Groups synchronizing a transformation of non-uniform kernel
Araújo, João; Bentz, Wolfram; Cameron, Peter
Theoretical Computer Science, 498 (2013), 1--9
http://dx.doi.org/10.1016/j.tcs.2013.06.016 (preprint - http://arxiv.org/pdf/1205.0682v1)
Suppose that a deterministic finite automata A=(Q,?)A=(Q,?) is such that all but one letters from the alphabet ? act as permutations of the state set Q and the exceptional letter acts as a transformation with non-uniform kernel. Which properties of the permutation group G generated by the letters acting as permutations ensure that A becomes a synchronizing automaton under every possible choice of the exceptional letter (provided the exceptional letter acts as a transformation of non-uniform kernel)? Such permutation groups are called almost synchronizing. It is easy to see that an almost synchronizing group must be primitive; our conjecture is that every primitive group is almost synchronizing.
Clearly every synchronizing group is almost synchronizing. In this paper we provide two different methods to find non-synchronizing, but almost synchronizing groups. The infinite families of examples provided by the two different methods have few overlaps.
The paper closes with a number of open problems on group theory and combinatorics.