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Mathematics & Statistics

Colloquia — Fall 2005

Wednesday, November 23, 2005

Title
Speaker


Time
Place
Sponsor

Quasi-stationarity and exit times for a size-dependent branching process
Göran Högnäs
Åbo Akademi University
Finland
3:00pm-4:00pm
PHY 118
Arunava Mukherjea

Abstract

A size-dependent branching model of the evolution of a single species population is introduced. The short-term behavior mimics the corresponding deterministic dynamical system very closely, but the branching model hits \(0\) eventually, i.e., the population goes extinct in contrast with the deterministic model which remains positive at all times. It turns out that the so-called quasi-stationary distribution (q.s.d.) of the branching model gives the right asymptotics. The q.s.d. approximates the attracting limit cycles of the deterministic system. I will also discuss some results, mainly due to Klebaner and Liptser, on the order of magnitude of the extinction times.

Tuesday, November 1, 2005

Title
Speaker


Time
Place
Sponsor

Some Problems on the Chromatic Number of Infinite graphs
Peter Komjath
Eotovos University
Budapest, Hungary
4:00pm-5:00pm
PHY 120
Vilmos Totik

Abstract

We survey some problems concerning the chromatic number of infinite graphs. A recent negative solution to Taylor's problems will be sketched.