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Monday, May 9, 2022 11:30 am - 11:30 am EDT (GMT -04:00)

Algebraic Graph Theory Seminar - Péter Pál Pach

Title: Polynomials, rank and cap sets

Speaker:

Péter Pál Pach

Affiliation:

Budapest University of Technology

Zoom: Contact Sabrina Lato for link

Abstract:

In this talk we will look at a variant of the polynomial method which was first used to prove that sets avoiding 3-term arithmetic progressions in groups like Z_4^n and F_q^n are exponentially small (compared to the size of the group). We will discuss lower and upper bounds for the size of the extremal subsets.  We will also mention some further applications of the method, for instance, the solution of the Erdős–Szemerédi theorem sunflower conjecture.

Tuesday, May 10, 2022 3:00 pm - 3:00 pm EDT (GMT -04:00)

Graphs and Matroids Seminar - Jim Geelen

Title: Connectivity functions and connectivity intertwining

Speaker: Jim Geelen
Affiliation: University of Waterloo
Room: MC 5417

Abstract:

Connectivity functions provide a nice way of unifying matroid connectivity with various notions of connectivity in graphs. I will present some new and old open problems.

Thursday, May 12, 2022 1:00 pm - 1:00 pm EDT (GMT -04:00)

Algebraic Combinatorics Seminar - Andrew Gitlin

Title:  A vertex model for LLT polynomials and k-tilings of the Aztec diamond

Speaker: Andrew Gitlin
Affiliation: UC Berkeley
Room/Zoom: MC5479 or for Zoom link contact Logan Crew or Olya Mandelshtam

Abstract:

We describe a Yang-Baxter integrable colored vertex model, from which we construct a class of partition functions that equal the LLT polynomials of Lascoux, Leclerc, and Thibon. Using the vertex model formalism, we can prove many properties of these polynomials.

Friday, May 13, 2022 8:30 am - Saturday, May 14, 2022 5:00 pm EDT (GMT -04:00)

26th Ontario Combinatorics Workshop

The Ontario Combinatorics Workshop is a meeting for researchers working in combinatorics from Ontario and surrounding areas to gather and share their latest research developments. The objective of this meeting is to have an atmosphere conducive to research discussion and collaboration. The setting of the meeting is informal to provide a friendly environment for students and post-doctoral fellows to present their results, to exchange ideas, and to gain exposure to various topics in combinatorics. It is also a place where students and faculties meet, which may foster future collaborations. 

Registration

To register, click here.

Friday, May 13, 2022 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Rafael Oliveira

Title: Radical Sylvester-Gallai theorem for cubics - and beyond

Speaker: Rafael Oliveira
Affiliation: University of Waterloo
Location: MC 5501 or please contact Emma Watson for Zoom link

Abstract:

In 1893, Sylvester asked a basic question in combinatorial geometry: given a finite set of distinct points $v_1, \ldots, v_m \in \R^N$ such that the line defined by any pair of distinct points $v_i, v_j$ contains a third point $v_k$ in the set, must all points in the set be collinear?

Thursday, May 19, 2022 1:00 pm - 1:00 pm EDT (GMT -04:00)

Algebraic Combinatorics Seminar - Victor Wang

Title: P-partition power sums

Speaker: Victor Wang
Affiliation: University of British Columbia
Room/Zoom: MC5479 or for Zoom link contact Logan Crew or Olya Mandelshtam

Abstract:

The Hopf algebra of symmetric functions is spanned by several important bases, including by power sum symmetric functions, which encode the class values of the characters of the symmetric group under the Frobenius characteristic map.

Tuesday, May 24, 2022 3:00 pm - 3:00 pm EDT (GMT -04:00)

Graphs and Matroids Seminar - Peter Nelson

Title: On Donuts and Quasigraphic matroids

Speaker: Peter Nelson
Affiliation: University of Waterloo
Room: MC 5417

Abstract:

Quasigraphic matroids are graph-like objects that give a common generalization of lift and frame matroids. Donuts are edible topological surfaces. I will talk about a surprising link between these two types of object, assuming no prior knowledge of quasigraphic matroids or donuts.

Thursday, May 26, 2022 11:30 am - 11:30 am EDT (GMT -04:00)

Cryptography Reading Group - Dinesh Valluri

Title: Faster Algorithms for Isogeny Problems using Torsion Point Images. 

Speaker: Dinesh Valluri
Affiliation: University of Waterloo
Attend: Contact Jesse Elliott

Abstract:

In this talk, we will discuss cryptanalysis of some SIDH-type protocols due to Christophe Petit: https://eprint.iacr.org/2017/571.pdf. While finding isogenies between supersingular elliptic curves remains computationally hard to solve, knowledge of images of specific torsion points by the unknown isogeny helps build faster attacks.

Thursday, June 2, 2022 12:00 pm - 12:00 pm EDT (GMT -04:00)

Algebraic Combinatorics Seminar - Per Alexandersson

Title: Cyclic sieving with focus on open problems

Speaker:

Per Alexandersson

Affiliation:

Stockholm University

Room/Zoom: MC5479 or for Zoom link contact Logan Crew or Olya Mandelshtam

Abstract:

The cyclic sieving phenomenon (CSP) connects a cyclic group action on a family of combinatorial objects with some q-analog of that set. We discuss some recent results and open problems for standard and semistandard tableaux, as well as some other families of combinatorial objects.
Several open problems with various levels of difficulty will be presented.