To add a seminar or a talk, please email Aram directly. If you want to see math seminars of all disciplines, you can try the following website.

If you want to see old seminars: Videos of Past Conferences/Seminars

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The following is a list of online conferences that are happening during the pandemic! If you have a conference you'd like to add, feel free to email me. đ

- REACT - Research Encounters in Algebraic and Combinatorial Topics
**15 February - 5 March 2021** - (Polytop)ics - Recent advances on polytopes
**06-09 April 2021** - SCDMS - 6th Southern California Discrete Mathematics Symposium
**10 April 2021** - GSCC - Graduate Student Combinatorics Conference
**23 - 25 April 2021** - Diversity and Excellence Workshop - Women in Combinatorics and Representation Thoery
**15-16 May 2021** - WAM - Representation theory: Categories and Combinatorics (Program for women)
**22-28 May 2021**

All times are denoted in your local computer time. Roughly the next two weeks are shown.

It is currently: **Sun 07 Mar 2021 11:43 UTC**

Last updated: Mon 01 Mar 2021 15:29 UTC

Green - Talk is currently happening.

Yellow - Talk is coming up within the hour.

Red - Talk is in under 10 minutes.

**Zoom links can be found on seminar/conference websites** (They have been removed for security reasons)

Speaker | Title | Date & Time | Duration | Abstract | Seminar |
---|---|---|---|---|---|

David Anderson (Ohio State) | TBA | Mon 08 Mar 2021 16:00 UTC | 50 minutes | No abstract available | 15 |

Joy Morris | TBA | Mon 08 Mar 2021 16:30 UTC | Check Seminar Page | No abstract available | 36 |

Fu Liu (UC Davis) | TBA | Mon 08 Mar 2021 19:00 UTC | 60 minutes | No abstract available | 30 |

Daniel Tamayo (UniversitĂ© Paris-Saclay) | TBA | Mon 08 Mar 2021 20:00 UTC | 60 minutes | No abstract available | York |

Nick Brettell | TBA | Mon 08 Mar 2021 20:00 UTC | Check Seminar Page | No abstract available | 10 |

Alejandro Morales UMass Amherst | Refinements and symmetries for volumes of flow polytopes | Mon 08 Mar 2021 20:10 UTC | 50 minutes | Show | 24 |

BĂ©nĂ©dicte Haas (Paris 13) | TBA | Tue 09 Mar 2021 14:00 UTC | Check Seminar Page | No abstract available | 19 |

Corrine Yap (Rutgers) | A Topological TurĂĄn Problem | Tue 09 Mar 2021 15:30 UTC | Check Seminar Page | Show | 19 |

Anna Barbieri (UniversitĂ degli Studi di Milano Statale) | TBA | Tue 09 Mar 2021 16:00 UTC | Check Seminar Page | No abstract available | 18 |

Jiuzu Hong | TBA | Wed 10 Mar 2021 16:00 UTC | 60 minutes | No abstract available | 21 |

Cameron Wright (University of Washington) | Torsor Structures on Spanning Trees | Wed 10 Mar 2021 18:00 UTC | 60 minutes | Show | 17 |

Jose Perea (Michigan State University) | Quasiperiodicy in data - an applied topology view | Thu 11 Mar 2021 15:10 UTC | 50 minutes | Show | 1 |

David Rose, UNC | TBA | Thu 11 Mar 2021 17:30 UTC | 50 minutes | No abstract available | 25 |

Dr. Emily Sergel, University of Pennsylvania | TBA | Thu 11 Mar 2021 19:00 UTC | Check Seminar Page | No abstract available | 39 |

David Conlon (CalTech) | Subset sums, completeness and colorings | Thu 11 Mar 2021 20:00 UTC | Check Seminar Page | Show | 20 |

Michael Kiessling, Rutgers University | A Maple-assisted study of a Schroedinger-Newton, a.k.a. Schroedinger-Poisson, a.k.a. Choquard, a.k.a. Pekar, a.k.a. ... equation | Thu 11 Mar 2021 22:00 UTC | 48 minutes | Show | 22 |

Erkko Lehtonen (Universidade Nova de Lisboa, Portugual) | Associative spectra of graph algebras | Fri 12 Mar 2021 17:00 UTC | 60 minutes | Show | 3 |

Richard P. Stanley (MIT / University of Miami) | TBA | Fri 12 Mar 2021 19:30 UTC | Check Seminar Page | No abstract available | 31 |

Reuven Hodges (University of Illinois at Urbana-Champaign) | TBA | Fri 12 Mar 2021 20:00 UTC | 60 minutes | No abstract available | 32 |

Speaker | Title | Date & Time | Duration | Abstract | Seminar |
---|---|---|---|---|---|

Katharina Jochemko (KTH Royal Institute of Technology) | TBA | Mon 15 Mar 2021 18:00 UTC | 60 minutes | No abstract available | 30 |

Rosa Orellana (Dartmouth College) | TBA | Mon 15 Mar 2021 19:00 UTC | 60 minutes | No abstract available | York |

Raul Penaguiao SFSU | Feasible regions meets pattern avoidance - The long awaited part three of feasible regions | Mon 15 Mar 2021 19:10 UTC | 50 minutes | Show | 24 |

Eunjeong Lee (IBS-CGP) | Tue 16 Mar 2021 00:00 UTC | 60 minutes | No abstract available | 38 | |

Liam Solus (KTH Royal Institute of Technology) | Some recent developments on the geometry of causation | Tue 16 Mar 2021 16:00 UTC | 45 minutes | Show | 11 |

Elie Casbi (Max Planck Institut fĂŒr Mathematik) | TBA | Tue 16 Mar 2021 16:00 UTC | Check Seminar Page | No abstract available | 18 |

Lisa Nicklasson (MPI MIS, Leipzig) | Toric ideals of polymatroids and Whiteâs conjecture | Tue 16 Mar 2021 16:45 UTC | 45 minutes | No abstract available | 11 |

Peter Tingley | A quiver approach to root multiplicities | Wed 17 Mar 2021 16:00 UTC | 60 minutes | Show | 21 |

Sylvester W Zhang (University of Minnesota) | TBA | Wed 17 Mar 2021 17:00 UTC | 60 minutes | No abstract available | 17 |

Florencia Orosz Hunziker (University of Colorado) | TBA | Thu 18 Mar 2021 15:10 UTC | 50 minutes | No abstract available | 1 |

Dr. Karen Yeates, University of Waterloo | TBA | Thu 18 Mar 2021 18:00 UTC | Check Seminar Page | No abstract available | 39 |

John Saccoman (Seton Hall University) | TBA | Fri 19 Mar 2021 16:00 UTC | 60 minutes | No abstract available | 3 |

Rafael Potrie (Universidad de la RepĂșblica) | Fri 19 Mar 2021 16:00 UTC | 60 minutes | No abstract available | 16 | |

Mariel Supina (UC Berkeley) | TBA | Fri 19 Mar 2021 18:30 UTC | Check Seminar Page | No abstract available | 31 |

Rob Davis (Colgate University) | TBA | Fri 19 Mar 2021 20:30 UTC | 60 minutes | No abstract available | 14 |

Hannah Burson (UMN) | TBA | Fri 19 Mar 2021 20:35 UTC | 50 minutes | No abstract available | 33 |

Willem Haemers | TBA | Mon 22 Mar 2021 15:30 UTC | Check Seminar Page | No abstract available | 36 |

Trey Trampel (University of Notre Dame) | TBA | Tue 23 Mar 2021 16:00 UTC | Check Seminar Page | No abstract available | 18 |

Alejandro Morales, UMass, Amherst, and William Shi, Northview highschool, Johns Creek, GA | Refinements and symmetries for volumes of flow polytopes | Thu 25 Mar 2021 21:00 UTC | 48 minutes | Show | 22 |

Seminar Number | Name | Institution | Website |
---|---|---|---|

1 | Geometry, Algebra, Mathematical Physics and Topology Research Group | Cardiff Univesity | Seminar Website |

2 | Algorithms, Combinatorics and Optimization Seminar | Carnegie Mellon University | Seminar Website |

3 | New York Combinatorics Seminar | City University of New York | Seminar Website |

4 | Rocky Mountain Algebraic Combinatorics Seminar | Colorado State University | Seminar Website |

5 | Algebraic Combinatorics Seminar | Institute of Mathematical Sciences | Seminar Website |

6 | LIPN Seminar | Laboratoire d'Informatique de Paris Nord | Seminar Website |

7 | Los Angeles Combinatorics and Complexity Seminar | Los Angeles | Seminar Website |

8 | MIT-Harvard-MSR Combinatorics Seminar | MIT, Harvard, MSR | Seminar Website |

9 | Virtual seminar on algebraic matroids and rigidity theory | Massachussetts Institute of Technology | Seminar Website |

10 | Online Matroid Theory Seminar | Matroid Union | Seminar Website |

11 | Nonlinear Algebra Seminar Online | Max-Planck-Instut fĂŒr Mathematik (MPI) | Seminar Website |

12 | Combinatorics and Graph Theory | Michigan State University | Seminar Website |

13 | Virtual Combinatorics Colloquium | Northeast Combinatorics Network | Seminar Website |

14 | Algebra and Representation Theory Seminar | Oklahoma University | Seminar Website |

15 | Algebra, Geometry and Combinatorics | Online | Seminar Website |

16 | Cibercoloquio Latinoamericano de MathemĂĄticas | Online | Seminar Website |

17 | Graduate Online Combinatorics Colloquium | Online | Seminar Website |

18 | Online Cluster Algebra Seminar | Online | Seminar Website |

19 | Oxford Discrete mathematics and probability seminar | Oxford University | Seminar Website |

20 | Princeton Discrete Mathematics Seminar | Princeton University | Seminar Website |

21 | The RepNet Virtual Seminar | RepNet | Seminar Website |

22 | Rutgers Experimental Mathematics Seminar | Rutgers University | Seminar Website |

23 | Workshop on combinatorics, discrete geometry and algorithms | St. Petersburg State University | Seminar Website |

24 | Combinatorics Seminar | UC Berkeley | Seminar Website |

25 | Algebra and Discrete Mathematics Seminar | UC Davis | Seminar Website |

26 | UCLA Combinatorics Seminar | UCLA | Seminar Website |

27 | Algebraic (and enumerative) combinatorics seminar | UWaterloo | Seminar Website |

28 | Seminario de Ălgebra, Combinatoria y TeorĂa de Lie | Universidad Nacional del Sur | Seminar Website |

29 | Lie Theory seminar | University of Colorado, Boulder | Seminar Website |

30 | Discrete CATS Seminar | University of Kentucky | Seminar Website |

31 | Discrete Math Seminar | University of Massachusetts Amherst | Seminar Website |

32 | Combinatorics Seminar | University of Michigan | Seminar Website |

33 | Combinatorics Seminar | University of Minnesota | Seminar Website |

34 | USC Combinatorics Seminar | University of Southern California | Seminar Website |

35 | Combinatorics and Geometry Seminar | University of Washington | Seminar Website |

36 | Algebraic Graph Theory | University of Waterloo | Seminar Website |

37 | SĂ©minaire de combinatoire et d'informatique mathĂ©matique du LaCIM | UniversitĂ© du QuĂ©bec Ă MontrĂ©al | Seminar Website |

38 | WUSTL Combinatorics Seminar | Washington University in St. Louis | Seminar Website |

39 | WinCom Virtual Colloquium | Women in Combinatorics | Seminar Website |

40 | Applied Algebra Seminar | York University | Seminar Website |

Flow polytopes are an important class of polytopes in combinatorics whose lattice points and volumes have interesting properties and relations. The Chan-Robbins-Yuen (CRY) polytope is a flow polytope with normalized volume equal to the product of consecutive Catalan numbers. Zeilberger proved this by evaluating the Morris constant term identity, but no combinatorial proof is known. There is a refinement of this formula that splits the largest Catalan number into Narayana numbers, which MĂ©szĂĄros gave an interpretation as the volume of a collection of flow polytopes. We introduce a new refinement of the Morris identity with combinatorial interpretations both in terms of lattice points and volumes of flow polytopes. Our results generalize MĂ©szĂĄros's construction and a recent flow polytope interpretation of the Morris identity by Corteel-Kim-MĂ©szĂĄros. We prove the product formula of our refinement following the strategy of the Baldoni-Vergne proof of the Morris identity. This is joint work with William Shi.

CloseThe classical TurĂĄn problem asks: given a graph H, how many edges can an n-vertex graph have while containing no isomorphic copy of H? By viewing (k+1)-uniform hypergraphs as k-dimensional simplicial complexes, we can ask a topological version (first posed by Nati Linial): given a k-dimensional simplicial complex S, how many facets can an n-vertex k-dimensional simplicial complex have while containing no homeomorphic copy of S? Until recently, little was known for k > 2. In this talk, we give an answer for general k, by way of dependent random choice and the combinatorial notion of a trace-bounded hypergraph. Joint work with Jason Long and Bhargav Narayanan.

CloseThe classical Kirchoff matrix-tree theorem states that the number of spanning trees of a finite connected graph is equal to the determinant of the graph's reduced Laplacian matrix. This result actually evinces the equality of the number of spanning trees of a graph and the cardinality of a finite group, referred to alternately as the sandpile group, Jacobian group, or Picard group of the graph. Further, one can endow the graph with a ribbon structure, an ordering of the edges around each vertex, in order to turn the set of spanning trees into a torsor for the Picard group. We present two such torsor structures in particular, survey some results comparing the two, and discuss a conjecture of Baker and Wang on these structures in nonplanar ribbon graphs.

CloseThe analysis of time-varying systems using topological methods has gained considerable attention over the last few years. This talk will be about quasiperiodic recurrence in time series data; i.e., the superposition of periodic oscillators with non-commensurate frequencies. The sliding window (or time delay) embeddings of such functions can be shown to be dense in high-dimensional tori, and we will discuss techniques to study the persistent homology of such sets. Along the way, we will present a recent KĂŒnneth theorem for persistent homology, as well as several applications to data science and engineering.

CloseWe develop novel techniques which allow us to prove a diverse range of results relating to subset sums and complete sequences of positive integers, including solutions to several longstanding open problems. These include: solutions to three problems of Burr and ErdĆs on Ramsey complete sequences, for which ErdĆs later offered a combined total of $350; analogous results for the new notion of density complete sequences; the solution to a conjecture of Alon and ErdĆs on the minimum number of colors needed to color the positive integers less than n so that n cannot be written as a monochromatic sum; the exact determination of an extremal function introduced by ErdĆs and Graham on sets of integers avoiding a given subset sum; and, answering a question of Tran, Vu and Wood, a homogeneous strengthening of a seminal result of SzemerĂ©di and Vu on long arithmetic progressions in subset sums.

Joint work with Jacob Fox and Huy Tuan Pham.

In several different contexts (mathematical) physicists have proposed a nonlinear system of PDEs which can be recast into a single Schroedinger equation with a Schroedinger potential that is the solution to a Poisson equation with the square of the solution of the Schroedinger equation as source term; as such it is known under a variety of names (see above). For instance, Roger Penrose proposed it in his theory of gravity-induced quantum-mechanical wave function collapse, but also down-to-earth condensed matter theories, by Pekar and later by Choquard, produce this equation without invoking gravity. Interestingly, the question of the asymptotic large-distance behavior has received several plausible but conflicting answers which cannot all be true simultaneously. Recently I managed to settle the issue of the leading order term --- partly rigorously, partly with the help of Maple. Subsequently Andrey Yudin from Moskow managed to tickle Maple to produce an intriguing formula for all the putative asymptotic correction terms to the leading order term which are of power law type. Numerically this formula seems pretty accurate, but it has yet to be proved; moreover, there are correction terms beyond all orders of powers, and a formula for these terms has yet to be found

CloseThe associative spectrum was introduced by Csakany and Waldhauser in 2000 as a method of quantifying the non-associativity of binary operations or the corresponding groupoids. The associative spectrum of a groupoid G is an integer sequence, the n-th member of which equals the number of distinct term operations induced on G by the bracketings of n variables. Graph algebras were introduced by Shallon in 1979 and provide a useful representation of directed graphs as algebras with a binary operation. In this talk, we report our work on associative spectra of graph algebras. We classify undirected graphs according to the associative spectra of their graph algebras; there are only three distinct possibilities: constant 1, powers of 2, and Catalan numbers. For arbitrary digraphs, the situation is considerably more complicated. We provide a necessary and sufficient condition for a graph algebra to satisfy a given bracketing identity, expressed in terms of several numerical structural parameters associated, on the one hand, with the graph and, on the other hand, with a pair of bracketings. Based on this, we establish bounds on the possible associative spectra of graph algebras; such a spectrum is either a constant sequence bounded above by 2 or it grows exponentially. This stands in stark contrast with associative spectra of arbitrary groupoids, for which other constant and subexponential spectra are also possible. This is joint work with Tamas Waldhauser (University of Szeged).

CloseGlebbov, Hoppen and others introduced the notion of feasible regions for permutation patterns. Given a fixed integer $k$, the feasible region is a set in $\mathbb{R}^{S_k}$ defined as follows: for a sequence of permutations $\sigma_k$ with growing size, compute the limit of the proportion of occurrences of each pattern of size $k$ in $\sigma_n$, obtaining a vector indeed by $S_n$. The feasible region arises as the set of such limits. Many interesting problems were studied in this context, like computing the dimension of the feasible region and its extreme points. Sometimes full descriptions can be given, but an overarching result is missing. If we consider consecutive patterns instead of classical patterns, we get simpler results, and we can characterize the feasible region: it is a polytope, and the vertices are given by cycles of a particular graph called overlap graph. Finally, we will talk about the feasible region for consecutive patterns resulting from considering permutations avoiding certain patterns. These new feasible regions, called the pattern-avoiding feasible regions, are now governed by different versions of the overlap graph, and we propose a unified characterization for all pattern-avoiding feasible regions avoiding one pattern. Along the way, we discuss connections of this work with the problem of packing patterns in pattern-avoiding permutations.

CloseA fundamental task in modern artificial intelligence is to identify transparent ways to represent cause-effect relations and then design efficient and reliable methods for learning such representations from data. These tasks can, respectively, be termed the problem of representation and the problem of causal discovery, and each problem has close connections to the world of nonlinear algebra. Classically, the problem of representation is solved using directed acyclic graphical (DAG) models, which are then learned from data using a variety of techniques - among which the most popular is greedy search. After taking a geometric view of this classical story, we will dive into the newest trends in causal discovery algorithms, which rely on a combination of observational and interventional data to learn a causal DAG. To understand the geometry and algebra of such causal models, we will broaden our perspective beyond DAGs to the family of staged trees. This new perspective will not only allow us to generalize and unify some previous results on the algebraic geometry of DAG models and staged trees, but it will also motivate a new family of context-specific causal models, called CStrees, that admit nice representation theorems analogous to those of DAGs. Time permitting, we will discuss the statistical theory of these new models, and see some applications to real data.

CloseWe present combinatorial upper bounds on dimensions of certain imaginary root spaces for symmetric Kac-Moody algebras. These come from the realization of the corresponding infinity-crystal using quiver varieties. The framework is general, but we only work out specifics in rank two and certain rank 3 cases. There we give explicit bounds. These turn out to be quite accurate, and in many cases exact, even for some fairly large roots. Perhaps surprisingly, things are cleanest and most accurate in rank 2. This includes joint work with Colin Williams and with Patrick Chan.

CloseFlow polytopes are an important class of polytopes in combinatorics whose lattice points and volumes have interesting properties and relations. The Chan-Robbins-Yuen (CRY) polytope is a flow polytope with normalized volume equal to the product of consecutive Catalan numbers. Zeilberger proved this by evaluating the Morris constant term identity, but no combinatorial proof is known. There is a refinement of this formula that splits the largest Catalan number into Narayana numbers, which MĂ©szĂĄros gave an interpretation as the volume of a collection of flow polytopes. We introduce a new refinement of the Morris identity with combinatorial interpretations both in terms of lattice points and volumes of flow polytopes. Our results generalize MĂ©szĂĄros's construction and a recent flow polytope interpretation of the Morris identity by Corteel-Kim-MĂ©szĂĄros. We prove the product formula of our refinement following the strategy of the Baldoni-Vergne proof of the Morris identity.