January 2020

Thursday, January 9, 2020 — 1:00 PM EST

Title: Periodicity in Quantum Walks

Speaker: Chris Godsil Affiliation: University of Waterloo Room: MC 5417

Abstract:

Despite the title, quantum walks are, in general, not periodic. However they are, in general, periodic to any desired degree of accuracy.

Friday, January 10, 2020 — 1:00 PM EST

Title: Beating 3/2 for Approximating TSP in the Half-Integral Case

Speaker: Logan Grout Affiliation: University of Waterloo Room: MC 5417

Abstract:

In 2013, Schalekamp, Williamson, and van Zuylen conjectured that the integrality gap for the Subtour Polytope was attained on its half-integral vertices.

Thursday, January 16, 2020 — 1:00 PM EST

Title: Covers of Complete Bipartite Graphs

Speaker: Chris Godsil Affiliation: University of Waterloo Room: MC 5417

Abstract:

I will discuss antipodal distance-regular covers of complete bipartite graphs $K_{n,n}$. The index of such a cover is at most $n$.

Thursday, January 16, 2020 — 2:03 PM EST

Title: Electrical networks, random spanning trees, and matroids

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

Abstract:

This is a reprise of a survey talk I gave at the East Coast Combinatorics Conference in August 2019, and a variation of one I gave in the graphs and matroids seminar last year.

Friday, January 17, 2020 — 1:00 PM EST

Title: The Capacitated Survivable Network Design Problem

Speaker: Ishan Bansal Affiliation: University of Waterloo Room: MC 5417

Abstract:

The Capacitated Survivable Network Design Problem or Cap-SNDP models a network reinforcement problem where the network designer wants to find a minimum-cost set of reinforcements that protects the network from an adversary.

Thursday, January 23, 2020 — 2:30 PM EST

Title: Some places matroids appear in quantum field theory and some places I would like them to

Speaker: Karen Yeats Affiliation: University of Waterloo Room: MC 5417

Abstract:

I will discuss some places matroids have appeared in my work in quantum field theory, including some older work on numerator structure with Dirk Kreimer and some work in progress with Iain Crump on period identities.

Thursday, January 23, 2020 — 4:00 PM EST

Title: Uniformly generate graphs with given degrees rapidly

Speaker: Jane Gao Affiliation: University of Waterloo Room: MC 5479

Abstract:

I will survey the research on exact/approximate uniform generation of graphs with prescribed degrees.

Friday, January 24, 2020 — 1:00 PM EST

Title: On the Strong Nine Dragon Tree Conjecture

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

Abstract:

Nash-Williams forest covering theorem says that a graph decomposes into $k$ forests if and only if it has fractional arboricity at most $k$. In 2012 Mickeal Montassier, Patrice Ossona de Mendez, Andre Raspaud, and Xuding Zhu  proposed a significant strengthening of Nash-Williams Theorem, called the Strong Nine Dragon Tree Conjecture.

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