In this paper an algorithm is presented that can be used to calculate the automorphism group of a finite transformation semigroup. The general algorithm employs a special method to compute the automorphism group of a finite simple semigroup. As an application of the algorithm, all the automorphism groups of semigroup of order at most 7 and of the multiplicative semigroups of some group rings ar...

We estimate the Bowen parameters and the Hausdorff dimensions of the Julia sets of expanding finitely generated rational semigroups. We show that the Bowen parameter is larger than or equal to the ratio of the entropy of the skew product map f̃ and the Lyapunov exponent of f̃ with respect to the maximal entropy measure for f̃ . Moreover, we show that the equality holds if and only if the generator...

The main result of the paper is the reduction of the problem of satisfiability of equations in free groups to the satisfiability of equations in free semigroups with anti-involution (SGA), by a non-deterministic polynomial time transformation. A free SGA is essentially the set of words over a given alphabet plus an operator which reverses words. We study equations in free SGA, generalizing seve...

In this paper we are concerned with the following question: for a semigroup S, what is the largest size of a subsemigroup T ≤ S where T has a given property? The semigroups S that we consider are the full transformation semigroups; all mappings from a finite set to itself under composition of mappings. The subsemigroups T that we consider are of one of the following types: left zero, right zero...