SPEAKER: Anna Ingólfsdóttir, BRICS, Aalborg University
DATE: Friday, 9 April 1999
PLACE and TIME: Room E3-209 at 14:00.
ABSTRACT:
In this talk, I shall show that the collection of identities which hold in the algebra N of the natural numbers with constant zero, and binary operations of sum and maximum is not finitely based. Moreover, I shall argue that, for every n, the equations in at most n variables that hold in that algebra do not form an equational basis. As a stepping stone in the proof of these results, several results of independent interest will be presented. In particular, explicit descriptions of the free algebras in the variety generated by N are offered. Such descriptions are based upon a geometric characterization of the equations that hold in N.
This talk is based upon joint work with Luca Aceto (BRICS, Aalborg) and Zoltan Esik (University of Szeged).