On groups whose word problem is solved by a counter automaton

  • Authors:
  • Gillian Z. Elston;Gretchen Ostheimer

  • Affiliations:
  • Department of Mathematics, Hofstra University, Hempstead, NY;Department of Computer Science, Hofstra University, Hempstead, NY

  • Venue:
  • Theoretical Computer Science
  • Year:
  • 2004

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Abstract

We prove that a group G has a word problem that is accepted by a deterministic counter automaton with a weak inverse property if and only if G is virtually abelian. We extend this result to larger classes of groups by considering a generalization of finite state automata, counter automata and pushdown automata. Natural corollaries of our general result include a restricted version of Herbst's classification of groups for which the word problem is a one counter language and a new classification of automata that accept context-free word problems.