Amalgams of inverse semigroups and reversible two-counter machines

Emanuele Rodaro, Pedro V. Silva

We show that the word problem for an amalgam $[S_1,S_2;U,{\omega }_1,{\omega }_2]$ of inverse semigroups may be undecidable even if we assume $S_1$ and $S_2$ (and therefore $U$) to have finite $\m…