John C. Meakin

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Birget, J.-C., SW. Margolis and J.C. Meakin, The word problem for inverse monoids presented by one idempotent relator, Theoretical Computer Science 123 (1994) 2733289. We study inverse monoids presented by a finite set of generators and one relation e= I, where e is a word representing an idempotent in the free inverse monoid, and 1 is the empty word. We(More)
We investigate the complexity of algorithmic problems on finitely generated subgroups of free groups. Margolis and Meakin showed how a finite monoid Synt(H) can be canonically and effectively associated with such a subgroup H. We show that H is pure (that is, closed under radical) if and only if Synt(H) is aperiodic. We also show that testing for this(More)
We prove that the word problem for the free product with amalgamation S U T of monoids can be undecidable, even when S and T are nitely presented monoids with word problems that are decidable in linear time, the factorization problems for U in each of S and T , as well as other problems, are decidable in polynomial time, and U is a free nitely generated(More)
We study a class of inverse monoids of the form M = InvX | w = 1, where the single relator w has a combinatorial property that we call sparse. For a sparse word w, we prove that the Schützenberger complex of the identity of M has a particularly nice topology. We analyze the manner in which the Schützenberger complex is constructed using an iterative(More)
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