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Abstract. We derive necessary and sufficient conditions for the Birget--Rhodes prefix expansion [BR1] of a monoid to be (weakly) left ample, thereby proving analogues of the results already obtained for the related Szendrei expansion by Fountain, Gomes and Gould [FGG] and Fountain and Gomes [FG]. As a corollary, we obtain conditions for the prefix expansion to be inverse.
AMS Subject Classification
(1991): 20M99
Keyword(s):
prefix expansion,
(weakly) left ample monoid,
inverse monoid
Received October 31, 2006, and in final form March 15, 2007. (Registered under 6450/2009.)
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