Two-way automata and length-preserving homomorphisms

  title={Two-way automata and length-preserving homomorphisms},
  author={Jean-Camille Birget},
  journal={Mathematical systems theory},
Closure underlength-preserving homomorphisms is interesting because of its similarity tonondeterminism. We give a characterization of NP in terms of length-preserving homomorphisms and present related complexity results. However, we mostly study the case of two-way finite automata: Let l.p.hom[n state 2DFA] denote the class of languages that are length-preserving homomorphic images of languages recognized byn-state 2DFAs. We give a machine characterization of this class. We show that any… CONTINUE READING