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Thursday, April 7, 2022 1:00 pm - 1:00 pm EDT (GMT -04:00)

Algebraic Combinatorics Seminar - Farid Aliniaeifard

Title: Modular relations between chromatic symmetric functions

Speaker: Farid Aliniaeifard
Affiliation: University of British Columbia
Zoom: Contact Logan Crew or Olya Mandelshtam

Abstract:

In 1995, Stanley introduced the chromatic symmetric functions. The study of chromatic symmetric functions of graphs inspired two main research directions.

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

Algebraic Graph Theory Seminar - Victor Wang

Title: Deletion-contraction for a unified Laplacian and applications

Speaker: Victor Wang
Affiliation: University of British Columbia
Zoom: Contact Sabrina Lato

Abstract:

We define a graph Laplacian with vertex weights in addition to the more classical edge weights, which unifies the combinatorial Laplacian and the normalised Laplacian.

Tuesday, April 12, 2022 3:00 pm - 3:00 pm EDT (GMT -04:00)

Graphs and Matroids Seminar - Carolyn Chun

Title: Lattice path matroids, lattice path polymatroids, and excluded minors

Speaker: Carolyn Chun
Affiliation: US Naval Academy
Zoom: http://matroidunion.org/?page_id=2477 or contact Shayla Redlin

Abstract:

We define lattice path matroids, polymatroids, Boolean polymatroids, and lattice path polymatroids, which are a subclass of Boolean polymatroids. 

Wednesday, April 13, 2022 2:00 pm - 2:00 pm EDT (GMT -04:00)

Reading Group Talk - Sean Kafer

Title: Generating Short Monotone Paths in 0/1 LPs: From Circuits to Simplex

Speaker: Sean Kafer
Affiliation: University of Waterloo
Zoom: 945 0789 9910 (passcode: kafer)

Abstract: 

Even after decades of study, it is unknown whether there exists a pivot rule for the Simplex method that always solves an LP with only a polynomial number of pivots.  This remains unknown even in the special case of 0/1 LPs - i.e., LPs defined over 0/1 polytopes - a case that includes many extensively studied problems in combinatorial optimization.

Thursday, April 14, 2022 1:00 pm - 1:00 pm EDT (GMT -04:00)

Algebraic Combinatorics Seminar - Darij Grinberg

Title: The one-sided cycle shuffles in the symmetric group algebra

Speaker: Darij Grinberg
Affiliation: Drexel University
Zoom: Contact Logan Crew or Olya Mandelshtam

Abstract:

Elements in the group algebra of a symmetric group S_n are known to have an interpretation in terms of card shuffling. I will discuss a new family of such elements, recently constructed by Nadia Lafrenière: Given a positive integer n, we define n elements t_1, t_2, ..., t_n in

Thursday, April 21, 2022 11:30 am - 11:30 am EDT (GMT -04:00)

Cryptography Reading Group - Guiwen Luo

Title: Speeding up Multi-Scalar Multiplication over Fixed Points towards Efficient zkSNARKs

Speaker: Guiwen Luo
Affiliation: University of Waterloo
Attend: Contact Jesse Elliott

Abstract:

The arithmetic of computing multiple scalar multiplications in an elliptic curve group then adding them together is called multi-scalar multiplication (MSM). MSM over fixed points dominates the time consumption in pairing-based trusted setup zero-knowledge succinct non-interactive arguments of knowledge (zkSNARKs), thus fast algorithms of MSM over fixed points are desirable for practical applications.

Monday, April 25, 2022 11:30 am - 11:30 am EDT (GMT -04:00)

Algebraic Graph Theory Seminar - Mahsa N. Shirazi

Title: On the eigenvalues of the perfect matching derangement graph

Speaker: Mahsa N. Shirazi
Affiliation: University of Regina
Zoom: Contact Sabrina Lato for link

Abstract:

The perfect matching derangement graph $M_{2n}$ is defined to be the graph whose vertices are all the perfect matchings of the complete graph $K_{2n}$, and two vertices are adjacent if they contain no common edges. The graph $M_{2n}$ is part of a larger study on the analogs of the Erdős-Ko-Rado theorem, and recently there have been interesting works on $M_{2n}$ and its eigenvalues.

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.