The cost of being coBuchi is nonlinear
Abstract
It is well known, and easy to see, that not each nondeterministic Buchi automaton on infinite words can be simulated by a nondeterministic coBuchi automaton. We show that in the cases when such a simulation is possible, the number of states needed for it can grow nonlinearly. More precisely, we show a sequence of  as we believe, simple and elegant  languages which witness the existence of a nondeterministic Buchi automaton with n states, which can be simulated by a nondeterministic coBuchi automaton, but cannot be simulated by any nondeterministic coBuchi automaton with less than c*n^{7/6} states for some constant c. This improves on the best previously known lower bound of 3(n1)/2.
 Publication:

arXiv eprints
 Pub Date:
 June 2009
 arXiv:
 arXiv:0906.0072
 Bibcode:
 2009arXiv0906.0072M
 Keywords:

 Computer Science  Formal Languages and Automata Theory
 EPrint:
 12 pages, 4 figures