Dipartimento di Scienze Pedagogiche e Filosofiche

Università degli studi di di Cagliari

 

Mercoledì 10 febbraio, ore 16, aula 1C, Viale S. Vincenzo 57, il Prof. Tomasz Kowalski, terrà il seguente seminario:

 

We generalise in three different directions two well-known results in universal algebra. Grätzer, Lakser and Płonka proved that independent subvarieties V1,V2 of a variety V are disjoint and such that their join V1v V2 (in the lattice of subvarieties of V) is their direct product V1× V2. Jónsson and Tsinakis provided a partial converse to this result: if V is congruence permutable and V1, V2 are disjoint, then they are independent (and so V1 v V2= V1× V2). We show that: i) if V is subtractive, then Jónsson’s and Tsinakis’ result holds under some minimal assumptions; ii) if V satisfies some weakened permutability conditions, then disjointness implies a generalised notion of independence and V1 v V2 is the subdirect product of V1 and V2; iii) the same holds if V is congruence 3-permutable.

 

Gli incontri sono aperti a tutti gli interessati.

 

Francesco Paoli

Associate Professor of Logic

Dept. of Education, University of Cagliari

Via Is Mirrionis 1, 09123 Cagliari, Italy

Tel. No. 070.6757330

E-mail: paoli@unica.it