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Friday, November 22, 2019 1:00 pm - 1:00 pm EST (GMT -05:00)

Combinatorial Optimization Reading Group - Sharat Ibrahimpur

Title: Submodular function maximization via the multilinear relaxation and contention resolution schemes

Speaker: Sharat Ibrahimpur
Affiliation: University of Waterloo
Room: MC 5417

Abstract:

I will present a general framework for maximizing a nonnegative submodular set function $f$ subject to a variety of packing type constraints including multiple matroid constraints, knapsack constraints, and their intersections.

Friday, November 22, 2019 3:30 pm - 3:30 pm EST (GMT -05:00)

Tutte Colloquium - Aleksandr Kazachkov

Title: Disjunctive Cuts through the V-Polyhedral Lens

Speaker: Aleksandr Kazachkov
Affiliation: Polytechnique Montréal
Room: MC 5501

Abstract:

Cutting planes, or cuts, are a critical component of modern integer programming solvers, but existing cuts implemented in solvers are relatively simple compared to those in the literature. We discuss the primary reasons for this disparity, as well as our recently-proposed V-polyhedral framework for mitigating some of these difficulties encountered by prior "stronger" cuts.

Friday, November 29, 2019 3:30 pm - 3:30 pm EST (GMT -05:00)

Tutte Colloquium - Debbie Leung

Title: Incompressibility of classical distributions

Speaker: Debbie Leung
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

We prove a general, robust, single-letter lower bound on the achievable rate for ensembles of classical states, which holds even when Alice and Bob share free entanglement and allow a constant local error. 

Thursday, December 5, 2019 9:30 am - 9:30 am EST (GMT -05:00)

CompMath & CO Joint Seminar - Andreas Griewank

Title: How can we optimize nonsmooth objectives globally?

Speaker: Andreas Griewank
Affiliation: Humboldt University, Germany
Room: MC 5501

Abstract:

In machine learning objective functions that are only piecewise smooth and should be globally minimized abound. The standard method of dealing with them is to apply a stochastic gradient method disregarding the rare points of nonsmoothness and hoping for the best as far as global optimality of the computed solution is concerned.

Thursday, December 5, 2019 3:00 pm - 3:00 pm EST (GMT -05:00)

Algebraic Combinatorics Seminar - Krystal Guo

Title: Inverses of Trees

Speaker: Krystal Guo
Affiliation: Centre de Recherches Mathématiques & Université de Montréal
Room: MC 5417

Abstract:

A tree is invertible if and only if it has a perfect matching.

Godsil considers an invertible tree T and finds that the inverse of the adjacency matrix has entries in {0, ±1} and is the signed adjacency matrix of a graph which contains T.

Friday, December 6, 2019 3:03 pm - 3:03 pm EST (GMT -05:00)

Tutte Colloquium - Koray Karabina

Title: Biometric security: Design, implementation, and challenges

Speaker: Koray Karabina
Affiliation: Florida Atlantic University
Room: MC 5501

Abstract:

Biometric based cybersecurity technologies offer significant advantages in authentication, identification, and access control mechanisms.

Thursday, December 12, 2019 1:00 pm - 1:00 pm EST (GMT -05:00)

Algebraic Graph Theory Seminar - Olha Silina

Title: Graph covers with two new eigenvalues

Speaker: Olha Silina
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

I am going to talk about graph covers. If $Y$ is a cyclic cover of $X$, it turns out that $Y$ has the same spectrum as $X$ plus (possibly) some new eigenvalues. 

Thursday, December 12, 2019 3:00 pm - 3:00 pm EST (GMT -05:00)

Algebraic Combinatorics Seminar - Michael Borinsky

Title: OutFn, M_gn and renormalized topological field theory

Speaker: Michael Borinsky
Affiliation: Nikhef
Room: MC 5417

Abstract:

I will report on recent joint work with Karen Vogtmann on the Euler characteristic of Out(F_n) and the moduli space of graphs.