Department of Mathematics, TUCS—Turku Centre for Computer Science, University of Turku, Turku FIN-20014, Finland
Abstract:
We shall show that it is decidable for binary instances of the Post Correspondence Problem whether the instance has an infinite solution. In this context, a binary instance (h,g) consists of two morphisms h and g with a common two element domain alphabet. An infinite solution ω is an infinite word ω=a1a2… such that h(ω)=g(ω). This problem is known to be undecidable for the unrestricted instances of the Post Correspondence Problem.