#
Monday Lecture and Colloquium

**Monday, November 12, 2012**

Freie Universität Berlin

Institut für Informatik

Takustraße 9

14195 Berlin Berlin

room 005

** Lecture - 14:15**

###
Bernard Chazelle - Princeton University and College de France

###
The Surprising Dynamics of Influence Systems

*Abstract:*

Imagine a group of interacting agents (eg, people, computers, birds, bacteria) subject to the attracting influence of the agents with which they communicate. Assume further that each agent is entitled to its own, distinct algorithm for deciding whom to listen to when.

The communication graph thus evolves endogenously in arbitrarily complex ways. We show that such an "influence system" is almost surely convergent if the communication is bidirectional and asymptotically periodic in general.

This suggests that social networks are more conducive to consensus
than are older media like radio, tv, and newspapers. The proof introduces a technique of "algorithmic renormalization"likely to be of broader interest.

** Colloquium - 16:00**

### Balazs Keszegh - Budapest

### Non-crossing covering paths for planar point sets

*Abstract:*

Given a set of points, a covering path is a directed polygonal
path that visits all the points. If no three points are collinear, any
covering path (self-crossing or non-crossing) needs at least n/2
segments.

In both cases n-1 straight line segments obviously suffice. If the
path can be self-crossing, then it is known that there exists a path
with only n/2+O(n/log(n)) segments. The non-crossing case seems to be
harder, we show an algorithm that finds a non-crossing covering path
with at most (1-d)n segments, where d is a small constant.

joint work with Daniel Gerbner

Letzte Aktualisierung:
29.10.2012