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Thursday, January 16, 2020 2:03 pm - 2:03 pm EST (GMT -05:00)

Algebraic Combinatorics Seminar - David Wagner

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 - 1:00 pm EST (GMT -05:00)

Combinatorial Optimization Reading Group - Ishan Bansal

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 - 2:30 pm EST (GMT -05:00)

Algebraic Combinatorics Seminar - Karen Yeats

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.

Friday, January 24, 2020 1:00 pm - 1:00 pm EST (GMT -05:00)

Combinatorial Optimization Reading Group - Ben Moore

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.

Thursday, January 30, 2020 2:30 pm - 2:30 pm EST (GMT -05:00)

Algebraic Combinatorics Seminar - Neal Madras

Title: Random Pattern-Avoiding Permutations

Speaker: Neal Madras
Affiliation: York University
Room: MC 5417

Abstract:

A "pattern of length k" is simply a permutation of {1,..,k}.  This pattern is said to be contained in a permutation of {1,...,N} (for N>k) if there is a subsequence of k elements of the (long) permutation that appears in the same relative order as the pattern.

Friday, January 31, 2020 1:00 pm - 1:00 pm EST (GMT -05:00)

Combinatorial Optimization Reading Group - Hong Zhou

Title: Network Design $s$-$t$ Effective Resistance

Speaker: Hong Zhou
Affiliation: University of Waterloo
Room: MC 5417

Abstract:

We consider a problem of designing a network with small $s$-$t$ effective resistance. In the problem, we are given an undirected graph $G=(V,E)$, two designated vertices $s,t \in V$, and a budget $k$.

Thursday, February 6, 2020 4:00 pm - 4:00 pm EST (GMT -05:00)

Graphs and Matroids Seminar - Richard Lang

Title: Minimum degree conditions for Hamilton cycles in hypergrahs

Speaker: Richard Lang
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

A classic result of Dirac states that a graph in which every vertex is connected to at least half of the other vertices contains a Hamilton cycle. How can we generalize Dirac's theorem to hypergraphs?