## University COVID-19 update

### Questions about buildings and services? Visit the list of Modified Services.

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

# Events - 2020

Friday, June 12, 2020 — 1:30 PM EDT

## Combinatorial Optimization Reading Group - Vishnu V. Narayan

Title: One Dollar Each Eliminates Envy

 Speaker: Vishnu V. Narayan Affiliation: McGill University Zoom: Contact Sharat Ibrahimpur

Abstract:

We study the fair division of a collection of $m$ indivisible goods amongst a set of $n$ agents. Whilst envy-free allocations typically do not exist in the indivisible goods setting, envy-freeness can be achieved if some amount of a divisible good (money) is introduced.

Thursday, June 11, 2020 — 2:30 PM EDT

## Algebraic Combinatorics Seminar - Steve Melczer

Title: An Upper Bound on Graphical Partitions

 Speaker: Steve Melczer Affiliation: UQAM/CRM Zoom Contact Karen Yeats

Abstract:

An integer partition is called graphical if it can be realized as the size-ordered degree sequence of a simple graph (with no loops or multiple edges).  In his 1736 paper on the Königsberg bridge problem, arguably the origin of graph theory, Euler gave a necessary condition for a partition to be graphical: its sum must be even.

Friday, June 5, 2020 — 3:30 PM EDT

## Distinguished Tutte Lecture - Lauren K. Williams

Title: Matroids, tropical geometry, and positivity

 Speaker: Lauren K. Williams Affiliation: Harvard University & Radcliffe Institute Zoom: Please email Emma Watson.

Abstract:

The theory of matroids -- a class of combinatorial objects which simultaneously generalize graphs as well as vectors in a vector space -- was pioneered by William Tutte in his 1948 PhD thesis. Matroids are also closely connected to the Grassmannian and the tropical Grassmannian.  In recent years, mathematicians and physicists have been exploring positive notions of all of these objects, finding applications to scattering amplitudes and shallow water waves.  In my talk I will give an introduction to matroids, tropical geometry, and positivity, and survey some of the beautiful results and applications.

Friday, June 5, 2020 — 1:00 PM EDT

## Combinatorial Optimization Reading Group - Cedric Koh

Title: A Strongly Polynomial Label-Correcting Algorithm for Linear Systems with Two Variables per Inequality

 Speaker: Cedric Koh Affiliation: London School of Economics and Political Science Zoom: Contact Sharat Ibrahimpur

Abstract:

In this talk, I will present a strongly polynomial label-correcting algorithm for solving the feasibility of linear systems with two variables per inequality. The algorithm is based on the Newton–Dinkelbach method for fractional combinatorial optimization, and extends previous work of Madani (2002).

Thursday, June 4, 2020 — 2:30 PM EDT

## Algebraic Combinatorics Seminar - Lukas Nabergall

Title: Weighted generating functions for weighted chord diagrams

 Speaker: Lukas Nabergall Affiliation: University of Waterloo Zoom: Contact Karen Yeats

Abstract:

Motivated by the universal property of the Connes-Kreimer Hopf algebra of rooted trees and Hopf subalgebras arising from so-called combinatorial Dyson-Schwinger equations, we introduce a class of two-variable recursive functional equations involving Hochschild 1-cocycle operators.

Friday, May 29, 2020 — 3:30 PM EDT

## Tutte Colloquium - Jane Gao

Title: Symmetry of random graphs

 Speaker: Jane Gao Affiliation: University of Waterloo Zoom: Please email Emma Watson

Abstract:

A graph is said asymmetric if its automorphism group contains only the identity permutation. Otherwise, it is said symmetric. In this talk we will survey symmetry of Erdos-Renyi random graphs, of random regular graphs, and of random graphs with moderate degree sequences.

Thursday, May 28, 2020 — 2:30 PM EDT

## Algebraic Combinatorics Seminar - Steph van Willigenburg

Title: The e-positivity of chromatic symmetric functions

 Speaker: Steph van Willigenburg Affiliation: University of British Columbia Zoom: Contact Karen Yeats

Abstract:

The chromatic polynomial was generalized to the chromatic symmetric function by Stanley in his seminal 1995 paper. This function is currently experiencing a flourishing renaissance, in particular the study of the positivity of chromatic symmetric functions when expanded into the basis of elementary symmetric functions, that is, e-positivity.

Thursday, May 21, 2020 — 2:30 PM EDT

## Algebraic Combinatorics Seminar - Mee Seong

Title: Nakajima quiver varietites and irreducible components of Springer fibers

 Speaker: Mee Seong Affiliation: United States Military Academy and Army Research Laboratory Zoom: Contact Karen Yeats

Abstract:

Springer fibers and Nakajima quiver varieties are amongst the most important objects in geometric representation theory. While Springer fibers can be used to geometrically construct and classify irreducible representations of Weyl groups, Nakajima quiver varieties play a key role in the geometric representation theory of Kac--Moody Lie algebras.

Friday, May 15, 2020 — 3:30 PM EDT

## Tutte Colloquium - Daniel Grier

Zoom (for information email emma.watson@uwaterloo.ca

Title: Permanent Hardness from Linear Optics

 Speaker: Daniel Grier Affiliation: University of Waterloo Location: Online (Zoom)

Abstract:

One of the great accomplishments in complexity theory was Valiant's 1979 proof that the permanent of a matrix is #P-hard to compute.  Subsequent work simplified Valiant's ideas and even began to recast them as problems in quantum computing.  In 2011, this culminated in a striking proof by Aaronson, based solely on quantum linear optics, of the #P-hardness of the permanent.

Thursday, May 14, 2020 — 10:00 AM EDT

## Algebraic Combinatorics Seminar - Oliver Schnetz

Title: Combinatorial masters in QED

 Speaker: Oliver Schnetz Affiliation: Friedrich-Alexander Universität Erlangen Zoom: Contact Karen Yeats

Abstract:

Calculations in perturbative QED (and also in QCD) use a reduction from Feynman integrals to `master integrals'. In general, the reduction to master integrals is performed by excessive use of computer power.

Friday, May 8, 2020 — 3:30 PM EDT

## Tutte Colloquium - Ricardo Fukasawa

Zoom (for information email emma.watson@uwaterloo.ca

Title: Hardness of set-partitioning formulation for the vehicle routing problem with stochastic demands

 Speaker: Ricardo Fukasawa Affiliation: University of Waterloo Location: Online (Zoom)

Abstract:

The vehicle routing problem considers the cheapest way to serve a set of customers using a fixed set of vehicles. When a vehicle serves a customer, it picks up its demand which is given as an input, and the total demand picked up cannot exceed the vehicle’s capacity. This classical combinatorial optimization problem combines aspects of routing (like a traveling salesman problem) and packing (like a knapsack problem).

Friday, March 13, 2020 — 3:30 PM EDT

## CANCELLED Tutte Colloquium - Nicolas Trotignon

Title: Widths in even-hole-free graphs

 Speaker: Nicolas Trotignon Affiliation: École Normale Supérieure de Lyon Room: MC 5501

Abstract:

Historically, the study of even-hole-free graphs is motivated by the analogy with perfect graphs. The decomposition theorems that are known for even-hole-free graphs are seemingly more powerful than the ones for perfect graphs: the basic classes and the decompositions are more restricted.

Friday, March 13, 2020 — 1:00 PM EDT

## Combinatorial Optimization Reading Group - Harry Sivasubramaniam

Title:

 Speaker: Harry Sivasubramaniam Affiliation: University of Waterloo Room: MC 5417

Abstract:

Differential privacy is about preserving an individuals privacy while maintaining utility in the context of data analysis.

Thursday, March 12, 2020 — 4:00 PM EDT

## Graphs and Matroids Seminar - Luke Postle

Title: Improving the general upper bound for Hadwiger's conjecture

 Speaker: Luke Postle Affiliation: University of Waterloo Room: MC 5479

Abstract:

In 1943, Hadwiger conjectured that every K_t-minor-free graph has chromatic number at most t-1.

Thursday, March 12, 2020 — 2:30 PM EDT

## Algebraic Combinatorics Seminar - David Wagner

Title: Proof of the monotone column permanent conjecture

 Speaker: David Wagner Affiliation: University of Waterloo Room: MC 5417

Abstract:

In 1993, Jim Haglund conjectured the following.  If  A  is a  square matrix of real numbers which are weakly decreasing down each column, and J is the all-ones matrix of the same size, then the permanent of the matrix xJ+A is a polynomial with only real roots.

Tuesday, March 10, 2020 — 8:42 AM EDT

## Tutte Colloquium - François Bergeron

Title: Rectangular Catalan Algebraic Combinatorics

 Speaker François Bergeron Affiliation LACIM - Université du Québec à Montréal Room MC 5501

Abstract:

The enumeration of Dyck-like lattice paths in a m x n rectangle has a long and fruitful history culminating in Bizley-Grossman’s formula (1954). We will discuss how it is natural to extend this formula to weighted enumeration, with parameters accounting for such statistics as area; and to consider parking-function analogs.

Friday, March 6, 2020 — 3:30 PM EST

## Tutte Colloquium - Peter Nelson

Title: Binary Submatroids

 Speaker: Peter Nelson Affiliation: University of Waterloo Room: MC 5501

Abstract:

A binary matroid can be thought of as a set of nonzero binary vectors.

Friday, March 6, 2020 — 1:00 PM EST

## Combinatorial Optimization Reading Group - Matt Gerstbrein

Title: Recognizing slack matrices

 Speaker: Matt Gerstbrein Affiliation: University of Waterloo Room: MC 5417

Abstract:

This week, we will be discussing the topic of slack matrices. Slack matrices arise in the context of lifts of polytopes, where, given a polytope P, we can characterize the existence of a lift of P of a given size in terms of properties of an associated slack matrix.

Thursday, March 5, 2020 — 2:30 PM EST

## Algebraic Combinatorics Seminar - Matt Szczesny

Title: Combinatorial Hall algebras

 Speaker: Matt Szczesny Affiliation: Boston University Room: MC 5417

Abstract:

The Hall algebra of a finitary category is an associative (and sometimes Hopf) algebra whose structure constants count the number of extensions between objects.

Thursday, March 5, 2020 — 1:00 PM EST

## Algebraic Graph Theory Seminar - Soffia Arnadottir

Title: Strongly cospectral vertices in cubelike graphs

 Speaker: Soffia Arnadottir Affiliation: University of Waterloo Room: MC 5417

Abstract:

A cubelike graph is a Cayley graph of the elementary abelian 2-group. Two vertices in a graph are strongly copsectral if they are cospectral and parallel.

Wednesday, March 4, 2020 — 2:00 PM EST

## Graphs and Matroids Seminar - Rose McCarty

Title: Vertex-minors and sparsity

 Speaker: Rose McCarty Affiliation: University of Waterloo Room: MC 5479

Abstract:

We discuss an ongoing project with Jim Geelen and Paul Wollan to describe the structure of graph classes excluding a vertex-minor.

Tuesday, March 3, 2020 — 1:15 PM EST

## Continuous Optimization Seminar - Naomi Graham

Title: Introduction to Monotone Operators

 Speaker: Naomi Graham Affiliation: University of Waterloo Room: MC 5501

Abstract:

This talk will be an entry level introduction to the theory of monotone operators as they are presented in Bauschke and Combette’s Convex Analysis and Monotone Operator Theory in Hilbert Spaces.

Friday, February 28, 2020 — 3:30 PM EST

## Tutte Colloquium - Francisco Rodríguez-Henríquez

Title: Parallel strategies for SIDH: towards computing SIDH twice as fast

 Speaker: Francisco Rodríguez-Henríquez Affiliation: CINVESTAV-IPN Room: MC 5501

Abstrtact:

Over the last ten years, there has been an intense research effort to find hard mathematical problems that would be presumably hard to solve by a quantum attacker and at the same time could be used to build reasonably efficient public-key cryptoschemes.

Friday, February 28, 2020 — 1:00 PM EST

## Combinatorial Optimization Reading Group - Sean Kafer

Title: An Introduction to the Circuits of Polyhedra, The Circuit Diameter, and Their Applications

 Speaker: Sean Kafer Affiliation: University of Waterloo Room: MC 5417

Abstract:

The combinatorial diameter of a polyhedron P is the maximum value of a shortest path between two vertices of P, where the path moves along edges of P. Its study is motivated largely by its implications on the running time of the Simplex algorithm.

Thursday, February 27, 2020 — 4:00 PM EST

## Graphs and Matroids Seminar - Farbod Yadegarian

Title: Excluding an asymmetric group labelled graph

 Speaker: Farbod Yadegarian Affiliation: University of Waterloo Room: MC 5479

Abstract:

There are several models of group labelled graphs. In the simpler, undirected model, for an abelian group Γ, every edge e receives a label γ(e) in Γ.

## Pages

### January 2021

S M T W T F S
27
28
29
30
31
1
2
3
5
6
7
8
9
10
12
13
16
17
19
20
23
24
26
27
30
31
1
2
3
4
5
6
1. 2021 (45)
1. May (5)
2. April (9)
3. March (13)
4. February (8)
5. January (10)
2. 2020 (119)
1. December (5)
2. November (12)
3. October (12)
4. September (12)
5. August (11)
6. July (17)
7. June (11)
8. May (6)
9. March (11)
10. February (11)
11. January (11)
3. 2019 (167)
4. 2018 (136)
5. 2017 (103)
6. 2016 (137)
7. 2015 (136)
8. 2014 (88)
9. 2013 (48)
10. 2012 (39)
11. 2011 (36)
12. 2010 (40)
13. 2009 (40)
14. 2008 (39)
15. 2007 (15)