Complete reducibility of systems of equations with respect to R

It is shown that the pseudovariety R of all finite R-trivial semigroups is completely reducible with respect to the canonical signature. Informally, if the variables in a finite system of equations with rational constraints may be evaluated by pseudowords so that each value belongs to the closure of...

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Bibliographic Details
Main Author: Almeida, Jorge (author)
Other Authors: Costa, José Carlos (author), Zeitoun, Marc (author)
Format: article
Language:eng
Published: 2007
Subjects:
Online Access:http://hdl.handle.net/1822/7669
Country:Portugal
Oai:oai:repositorium.sdum.uminho.pt:1822/7669
Description
Summary:It is shown that the pseudovariety R of all finite R-trivial semigroups is completely reducible with respect to the canonical signature. Informally, if the variables in a finite system of equations with rational constraints may be evaluated by pseudowords so that each value belongs to the closure of the corresponding rational constraint and the system is verified in R, then there is some such evaluation which is “regular”, that is one in which, additionally, the pseudowords only involve multiplications and ω-powers.