2001/03/26 by Volker Diekert, Claudio Gutierrez, Diekert, Volker +3 · 2 citations
Computer Science · #Data Structures and Algorithms (cs.DS) #F.2.2 #F.4 #FOS: Computer and information sciences #Logic in Computer Science (cs.LO) #cs.DS #cs.LO
paper · pdf · doi:10.48550/arxiv.cs/0103018
45 pages. LaTeX source
arxiv created 2001/03/26 · arxiv updated 2009/11/30
It is known that the existential theory of equations in free groups is decidable. This is a famous result of Makanin. On the other hand it has been shown that the scheme of his algorithm is not primitive recursive. In this paper we present an algorithm that works in polynomial space, even in the more general setting where each variable has a rational constraint, that is, the solution has to respect a specification given by a regular word language. Our main result states that the existential theory of equations in free groups with rational constraints is PSPACE-complete. We obtain this result as a corollary of the corresponding statement about free monoids with involution.