**Date: **
17:00,
Tuesday, July 8, 2014

**Speaker: **
Anthony Widjaja Lin

**Venue: **TU Wien

The orbit problem is at the heart of symmetry reduction methods for

model checking concurrent systems. It asks whether two given

configurations in a concurrent system (represented as finite sequences

over some finite alphabet) are in the same orbit with respect to a

given finite permutation group (represented by their generators)

acting on this set of configurations. It is known that the problem is

in general as hard as the graph isomorphism problem, which is widely

believed to be not solvable in polynomial time. In this talk, we

consider the restriction of the orbit problem when the permutation

group is cyclic (i.e. generated by a single arbitrary permutation), an

important restriction of the orbit problem. The main result is a

linear-time algorithm for this subproblem.