On the complexity of the word problem for finitely presented commutative semigroups.
We prove that the converse of Theorem 9 in "On generalized inverses in C*-algebras" by Harte and Mbekhta (Studia Math. 103 (1992)) is indeed true.
This paper deals with the decidability of semigroup freeness. More precisely, the freeness problem over a semigroup S is defined as: given a finite subset X ⊆ S, decide whether each element of S has at most one factorization over X. To date, the decidabilities of the following two freeness problems have been closely examined. In 1953, Sardinas and Patterson proposed a now famous algorithm for the freeness problem over the free monoids....
This paper deals with the decidability of semigroup freeness. More precisely, the freeness problem over a semigroup S is defined as: given a finite subset X ⊆ S, decide whether each element of S has at most one factorization over X. To date, the decidabilities of the following two freeness problems have been closely examined. In 1953, Sardinas and Patterson proposed a now famous algorithm for the freeness problem over the free monoids. In 1991, Klarner, Birget and Satterfield proved the undecidability...
This paper deals with the decidability of semigroup freeness. More precisely, the freeness problem over a semigroup S is defined as: given a finite subset X ⊆ S, decide whether each element of S has at most one factorization over X. To date, the decidabilities of the following two freeness problems have been closely examined. In 1953, Sardinas and Patterson proposed a now famous algorithm for the freeness problem over the free monoids....
If and are positive integers with and , then the setis a multiplicative monoid known as an arithmetical congruence monoid (or ACM). For any monoid with units and any we say that is a factorization length of if and only if there exist irreducible elements of and . Let be the set of all such lengths (where whenever ). The Delta-set of the element is defined as the set of gaps in : and the Delta-set of the monoid is given by . We consider the when is an ACM with...
It was shown in [7] that any right reversible, cancellative ordered semigroup can be embedded into an ordered group and as a consequence, it was shown that a commutative ordered semigroup can be embedded into an ordered group if and only if it is cancellative. In this paper we introduce the concept of -maher and -maher semigroups and use a technique similar to that used in [7] to show that any left reversible cancellative ordered or -maher semigroup can be embedded into an ordered group.