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

Events tagged with Faculty

Monday, March 8, 2021 — 11:30 AM EST

Title: Lexicographic products, wreath products, and generalisations

Speaker: Joy Morris
Affiliation: University of Lethbridge
Zoom: Contact Soffia Arnadottir

Abstract:

I will present a history and overview of some of the work that has been done on the lexicographic product of graphs, and related generalisations. The focus of my talk will be on the automorphism groups of such graphs, and the relationship to the wreath product of permutation groups.

Thursday, March 11, 2021 — 1:00 PM EST

Title: Equivalences of Wilson loop diagrams

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

Abstract:

I will talk about Wilson loop diagrams, explain a bit about what they are, and some of the combinatorial questions that come out of them, with a focus on when they are equivalent.  This is joint work with Susama Agarwala and Zee Fryer.

Friday, March 12, 2021 — 3:30 PM EST

Title: An approximate solution to a 2,079,471-point traveling salesman problem

Speaker: Bill Cook
Affliation: University of Waterloo
Zoom: Please email Emma Watson

Abstract:

Together with Keld Helsguan, we have found a TSP tour through the 3D positions of 2,079,471 stars. We discuss how linear programming allows us to prove the tour is at most a factor of 0.0000074 longer than an optimal solution. The talk will focus on the use of minimum cuts and GF(2) linear systems, to drive the cutting-plane method towards strong LP relaxations.

Thursday, March 25, 2021 — 1:00 PM EDT

Title: An Efficient Algorithm for Deciding the Vanishing of Schubert Polynomial Coefficients

Speaker: Colleen Robichaux
Affiliation: University of Illinois at Urbana-Champaign
Zoom: Contact Karen Yeats

Abstract:

 Schubert polynomials form a basis of all polynomials and appear in the study of cohomology rings of flag manifolds. The vanishing problem for Schubert polynomials asks if a coefficient of a Schubert polynomial is zero. We give a tableau criterion to solve this problem, from which we deduce the first polynomial time algorithm. These results are obtained from new characterizations of the Schubitope, a generalization of the permutahedron defined for any subset of the n x n grid. In contrast, we show that computing these coefficients explicitly is #P-complete. This is joint work with Anshul Adve and Alexander Yong.

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