duke University
    Abstract
    I will introduce Hodge structures and describe the linear structures underlying the Hard Lefschetz Theorem and Hodge--Riemann Bilinear Relations.
  • 11:00 am - 12:00 pm EST
    Problem Session 1
    Problem Session - Virtual
  • 12:00 - 12:30 pm EST
    Short Introduction to Hodge Structures Part 2
    Virtual
    • Colleen Robles, Duke University
    Abstract
    I will introduce Hodge structures and describe the linear structures underlying the Hard Lefschetz Theorem and Hodge--Riemann Bilinear Relations.
  • 12:30 - 2:00 pm EST
    Lunch/Free Time
    Virtual
  • 2:00 - 2:45 pm EST
    Basic Schubert Calculus Part 1
    Virtual
    • Sara Billey, University of Washington
  • 3:00 - 4:00 pm EST
    Problem Session 2
    Problem Session - Virtual
  • 4:00 - 4:30 pm EST
    Basic Schubert Calculus Part 2
    Virtual
    • Sara Billey, University of Washington
  • 4:30 - 5:15 pm EST
    Reception
    Virtual
Tuesday, February 2, 2021
  • 9:00 - 9:45 am EST
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 10:00 - 10:45 am EST
    Basic notions in cotangent Schubert calculus - Part 1
    Virtual
    • Richard Rimanyi, University of North Carolina at Chapel Hill
    Abstract
    A key notion of Schubert Calculus is the cohomology ring of a homogeneous space, together with a distinguished basis: the collection of Schubert classes. There is a one-parameter deformation of the notion "Schubert class", called Chern-Schwartz-MacPherson (CSM-) class (a.k.a. characteristic cycle class, or cohomological stable envelope). In this lecture/workshop we will define the CSM class, and illustrate many of its properties through examples.
  • 11:00 am - 12:00 pm EST
    Problem Session 3
    Problem Session - Virtual
  • 12:00 - 12:30 pm EST
    Basic notions in cotangent Schubert calculus - Part 2
    Virtual
    • Richard Rimanyi, University of North Carolina at Chapel Hill
    Abstract
    A key notion of Schubert Calculus is the cohomology ring of a homogeneous space, together with a distinguished basis: the collection of Schubert classes. There is a one-parameter deformation of the notion "Schubert class", called Chern-Schwartz-MacPherson (CSM-) class (a.k.a. characteristic cycle class, or cohomological stable envelope). In this lecture/workshop we will define the CSM class, and illustrate many of its properties through examples.
  • 12:30 - 2:00 pm EST
    Lunch/Free Time
    Virtual
  • 2:00 - 2:45 pm EST
    Matroids Part 1
    Virtual
    • Christopher Eur, Stanford University
    Abstract
    We give an introduction to matroid theory with a view towards its recent interactions with algebraic geometry. In the first half, we study matroids as combinatorial abstractions of hyperplane arrangements, which will lead us to Chow rings of matroids, modeled after the geometry of wonderful compactifications of hyperplane arrangement complements. In the second half, we give a broad survey of some recent developments involving other different but related algebro-geometric models of matroids.
  • 3:00 - 4:00 pm EST
    Problem Session 4
    Problem Session - Virtual
  • 4:00 - 4:30 pm EST
    Matroids Part 2
    Virtual
    • Christopher Eur, Stanford University
    Abstract
    We give an introduction to matroid theory with a view towards its recent interactions with algebraic geometry. In the first half, we study matroids as combinatorial abstractions of hyperplane arrangements, which will lead us to Chow rings of matroids, modeled after the geometry of wonderful compactifications of hyperplane arrangement complements. In the second half, we give a broad survey of some recent developments involving other different but related algebro-geometric models of matroids.
Wednesday, February 3, 2021
  • 10:00 - 10:45 am EST
    Quantum Cohomology Part 1
    Virtual
    • Nicolas Perrin, Versailles Saint-Quentin-en-Yvelines University
  • 11:00 am - 12:00 pm EST
    Problem Session 5
    Problem Session - Virtual
  • 12:00 - 12:30 pm EST
    Quantum Cohomology Part 2
    Virtual
    • Nicolas Perrin, Versailles Saint-Quentin-en-Yvelines University
  • 12:30 - 2:00 pm EST
    Lunch/Free Time
    Virtual
  • 2:00 - 2:45 pm EST
    Affine Schubert Calculus Part 1
    Virtual
    • Mark Shimozono, Virginia Tech
  • 3:00 - 4:00 pm EST
    Problem Session 6
    Problem Session - Virtual
  • 4:00 - 4:30 pm EST
    Affine Schubert Calculus Part 2
    Virtual
    • Mark Shimozono, Virginia Tech
  • 4:30 - 5:15 pm EST
    Gathertown Afternoon Coffee - Informal Grad Student / Postdoc Focused
    Coffee Break - Virtual
Thursday, February 4, 2021
  • 9:00 - 9:45 am EST
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 10:00 - 10:45 am EST
    Introduction to Tropical Geometry Through Curves - Part 1
    Virtual
    • Madeline Brandt, Brown University
    Abstract
    Tropical geometry equips varieties with a combinatorial counterpart called the tropicalization. In this talk, I will introduce some of the key ideas in tropical geometry by studying curves. This will include definitions and examples of embedded tropicalization for curves in the plane, abstract tropicalization / dual graphs, and Berkovich skeleta.
  • 11:00 am - 12:00 pm EST
    Problem Session 7
    Problem Session - Virtual
  • 12:00 - 12:30 pm EST
    Introduction to Tropical Geometry Through Curves - Part 2
    Virtual
    • Madeline Brandt, Brown University
    Abstract
    Tropical geometry equips varieties with a combinatorial counterpart called the tropicalization. In this talk, I will introduce some of the key ideas in tropical geometry by studying curves. This will include definitions and examples of embedded tropicalization for curves in the plane, abstract tropicalization / dual graphs, and Berkovich skeleta.
  • 12:30 - 2:00 pm EST
    Lunch/Free Time
    Virtual
  • 2:00 - 2:45 pm EST
    Moduli spaces of tropical curves Part 1
    Virtual
    • Sam Payne, University of Texas at Austin
    Abstract
    In the first part of this talk, I will introduce the moduli space of stable tropical curves and discuss its combinatorial structure and topology, illustrating with simple examples in low genus. In the problem session, you will compute one further example. And in the second half of the talk, I will explain some general results about the topology of moduli spaces of stable tropical curves, how these relate to the topology of the algebraic moduli spaces M_g and M_{g,n}, and then state some open problems and conjectures that you may find interesting to think about during the semester.
  • 3:00 - 4:00 pm EST
    Problem Session 8
    Problem Session - Virtual
  • 4:00 - 4:30 pm EST
    Moduli spaces of tropical curves Part 2
    Virtual
    • Sam Payne, University of Texas at Austin
    Abstract
    In the first part of this talk, I will introduce the moduli space of stable tropical curves and discuss its combinatorial structure and topology, illustrating with simple examples in low genus. In the problem session, you will compute one further example. And in the second half of the talk, I will explain some general results about the topology of moduli spaces of stable tropical curves, how these relate to the topology of the algebraic moduli spaces M_g and M_{g,n}, and then state some open problems and conjectures that you may find interesting to think about during the semester.
Friday, February 5, 2021
  • 10:00 - 10:45 am EST
    Cluster structures in commutative rings Part 1
    Virtual
    • Lauren Williams, Harvard University
    Abstract
    In my first talk, I will give a gentle introduction to cluster algebras. In the second talk, I will describe how to identify a commutative ring (such as the coordinate ring of an algebraic variety) with a cluster algebra, and provide several examples. I will also discuss how to describe cluster algebras by generators and relations.
  • 11:00 am - 12:00 pm EST
    Problem Session 9
    Problem Session - Virtual
  • 12:00 - 12:30 pm EST
    Cluster structures in commutative rings Part 2
    Virtual
    • Lauren Williams, Harvard University
    Abstract
    In my first talk, I will give a gentle introduction to cluster algebras. In the second talk, I will describe how to identify a commutative ring (such as the coordinate ring of an algebraic variety) with a cluster algebra, and provide several examples. I will also discuss how to describe cluster algebras by generators and relations.
  • 12:30 - 2:00 pm EST
    Lunch/Free Time
    Virtual
  • 2:00 - 2:45 pm EST
    Cluster varieties Part 1
    Virtual
    • David Speyer, University of Michigan
    Abstract
    We will discuss the geometry of the affine algebraic varieties associated to cluster algebras. In the first hour, we will give examples and talk about open sets, smoothness and covering maps; in the second hour, we will talk about mixed Hodge structures.
  • 3:00 - 4:00 pm EST
    Problem Session 10
    Problem Session - Virtual
  • 4:00 - 4:45 pm EST
    Cluster varieties Part 2
    Virtual
    • David Speyer, University of Michigan
    Abstract
    We will discuss the geometry of the affine algebraic varieties associated to cluster algebras. In the first hour, we will give examples and talk about open sets, smoothness and covering maps; in the second hour, we will talk about mixed Hodge structures.
Monday, February 8, 2021
Combinatorial Algebraic Geometry
  • 11:00 - 11:30 am EST
    Welcome to ICERM
    Welcome - Virtual
    • Brendan Hassett, ICERM/Brown University
  • 1:30 - 2:00 pm EST
    Organizer / Directorate Meeting
    Meeting - Virtual
Tuesday, February 9, 2021
Combinatorial Algebraic Geometry
  • 2:30 - 3:50 pm EST
    Brown Graduate Course: Algebraic Geometry
    Virtual
    • Jeremy Usatine, Brown University
Wednesday, February 10, 2021
Combinatorial Algebraic Geometry
  • 11:00 am - 12:00 pm EST
    Graduate Students/Postdocs Meeting with Directorate
    Meeting - Virtual
  • 3:30 - 4:30 pm EST
    Degeneracy Loci and Schubert Polynomials
    Virtual
    • William Fulton, University of Michigan
    Abstract
    This talk emphasizes how finding formulae for degeneracy loci leads naturally to the algebra of Schubert polynomials. We'll see how this illuminates the study of Schubert polynomials in the 19th, 20th, and 21st century. (Joint work with Dave Anderson.)
Thursday, February 11, 2021
Combinatorial Algebraic Geometry
  • 2:30 - 3:50 pm EST
    Brown Graduate Course: Algebraic Geometry
    Virtual
    • Jeremy Usatine, Brown University
  • 4:30 - 5:15 pm EST
    Hodge-Riemann relations and Lorentzian polynomials
    Virtual
    • Christopher Eur, Stanford University
    Abstract
    We introduce the theory of Lorentzian polynomials, motivated by the Hodge-Riemann relations and the resulting properties that cohomology rings of smooth complex projective varieties satisfy.
Friday, February 12, 2021
Combinatorial Algebraic Geometry
  • 10:30 - 11:30 am EST
    Post Doc/Graduate Student Seminar
    Virtual
  • 11:30 am - 12:00 pm EST
    Graduate Student/postdoc post-seminar break in Gather
    Coffee Break - Virtual
  • 4:30 - 5:00 pm EST
    Hodge-Riemann relations and Lorentzian polynomials cont.
    Virtual
    • Christopher Eur, Stanford University
    Abstract
    We introduce the theory of Lorentzian polynomials, motivated by the Hodge-Riemann relations and the resulting properties that cohomology rings of smooth complex projective varieties satisfy.
Monday, February 15, 2021
  • 9:45 - 10:00 am EST
    Welcome
    Virtual
    • Brendan Hassett, ICERM/Brown University
  • 10:00 - 10:30 am EST
    A brief tour of Sage
    Virtual
    • Nicolas Thiéry, Université Paris Sud
    Abstract
    I will offer a brief tour of Sage, showcasing some features and use cases, hinting at its development model, pointing to some recent trends, and highlighting how it fits within the larger ecosystem of free computational (mathematics) software.
  • 10:45 - 11:15 am EST
    Rings and fields in Sage
    Virtual
    • David Roe, Massachusetts Institute of Technology
    Abstract
    I will give an introduction to basic algebraic structures in Sage, with a focus on the coercion model, finite fields and extensions of rings. I will also give an overview of how you can contribute to Sage.
  • 11:15 - 11:30 am EST
    Coffee Break
    Virtual
  • 11:30 am - 12:00 pm EST
    Celestial mechanics via tropical geometry (gfan and Macaulay2)
    Virtual
    • Anton Leykin, Georgia Tech
  • 12:15 - 12:45 pm EST
    FusionRings in Sage 9.2
    Virtual
    • Daniel Bump, Stanford University
    Abstract
    The FusionRing class implements useful methods for Verlinde Algebras. These are elegant rings similar to WeylCharacterRings (representation rings of Lie groups) except that the fusion categories have only finitely many objects. These rings have applications to conformal field theory, quantum groups, topological quantum computing and knot theory. Most of the methods needed to work with these have been implemented in Sage 9.2. We will review the math and show what the code can do. The FusionRing code is joint work with Guillermo Aboumrad.
  • 1:00 - 2:00 pm EST
    Lunch/Free Time
    Virtual
  • 2:00 - 3:00 pm EST
    Gathertown Welcome Reception
    Reception - Virtual
  • 3:00 - 4:00 pm EST
    Sage/Oscar Installation Help
    Tutorial - Virtual
Tuesday, February 16, 2021
  • 9:00 - 9:45 am EST
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 10:00 - 10:30 am EST
    OSCAR - The Project
    Virtual
    • Michael Joswig, TU Berlin & MPI Leipzig
    Abstract
    The OSCAR project is a collaborative effort to shape a new computer algebra system, written in Julia. OSCAR is built on top of the four "cornerstone systems" ANTIC (for number theory), GAP (for group and representation theory), polymake (for polyhedral and tropical geometry) and Singular (for commutative algebra and algebraic geometry). We present three examples to showcase the current version 0.5.1. This is joint work with The OSCAR Development Team.
  • 10:45 - 11:15 am EST
    OSCAR - Selected Features
    Virtual
    • Daniel Schultz, Technische Universität Kaiserslautern
    Abstract
    Introducing OSCAR, a new computer algebra system combining GAP, Polymake, Hecke and Singular.
  • 11:15 - 11:30 am EST
    Coffee Break
    Virtual
  • 11:30 am - 12:00 pm EST
    Computing the Newton polytope of a large discriminant
    Virtual
    • Lars Kastner, Institute of Mathematics of the Technical University
    Abstract
    The Newton polytope of the discriminant of a quaternary cubic form has 166'104 vertices. One way to obtain these vertices is to enumerate all D-equivalence classes of regular triangulations of the 3- dilated tetrahedron. The only known way to do this is to enumerate all regular triangulations of the 3-dilated tetrahedron and group them into classes in a second step. This talk will focus on the computations carried out to arrive at this result. It involved the use of polymake and mptopcom on large computing clusters in parallel which in turn brought other obstacles. This software can also be used via polymake.jl in OSCAR. Since computer experiments in algebraic geometry are becoming larger and larger, this talks aims at providing insights on how to set up these experiments such that they give reliable results, and how to avoid the pitfalls we encountered. This is joint work with Robert Loewe.
  • 12:15 - 12:45 pm EST
    Some hybrid symbolic-numeric methods in algebraic geometry
    Virtual
    • Jonathan Hauenstein, University of Notre Dame
    Abstract
    On the theoretical side, algebraic geometry combines aspects of algebra and geometry to provide many tools to prove new results. On the computational side, symbolic computations typically based on algebra and numerical computations typically based on geometry can be combined to provide many new computational tools to study a variety of problems in algebraic geometry. This talk will explore some hybrid symbolic-numeric methods and applications in computational algebraic geometry.
  • 1:00 - 2:00 pm EST
    Lunch/Free Time
    Virtual
  • 2:00 - 3:00 pm EST
    Problem Session
    Virtual
  • 3:00 - 4:00 pm EST
    Contributing to Sage Tutorial
    Tutorial - Virtual
Wednesday, February 17, 2021
  • 9:00 - 9:45 am EST
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 10:00 - 10:45 am EST
    Parallelization of Triangular Decompositions- Design and implementation with the BPAS library
    Virtual
    • Marc Moreno, University of Western Ontario
    Abstract
    We discuss the parallelization of algorithms for solving polynomial systems by way of triangular decomposition. The "Triangularize" algorithm proceeds through incremental intersections of polynomials to produce the different components of the solution set. Independent components imply the opportunity for concurrency. This "component-level" parallelization of triangular decompositions, our focus here, belongs to the class of dynamic irregular parallelism. Potential parallel speed-up depends only on geometrical properties of the solution set (number of components, their dimensions and degrees); these algorithms do not scale with the number of processors. To manage the irregularities of component-level parallelization we combine different concurrency patterns: map, workpile, producer-consumer, pipeline and fork/join. We report on our implementation in the freely available BPAS library. Comprehensive experimentation with thousands of polynomial systems yields examples with up to 10.8-times speed up on a 12-core machine.
  • 11:00 - 11:30 am EST
    Coffee Break
    Virtual
  • 11:30 am - 12:00 pm EST
    Rational integrals and periods with Sagemath and Julia
    Virtual
    • Pierre Lairez, INRIA
    Abstract
    Based on symbolic integration and numerical analytic continuation, we can compute to high precision integrals of multivariate rational functions. I will show applications to volume computation and to the study of quartic surfaces. I will emphasize on some software aspects, specific to Sagemath and Julia.
  • 12:15 - 12:45 pm EST
    Generalized cohomology quotients of the symmetric functions
    Virtual
    • Darij Grinberg, Drexel University
  • 1:00 - 2:00 pm EST
    Lunch/Free Time
    Virtual
  • 2:00 - 2:40 pm EST
    Lightning Talks
    Virtual
    • Adam Afandi, Colorado State University
    • Jose Brox, Centre for Mathematics of the University of Coimbra
    • Juliette Bruce, University of California, Berkeley / MSRI
    • Laura Brustenga i Moncusi, University of Copenhagen
    • Taylor Brysiewicz, Max Planck Institute for Mathematics in the Sciences
    • Papri Dey, University of Missouri
    • Sean Griffin, Brown University
    • Shinyoung KIM, Institute for Basic Science Center for Geometry and Physics
  • 2:40 - 2:50 pm EST
    Coffee Break
    Virtual
  • 2:50 - 3:30 pm EST
    Lightning Talks
    Virtual
    • Lukas Kühne, Max Planck Institute for Mathematics in the Sciences
    • Jianping Pan, University of California, Davis
    • Marta Panizzut, TU Berlin
    • Theodoros Stylianos Papazachariou, University of Essex
    • Colleen Robichaux, University of Illinois at Urbana-Champaign
    • Mahrud Sayrafi, University of Minnesota
    • Weihong Xu, Rutgers
  • 3:30 - 4:30 pm EST
    Code Demonstrations
    Tutorial - Virtual
Thursday, February 18, 2021
  • 9:00 - 9:45 am EST
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 10:00 - 10:45 am EST
    msolve - A Library for Solving Polynomial Systems
    Virtual
    • Christian Eder, University of Kaiserslautern
    Abstract
    We present a new open source C library msolve dedicated to solve multivariate polynomial systems exactly through computer algebra methods. The core algorithmic framework of msolve relies on Gröbner bases and linear algebra based algorithms for polynomial system solving. It relies on Gröbner basis computation w.r.t. the degree reverse lexicographical order, Gröbner conversion to a lexicographical Gröbner basis and real solving of univariate polynomials. We explain in detail how these three main steps of the solving process are implemented exploiting the computational capabilities of the framework. We compare the practical performance of the different parts of msolve with similar functionalities of leading computer algebra systems such as Magma and Maple on a wide range of polynomial systems with a particular focus on those which have finitely many complex solutions, showing that msolve can tackle systems which were out of reach by the software state-of-the-art. This is joint work with Jérémy Berthomieu, Jean-Charles Faugère and Mohab Safey El Din from the PolSys Team at the Sorbonne Université in Paris.
  • 11:00 - 11:30 am EST
    Parallelism in Algebraic Geometry - Examples with Singular and GPI-Space
    Virtual
    • Anne Frühbis-Krüger, University of Oldenburg
    Abstract
    I shall illustrate the use of the Singular - GPI-space interplay in some examples including a smoothness test, GIT-fans and desingularization.
  • 11:45 am - 12:45 pm EST
    Coffee Break
    Virtual
  • 12:45 - 1:15 pm EST
    Computing Galois groups in enumerative geometry
    Virtual
    • Frank Sottile, Texas A&M University
  • 1:30 - 2:30 pm EST
    Lunch/Free Time
    Virtual
  • 2:30 - 3:30 pm EST
    Problem Session
    Virtual
  • 3:30 - 4:30 pm EST
    Code Demonstrations
    Tutorial - Virtual
Friday, February 19, 2021
  • 9:00 - 9:45 am EST
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 10:00 - 10:30 am EST
    Factorizations into irreducibles and polytopes
    Virtual
    • Tommy Hofmann, TU Kaiserslautern
    Abstract
    Dedekind domains form a family of commutative rings that plays an important role in algebraic geometry and number theory. While elements of Dedekind domains factor into irreducible elements, such a factorization is in general not unique. We present an algorithm, which for a given element of the ring of integers of a number field, determines all factorizations into irreducible elements. The algorithm makes heavy use of computations with polytopes and is implemented in Oscar. This is joint work with Claus Fieker.
  • 10:45 - 11:30 am EST
    Computational challenges for tropical del Pezzo surfaces
    Virtual
    • María Angélica Cueto, Ohio State University
    Abstract
    A smooth degree d del Pezzo surface is obtained by blowing up the projective plane at (9-d) generic points. In this talk, we will discuss how to tropicalize these surfaces for various embeddings as we vary the input points and the computational challenges that arise when doing so.
  • 11:15 - 11:30 am EST
    Coffee Break
    Virtual
  • 11:30 am - 12:00 pm EST
    Presenting the multipolynomial bases package
    Virtual
    • Viviane Pons, Université Paris Sud
    Abstract
    In this talk, we present an external SageMath package to work on multivariate polynomials seen as an algebra over integer vectors (the exponents). This allows for manipulation of divided differences operators and the definition of many bases of multivariate polynomials such as the Schubert polynomials, Grothendieck, and Demazure Characters.
  • 12:15 - 12:45 pm EST
    Hasse-Witt matrices and mirror toric pencils
    Virtual
    • Adriana Salerno, Bates College
  • 1:00 - 2:00 pm EST
    Lunch/Free Time
    Virtual
  • 2:00 - 3:00 pm EST
    Gathertown Closing Reception
    Reception - Virtual
Monday, February 22, 2021
Combinatorial Algebraic Geometry
  • 11:00 am - 12:00 pm EST
    Grad Student/ PostDoc Professional Development: Ethics 1
    Professional Development - Virtual
Wednesday, February 24, 2021
  • 3:30 - 4:30 pm EST
    Log-Concavity of Littlewood-Richardson Coefficients
    Virtual
    • Avery St. Dizier, Univeristy of Illinois at Urbana-Champaign
    Abstract
    We describe a log-concavity property of the Littlewood--Richardson numbers and explain its connection to the theory of Lorentzian polynomials.
Thursday, February 25, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 11:00 am EST
    Learning Seminar - Differential forms on tropical moduli spaces
    Seminar - Virtual
    • Melody Chan, Brown University
    • Sam Payne, University of Texas at Austin
    Abstract
    The goal is to understand Francis Brown's recent arXiv preprint Invariant differential forms on complexes of graphs and Feynman integrals. A sub-goal, which we hope takes shape over the course of the seminar, is to draw out the connection between Brown's article and tropical moduli spaces of curves and abelian varieties.

    This is not an introductory seminar per se in that the choice of topic is of specialized interest and of particular interest to us vis-a-vis our current work. On the other hand, we will try to develop the machinery without relying on background from tropical geometry, much as Brown's article is able to do.

    Resources to get started:

    1. Sam's lectures from the introductory Workshop, available from the webpage

    2. Draft of a survey articleon classical/tropical moduli spaces by Melody, which outlines the appearance of graph complexes in the study of tropical moduli.
  • 11:00 am - 12:00 pm EST
    Semistable Reduction Seminar
    Seminar - Virtual
    • Dan Abramovich, Brown University
Friday, February 26, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 10:30 am EST
    Graduate Student/ PostDoc pre-seminar break in Gather
    Coffee Break - Virtual
  • 10:30 - 11:30 am EST
    CM-regularity
    Post Doc/Graduate Student Seminar - Virtual
    • Matthew Larson, Stanford University
    • Mahrud Sayrafi, University of Minnesota
    Abstract
    The geometry of Castelnuovo-Mumford regularity - Matt Larson, Stanford University

    Castelnuovo-Mumford regularity is a tool for proving effective versions of Serre vanishing. I will explain why this is frequently necessary throughout algebraic geometry. I will also define Castelnuovo-Mumford regularity, state its basic properties, and explain its relationship to syzygies of graded module.

    Computing the Multigraded Castelnuovo-Mumford Regularity - Mahrud Sayrafi, University of Minnesota

    Motivated by toric geometry, Maclagan-Smith defined the multigraded Castelnuovo- Mumford regularity. While this definition reduces to the usual regularity for saturated modules in P^n, some properties of the classical regularity are not yet proven to be true in the multigraded case, while others hold true with subtle differences that illuminate the differences in geometry. In this talk I will focus on the case of a product of projective spaces and describe an algorithm for computing the multigraded regularity for saturated modules implemented in Macaulay2.
  • 11:30 am - 12:00 pm EST
    Graduate Student/ PostDoc post-seminar break in Gather
    Coffee Break - Virtual
Monday, March 1, 2021
Combinatorial Algebraic Geometry
  • 11:00 am - 12:00 pm EST
    Professional Development: Ethics II
    Professional Development - Virtual
Wednesday, March 3, 2021
Combinatorial Algebraic Geometry
  • 3:00 - 3:30 pm EST
    Gathertown Afternoon Coffee
    Coffee Break - Virtual
  • 4:00 - 5:00 pm EST
    Quantum integrability and Grassmannians
    Virtual
    • Paul Zinn-Justin, The University of Melbourne
    Abstract
    We will investigate in the simplest setting, how an``R-matrix'' (the building block of ``quantum integrable systems'') is attached to the equivariant cohomology of Grassmannians. We will compute the R-matrix in the case of CP^1 and discuss how the result generalizes to arbitrary Grassmannians. As an application, we shall derive the AJSBilley formula (restriction of Schubert classes to fixed points).
Thursday, March 4, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 11:00 am EST
    Learning Seminar - Differential forms on tropical moduli spaces
    Seminar - Virtual
    • Melody Chan, Brown University
    • Sam Payne, University of Texas at Austin
    Abstract
    The goal is to understand Francis Brown's recent arXiv preprint Invariant differential forms on complexes of graphs and Feynman integrals. A sub-goal, which we hope takes shape over the course of the seminar, is to draw out the connection between Brown's article and tropical moduli spaces of curves and abelian varieties.

    This is not an introductory seminar per se in that the choice of topic is of specialized interest and of particular interest to us vis-a-vis our current work. On the other hand, we will try to develop the machinery without relying on background from tropical geometry, much as Brown's article is able to do.

    Resources to get started:

    1. Sam's lectures from the introductory Workshop, available from the webpage

    2. Draft of a survey articleon classical/tropical moduli spaces by Melody, which outlines the appearance of graph complexes in the study of tropical moduli.
  • 11:00 am - 12:00 pm EST
    Semistable Reduction Seminar
    Seminar - Virtual
    • Dan Abramovich, Brown University
Friday, March 5, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 10:30 am EST
    Graduate Student/ PostDoc pre-seminar break in Gather
    Coffee Break - Virtual
  • 10:30 - 11:30 am EST
    Tropical Geometry
    Post Doc/Graduate Student Seminar - Virtual
    • Claudia Yun, Brown University
    Abstract
    The $S_n$-equivariant rational homology of the tropical moduli spaces $\Delta_{2,n}$ Abstract: Fix non-negative integers $g$ and $n$ such that $2g-2+n>0$, the tropical moduli space $\Delta_{g,n}$ is a topological space that parametrizes isomorphism classes of $n$-marked stable tropical curves of genus $g$ with total edge length 1. These spaces are important because their reduced rational homology is identified equivariantly with the top weight cohomology of the algebraic moduli spaces $M_{g,n}$, with respect to the $S_n$-action of permuting marked points. In this talk, we focus on the genus 2 case and compute the characters of $\tilde{H}_i(\Delta_{2,n};\Q)$ as $S_n$-representations for $n$ up to 8. To carry out the computations, we use a cellular chain complex for symmetric $\Delta$-complexes, a technique developed by Chan, Glatius, and Payne. The computation is done in SageMath.
  • 11:30 am - 12:00 pm EST
    Graduate Student/ PostDoc post-seminar break in Gather
    Coffee Break - Virtual
Wednesday, March 10, 2021
Combinatorial Algebraic Geometry
  • 3:00 - 3:30 pm EST
    Gathertown Afternoon Coffee
    Coffee Break - Virtual
  • 3:30 - 4:30 pm EST
    Springer fibers and the Delta Conjecture
    Virtual
    • Sean Griffin, Brown University
    Abstract
    Springer fibers are a family of varieties that have remarkable connections to representation theory and combinatorics. Springer constructed an action of the symmetric group on the cohomology ring of a Springer fiber, and used it to geometrically construct the Specht modules (in type A), which are the irreducible representations of the symmetric group. In this talk, I will survey some of the many nice properties of Springer fibers. I will then introduce a new family of varieties generalizing the Springer fibers, and show how they are connected to the (recently proved) Delta Conjecture from algebraic combinatorics. We’ll then use these varieties to geometrically construct the induced Specht modules. This is joint work with Jake Levinson and Alexander Woo.
Thursday, March 11, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 11:00 am EST
    Learning Seminar - Differential forms on tropical moduli spaces
    Seminar - Virtual
    • Melody Chan, Brown University
    • Sam Payne, University of Texas at Austin
    Abstract
    The goal is to understand Francis Brown's recent arXiv preprint Invariant differential forms on complexes of graphs and Feynman integrals. A sub-goal, which we hope takes shape over the course of the seminar, is to draw out the connection between Brown's article and tropical moduli spaces of curves and abelian varieties.

    This is not an introductory seminar per se in that the choice of topic is of specialized interest and of particular interest to us vis-a-vis our current work. On the other hand, we will try to develop the machinery without relying on background from tropical geometry, much as Brown's article is able to do.

    Resources to get started:

    1. Sam's lectures from the introductory Workshop, available from the webpage

    2. Draft of a survey articleon classical/tropical moduli spaces by Melody, which outlines the appearance of graph complexes in the study of tropical moduli.
  • 11:00 am - 12:00 pm EST
    Semistable Reduction Seminar
    Seminar - Virtual
    • Dan Abramovich, Brown University
Friday, March 12, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 10:30 am EST
    Graduate Student/ PostDoc pre-seminar break in Gather
    Coffee Break - Virtual
  • 10:30 - 11:30 am EST
    Matroids
    Post Doc/Graduate Student Seminar - Virtual
    • Ahmed Umer Ashraf, University of Western Ontario
    • Alex McDonough, Brown University
    Abstract
    Arithmetic Matroids Alex McDonough Alex will introduce matroids and show the relationship between orientable arithmetic matroids and the row lattice of integer matrices. Ahmed will give an understanding of some coefficients of the Tutte polynomial of a matroid as tropical intersection numbers. Tropical Intersection Numbers Ahmed Umer Ashraf
  • 11:30 am - 12:00 pm EST
    Graduate Student/ PostDoc post-seminar break in Gather
    Coffee Break - Virtual
Monday, March 15, 2021
Combinatorial Algebraic Geometry
  • 11:00 am - 12:00 pm EDT
    Professional Development: Job Applications
    Professional Development - Virtual
Wednesday, March 17, 2021
Combinatorial Algebraic Geometry
  • 3:00 - 3:30 pm EDT
    Gathertown Afternoon Coffee
    Coffee Break - Virtual
  • 3:30 - 4:30 pm EDT
    Schubert Products for Permutations with Separated Descents
    Virtual
    • Daoji Huang, Brown University
    Abstract
    We say that two permutations w and v have separated descents at position k if w has no descents before k and v has no descents after k. We give a counting formula in terms of reduced word tableaux for computing the structure constants of products of Schubert polynomials indexed by permutations with separated descents. This generalizes previous results by Kogan '00, rediscovered using different methods by Knutson-Yong '04, Lenart '10, and Assaf '17, that solved special cases of this separated descent problem where one of the permutations is required to have a single descent. Our approach uses generalizations of Schutzenberger's jeu de taquin and the Edelman-Greene correspondence via bumpless pipe dreams.
Thursday, March 18, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 11:00 am EDT
    Learning Seminar - Differential forms on tropical moduli spaces
    Seminar - Virtual
    • Melody Chan, Brown University
    • Sam Payne, University of Texas at Austin
    Abstract
    The goal is to understand Francis Brown's recent arXiv preprint Invariant differential forms on complexes of graphs and Feynman integrals. A sub-goal, which we hope takes shape over the course of the seminar, is to draw out the connection between Brown's article and tropical moduli spaces of curves and abelian varieties.

    This is not an introductory seminar per se in that the choice of topic is of specialized interest and of particular interest to us vis-a-vis our current work. On the other hand, we will try to develop the machinery without relying on background from tropical geometry, much as Brown's article is able to do.

    Resources to get started:

    1. Sam's lectures from the introductory Workshop, available from the webpage

    2. Draft of a survey articleon classical/tropical moduli spaces by Melody, which outlines the appearance of graph complexes in the study of tropical moduli.
  • 11:00 am - 12:00 pm EDT
    Semistable Reduction Seminar
    Seminar - Virtual
    • Dan Abramovich, Brown University
Friday, March 19, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 10:30 am EDT
    Graduate Student/postdoc pre-seminar break in Gather
    Coffee Break - Virtual
  • 10:30 - 11:30 am EDT
    Matroids and Algebra
    Post Doc/Graduate Student Seminar - Virtual
    • Lukas Kühne, Max Planck Institute for Mathematics in the Sciences
    Abstract
    A matroid is a combinatorial object based on an abstraction of linear independence in vector spaces and forests in graphs. I will discuss how matroid theory interacts with algebra via the so-called von Staudt constructions. These are combinatorial gadgets to encode polynomials in matroids. A main application is concerned with generalized matroid representations over division rings and matrix rings and their relation to group theory.
  • 11:30 am - 12:00 pm EDT
    Graduate Student/postdoc post-seminar break in Gather
    Coffee Break - Virtual
Monday, March 22, 2021
  • 10:00 - 10:15 am EDT
    Welcome
    Virtual
    • Brendan Hassett, ICERM/Brown University
  • 10:15 - 10:45 am EDT
    Hey Series, Tell Me About the Extended Delta Conjecture
    Virtual
    • Speaker
    • Jennifer Morse, University of Virginia
    • Session Chair
    • Leonardo Mihalcea, Virginia Polytechnic Institute and State University
    Abstract
    The space of diagonal harmonics $DH_n$ is an $S_n$-module in two sets of $n$ variables, which arose from a representation theoretic program to study Macdonald polynomials initiated by Garsia and Haiman. The doubly graded character of $DH_n$ has both a symmetric function and a combinatorial description: Haiman proved it is $\Delta'_{e_{n-1}}e_n$ for an eigenoperator $\Delta'$ of modified Macdonald polynomials, while Carlsson and Mellit established the combinatorial ``Shuffle Conjecture"" of Haiman, Haglund, Loehr, Remmel, and Ulyanov, expressing it as as a sum of LLT polynomials over Dyck paths. An expanded investigation led Haglund, Remmel and Wilson to the Extended Delta Conjecture, a combinatorial prediction for $\Delta_{h_l}\Delta'_{e_k}e_n$, allowing for any $0\leq l,k<n$. Bringing in new results about the action of the elliptic Hall algebra on symmetric functions, we reformulate the conjecture as the polynomial truncation of an identity of infinite series of $GL_l$ characters, expressed in terms of LLT series. The stronger infinite series identity is not difficult to prove using identities on non-symmetric Hall-Littlewood polynomials. This is joint work with Blasiak, Haiman, Pun, and Seelinger.
  • 11:00 - 11:15 am EDT
    Break
    Coffee Break - Virtual
  • 11:15 - 11:45 am EDT
    Castelnuovo-Mumford regularity of matrix Schubert varieties
    Virtual
    • Speaker
    • Oliver Pechenik, University of Waterloo
    • Session Chair
    • Leonardo Mihalcea, Virginia Polytechnic Institute and State University
    Abstract
    Jenna Rajchgot observed that the Castelnuovo-Mumford regularity of matrix Schubert varieties is computed by the degrees of the corresponding Grothendieck polynomials. We give a formula for these degrees. Indeed, we compute the leading terms of the top degree pieces of Grothendieck polynomials and give a complete description of when two Grothendieck polynomials have the same top degree piece (up to scalars). Our formulas rely on some new facts about major index of permutations.
  • 11:45 am - 2:00 pm EDT
    Lunch/Free Time
    Virtual
  • 2:00 - 2:30 pm EDT
    Conformal blocks: an overview
    Virtual
    • Speaker
    • Chiara Damiolini, Rutgers University
    • Session Chair
    • June Huh, Stanford University
    Abstract
    In this talk I will introduce simple examples of sheaves of conformal blocks arising from representations of Lie algebras and discuss how they can be used to study certain moduli spaces. I will further discuss generalizations of these sheaves which go beyond the representation theory of Lie algebras, and related works in progress.
  • 2:45 - 3:15 pm EDT
    Quantum geometric Satake at a root of unity and Schubert calculus for G(m,m,n)
    Virtual
    • Speaker
    • Ben Elias, University of Oregon
    • Session Chair
    • June Huh, Stanford University
    Abstract
    There is a q-deformation of the reflection representation of the affine Weyl group in type A which leads to a q-deformation of many common constructions: Demazure operators, Soergel bimodules, geometric Satake, etcetera. When q is set to a root of unity, the action of the affine Weyl group factors through a finite quotient, the complex reflection group G(m,m,n), and a new kind of "Schubert calculus" appears. This talk will demonstrate this unusual construction in the well-understood case of affine A_1 and the mysterious case of affine A_2.
  • 3:15 - 4:30 pm EDT
    Gathertown Reception
    Reception - Virtual
Tuesday, March 23, 2021
  • 9:00 - 9:45 am EDT
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 9:45 - 10:15 am EDT
    Geometry of semi-infinite flag manifolds
    Virtual
    • Speaker
    • Syu Kato, Kyoto University
    • Session Chair
    • Thomas Lam, University of Michigan
    Abstract
    Semi-infinite flag manifolds are variants of affine flag manifolds whose Schubert cells are simultaneously infinite-dimensional and infinite-codimensional. Such objects are introduced by Drinfeld and Lusztig around 1980 (as sets), and its finite-dimensional approximation model was presented by Finkelberg-Mirkovic in 1999. Recently, we described them as an explicit ind-scheme of ind-infinite type that satisfies a certain universal property. It lead us to a description of quantum $K$-groups of partial flag manifolds and some functorial relations between them. In this talk, I will start from a brief review of affine flag manifolds/varieties, define semi-infinite flag manifolds and their natural subschemes, and then explain their combinatorial and algebro-geometric properties (trying to stress the difference from affine flag manifolds/varieties). If time allows, then I will explain how some of these properties are derived as a shadow of the homological properties of affine Lie algebras. This talks is mainly based on arXiv:1810.07106.
  • 10:30 - 10:45 am EDT
    Break
    Coffee Break - Virtual
  • 10:45 - 11:35 am EDT
    Lightning Talks
    Virtual
    • Speakers
    • Aram Bingham, Tulane University
    • Papri Dey, University of Missouri
    • Yifeng Huang, University of Michigan
    • Michael Perlman, Queen's University
    • Semin Yoo, University of Rochester
    • Session Chair
    • David Anderson, Ohio State University
    Abstract
    Combinatorics of quadratic spaces over finite fields
    Semin Yoo, University of Rochester
    Let $\mathbb{F}_q^n$ be the finite field with $q$ elements, where the char$F$ is not $2$. The size of the set of $k$-dimensional subspaces of $\mathbb{F}_q^n$ is called $q$-binomial coefficient, (or Gaussian binomial coefficient.) which has various interesting combinatorial descriptions and related works. Furthermore, the fact that makes $q$-binomial coefficients more interesting is that $q$-binomial coefficients have $q$-analogues. $\mathbf{q}$-\textbf{analogues} of quantities in mathematics involve perturbations of classical quantities using the parameter $q$ and revert to the original quantities when $q$ goes to $1$. In this talk, we add one more structure, called a quadratic form. We are mainly interested in the size of the set of $k$-dimensional subspaces that have orthonormal bases, which can be also written as analogues of binomial coefficients. Various combinatorial properties of this new binomial coefficient will be discussed. We will also show what will happen in the set side if we take the limit when $q$ goes to $1$.

    Mixed Hodge structure on local cohomology with support in determinantal varieties
    Michael Perlman, Queen's University
    Given a closed subvariety Z in a smooth variety, the local cohomology sheaves with support in Z are functorially endowed with structures as mixed Hodge modules. This implies that they are equipped with two increasing filtrations: the Hodge filtration and the weight filtration. We will discuss new calculations of these filtrations in the case when Z is a generic determinantal variety. This talk includes joint work with Claudiu Raicu.

    Geometric and Combinatorial aspects of Nonlinear Algebra
    Papri Dey, University of Missouri-Columbia
    Nonlinear algebra is an interdisciplinary area and I shall talk about some interaction among algebraic, geometric and combinatorial objects in this field.

    Clans, sects, and symmetric space closure orders
    Aram Bingham, Tulane University of Louisiana
    We will give a combinatorial description of the closure order on Borel orbits in symmetric spaces of Hermitian type in terms of parameterizing objects called clans and their projections onto $G/P$ (sects). This description resolves part of a conjecture of Wyser on the restriction of Bruhat orders on these spaces.

    A generating function for counting mutually annihilating matrices over a finite field
    Yifeng Huang, University of Michigan
    We count the number of pairs of n x n matrices (A, B) over a finite field such that AB=BA=0. We then give an explicit factorization of a generating function associated to this count, which in particular shows that the function can be meromorphically extended to the entire complex plane. This essentially says that the motivic formula about (the stack of) finite-length coherent sheaves on a nodal singular curve behaves as the geometry predicts.
  • 11:35 am - 2:00 pm EDT
    Gathertown with Lightning speakers / Lunch
    Lunch/Free Time - Virtual
  • 2:00 - 2:30 pm EDT
    Gröbner Geometry of Schubert Polynomials Through Ice
    Virtual
    • Speaker
    • Anna Weigandt, University of Michigan
    • Session Chair
    • Angela Gibney, Rutgers University, New Brunswick
    Abstract
    The geometric naturality of Schubert polynomials and the related combinatorics of pipe dreams was established by Knutson and Miller (2005) via antidiagonal Gröbner degeneration of matrix Schubert varieties. We consider instead diagonal Gröbner degenerations. In this dual setting, Knutson, Miller, and Yong (2009) obtained alternative combinatorics for the class of vexillary matrix Schubert varieties. We will discuss general diagonal degenerations, relating them to an older formula of Lascoux (2002) in terms of the 6-vertex ice model. Lascoux's formula was recently rediscovered by Lam, Lee, and Shimozono (2018), as "bumpless pipe dreams." We will explain this connection and discuss conjectures and progress towards understanding diagonal Gröbner degenerations of matrix Schubert varieties.
  • 2:45 - 3:00 pm EDT
    Break
    Coffee Break - Virtual
  • 3:00 - 3:30 pm EDT
    Rigid local systems and the multiplicative eigenvalue problem
    Virtual
    • Speaker
    • Prakash Belkale, University of North Carolina at Chapel Hill
    • Session Chair
    • Angela Gibney, Rutgers University, New Brunswick
    Abstract
    Local systems are sheaves which describe the behavior of solutions of differential equations. A local system is rigid if local monodromy determines global monodromy. We give a construction which produces irreducible complex rigid local systems on a punctured Riemann sphere via quantum Schubert calculus and strange duality. These local systems are unitary and arise from a study of vertices in the polytopes controlling the multiplicative eigenvalue problem for the special unitary groups SU(n) (i.e., determination of the possible eigenvalues of a product of unitary matrices given the eigenvalues of the matrices). Roughly speaking, we show that the strange duals of the simplest vertices (which can be inductively determined) of these polytopes give (all) possible unitary irreducible rigid local systems. We note that these polytopes are generalizations of the classical Littlewood-Richardson cones of algebraic combinatorics. Answering a question of Nick Katz, we show that there are no irreducible rigid local systems on a punctured Riemann sphere of rank greater than one, with finite global monodromy, all of whose local monodromies have orders dividing n, when n is a prime number.
  • 3:45 - 4:15 pm EDT
    Cyclotomic generating functions
    Virtual
    • Speaker
    • Joshua Swanson, University of California, San Diego
    • Session Chair
    • Angela Gibney, Rutgers University, New Brunswick
    Abstract
    Generating functions are a major theme in mathematics which unify many disciplines. It is remarkably common to find a combinatorial generating function which factors as a ratio of products of $q$-integers. Examples of such quotients arise from enumerative combinatorics (e.g. subset sums and $q$-binomials), representation theory (the $q$-Weyl dimension formula), geometry (iterated $\mathbb{P}^1$-bundles), probability (random variable decompositions), commutative algebra (homogeneous systems of parameters), and more. We call such quotients "cyclotomic generating functions" (CGFs) and initiate their general study. This talk will review some of the many known constructions of CGFs and give asymptotic estimates of their coefficients. We will also highlight a range of conjectures and accessible open problems. Joint work in progress with Sara Billey.
Wednesday, March 24, 2021
  • 9:00 - 9:45 am EDT
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 9:45 - 10:15 am EDT
    Doing Schubert Calculus with Bumpless Pipe Dreams
    Virtual
    • Speaker
    • Daoji Huang, Brown University
    • Session Chair
    • Laura Escobar, Washington University- St. Louis
    Abstract
    Bumpless pipe dreams were introduced by Lam, Lee, and Shimozono in the context of back stable Schubert calculus. Like ordinary pipe dreams, they compute Schubert and double Schubert polynomials. In this talk, I will give a bijective proof of Monk's rule for Schubert polynomials, and show that the proof extends easily to the proof of Monk's rule for double Schubert polynomials. As an application, I will explain how to biject bumpless pipe dreams and ordinary pipe dreams using the transition and co-transition formulas, which are specializations of Monk's rule. If time permits I will also briefly discuss some work on how bumpless pipe dreams can be used to compute products of certain Schubert polynomials that generalize the Grassmannian case.
  • 10:30 - 10:45 am EDT
    Break
    Coffee Break - Virtual
  • 10:45 - 11:35 am EDT
    Lightning Talks
    Virtual
    • Speakers
    • anastasia chavez, University of California, Davis
    • Theo Douvropoulos, University of Massachusetts, Amherst
    • Brian Hwang, Cornell University
    • Maiko Serizawa, University of Ottawa
    • Weihong Xu, Rutgers
    • Session Chair
    • Leonardo Mihalcea, Virginia Polytechnic Institute and State University
    Abstract
    Volumes of Root Zonotopes via the W-Laplacian
    Theo Douvropoulos, University of Massachusetts, Amherst
    The normalized volume of the classical permutahedron is given by the formula n^{n-2} which, ask any combinatorialist and they will tell you, agrees with the number of trees on n vertices. This coincidence is well understood; the classical permutahedron is a unimodular zonotope, on the set of positive roots of the Symmetric group S_n, and its bases are indexed by trees and hence enumerated by the determinant of a Laplacian matrix. This description of the permutahedron lends itself to a natural generalization: for a Weyl group W, the zonotope associated to the collection of positive roots of W will be called the root zonotope Z_W. These zonotopes Z_W are not unimodular, but their bases can be differentiated with respect to the reflection subgroup they generate (and its connection index). In joint work with Guillaume Chapuy (arxiv.2012.04519) we have introduced for any Weyl group W a (nxn) Laplacian matrix L_W whose spectrum encodes (nontrivially) many enumerative properties of W. In particular we will present new short formulas (ibid: Section 8.3) for the volumes of the root zonotopes Z_W involving only the Coxeter numbers of W and its reflection subgroups. Our approach is uniform and does not rely on the classification.

    Effective point-counting for polygons in flag varieties
    Brian Hwang, Cornell University
    There are a number of seemingly similar "big" (e.g. affine, open) spaces that arise in the context of flag varieties. Certain classes of these spaces are known to exhibit special features. For example, open Richardson varieties have a decomposition into a disjoint union of simple components and the coordinate rings of double Bruhat cells are known to be cluster algebras. There are often combinatorial objects that govern their geometry, such as subword complexes for brick manifolds or various kinds of polytopes, especially in the context of toric varieties and related deformations and degenerations. The bestiary is rich and multifarious. Many of these spaces, however, turn out to admit a description as a polygon in a flag variety, that is, a (cyclic) tuple of flags where each flag is a prescribed distance from its immediate neighbors. Here, the distance is taken not with respect to the Euclidean metric, but with a non-symmetric Weyl-group-valued notion of "distance." Such polygons in flag varieties turn out to admit simple decompositions that can be phrased in terms of triangulations of the polygon into certain triangles with an "easy-exit" property. As an illustration of this organizing principle, we show how we can use this to easily count the points of open Richardson varieties over finite fields–––recovering a classic result of Deodhar, as well as its later enhancement by Marsh and Rietsch–––and how this naturally extends to spaces like double Bruhat cells and their amalgamations.

    A 'Quantum Equals Classical' Theorem for n-pointed (K-theoretic) Gromov-Witten Invariants of Lines in Homogeneous Spaces
    Weihong Xu, Rutgers University
    'Quantum equals classical' refers to ways of identifying (K-theoretic) Gromov-Witten invariants on a flag variety G/P with (K-theoretic) classical invariants on a possibly different flag variety G/Q. It has been an active research topic in the last 20 years, but by far all the work has been for 3-pointed invariants. We obtain a 'quantum equals classical' theorem for n-pointed, genus 0 (T-equivariant K-theoretic) Gromov-Witten invariants of lines in G/P, which generalizes the 3-pointed result of Leonardo Mihalcea and Changzheng Li from 2013. This talk is based on joint work with Anders Buch, Linda Chen, Angela Gibney, Lauren Heller, Elana Kalashnikov, and Hannah Larson.

    Matroids, Positroids, and Combinatorial Characterizations
    Anastasia Chavez, UC Davis
    Positroids are a special class of representable matroids introduced by Postnikov in the study of the nonnegative part of the Grassmannian. Postnikov defined several combinatorial objects that index positroids. In this talk, I'll briefly introduce some of these objects and how they can combinatorially characterize matroid properties.

    Twisted quadratic foldings of root systems and combinatorial Schubert calculus
    Maiko Serizawa, University of Ottawa
    This thesis builds on the connection of two widely studied objects in the literature, that is, foldings of finite root systems and the structure algebras of moment graphs associated with finite root systems. Given a finite crystallographic root system <I> whose Dynkin diagram has a non­trivial automorphism, it yields a new root system <l>7 by a so-called classical folding. On the other hand, Lusztig's folding (1983) folds the root system of type Es to type H4 starting from an automorphism of the root lattice of type Es. Lanini-Zainoulline (2018) developed the notion of a twisted quadratic folding of a root system, which describes both the classical foldings and Lusztig's folding on the same footing. Our second key object of study is the structure algebra Z(Q) of the moment graph g associated with a finite root system and its reflection group W. The structure algebra Z(Q) is an algebra over a certain polynomial ring S whose underlying module is free with a distinguished basis { a( w) I w E W} called combinatorial Schubert classes. Each Schubert class a(w) is an S-valued function on W, whose value is explicitly known for any finite reflection group W. Lanini-Zainoulline (2018) showed that a twisted quadratic folding <I> -v--; <l>7 in­duces an embedding of the respective Coxeter groups E : W7 Y W and a ring homomorphism c:* : Z(Q) ➔ Z(Q7 ) between the corresponding structure algebras. This thesis investigates how the induced map c:* relates the Schubert classes of the original structure algebra Z(Q) to those of the folded structure algebra Z(Q7 ). In particular, we will provide a combinatorial criterion for a Schubert class a?u) of Z(Q7 ) to admit a Schubert class a(w) of Z(Q) such that the relation c:*(a(w) ) = c · a?u) holds for some nonzero scalar c. We will also prove that c:* is surjective after an appropriate extension of the coefficient ring.
  • 11:35 am - 2:00 pm EDT
    Gathertown with Lightning speakers / Lunch
    Lunch/Free Time - Virtual
  • 2:00 - 2:30 pm EDT
    Differential operators for Schur and Schubert polynomials
    Virtual
    • Speaker
    • Gleb Nenashev, Brown University
    • Session Chair
    • Alexander Yong, University of Illinois at Urbana-Champaign
    Abstract
    We study differential operators for Schur and back stable Schubert polynomials. Our operators are based on two operators of degree (-1), which satisfy Leibniz rule. For the case of Schur functions, these two operators fully determine the product of Schur functions, i.e., it is possible to define Littlewood-Richardson coefficients only using these operators. This new point of view on Schur functions gives us an elementary proof of The Giambelli identity and Jacobi-Trudi identities. For the case of Schubert polynomials, we construct a larger class of decreasing operators, which are indexed by Young diagrams. Operators from this family are related to Stanley symmetric functions. In particular, we extend bosonic operators from Schur to Schubert polynomials.
  • 2:45 - 3:00 pm EDT
    Break
    Coffee Break - Virtual
  • 3:00 - 3:30 pm EDT
    Backstable K-theory Schubert calculus
    Virtual
    • Speaker
    • Mark Shimozono, Virginia Tech
    • Session Chair
    • Alexander Yong, University of Illinois at Urbana-Champaign
    Abstract
    We explain some properties of back-stable limits of double Grothendieck polynomials. We discuss the dual basis of equivariant K-homology of the infinite Grassmannian.
  • 3:45 - 4:15 pm EDT
    Bow varieties
    Virtual
    • Speaker
    • Richard Rimanyi, University of North Carolina at Chapel Hill
    • Session Chair
    • Alexander Yong, University of Illinois at Urbana-Champaign
    Abstract
    There are pairs of seemingly unrelated spaces such that Schubert calculus on the two spaces `match’ in some concrete sense. This duality, called 3d mirror symmetry, is best observed in equivariant elliptic cohomology. For example, the dual of the 12-dimensional $T^*Gr(2,5)$ is a certain 4-dimensional Nakajima quiver variety. However, the set of cotangent bundles of homogeneous spaces, or even the set of quiver varieties are not closed for 3d mirror symmetry. In this talk, based on a joint work with Y. Shou, we present a larger pool of spaces: Cherkis bow varieties. Superstring theory predicts that bow varieties are closed for 3d mirror symmetry. The combinatorics necessary to play Schubert calculus on bow varieties includes binary contingency tables and tie diagrams. The existence of an operation (called Hanany-Witten transition) gives bow varieties extra flexibility. We will illustrate the combinatorics and geometry of bow varieties with examples, and we will calculate cohomological and elliptic Schubert classes (rather, `stable envelopes’) to explain the `matching Schubert calculus’ phenomenon.
Thursday, March 25, 2021
  • 9:00 - 9:45 am EDT
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 9:45 - 10:15 am EDT
    Refined Dubrovin's conjecture for coadjoint varieties
    Virtual
    • Speaker
    • Nicolas Perrin, Versailles Saint-Quentin-en-Yvelines University
    • Session Chair
    • Anders Buch, Rutgers University
    Abstract
    Let X be a Fano variety. Dubrovin’s conjecture predicts, among other things, an equivalence between the semi-simplicity of QH(X) the big quantum cohomology of X and the existence of a full exceptional collection in D(X) the bounded derived category of X. Recently, Kuznetsov and Smirnov proposed a refinement of this conjecture if qH(X) the small quantum cohomology is not semi-simple. I will present this conjecture, discuss it in the case of coadjoint varieties and make connections with roots systems and simple surface singularities. This is a joint work with Maxim Smirnov
  • 10:30 - 10:45 am EDT
    Break
    Coffee Break - Virtual
  • 10:45 - 11:15 am EDT
    motivic Chern classes of Schubert cells and applications
    Virtual
    • Speaker
    • Changjian Su, University of Toronto
    • Session Chair
    • Anders Buch, Rutgers University
    Abstract
    The motivic Chern class in K-theory is a generalization of the Chern-Schwartz-MacPherson class in homology. As the affine Hecke algebra, the motivic Chern classes of Schubert cells have a Langlands dual description. In joint works with P. Aluffi, L. Mihalcea, and J. Schurmann, we use this description to solve some problems about the Casselman basis for the p-adic dual group, and relate the Euler characteristic of the motivic Chern classes to the Iwahori-Whittaker functions. 
  • 11:30 am - 1:30 pm EDT
    Lunch/Free Time
    Virtual
  • 2:00 - 2:30 pm EDT
    Skew-symmetric matrix Schubert varieties
    Virtual
    • Speaker
    • Brendan Pawlowski, University of Southern California
    • Session Chair
    • Thomas Lam, University of Michigan
    Abstract
    Imposing conditions on the ranks of upper-left corners of a skew-symmetric matrix defines a skew-symmetric matrix Schubert variety. We give Gröbner bases for the prime ideals of these varieties, and identify the corresponding initial ideals as the Stanley-Reisner ideals of certain explicit shellable simplicial complexes. These results are analogous to results of Knutson and Miller in the setting of ordinary matrix Schubert varieties, but the techniques are new, and can be used to give new proofs of some of their results. Based on joint work with Eric Marberg.
  • 2:45 - 3:00 pm EDT
    Break
    Coffee Break - Virtual
  • 3:00 - 3:30 pm EDT
    Canonical Bases for Coulomb Branches
    Virtual
    • Speaker
    • Harold Williams, University of Southern California
    • Session Chair
    • Thomas Lam, University of Michigan
    Abstract
    Coulomb branches of 4d N=2 gauge theories are a class of algebraic varieties which, together with their quantizations, appear in a variety of guises in geometry and representation theory. In this talk we outline a construction of canonical bases in the quantized coordinate rings of these varieties. These bases appear as byproducts of a more fundamental construction, a nonstandard t-structure on the dg category of coherent sheaves on the Braverman-Finkelberg-Nakajima space of triples. The heart of this t-structure is a tensor category which is not braided, but admits renormalized r-matrices abstracting those appearing in the finite dimensional representation theory of quantum affine algebras and KLR algebras. It is intended to provide a mathematical model of the category of half-BPS line defects in the relevant gauge theory, and is inspired by earlier work of Kapustin-Saulina and Gaiotto-Moore-Neitzke. On a combinatorial level, the resulting bases are expected to be controlled by specific cluster algebras, which we can confirm in simple examples. This is joint work with Sabin Cautis.
  • 3:45 - 4:00 pm EDT
    Break
    Coffee Break - Virtual
  • 4:00 - 4:30 pm EDT
    Schubert puzzles from Lagrangian correspondences
    Virtual
    • Speaker
    • Allen Knutson, Cornell University
    • Session Chair
    • Thomas Lam, University of Michigan
    Abstract
    Correspondences Z inside M x N induce maps on cohomology H^*(M) -> H^*(N), modulo smoothness and compactness issues. We soup up the diagonal inclusion Gr(k,n) -> Gr(k,n)^2 (whose induced cohomology map is multiplication) to a correspondence of cotangent bundles, which we then factor through T^*(a 2-step flag manifold). Grassmannian Schubert puzzles turn out to be a calculation on this intermediate manifold. As an application of this viewpoint we get a puzzle rule for the Euler characteristic of the intersection of three generically translated Bruhat cells (in up-to-4-step flag manifolds).
Friday, March 26, 2021
  • 9:00 - 9:45 am EDT
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 9:45 - 10:15 am EDT
    A combinatorial Chevalley formula for semi-infinite flag manifolds and its applications
    Virtual
    • Speaker
    • Cristian Lenart, University at Albany
    • Session Chair
    • David Anderson, Ohio State University
    Abstract
    I present a combinatorial Chevalley formula for an arbitrary weight, in the torus-equivariant K-group of semi-infinite flag manifolds, which is expressed in terms of the so-called quantum alcove model. One application is the Chevalley formula for anti-dominant fundamental weights in the (small) torus-equivariant quantum K-theory of the flag manifold G/B; this has been a longstanding conjecture. I also discuss the Chevalley formula for partial flag manifolds G/P. Another application is that the so-called quantum Grothendieck polynomials indeed represent Schubert classes in the (non-equivariant) quantum K-theory of the type A flag manifold. This is joint work with Satoshi Naito and Daisuke Sagaki.
  • 10:30 - 10:45 am EDT
    Break
    Coffee Break - Virtual
  • 10:45 - 11:15 am EDT
    Coxeter-like elements, Schubert geometry, and multiplicity-freeness in algebraic combinatorics
    Virtual
    • Speaker
    • Alexander Yong, University of Illinois at Urbana-Champaign
    • Session Chair
    • David Anderson, Ohio State University
    Abstract
    For a finite Coxeter system, we define “spherical elements” (extending Coxeter elements). Conjecturally, for Weyl groups, spherical elements index Levi-spherical Schubert varieties in G/B. In type A, this connects to key polynomials (Demazure characters), multiplicity-freeness, and “split-symmetry” in algebraic combinatorics. This is joint work (some ongoing) with subsets of David Brewster (UIUC), Yibo Gao (MIT), and Reuven Hodges (UIUC). See arXiv:2007.09238, arXiv:2007.09229, and arXiv:2012.09749.
  • 11:30 am - 2:00 pm EDT
    Lunch/Free Time
    Virtual
  • 2:00 - 2:30 pm EDT
    Positroids, knots, and q,t-Catalan numbers
    Virtual
    • Speaker
    • Pavel Galashin, University of California, Los Angeles
    • Session Chair
    • Angela Gibney, Rutgers University, New Brunswick
    Abstract
    We relate the cohomology of open positroid varieties and their point counts over finite fields to knot homology. In particular, we show that the bigraded Poincaré polynomials of top-dimensional open positroid varieties are given by rational q,t-Catalan numbers. As a consequence of the curious Lefschetz property, we obtain q,t-symmetry and unimodality statements for rational q,t-Catalan numbers. Joint work with Thomas Lam. No special background on the above objects will be assumed.
  • 2:45 - 3:00 pm EDT
    Break
    Coffee Break - Virtual
  • 3:00 - 3:30 pm EDT
    Puzzle rules in cotangent Schubert calculus
    Virtual
    • Speaker
    • Paul Zinn-Justin, The University of Melbourne
    • Session Chair
    • Angela Gibney, Rutgers University, New Brunswick
    Abstract
    We'll present several combinatorial rules (in terms of ``puzzles'') for the expansion of the product of motivic Segre classes (in equivariant K-theory) and Segre-Schwartz-MacPherson classes (in equivariant cohomology) in partial flag varieties. We'll show how to compute such classes and puzzles using the software Macaulay2.
Monday, March 29, 2021
Combinatorial Algebraic Geometry
  • 11:00 am - 12:00 pm EDT
    Professional Development: Hiring Process
    Professional Development - Virtual
Wednesday, March 31, 2021
Combinatorial Algebraic Geometry
  • 3:00 - 3:30 pm EDT
    Gathertown Afternoon Coffee
    Coffee Break - Virtual
  • 3:30 - 4:30 pm EDT
    The isomorphism problem for Schubert varieties.
    Virtual
    • Edward Richmond, Oklahoma State University
    Abstract
    Schubert varieties in the full flag variety of Kac-Moody type are indexed by elements of the corresponding Weyl group. In this talk, I will discuss recent work with William Slofstra where we give a practical criterion for when two such Schubert varieties (from potentially different flag varieties) are isomorphic, in terms of the Cartan matrix and reduced words for the indexing Weyl group elements. As a corollary, we show that two such Schubert varieties are isomorphic if and only if there is an isomorphism between their integral cohomology rings that preserves the Schubert basis. As an application, we show that the isomorphism classes of Schubert varieties in a given flag variety are controlled by graph automorphisms of the Dynkin diagram.
Thursday, April 1, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 11:00 am EDT
    Learning Seminar - Differential forms on tropical moduli spaces
    Seminar - Virtual
    • Melody Chan, Brown University
    • Sam Payne, University of Texas at Austin
    Abstract
    The goal is to understand Francis Brown's recent arXiv preprint Invariant differential forms on complexes of graphs and Feynman integrals. A sub-goal, which we hope takes shape over the course of the seminar, is to draw out the connection between Brown's article and tropical moduli spaces of curves and abelian varieties.

    This is not an introductory seminar per se in that the choice of topic is of specialized interest and of particular interest to us vis-a-vis our current work. On the other hand, we will try to develop the machinery without relying on background from tropical geometry, much as Brown's article is able to do.

    Resources to get started:

    1. Sam's lectures from the introductory Workshop, available from the webpage

    2. Draft of a survey articleon classical/tropical moduli spaces by Melody, which outlines the appearance of graph complexes in the study of tropical moduli.
  • 11:00 am - 12:00 pm EDT
    Semistable Reduction Seminar
    Seminar - Virtual
    • Dan Abramovich, Brown University
  • 3:30 - 4:40 pm EDT
    A trinity in affine Schubert calculus
    Virtual
    • Syu Kato, Kyoto University
    Abstract
    One of the most famous results in affine Schubert calculus is Peterson's quantum = affine theorem (proved by Lam-Shimozono based on a work of Mihalcea). It states that the homology of affine Grassmanian of a simple algebraic group $G$ is equivalent to the quantum cohomology of the flag manifold of $G$ as based rings. Such an equivalence has a $K$-theoretic counterpart conjectured by Lam-Li-Mihalcea-Shimozono. In this talk, we add the semi-infinite flag manifold of $G$ into this picture. In particular, the $K$-theoretic analogue of the both sides of the Peterson theorem are related to the equivariant $K$-group of the semi-infinite flag manifold. This establishes the above conjecture of Lam-Li-Mihalcea-Shimozono. Arguably, our picture provides the first explanation as to why Peterson's isomorphism should respect the basis. In addition, it has a wide range of implications including the finiteness of the quantum multiplication for the full flag manifold. This talk is based on arXiv:1805.01718. For the semi-infinite flag manifold and its equivariant $K$-group, please refer to the slide of my talk on March 23rd.
Friday, April 2, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 10:30 am EDT
    Graduate Student/Postdoc pre-seminar break in Gather
    Coffee Break - Virtual
  • 10:30 - 11:30 am EDT
    Cluster Algebras and Total Positivity
    Post Doc/Graduate Student Seminar - Virtual
    • Sunita Chepuri, University of Michigan
    Abstract
    We will first define cluster algebras and explain their historical motivation from total positivity. The research portion of the talk will move to the setting of k-positivity, a generalization of total positivity. We will explore how much of the cluster algebraic structure of totally positive matrices extends to k-positive matrices.
  • 11:30 am - 12:00 pm EDT
    Graduate Student/Postdoc post-seminar break in Gather
    Coffee Break - Virtual
Monday, April 5, 2021
Combinatorial Algebraic Geometry
  • 11:00 am - 12:00 pm EDT
    Directorate Check-In with Grads and Postdocs
    Meeting - Virtual
Wednesday, April 7, 2021
Combinatorial Algebraic Geometry
  • 3:00 - 3:30 pm EDT
    Gathertown Afternoon Coffee
    Coffee Break - Virtual
  • 2:00 - 3:00 pm EDT
    The unramified affine springer fiber and the nabla operator
    Virtual
    • Erik Carlsson, UC Davis
    Abstract
    I'll present a new result with A. Mellit, which gives a combinatorial formula for a diagonalizing operator for the modified Macdonald polynomials, known as the nabla operator. This formula was discovered by searching for a Schubert-type basis of a certain explicit module from Haiman's polygraph theory, which is identified with both the matrix elements of this operator, and the equivariant homology of the unramified affine Springer fiber studied by Goresky, Kottwitz, and Macpherson.
Thursday, April 8, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 11:00 am EDT
    Learning Seminar - Differential forms on tropical moduli spaces
    Seminar - Virtual
    • Melody Chan, Brown University
    • Sam Payne, University of Texas at Austin
    Abstract
    The goal is to understand Francis Brown's recent arXiv preprint Invariant differential forms on complexes of graphs and Feynman integrals. A sub-goal, which we hope takes shape over the course of the seminar, is to draw out the connection between Brown's article and tropical moduli spaces of curves and abelian varieties.

    This is not an introductory seminar per se in that the choice of topic is of specialized interest and of particular interest to us vis-a-vis our current work. On the other hand, we will try to develop the machinery without relying on background from tropical geometry, much as Brown's article is able to do.

    Resources to get started:

    1. Sam's lectures from the introductory Workshop, available from the webpage

    2. Draft of a survey articleon classical/tropical moduli spaces by Melody, which outlines the appearance of graph complexes in the study of tropical moduli.
  • 11:00 am - 12:00 pm EDT
    Semistable Reduction Seminar
    Seminar - Virtual
    • Dan Abramovich, Brown University
Friday, April 9, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 10:30 am EDT
    Graduate Student/Postdoc pre-seminar break in Gather
    Coffee Break - Virtual
  • 10:30 - 11:30 am EDT
    Schubert Calculus
    Post Doc/Graduate Student Seminar - Virtual
    • Gleb Nenashev, Brown University
    • Jianping Pan, University of California, Davis
    Abstract
    Decreasing operators for Schur functions.
    Gleb Nenashev
    I will discuss decreasing operators for Young diagrams. These operators give elementary proofs of some famous properties of Schur functions, e.g. for Murnaghan-Nakayama rule, Giambelli identity, and Jacobi-Trudi identities. They also fully determine Littlewood-Richardson coefficients. I will present some of these proofs. Furthermore, the decreasing operators are well defined for Back stable Schubert polynomials, but I will not discuss it.

    Crystal combinatorics with stable Grothendieck polynomials
    Jianping Pan
    Grothendieck polynomials are representatives of Schubert varieties in the K-theory of the flag manifold. Taking stable limit, we obtain symmetric functions called the stable Grothendieck polynomials. I will talk about a combinatorial construction of it, developed by Fomin and Kirillov, which turns out to have some nice crystal structure (directed, edge-labeled graphs from representation theory). There are also several properties associated with it, including some insertion algorithms. This talk is based on arXiv:1911.08732.
  • 11:30 am - 12:00 pm EDT
    Graduate Student/Postdoc post-seminar break in Gather
    Coffee Break - Virtual
Monday, April 12, 2021
  • 9:45 - 10:00 am EDT
    Welcome
    Virtual
    • Brendan Hassett, ICERM/Brown University
  • 10:00 - 10:45 am EDT
    The Foundation of a Matroid
    Virtual
    • Speaker
    • Matthew Baker, Georgia Institute of Technology
    • Session Chair
    • Lauren Williams, Harvard University
    Abstract
    Matroid theorists are typically interested in questions concerning representability of matroids over fields. More generally, one can ask about representability over partial fields in the sense of Semple and Whittle. Pendavingh and van Zwam introduced the universal partial field of a matroid, which governs the representations of over all partial fields. Unfortunately, almost all matroids are not representable over any partial field, and in this case, the universal partial field gives no information. Oliver Lorscheid and I have introduced a generalization of the universal partial field which we call the foundation of a matroid. The foundation of is a type of algebraic object which we call a pasture; pastures include both hyperfields and partial fields. As a particular application of this point of view, I will explain the classification which Lorscheid and I have recently obtained of all possible foundations for matroids having no minor isomorphic to U(2,5) or U(3,5). Among other things, our classification provides a short conceptual proof of the 1997 theorem of Lee and Scobee which says that a matroid is both ternary and orientable if and only if it is dyadic.
  • 11:00 - 11:15 am EDT
    Break
    Coffee Break
  • 11:15 am - 12:00 pm EDT
    Lagrangian geometry of matroids
    Virtual
    • Speaker
    • Graham Denham, University of Western Ontario
    • Session Chair
    • Lauren Williams, Harvard University
    Abstract
    In joint work with Federico Ardila and June Huh, we introduce the conormal fan of a matroid, which is the Lagrangian analogue of the Bergman fan. We use it to give a Lagrangian interpretation of the Chern-Schwartz-MacPherson cycle of a matroid. We develop tools for tropical Hodge theory to show that the conormal fan satisfies Poincaré duality, the Hard Lefschetz property, and the Hodge--Riemann relations. Together, these imply conjectures of Brylawski and Dawson about the log-concavity of the h-vectors of the broken circuit complex and independence complex of a matroid.
  • 12:00 - 1:30 pm EDT
    Lunch/Free Time
  • 1:30 - 2:15 pm EDT
    Tautological classes of matroids
    Virtual
    • Speaker
    • Christopher Eur, Stanford University
    • Session Chair
    • Sam Payne, University of Texas at Austin
    Abstract
    We introduce certain torus-equivariant classes on permutohedral varieties which we call ``tautological classes of matroids'' as a new geometric framework for studying matroids. Using this framework, we unify and extend many recent developments in matroid theory arising from its interaction with algebraic geometry. We achieve this by establishing a Chow-theoretic description and a log-concavity property for a 4-variable transformation of the Tutte polynomial, and by establishing an exceptional Hirzebruch-Riemann-Roch-type formula for permutohedral varieties that translates between K-theory and Chow theory. This is joint work with Andrew Berget, Hunter Spink, and Dennis Tseng.
  • 2:30 - 2:45 pm EDT
    Break
    Coffee Break
  • 2:45 - 3:30 pm EDT
    Kazhdan-Lusztig theory and singular Hodge theory for matroids
    Virtual
    • Speaker
    • June Huh, Stanford University
    • Session Chair
    • Sam Payne, University of Texas at Austin
    Abstract
    There is a remarkable parallel between the theory of Coxeter groups (think of the symmetric group or the dihedral group) and matroids (think of your favorite graph or point configuration) from the perspective of combinatorial cohomology theories. I will give an overview of the similarity and report on recent my joint work with Tom Braden, Jacob Matherne, Nick Proudfoot, and Botong Wang on singular Hodge theory for combinatorial geometries: https://arxiv.org/abs/2010.06088
  • 3:45 - 4:45 pm EDT
    Gathertown Reception
    Reception - Virtual
Tuesday, April 13, 2021
  • 9:00 - 9:45 am EDT
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 10:00 - 10:45 am EDT
    Real phase structures on matroid fans
    Virtual
    • Speaker
    • Kristin Shaw, University of Oslo
    • Session Chair
    • Melody Chan, Brown University
    Abstract
    In this talk, I will propose a definition of real phase structures on polyhedral complexes. I’ll explain that in the case of matroid fans, specifying a real phase structure is cryptomorphic to providing an orientation of the underlying matroid. Then I’ll define the real part of a polyhedral complex with a real phase structure. This determines a closed chain in the real part of a toric variety. In the case when the polyhedral complex is a non-singular tropical variety, the real part is a PL-manifold. Moreover, for a non-singular tropical variety with a real phase structures we can apply the same spectral sequence for tropical hypersurfaces, obtained by Renaudineau and myself, to bound the Betti numbers of the real part by the dimensions of the tropical homology groups. This is joint work in progress with Johannes Rau and Arthur Renaudineau.
  • 11:00 - 11:15 am EDT
    Break
    Coffee Break
  • 11:15 am - 12:00 pm EDT
    Combinatorics and real lifts of bitangents to tropical quartic curves
    Virtual
    • Speaker
    • María Angélica Cueto, Ohio State University
    • Session Chair
    • Melody Chan, Brown University
    Abstract
    Smooth algebraic plane quartics over algebraically closed fields have 28 bitangent lines. By contrast, their tropical counterparts have infinitely many bitangents. They are grouped into seven equivalence classes, one for each linear system associated to an effective tropical theta characteristic on the tropical quartic curve. In this talk, I will discuss recent work joint with Hannah Markwig (arXiv:2004.10891) on the combinatorics of these bitangent classes and its connection to the number of real bitangents to real smooth quartic curves characterized by Pluecker. We will see that they are tropically convex sets and they come in 41 symmetry classes. The classical bitangents map to specific vertices of these polyhedral complexes, and each tropical bitangent class captures four of the 28 bitangents. We will discuss the situation over the reals and show that each tropical bitangent class has either zero or four lifts to classical bitangent defined over the reals, in agreement with Pluecker's classification.
  • 12:00 - 1:30 pm EDT
    Lunch/Free Time
  • 1:30 - 2:15 pm EDT
    Tropical psi classes
    Virtual
    • Speaker
    • Renzo Cavalieri, Colorado State University
    • Session Chair
    • Dhruv Ranganathan, University of Cambridge
    Abstract
    We introduce a tropical geometric framework that allows us to define $\psi$ classes for moduli spaces of tropical curves of arbitrary genus. We prove correspondence theorems between algebraic and tropical $\psi$ classes for some one-dimensional families of genus-one tropical curves.
  • 2:30 - 2:45 pm EDT
    Break
    Coffee Break
  • 2:45 - 3:30 pm EDT
    When are multidegrees positive?
    Virtual
    • Speaker
    • Federico Castillo, University of Kansas
    • Session Chair
    • Dhruv Ranganathan, University of Cambridge
    Abstract
    The notion of multidegree for multiprojective varieties extends that of degree for projective varieties. They can be defined in geometric terms, using intersection theory, or alternatively in algebraic terms, via multigraded hilbert polynomial. We study the problem of their positivity and establish a combinatorial description using polyhedral geometry. We will show applications for Schubert polynomials and mixed volumes. This is joint work with Y.Cid-Ruiz, B.Li, J.Montano, and N.Zhang.
Wednesday, April 14, 2021
  • 9:00 - 9:45 am EDT
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 10:00 - 10:45 am EDT
    Wall-crossing phenomenon for Newton-Okounkov bodies
    Virtual
    • Speaker
    • Laura Escobar, Washington University- St. Louis
    • Session Chair
    • Lara Bossinger, Mathematics Institute UNAM, Oaxaca
    Abstract
    A Newton-Okounkov body is a convex set associated to a projective variety, equipped with a valuation. These bodies generalize the theory of Newton polytopes and the correspondence between polytopes and projective toric varieties. Work of Kaveh-Manon gives an explicit link between tropical geometry and Newton-Okounkov bodies. We use this link to describe a wall-crossing phenomenon for Newton-Okounkov bodies. As an example, we describe wall-crossing formula in the case of the Grassmannian Gr(2,m). This is joint work with Megumi Harada.
  • 11:00 - 11:15 am EDT
    Break
    Coffee Break - Virtual
  • 11:15 am - 12:00 pm EDT
    On combinatorics of Arthur's trace formula, convex polytopes, and toric varieties
    Virtual
    • Speaker
    • Kiumars Kaveh, University of Pittsburgh
    • Session Chair
    • Lara Bossinger, Mathematics Institute UNAM, Oaxaca
    Abstract
    I start by discussing two beautiful well-known theorems about decomposing a convex polytope into an signed sum of cones, namely the classical Brianchon-Gram theorem and Lawrence-Varchenko theorem. I will then explain a generalization of the Brianchon-Gram which can be summerized as ""truncating a function on the Euclidean space with respect to a polytope"". This is an extraction of the combinatorial ingredients of Arthur's ''convergence'' and ''polynomiality'' results in his famous trace formula. Arthur's trace formula concerns the trace of left action of a reductive group $G$ on the space $L^2(G / \Gamma)$ where $\Gamma$ is a discrete (arithmetic) subgroup. The combinatorics involved is closely related to compactifications of ''locally summetric spaces'' (which btw are hyperbolic manifolds). Our ''combinatorial truncation'' can be thought of as an analogue of Arthur's truncation over a toric variety (in place of a compactification of a locally symmetric space). If there is time, I will briefly sketch geometric interpretations of our combinatorial truncation as a measure and a Lefschetz number on a toric variety respectively. This is a joint work in progress with Mahdi Asgari (Oklahoma State).
  • 12:00 - 1:30 pm EDT
    Lunch/Free Time
  • 1:30 - 2:30 pm EDT
    Poster Session
    Virtual
    Abstract
    Ideal Preserving Operations on Chemical Reaction Networks
    Mark Curiel, University of Hawaii at Manoa
    Under the assumption of mass action kinetics, the associated dynamical system of a reaction network is polynomial. We consider the ideals generated by these polynomials, which are called steady-state ideals. Steady-state ideals appear in multiple contexts within the chemical reaction network literature, however they have yet to be systematically studied. To begin such a study, we ask and partially answer the following question: when do two reaction networks give rise to the same steady-state ideal? In particular, our main results describe three operations on the reaction graph that preserve the steady-state ideal. Furthermore, since the motivation for this work is the classification of steady-state ideals, monomials play a primary role. To this end, combinatorial conditions are given to identify monomials in a steady-state ideal, and we give a sufficient condition for a steady-state ideal to be monomial.

    Construction and properties of Kanev surfaces in toric 3-folds
    Julius Giesler, University of Tuebingen
    In this poster Kanev surfaces, which are surfaces of general type, are considered, that arise as nondegenerate hypersurfaces in toric 3-folds. First such an hypersurface might have singularities but we show how to construct a minimal and a canonical model with toric methods. After this construction we consider nondegenerate hypersurfaces with fixed Newton polytope, thus obtaining a family of Kanev surfaces, and we both compute their number of moduli and check whether the infinitesimal Torelli theorem holds for such a family. The results constitute part of the author's doctoral thesis.

    On the shifted Littlewood-Richardson coefficients and the Littlewood-Richardson coefficients
    Nguyen Khanh, Institut Camille Jordan
    We give a new interpretation of the shifted Littlewood-Richardson coefficients $f_{\lambda\mu}^\nu$ ($\lambda,\mu,\nu$ are strict partitions). The coefficients $g_{\lambda\mu}$ which appear in the decomposition of Schur $Q$-function $Q_\lambda$ into the sum of Schur functions $Q_\lambda = 2^{l(\lambda)}\sum\limits_{\mu}g_{\lambda\mu}s_\mu$ can be considered as a special case of $f_{\lambda\mu}^\nu$ (here $\lambda$ is a strict partition of length $l(\lambda)$). We also give another description for $g_{\lambda\mu}$ as the cardinal of a subset of a set that counts Littlewood-Richardson coefficients $c_{\mu^t\mu}^{\tilde{\lambda}}$. This new point of view allows us to establish connections between $g_{\lambda\mu}$ and $c_{\mu^t \mu}^{\tilde{\lambda}}$. More precisely, we prove that $g_{\lambda\mu}=g_{\lambda\mu^t}$, and $g_{\lambda\mu} \leq c_{\mu^t\mu}^{\tilde{\lambda}}$. We conjecture that $g_{\lambda\mu}^2 \leq c^{\tilde{\lambda}}_{\mu^t\mu}$ and formulate some conjectures on our combinatorial models which would imply this inequality if it is valid.

    Computational complexity, Newton polytopes, and Schubert polynomials
    Colleen Robichaux, University of Illinois at Urbana-Champaign
    Schubert polynomials form a basis of all polynomials and appear in the study of cohomology rings of flag manifolds. The nonvanishing problem asks if a coefficient of a Schubert polynomial is nonzero. We give a tableau criterion for nonvanishing, from which we deduce the first polynomial time algorithm. These results are obtained from new characterizations of the Schubitope, a generalization of the permutahedron defined for any subset of the nxn grid. This is joint work with Anshul Adve and Alexander Yong.

    Enumeration of algebraic and tropical singular hypersurfaces
    Uriel Sinichkin, Tel Aviv University
    We develop a version of Mikhalkin's lattice path algorithm for projective hypersurfaces of arbitrary degree and dimension, which enumerates singular tropical hypersurfaces passing through appropriate configuration of points. By proving a correspondence theorem combined with the lattice path algorithm, we construct a $ \delta $ dimensional linear space of degree $ d $ real hypersurfaces containing $ \frac{1}{\delta!}(\gamma_nd^n)^{\delta}+O(d^{n\delta-1}) $ hypersurfaces with $ \delta $ real nodes, where $ \gamma_n $ are positive and given by a recursive formula.
    This is asymptotically comparable to the number $ \frac{1}{\delta!} \left( (n+1)(d-1)^n \right)^{\delta}+O\left(d^{n(\delta-1)} \right) $ of complex hypersurfaces having $ \delta $ nodes in a $ \delta $ dimensional linear space. In the case $ \delta=1 $ we give a slightly better leading term.
  • 2:30 - 3:15 pm EDT
    On Newton-Okounkov bodies associated to Grassmannians
    Virtual
    • Speaker
    • Alfredo Nájera Chávez, Mathematics Institute UNAM, Oaxaca
    • Session Chair
    • Travis Mandel, University of Oklahoma
    Abstract
    In this talk I will elaborate on a certain class of Newton-Okounkov bodies that one can associate to "nice" compactifications of cluster varieties. In particular, I will explain how this approach recovers Rietsch--Williams' construction of Newton--Okounkov bodies for Grassmannians. In order to make the precise connection it will be necessary to explain how the Marsh--Rietsch potential and the Gross--Hacking--Keel--Kontsevich potential for Grassmannians are related. Finally, I will draw some consequences from this relation such as an isomorphism of the toric degenerations obtained by Rietsch-Willimas and the toric degenerations obtained by the celebrated "principal coefficient" construction. Time permitting, I will briefly elaborate on the interpretation of these results from the viewpoint of the representation theory of the associated dimer algebra.
  • 3:30 - 3:45 pm EDT
    Break
    Coffee Break
  • 3:45 - 4:30 pm EDT
    Broken line convexity
    Virtual
    • Speaker
    • Timothy Magee, University of Birmingham
    • Session Chair
    • Daping Weng, Michigan State University
    Abstract
    In this talk, I'll give an overview of how convex polytopes generalizes from the toric world to the cluster world, where the "polytopes" live in a tropical space rather than a vector space. In this setting, "broken line convex polytopes" define projective compactifications of cluster varieties. After this overview, I'll focus on two exciting applications of this more general notion of convexity: 1) an intrinsic version of Newton-Okounkov bodies and 2) a possible cluster version of a classic toric mirror symmetry construction due to Batyrev. The overview is based on joint work with Mandy Cheung and Alfredo Nájera Chávez, and the applications are based on ongoing joints works with Mandy, Alfredo, Lara Bossinger, and Bosco Frías Medina.
Thursday, April 15, 2021
  • 9:00 - 9:45 am EDT
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 10:00 - 10:45 am EDT
    Toric vector bundles -- an overview
    Virtual
    • Speaker
    • Milena Hering, The University of Edinburgh
    • Session Chair
    • Linda Chen, Swarthmore College
    Abstract
    I will give a brief introduction to toric vector bundles, an overview of what we know about them so far, and explain some more recent developments on the defining equations of embeddings of their projectivisations
  • 11:00 - 11:15 am EDT
    Break
    Coffee Break
  • 11:15 am - 12:00 pm EDT
    The Fulton-MacPherson compactification is not a Mori dream space
    Virtual
    • Speaker
    • José González, University of California, Riverside
    • Session Chair
    • Linda Chen, Swarthmore College
    Abstract
    We show that the Fulton-MacPherson compactification of the configuration space of n distinct labeled points in certain varieties of arbitrary dimension d, including projective space, is not a Mori dream space for n greater than or equal to d+9.
  • 12:00 - 1:30 pm EDT
    Lunch/Free Time
  • 1:30 - 2:15 pm EDT
    Schubert polynomials from a polytopal point of view
    Virtual
    • Speaker
    • Karola Meszaros, Cornell University
    • Session Chair
    • Laura Escobar, Washington University- St. Louis
    Abstract
    Schubert polynomials are multivariate polynomials representing cohomology classes on the flag manifold. Despite the beautiful formulas developed for them over the past three decades, the coefficients of these polynomials remained mysterious. I will explain Schubert polynomials from a polytopal point of view, answering, at least partially, the questions: Which coefficients are nonzero? How do the coefficients compare to each other in size? Are the Newton polytopes of these polynomials saturated? Are their coefficients log-concave along lines? Is there a polytope whose integer point transform specializes to Schubert polynomials? As the questions themselves suggest, we will find that polytopes play an outsized role in our understanding. The talk is based on joint works with Alex Fink, June Huh, Ricky Liu, Jacob Matherne and Avery St. Dizier.
  • 2:30 - 2:45 pm EDT
    Break
    Coffee Break
  • 2:45 - 3:30 pm EDT
    Families of Gröbner degenerations
    Virtual
    • Speaker
    • Lara Bossinger, Mathematics Institute UNAM, Oaxaca
    • Session Chair
    • Laura Escobar, Washington University- St. Louis
    Abstract
    Let V be the weighted projective variety defined by a weighted homogeneous ideal J and C a maximal cone in the Gröbner fan of J with m rays. We construct a flat family over affine m-space that assembles the Gröbner degenerations of V associated with all faces of C. This is a multi-parameter generalization of the classical one-parameter Gröbner degeneration associated to a weight. We explain how our family can be constructed from Kaveh--Manon's recent work on the classification of toric flat families over toric varieties: it is the pull-back of a toric family defined by a Rees algebra with base the toric variety associated to cone C along its universal torsor. We apply this construction to the Grassmannians of planes with their Plücker embeddings and the Grassmannian Gr(3,6) with its cluster embedding. In each case there exists a unique maximal Gröbner cone whose associated initial ideal is the Stanley--Reisner ideal of the cluster complex. We show that the corresponding cluster algebra with universal coefficients arises as the algebra defining the flat family associated to this cone. This talk is based on joint work with F. Mohammadi and A. Nájera Chávez, arxiv:2007.14972.
Friday, April 16, 2021
  • 9:00 - 9:45 am EDT
    Gathertown Morning Coffee
    Coffee Break - Virtual
  • 10:00 - 10:45 am EDT
    The logarithmic Hilbert scheme of curves
    Virtual
    • Speaker
    • Dhruv Ranganathan, University of Cambridge
    • Session Chair
    • Federico Ardila, San Francisco State University
    Abstract
    Within the Hilbert scheme of curves in projective space is a subscheme of curves that are "tropical" in the sense of Tevelev: they interact well with the coordinate subspaces. I will explain why, from the point of view of tropical and logarithmic geometry, this locus ought to be the principal open cell in another moduli space, of which the Hilbert scheme is only an approximation. This "logarithmic Hilbert scheme" was recently constructed in work with Davesh Maulik (MIT) and is the core of a new theory of logarithmic Donaldson-Thomas invariants. The story touches another major character in the story of polyhedral and algebraic geometry: the secondary polytope of Gel'fand-Kapranov-Zelevinsky. I'll try to give some sense for why.
  • 11:00 - 11:15 am EDT
    Break
    Coffee Break
  • 11:15 am - 12:00 pm EDT
    Initial degenerations of Grassmannians
    Virtual
    • Speaker
    • Daniel Corey, University of Wisconsin, Madison
    • Session Chair
    • Federico Ardila, San Francisco State University
    Abstract
    We construct closed immersions from initial degenerations of Gr_0(d,n)---the open cell in the Grassmannian Gr(d,n) given by the nonvanishing of all Plücker coordinates---to limits of thin Schubert cells associated to diagrams induced by the face poset of the corresponding tropical linear space. These are isomorphisms in many cases, including (d,n) equal to (2,n), (3,6) and (3,7). As an application, Gr_0(3,7) is schön, and the Chow quotient of Gr(3,7) by the maximal torus in PGL(7) is the log canonical compactification of the moduli space of 7 points in P^2 in linear general position, making progress on a conjecture of Hacking, Keel, and Tevelev. Time permitting, I will discuss recent work on extending these results to the Lie-type D setting.
  • 12:00 - 1:30 pm EDT
    Lunch/Free Time
  • 1:30 - 2:15 pm EDT
    On the top-weight rational cohomology of A_g
    Virtual
    • Speaker
    • Melody Chan, Brown University
    • Session Chair
    • Yoav Len, University of St Andrews
    Abstract
    I'll report on recent work using tropical techniques to find new rational cohomology classes in moduli spaces A_g of abelian varieties, building on previous joint work with Galatius and Payne on M_g. Joint work with Madeline Brandt, Juliette Bruce, Margarida Melo, Gwyneth Moreland, and Corey Wolfe.
  • 2:30 - 2:45 pm EDT
    Break
    Coffee Break
  • 2:45 - 3:30 pm EDT
    Tropical Flag Varieties
    Virtual
    • Speaker
    • Madeline Brandt, Brown University
    • Session Chair
    • Yoav Len, University of St Andrews
    Abstract
    Flag matroids are combinatorial abstractions of flags of linear subspaces, just as matroids are of linear subspaces. We introduce the flag Dressian as a tropical analogue of the partial flag variety, and give a correspondence between: (a) points on the flag Dressian, (b) valuated flag matroids, (c) flags of projective tropical linear spaces, and (d) coherent flag matroidal subdivisions of the flag matroid polytope. The ideas presented in this talk will be brought to life through examples.
Monday, April 19, 2021
Combinatorial Algebraic Geometry
  • 11:00 am - 12:00 pm EDT
    Papers and Journals
    Professional Development - Virtual
Wednesday, April 21, 2021
Combinatorial Algebraic Geometry
  • 3:00 - 3:30 pm EDT
    Gathertown Afternoon Coffee
    Coffee Break - Virtual
  • 3:30 - 4:30 pm EDT
    Schubert Calculus via bosonic operators
    Virtual
    • Gleb Nenashev, Brown University
    Abstract
    I will present a definition and some important properties of the bosonic operators for back-stable Schubert polynomials. The operators act on the left weak Bruhat order (divided difference and Monk’s rule use the right side action on permutations in my notations). These operators with an extra condition give sufficiently enough linear equations for the structure constants of flag varieties. In particular, they provide a recurrent formula for the structure constants. In some special cases it is easy to check the positivity of the structure constants using this formula, examples will be presented. One of the advantages of our method is that we do not need to use formulas for Schubert polynomials and back-stable Schubert polynomials. Nevertheless if time permits, I will also show how to establish the pipe dreams formula using these operators.
Thursday, April 22, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 11:00 am EDT
    Learning Seminar - Differential forms on tropical moduli spaces
    Seminar - Virtual
    • Melody Chan, Brown University
    • Sam Payne, University of Texas at Austin
    Abstract
    The goal is to understand Francis Brown's recent arXiv preprint Invariant differential forms on complexes of graphs and Feynman integrals. A sub-goal, which we hope takes shape over the course of the seminar, is to draw out the connection between Brown's article and tropical moduli spaces of curves and abelian varieties.

    This is not an introductory seminar per se in that the choice of topic is of specialized interest and of particular interest to us vis-a-vis our current work. On the other hand, we will try to develop the machinery without relying on background from tropical geometry, much as Brown's article is able to do.

    Resources to get started:

    1. Sam's lectures from the introductory Workshop, available from the webpage

    2. Draft of a survey articleon classical/tropical moduli spaces by Melody, which outlines the appearance of graph complexes in the study of tropical moduli.
  • 11:00 am - 12:00 pm EDT
    Semistable Reduction Seminar
    Seminar - Virtual
    • Dan Abramovich, Brown University
  • 3:30 - 4:40 pm EDT
    Bow Varieties---Combinatorics, Geometry, and Characteristic Classes
    Virtual
    • Speaker
    • Yiyan Shou, UNC - Chapel Hill
    • Session Chair
    • Anders Buch, Rutgers University
    Abstract
    Cherkis bow varieties are believed to be a natural setting for the study of 3d (N=4) mirror symmetry from the perspective of characteristic classes. This talk will review the "quiver" definition of bow varieties, due to Nakajima and Takayama, and introduce a combinatorial framework for their study. This framework includes brane diagrams and related combinatorial operations and constructions. Using this combinatorial framework, we will analyze the tangent bundle, torus fixed points, and invariant curves, key ingredients for defining characteristic classes. Finally, examples of cohomological stable envelopes will be calculated. This talk is based on a joint work with Richárd Rimányi.
Friday, April 23, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 10:30 am EDT
    Graduate Student/postdoc post-seminar break in Gather
    Coffee Break - Virtual
  • 10:30 - 11:00 am EDT
    Slack realization spaces and realizability of polytopes
    Post Doc/Graduate Student Seminar - Virtual
    • Antonio Macchia, Freie Universität Berlin
  • 11:00 - 11:30 am EDT
    Introduction to Hessenberg varieties
    Post Doc/Graduate Student Seminar - Virtual
    • Sean Griffin, Brown University
    Abstract
    Hessenberg varieties are a family of subvarieties of the complete flag variety that have many wonderful combinatorial properties. I'll survey some of these combinatorial properties, including an amazing connection to chromatic quasisymmetric functions, which was conjectured by Shareshian and Wachs and proven by Brosnan and Chow.
  • 11:30 am - 12:00 pm EDT
    Graduate Student/postdoc post-seminar break in Gather
    Coffee Break - Virtual
Monday, April 26, 2021
Combinatorial Algebraic Geometry
  • 11:00 am - 12:00 pm EDT
    Grant Proposals
    Professional Development - Virtual
Wednesday, April 28, 2021
Combinatorial Algebraic Geometry
  • 3:00 - 3:30 pm EDT
    Gathertown Afternoon Coffee
    Coffee Break - Virtual
  • 3:30 - 4:30 pm EDT
    The Abelian/non-Abelian correspondence and mirror symmetry
    Virtual
    • Elana Kalashnikov, Harvard University
    Abstract
    The Abelian/non-Abelian correspondence is a powerful tool that can be used to study GIT quotients V//G, where V is a vector space. Such GIT quotients include type A flag varieties and quiver flag varieties. The principle of the Abelian/non-Abelian correspondence is that a GIT quotient V//G can be studied by considering the much simpler Abelian GIT quotient V//T, where T is maximal torus of G. I'll discuss applications of the Abelian/non-Abelian correspondence to quantum cohomology and mirror symmetry of type A flag varieties and quiver flag varieties, focusing on rim-hook removal rules and Plücker coordinate mirrors. Part of this talk will report on joint work with Wei Gu.
Thursday, April 29, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 11:00 am EDT
    Learning Seminar - Differential forms on tropical moduli spaces
    Seminar - Virtual
    • Melody Chan, Brown University
    • Sam Payne, University of Texas at Austin
    Abstract
    The goal is to understand Francis Brown's recent arXiv preprint Invariant differential forms on complexes of graphs and Feynman integrals. A sub-goal, which we hope takes shape over the course of the seminar, is to draw out the connection between Brown's article and tropical moduli spaces of curves and abelian varieties.

    This is not an introductory seminar per se in that the choice of topic is of specialized interest and of particular interest to us vis-a-vis our current work. On the other hand, we will try to develop the machinery without relying on background from tropical geometry, much as Brown's article is able to do.

    Resources to get started:

    1. Sam's lectures from the introductory Workshop, available from the webpage

    2. Draft of a survey articleon classical/tropical moduli spaces by Melody, which outlines the appearance of graph complexes in the study of tropical moduli.
  • 11:00 am - 12:00 pm EDT
    Semistable Reduction Seminar
    Seminar - Virtual
    • Dan Abramovich, Brown University
Friday, April 30, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 10:30 am EDT
    Graduate Student/postdoc pre-seminar break in Gather
    Coffee Break - Virtual
  • 10:30 - 11:30 am EDT
    Toric Geometry
    Post Doc/Graduate Student Seminar - Virtual
    • Sean Griffin, Brown University
    • Mariel Supina, University of California, Berkeley
    Abstract
    An introduction to toric geometry
    Sean Griffin, Brown University
    I'll introduce the basics of toric geometry, including the construction of a toric variety from a rational convex polytope. We'll do lots of examples to illustrate the ideas.

    The equivariant Ehrhart theory of the permutahedron
    Mariel Supina, University of California, Berkeley
    Ehrhart theory is a topic in geometric combinatorics which involves counting the lattice points inside of lattice polytopes. Stapledon (2010) introduced equivariant Ehrhart theory and conjectured a relationship between the equivariant H*-series of a polytope and invariant hypersurfaces in its corresponding toric variety. In this talk, I will describe Stapledon's conjecture and discuss joint work with Ardila and Vindas Meléndez (2020) on verifying his conjecture in this special case.
  • 11:30 am - 12:00 pm EDT
    Graduate Student/postdoc post-seminar break in Gather
    Coffee Break - Virtual
Wednesday, May 5, 2021
Combinatorial Algebraic Geometry
  • 3:00 - 3:30 pm EDT
    Gathertown Afternoon Coffee
    Coffee Break - Virtual
  • 3:30 - 4:30 pm EDT
    Equivariant Schubert Calculus of Peterson Varieties
    Virtual
    • Rahul Singh, Virginia Polytechnic Institute and State University
    Abstract
    Peterson varieties are certain singular subvarieties of flag manifolds, naturally admitting one-dimensional torus action. Starting with a natural basis for the equivariant homology of a Peterson variety, we construct a dual basis in cohomology and show that the structure constants of the cohomology ring are positive with respect to this basis. We also discuss the sense in which the fundamental classes of the Peterson varieties exhibit a stability analogous to the stability of Schubert classes, and how this can be used to streamline various calculations in the Schubert calculus of Peterson varieties. This is joint work with Rebecca Goldin and Leonardo Mihalcea.
Thursday, May 6, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 11:00 am EDT
    Learning Seminar - Differential forms on tropical moduli spaces
    Seminar - Virtual
    • Melody Chan, Brown University
    • Sam Payne, University of Texas at Austin
    Abstract
    The goal is to understand Francis Brown's recent arXiv preprint Invariant differential forms on complexes of graphs and Feynman integrals. A sub-goal, which we hope takes shape over the course of the seminar, is to draw out the connection between Brown's article and tropical moduli spaces of curves and abelian varieties.

    This is not an introductory seminar per se in that the choice of topic is of specialized interest and of particular interest to us vis-a-vis our current work. On the other hand, we will try to develop the machinery without relying on background from tropical geometry, much as Brown's article is able to do.

    Resources to get started:

    1. Sam's lectures from the introductory Workshop, available from the webpage

    2. Draft of a survey articleon classical/tropical moduli spaces by Melody, which outlines the appearance of graph complexes in the study of tropical moduli.
  • 11:00 am - 12:00 pm EDT
    Semistable Reduction Seminar
    Seminar - Virtual
    • Dan Abramovich, Brown University
  • 12:00 - 1:00 pm EDT
    Socially Distanced Walk with Directorate
    Socially Distanced Walk - 121 South Main Street Main Entrance
Friday, May 7, 2021
Combinatorial Algebraic Geometry
  • 10:00 - 10:30 am EDT
    Graduate Student/postdoc pre-seminar break in Gather
    Coffee Break - Virtual
  • 10:30 - 11:30 am EDT
    Kac-Moody Schubert calculus
    Post Doc/Graduate Student Seminar - Virtual
    • Shuai Jiang, Virginia Tech
    Abstract
    Equivariant homology of infinite Grassmannian
    Let G be a semisimple algebraic group over C, B ⊂ G a Borel subgroup and T a maximal torus. Peterson discovered the ”quantum equals affine” phenomena and Lam and Shimozono proved that the equivariant Schubert homology structure constants of affine Grassmannian are the Schubert structure constants for the T-equivariant quantum cohomology rings QHT(G/B). Later, Lam and Shimozono found the equivariant homology Chevalley formula and more recently Lam, Lee and Shimozono use this formula to derive the j-basis coefficients of infinity Grassmannian for a hook. In the first part of this talk, I will discuss the j-basis in equivariant homology of affine Grassmannian. Then, I will explain their hook-formula.
  • 11:30 am - 12:00 pm EDT
    Graduate Student/postdoc post-seminar break in Gather
    Coffee Break - Virtual

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Associated Semester Workshops

Schubert Seminar Series
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VIRTUAL ONLY: Algebraic Geometry and Polyhedra
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