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).

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