Seminar

Title: Razborov's flag algebras: Ten years on

Abstract:

Many of the classical results in extremal combinatorics were obtained by ingenious application of elementary techniques, such as induction and Cauchy-Schwarz inequality.

Title: Primal-dual and Lagrangian relaxation techniques for k-median

Abstract: We will develop primal-dual algorithms to obtain constant-factor approximations for the uncapacitated facility location problem.

Title: New algorithms for maximum disjoint paths based on tree-likeness

Abstract:

We study the classical NP-hard problems of finding maximum-size subsets from given sets of k terminal pairs that can be routed via edge-disjoint paths (MaxEDP) or node-disjoint paths (MaxNDP) in a given graph.

Title: Offline Assisted Group Key Exchange

Abstract:

This talk will focus on the problem of forward secrecy in group key exchange (GKE), where most of the participants remain offline until they wish to compute the key.

Title: Controllable graphs

Abstract: A graph is controllable if no eigenvector is orthogonal to the all-ones vector.

Title: Representable orientable matroids that are not real-representable

Abstract: In this talk we will have a brief introduction to oriented matroids and their relation to real-representability.

Title: Review of martingale theory, stochastic gradient descent, and adaptive line-line-search for stochastic optimization.

Abstract: With the rise of large data sets, practical algorithms for machine learning often use probability and statistics.

Title: A characterization of (p,q)-mixing when p/q < 4

Abstract: Let Hom(G,H) be the graph whose vertex set is the set of H-colourings of G, and two H-colourings f and g are adjacent if f differs from g in at most one vertex.

Title: The Shapiro-Shapiro Conjecture

Abstract:

Given four lines in 3-space, can you find a fifth line that intersects the other four? How many?

This is the smallest non-trivial example of a "Schubert problem". The answer, in this case, is not hard to compute: there are two such lines. Generalizations of this fact date back to 19th century work of Schubert.

Title: Naji’s characterization of circle graphs

Abstract: A circle graph is the intersection graph of chords of a circle.