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Friday, March 29, 2019 1:00 pm - 1:00 pm EDT (GMT -04:00)

Combinatorial Optimization Seminar - Julian Romero Barbosa

Title: Using Lasserre Hierarchy for Graph Coloring  

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

Abstract:

In this talk, I will go over a technique introduced by Arora and Ge for coloring 3-colorable graphs having low threshold rank (i.e., graphs with few eigenvalues below certain negative constant).

Friday, March 29, 2019 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Distinguished Lecture - Bojan Mohar

Image of Professor Bojan Mohar

Title: Toward a Theory of Crossing-Critical Graphs

Speaker: Bojan Mohar
Affiliation: Simon Fraser University
Room: MC 5501

Abstract: 

The crossing number of a graph is defined as the minimum number of crossings of edges in a drawing of the graph in the plane. In his seminal 1970 paper Toward a Theory of Crossing Numbers, Tutte made a fundamental contribution by proving what is known today as the Hanani-Tutte Theorem.

Wednesday, April 3, 2019 4:30 pm - 4:30 pm EDT (GMT -04:00)

PMath/C&O Joint Colloquium - Ben Moore

Title: A proof of the Hell-Nešetřil Dichotomy via Siggers Polymorphisms

Speaker: Ben Moore
Affiliation: University of Waterloo
Room: MC 4020

Abstract:

In 2017, the constraint satisfaction dichotomy was proven via techniques from universal algebra. If we restrict this theorem to graphs, we get the Hell-Nešetřil Dichotomy, which is a statement about colouring graphs.

Thursday, April 4, 2019 4:00 pm - 4:00 pm EDT (GMT -04:00)

Continuous Optimization Seminar - Sina Baghal

Title: High dimensional probability: Estimation in high dimensions

Speaker: Sina Baghal
Affiliation: University of Waterloo
Room: MC 5417

Abstract:

In this talk, we discuss high dimensional estimation problems. The aim is to estimate some point x in a given ambient bounded space K using a small number of independent random observations.

Friday, April 5, 2019 3:30 pm - 3:30 pm EDT (GMT -04:00)

Tutte Colloquium - Maryam Fazel

Title: Online Competitive Algorithms for Resource Allocation

Speaker: Maryam Fazel
Affiliation: University of Washington
Room: MC 5501

Abstract:

In online optimization with budgets, the data in the optimization problem is revealed over time. At each step a decision variable needs to be set without knowing the future inputs, while there is a budget constraint that couples the decisions across time.

Thursday, April 11, 2019 4:00 pm - 4:00 pm EDT (GMT -04:00)

Continuous Optimization Seminar - Steve Vavasis

Title: Optimal detection of sparse principal components in high dimension

Speaker: Steve Vavasis
Affiliation: University of Waterloo
Room: MC 5417

Abstract:

I will present the paper with this title by Berthet and Rigollet (Ann. Stat., 41 (2013) 1780-1815, https://projecteuclid.org/download/pdfview_1/euclid.aos/1378386239). 

Thursday, April 18, 2019 4:00 pm - 4:00 pm EDT (GMT -04:00)

Continuous Optimization Seminar - Akshay Ramachandran

Title: Graph Sparsification by Effective Resistances

Speaker: Akshay Ramachandran
Affiliation: University of Waterloo
Room: MC 5417

Abstract:

We will discuss an application of the matrix concentration inequalities of Tropp to spectral sparsification of graphs.