[Facets-of-complexity] Invitation to Monday Lecture & Colloquium - October 22nd 2018

[Ita Brunke <i.brunke@inf.fu-berlin.de>]

You are cordially invited to our Monday Lecture & Colloquium on October 22nd at 14:15 h & 16:00 h at TU Berlin.

Location:

Room MA 041 - Ground Floor
Technische Universität Berlin
Straße des 17. Juni 136
10623 Berlin

Time: Monday, October 22nd - 14:15 h

Lecture: Alexander Fink (Queen Mary University London)

Title: Stiefel tropical linear spaces

Abstract:

As we tell our undergraduates, if K is a field, then there are a great number of different ways to describe a linear subspace of K^n. If the base is an algebraic object with less structure than a field, linear algebra becomes more subtle, and some of these descriptions cease to agree. One such setting is tropical geometry. Tropical geometers have reached consensus as to what the "correct" notion of tropical linear subspace is (one way to get it is by a vector of determinants). My subject will be one of the "wrong" descriptions, namely row spaces of matrices, which only produces a subset of the tropical linear spaces. Applications include generalisations of Mason's results from the '70s on presentations of transversal matroids, and a construction in the new area of tropical ideal theory.

This work is variously joint with Felipe Rinc\'on, Jorge Alberto Olarte, and Jeffrey and Noah Giansiracusa.

Coffee & Tea Break :

Room MA 316 - Third Floor

Time: Monday, October 22nd - 16:00 h

Colloquium: Akiyoshi Tsuchiya (Osaka University)

Title: Polyhedral characterizations of perfect graphs

Abstract:

Perfect graphs are important objects in graph theory. The perfect graphs include many important families of graphs, and serve to unify results relating colorings and cliques in those families. One of the most famous and most important results is the strong perfect graph theorem conjectured by Claude Berge and proved by Chudnovsky, Robertson and Thomas. This theorem characterizes perfect graphs. Our interest is to give other characterizations of perfect graphs. In this talk, we construct several lattice polytopes arising from a finite simple graph and characterize when the graph is perfect in terms of the lattice polytopes.

This talk is based on joint work with Takayuki Hibi and Hidefumi Ohsugi.