Semigroups, Automata and Languages

The word problem for κ-terms over LG

Speaker: 

José Carlos Costa (DMat-UM / CMat-UM)

Date: 

Friday, 22 March, 2013 - 14:30

Venue: 

Room S3 DCC-FCUP

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...

A visualisation package for the GAP computer algebra system

Speaker: 

Manuel Delgado (CMUP / DMat-FCUP)

Date: 

Monday, 21 January, 2013 - 15:30

Venue: 

Room M030 of the Mathematics Department, FCUP

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.

Incomplete Transition Complexity of Basic Operations on Regular Languages

Speaker: 

Eva Maia (CMUP / DCC-FCUP)

Date: 

Monday, 21 January, 2013 - 14:30

Venue: 

Room M030 of the Mathematics Department, FCUP

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...

Self-similar groups and automata: constructions, applications and open problems

Speaker: 

Daniele D'Angeli (UTAD)

Date: 

Friday, 30 November, 2012 - 14:30

Venue: 

Room M005 of the Mathematics Department, FCUP

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, rewriting systems, and biautomaticity

Speaker: 

Alan Cain (CMUP)

Date: 

Friday, 26 October, 2012 - 13:00

Venue: 

Room M005 of the Mathematics Department, FCUP

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...

Theory of Àtomata

Speaker: 

Janusz Brzozowski (University of Waterloo, ON, Canada)

Date: 

Wednesday, 3 October, 2012 - 14:30

Venue: 

: FC 029 (A2), DCC-FCUP

We show that every regular language defines a unique nondeterministic finite
...

Irreducibility of pseudovarieties of semigroups

Speaker: 

Jorge Almeida (FCUP / CMUP)

Date: 

Friday, 28 September, 2012 - 13:30

Venue: 

Room M030 of the Mathematics Department, FCUP

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...

Mal'cev products and the locality of pseudovarieties of semigroups

Speaker: 

Ana Escada (FCTUC / CMUC)

Date: 

Friday, 4 May, 2012 - 13:30

Venue: 

Room M007 of the Mathematics Department, FCUP

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...

Unary FA-presentable algebraic and relational structures

Speaker: 

Alan Cain (CMUP)

Date: 

Wednesday, 15 February, 2012 - 15:30

Venue: 

Room M007 of the Mathematics Department, FCUP

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...

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