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Please note: The University of Waterloo is closed for all events until further notice.

# Events - November 2019

Friday, November 29, 2019 — 3:30 PM EST

## Tutte Colloquium - Debbie Leung

Title: Incompressibility of classical distributions

 Speaker: Debbie Leung Affiliation: University of Waterloo Room: MC 5501

Abstract:

We prove a general, robust, single-letter lower bound on the achievable rate for ensembles of classical states, which holds even when Alice and Bob share free entanglement and allow a constant local error.

Thursday, November 28, 2019 — 4:00 PM EST

## Graphs and Matroids Seminar - Jorn van der Pol

Title: Resilience of the rank of random matrices

 Speaker: Jorn van der Pol Affiliation: University of Waterloo Room: MC 5501

Abstract:

I will discuss the preprint of this title by Ferber, Luh, and McKinley (arXiv:1910.03619).

Friday, November 22, 2019 — 3:30 PM EST

## Tutte Colloquium - Aleksandr Kazachkov

Title: Disjunctive Cuts through the V-Polyhedral Lens

 Speaker: Aleksandr Kazachkov Affiliation: Polytechnique Montréal Room: MC 5501

Abstract:

Cutting planes, or cuts, are a critical component of modern integer programming solvers, but existing cuts implemented in solvers are relatively simple compared to those in the literature. We discuss the primary reasons for this disparity, as well as our recently-proposed V-polyhedral framework for mitigating some of these difficulties encountered by prior "stronger" cuts.

Friday, November 22, 2019 — 1:00 PM EST

## Combinatorial Optimization Reading Group - Sharat Ibrahimpur

Title: Submodular function maximization via the multilinear relaxation and contention resolution schemes

 Speaker: Sharat Ibrahimpur Affiliation: University of Waterloo Room: MC 5417

Abstract:

I will present a general framework for maximizing a nonnegative submodular set function $f$ subject to a variety of packing type constraints including multiple matroid constraints, knapsack constraints, and their intersections.

Thursday, November 21, 2019 — 4:00 PM EST

## PMATH/C&O Joint Colloquium - John Schanck

Title: Kummer's Theorem on binomial coefficients, etc.

 Speaker: John Schanck Affiliation: University of Waterloo Room: MC 5501

Abstract:

Some of us like the primes and call ourselves pure mathematicians. Some of us like the Catalan numbers and call ourselves combinatorialists.

Friday, November 15, 2019 — 3:30 PM EST

## Tutte Colloquium - Marcel Golz

Title: The combinatorics of parametric Feynman integrals

 Speaker: Marcel Golz Affiliation: University of Waterloo Room: MC 5501

Abstract:

Feynman integrals are used in perturbative quantum field theory to compute the probabilities of processes involving elementary particles. They can be represented as Feynman graphs and exhibit a rich combinatorial structure. The parametric representation of Feynman integrals is particularly suitable to be studied from a combinatorial perspective since it contains well known objects like the Kirchhoff polynomial.

Friday, November 15, 2019 — 1:00 PM EST

## Combinatorial Optimization Reading Group - Benjamin Moore

Title: A deterministic (1/2 + epsilon)-approximation for submodular maximizztion over a matroid

 Speaker: Ben Moore Affiliation: University of Waterloo Room: MC 5417

Abstract:

In 1978, it was shown that a natural greedy algorithm gives a 1/2 approximation to submodular maximization subject to a matroid constraint.

Thursday, November 14, 2019 — 4:00 PM EST

## Graphs and Matroids Seminar - Shayla Redlin

Title: Halfway to Rota's Basis Conjecture

 Speaker: Shayla Redlin Affiliation: University of Waterloo Room: MC 5501

Abstract:

Rota’s Basis Conjecture is that any rank-n matroid with n disjoint bases B_1, …, B_n has n disjoint transversal bases; a basis is transversal if it contains exactly one element from each B_i.

Thursday, November 14, 2019 — 3:00 PM EST

## Algebraic Combinatorics Seminar - Nick Early

Title: From weakly separated collections to matroid subdivisions

 Speaker: Nick Early Affiliation: Perimeter Institute for Theoretical Physics Room: MC 5417

Abstract:

We study arrangements of slightly skewed tropical hyperplanes, called blades, on the vertices of a hypersimplex $\Delta_{k,n}$.

Friday, November 8, 2019 — 3:30 PM EST

## Tutte Colloquium - Jim Geelen

Title: Circuit-hyperplane relaxation and matroid representation

 Speaker: Jim Geelen Affiliation: University of Waterloo Room: MC 5501

Abstract:

Relaxing a circuit-hyperplane in a representable matroid can destroy representability.

Thursday, November 7, 2019 — 4:00 PM EST

## Graphs and Matroids Seminar - Adam Brown

Title: Counting Pentagons in Triangle-free Binary Matroids

 Speaker: Adam Brown Affiliation: University of Waterloo Room: MC 5501

Abstract:

Every triangle-free graph with n vertices contains at most (n/5)^5 cycles of length five, and this value is attained by the balanced blowup of the 5-cycle.

Thursday, November 7, 2019 — 3:00 PM EST

## Algebraic Combinatorics Seminar - Kevin Purbhoo

Title: Two-colouring hypersurface complements in open Richardson varities

 Speaker: Kevin Purbhoo Affiliation: University of Waterloo Room: MC 5417

Abstract:

Given an algebraic hypersurface $H \subset \mathbb{R}^n$, we can always 2-colour the components of the complement $\mathbb{R}^n \setminus H$ such that adjacent components are of opposite colours.

Thursday, November 7, 2019 — 1:00 PM EST

## Algebraic Graph Theory Seminar - Chris Godsil

Title: Cospectral and strongly cospectral vertices

 Speaker: Chris Godsil Affiliation: University of Waterloo Room: MC 5479

Abstract:

If $a$ is a vertex in a graph with adjacency matrix $A$, the \textsl{walk module} generated by $a$ is the $A$-invariant subspace spanned by the vectors $A^re_a$, for $r\ge0$.

Friday, November 1, 2019 — 3:30 PM EDT

## Tutte Collouium - Luke Schaeffer

Title: A Quantum Query Complexity Trichotomy for Regular Languages

 Speaker: Luke Schaeffer Affiliation: University of Waterloo Room: MC 5501

Abstract:

We consider the quantum query complexity of regular languages and discover a surprising trichotomy: each regular language has query complexity either Theta(1), ~Theta(sqrt(n)) or Theta(n).

Friday, November 1, 2019 — 1:00 PM EDT

## Combinatorial Optimization Reading Group - Zishen Qu

Title: Maximizing non-monotone submodular functions

 Speaker: Zishen Qu Affiliation: University of Waterloo Room: MC 5417

Abstract:

Optimization of non-monotone submodular functions has applications in the maximum cut and maximum directed cut problems for graphs.

### November 2019

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