On the decidability of the word problem for amalgamated free products of inverse semigroups

Abstract : We study inverse semigroup amalgams [S 1 , S 2 ; U ], where S 1 and S 2 are finitely presented inverse semigroups with decidable word problem and U is an inverse semigroup with decidable membership problem in S 1 and S 2. We use a modified version of Bennett's work on the structure of Schützenberger graphs of the R-classes of S 1 * U S 2 to state sufficient conditions for the amalgamated free products S 1 * U S 2 having decidable word problem.