Contact Info
Combinatorics & Optimization
University of Waterloo
Waterloo, Ontario
Canada N2L 3G1
Phone: 519-888-4567, ext 33038
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Friday, May 29, 2020 — 3:30 PM EDT
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
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
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
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
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
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).