16.04.2012 Lecturer: Rok Požar (IMFM Ljubljana).

Title: On the split structure  of lifted  groups

Abstract: Let p: X˜ → X be a regular covering projection of connected graphs, and let CTp  denote the group of covering transformations. We present an algorithm for testing whether a given group of automorphisms G˜ ≤ Aut(X˜ ) lifts along p as a split extension of CTp  by G in the case when CTp  is abelian. Next, we present an algorithm for testing whether G lifts as a split extension such that some complement of CTp within G˜ has an orbit which is a section over a G-invariant set of vertices of X . Both algorithms are part of a larger package (implemented in MAGMA)  for doing computations with graph covers.  The implementation allows computing with graphs having semiedges.

Slides from the talk are available here: DOWNLOAD!