Reducibility vs. definability for pseudovarieties of semigroups

• Type: Article in International Scientific Journal
• Date: 2016

Authors

Almeida, J (Author) FCUP; Klima, O (Author) Other

Journal

Title: International Journal of Algebra and Computation

Vol. 26

Pages: 1483-1495

ISSN: 0218-1967

Publisher: World Scientific

Indexing

ISI Web of Knowledge - 0 Citations

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Other information

Authenticus ID: P-00M-75D

DOI: 10.1142/s0218196716500648

Abstract (EN): It is easy to show that a pseudovariety which is reducible with respect to an implicit signature sigma for the equation x = y can also be defined by sigma-identities. We present several negative examples for the converse using signatures in which the pseudovarieties are usually defined. An ordered example issue from the extended Straubing-Therien hierarchy of regular languages is also shown to provide a positive example for the inequality x <= y.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 13