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Friday, November 24, 2017 — 3:30 PM EST

Title: Nash-Williams

Speaker: Joseph Cheriyan
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

Crispin Nash-Williams was one of the founding professors of C&O. The talk will cover a small sample of his mathematical work, and also his association with C&O.

Thursday, November 23, 2017 — 3:30 PM EST

Title: Ramsey theory for biased graphs

Speaker: Peter Nelson
Affiliation:  University of Waterloo
Room: MC 5479

Abstract:

We discuss the unavoidable subgraphs of biased graphs whose underlying graph is a clique.

Thursday, November 23, 2017 — 1:30 PM EST

Title: Orientations, Pseudoforests, Flows, and the Densest Subgraph
 

Speaker: Markus Blumenstock
Affiliation: University of Mainz, Germany
Room: MC 6486

Abstract:

Given an undirected graph, consider the problem of finding an orientation such that the max-imum indegree is minimized. The Gabow-Westermann algorithm can solve it by exploiting the matroid structure of pseudoforests.

Wednesday, November 22, 2017 — 4:30 PM EST

Title: Sum-of-Squares Proofs in Optimization

Speaker: Mehdi Karimi
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

The old concept of sum-of-squares found its way into optimization and even machine learning. I will talk about this quickly evolving research area known as convex algebraic geometry.

Wednesday, November 22, 2017 — 4:00 PM EST

Title: Alternating Direction Method of Multipliers for the SDP Relaxation of the Quadratic Assignment Problem

Speaker: Henry Wolkowicz
Affiliation: University of waterloo
Room: MC 5479

Abstract:

The semidefinite programming (SDP) relaxation has proven to be extremely strong for many hard discrete optimization problems. This is in particular true for the quadratic assignment problem (QAP), arguably one of the hardest NP-hard discrete optimization problems.

Friday, November 17, 2017 — 3:30 PM EST

Title: Recent Advances in Frank-Wolfe Optimization

Speaker: Simon Lacoste-Julien
Affiliation: University of Montreal
Room: MC 5501

Abstract:

The Frank-Wolfe (FW) optimization algorithm has lately re-gained popularity thanks in particular to its ability to nicely handle the structured constraints appearing in machine learning and signal processing applications. However, its convergence rate is known to be slow (sublinear) when the solution lies at the boundary.

Thursday, November 16, 2017 — 3:30 PM EST

Title: Constructing cospectral graphs with a different switching

Speaker: Chris Godsil
Affiliation: University of Waterloo
Room: MC 6486

Abstract:

Many years ago, Brendan McKay and I introduced a construction of pairs of cospectral graphs, sometimes known as local switching. In the same paper we introduced a second switching technique which produces, as special cases, the smallest pair of cospectral graphs and the smallest pair of connected cospectral graphs.

Thursday, November 16, 2017 — 3:30 PM EST

Title: Convex drawings of complete graphs:  topology meets geometry

Speaker: Bruce Richter
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

A drawing D of the complete graph K(n) is the sphere is characterized by, for each isomorph J of K(5), D[J] is homeomorphic to one of the three rectilinear drawings of K(5).  Every drawing of K(n) in the plane with all edges straight-line segments is obviously convex.  Thus, convex drawings generalize planar point sets that are in general position. 

Wednesday, November 15, 2017 — 4:00 PM EST

Title: Proximal alternating linearized minimization for nonconvex and nonsmooth problems

Speaker: Stefan Sremac
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

We will be discussing the paper (having the same title) by Jerome Bolte, Shoham Sabach and Marc Teboulle.  We introduce a proximal alternating linearized minimization (PALM) algorithm for solving a broad class of nonconvex and nonsmooth minimization problems.

Friday, November 10, 2017 — 3:30 PM EST

Title: Coloring (cap even hole)-free graphs

Speaker: Shenwei Huang
Affiliation: Wilfrid Laurier University
Room: MC 5501

Abstract:

An even cycle of length 4 or more is called an even hole. A cap is a cycle of length at least 5 with exactly one chord and that chord creates a triangle with the cycle. In this talk we consider (cap, even hole)-free graphs, i.e., graphs that do not contain any even hole or cap as an induced subgraph.

Thursday, November 9, 2017 — 3:30 PM EST

Title: An Introduction to Discrete Quantum Walks

Speaker: Harmony Zhan
Affiliation: University of waterloo
Room: MC 6486

Abstract:

Thursday, November 9, 2017 — 3:30 PM EST

Title: An application of graph "recolouring”

Speaker: Ben Moore
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

I will prove that for any graph G, if there is an edge e such that G-e has less than (k-1)!/2 cycles of length zero mod k, then the chromatic number of G is less or equal to k.

Wednesday, November 8, 2017 — 4:00 PM EST

Title: A Fast Iterative Shrinkage-Thresholding Algorithm for Linear Inverse Problems 

Speaker: Nargiz Kalantarova
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

We will be discussing the paper (having the same title) by Amir Beck and Marc Teboulle. We consider the class of iterative shrinkage-thresholding algorithms (ISTA) for solving linear inverse problems arising in signal/image processing. This class of methods, which can be viewed as an extension of the classical gradient algorithm, is attractive due to its simplicity and thus is adequate for solving large-scale problems even with dense matrix data.

Friday, November 3, 2017 — 3:30 PM EDT

Title: How we solve linear programs

Speaker: Laurent Poirrier
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

Linear programming is one of the most fundamental tools in optimization, and its theoretical complexity is well understood. In practice though, things are quite different: Which types of problems can we really solve? What sizes? With what algorithms?

Thursday, November 2, 2017 — 3:30 PM EDT

Title: A short proof of a forgotten result

Speaker: Bertrand Guenin
Affiliation: University of Waterloo
Room: MC 4042

Abstract:

Wednesday, November 1, 2017 — 4:00 PM EDT

Title: A Stochastic Gradient Method with an Exponential Convergence Rate for Finite Training Sets

Speaker: Ryan Kinnear
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

We will be discussing the paper (having the same title) by Roux, Schmidt, and Bach.  The authors propose a new stochastic gradient method for optimizing the sum of
 a finite set of smooth functions, where the sum is strongly convex.


Friday, October 27, 2017 — 3:30 PM EDT

Title: Some matrix problems in quantum information science

Speaker: Chi-Kwong Li
Affiliation: College of William and Mary, IQC
Room: MC 5501

Abstract:

In this talk, we present  some matrix results and techniques in solving certain optimization problems arising  in quantum information science.

No quantum mechanics background is required.

Thursday, October 26, 2017 — 3:30 PM EDT

Title: Progress on Continuous Quantum Walks

Speaker: Chris Godsil
Affiliation: University of Waterloo
Roon: MC 6486

Abstract:

I will discuss the progress we’ve made in our work on continuous walks. I will start with old stuff (last November) and continue on to current stuff (this week).

Thursday, October 26, 2017 — 3:30 PM EDT

Title: Extended odd holes and their blockers

Speaker:

Ahmad Abdi

Affiliation: University of Waterloo
Room: MC 5479

Abstract:

Wednesday, October 25, 2017 — 4:00 PM EDT

Title: Coordinate Descent Algorithms

Speaker: Julian Romero
Affiliation: University of Waterloo
Room: MC 5479

Abstract:

We will be discussing the survey of Stephen J. Wright on coordinate descent algorithms. Coordinate descent algorithms solve optimization problems by successively performing approximate minimization along coordinate directions or coordinate hyperplanes. They have been used in applications for many years, and their popularity continues to grow because of their usefulness in data analysis, machine learning, and other areas of current interest.

Friday, October 20, 2017 — 3:30 PM EDT

Title: The Paulsen problem, continuous operator scaling, and smoothed analysis

Speaker: Tsz Chiu Kwok
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

The Paulsen problem is a basic open problem in operator theory: Given vectors u1, ..., un in Rd that are eps-nearly satisfying the Parseval's condition and the equal norm condition, is it close to a set of vectors v1, ..., vn in Rd that exactly satisfy the Parseval's condition and the
equal norm condition? Given u1,..., un, we consider the squared distance to the set of exact solutions.

Thursday, October 19, 2017 — 3:30 PM EDT

Title: Sequences: random, structured or something in between?

Speaker: Fan Chung Graham
Affiliation:

University of California, San Diego

Room:  MC 5501

Abstract:

There are many fundamental problems concerning sequences that arise in many areas of mathematics and computation.  Typical problems include finding or avoiding patterns; testing or validating various `random-like’ behavior; analyzing or comparing different statistics, etc.

Thursday, October 12, 2017 — 3:30 PM EDT

Title: A Short Introduction to Projective Geometry

Speaker: Chris Godsil
Affiliation: University of Waterloo
Room: MC 6486

Abstract:

Basically, see the title. I will be considering the real and complex cases mainly, because that is
what is needed in quantum physics.

Friday, October 6, 2017 — 3:30 PM EDT

Title: Enumeration in quantum algebras

Speaker: Jason Bell
Affiliation: University of Waterloo
Room: MC 5501

Abstract:

Many of the classical algebras that occur in algebraic geometry and other mathematical fields have natural quantizations; that is, one can deform the multiplication rule using a parameter q, which has the property that when we specialize q at 1 we recover the classical object.  As part of the general goal of understanding the representation theory of these rings, one often wants to understand the prime spectra of these algebras, that is, the collection of prime ideals in these rigs. 

Thursday, October 5, 2017 — 3:30 PM EDT

Title: RSKy Business

Speaker: Nathan Lindzey
Affiliation: University of Waterloo
Room: MC 6486

Abstract:

We sketch the Robinson-Schensted-Knuth algorithm, then use it to glimpse into the representation theory of some classical combinatorial objects.

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