At the Jam Session on Semigroups and Automata that took place at CMUP in 2011, J. Almeida proposed the following question: Is LG tame? Here LG denotes the pseudovariety of local groups, consisting of all finite semigroups S such that eSe is a group for all idempotents e of S, and tameness is a...

My aim is to talk about some of my work concerning the development of GAP packages. Particular emphasis will be put on ongoing work concerning visualisation of GAP objects. Some of it is joint work with J. Mitchell, M. Pfeiffer and A. Egri-Nagy.

Descriptional complexity studies the measures of complexity of languages and operations. These studies are motivated by the need to have good estimates of the amount of resources required to manipulate the smallest representation for a given language. In general, having succinct objects will...

In this talk I will give an overview on the theory of self-similar groups. These groups act by automorphisms on a rooted tree, or, equivalently, are generated by (finite) automata. Self-similar groups have been used to find examples of groups with special and exotic properties. Moreover they have...

Plactic monoids have their origin in Schensted's algorithm for computing the length of the longest increasing or decreasing subsequence of a given sequence. Knuth later pointed out the monoid structure of Schensted's purely combinatorial ideas. Recently, Plactic monoids and their associated...

An atom of a regular language $L$ with $n$ (left) quotients is a non-empty
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We show that every regular language defines a unique nondeterministic finite
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We show that, for every pseudovariety of groups H, the pseudovariety consisting of all finite semigroups all of whose subgroups lie in H, is irreducible for join and the Mal'cev and semidirect products. This improves results of Margolis-Sapir-Weil and Rhodes-Steinberg. We further announce some...

The global of a pseudovariety of semigroups is the pseudovariety of semigroupoids it generates where its members are viewed as one-vertex semigroupoids. When the global of the pseudovariety is characterized by properties of the local semigroups of its semigroupoids, the pseudovariety is...

An automatic presentation or FA-presentation is a description of a relational structure using regular languages. Informally, in an FA-presentation, elements of the structure are represented by a regular language of abstract representatives, and each relation (of arity $n$, say) can be recognized...