Contact Info
Combinatorics & Optimization
University of Waterloo
Waterloo, Ontario
Canada N2L 3G1
Phone: 519-888-4567, ext 33038
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Thursday, March 23, 2023 — 1:00 PM EDT
Title: Quasisymmetric varieties, excedances, and bases for the Temperley--Lieb algebra
| Speaker: | Lucas Gagnon |
| Affiliation: | York University |
| Location: | MC 6029 please contact Olya Mandelshtam for Zoom link |
Abstract: This talk is about finding a quasisymmetric variety (QSV): a subset of permutations which (i) is a basis for the Temperley--Lieb algebra TL_n(2), and (ii) has a vanishing ideal (as points in n-space) that behaves similarly to the ideal generated by quasisymmetric polynomials. While this problem is primarily motivated by classical (co-)invariant theory and generalizations thereof, the course of our investigation uncovered a number of remarkable combinatorial properties related to our QSV, and I will survey these as well.
Friday, March 24, 2023 — 3:30 PM EDT
Title: On the complexity of quantum partition functions
| Speaker: | David Gosset |
| Affiliation: | University of Waterloo |
| Location: | MC 5501 or contact Eva Lee for Zoom link |
Abstract: Quantum complexity theory has been intertwined with the study of quantum many-body systems ever since Kitaev's insight that computing their ground energies is an intractable quantum constraint satisfaction problem that is complete for a quantum generalization of NP.
Monday, March 27, 2023 — 8:00 PM EDT
Title: Inverse eigenvalue problem of a graph
| Speaker: | Jephian C.-H. Lin |
| Affiliation: | National Sun Yat-sen University |
| Location: | Please contact Sabrina Lato for Zoom link |
Abstract: We often encounter matrices whose pattern (zero-nonzero, or sign) is known while the precise value of each entry is not clear. Thus, a natural question is what we can say about the spectral property of matrices of a given pattern. When the matrix is real and symmetric, one may use a simple graph to describe its off-diagonal nonzero support.
Wednesday, March 29, 2023 — 2:30 PM EDT
Title: Distance-Regular and Distance-Biregular Graphs
| Speaker: | Sabrina Lato |
| Affiliation: | University of Waterloo |
| Location: | MC |
Abstract: For a given diameter d and valency k, what is the maximum number of vertices a k-regular graph of diameter d can have, and what graphs meet that bound? Although there is a straightforward counting argument to bound the number of vertices using the structural information, the problem of characterizing the graphs that meet the bound turns out to be a problem in algebraic graph theory, and helps gives rise to the notion of distance-regular graphs.