English

Modifying the upper bound on the length of minimal synchronizing word

Discrete Mathematics 2014-03-24 v7

Abstract

A word ww is called synchronizing (recurrent, reset, magic, directable) word of deterministic finite automaton (DFA) if ww sends all states of the automaton to a unique state. In 1964 Jan \v{C}erny found a sequence of n-state complete DFA possessing a minimal synchronizing word of length (n1)2(n-1)^2. He conjectured that it is an upper bound on the length of such words for complete DFA. Nevertheless, the best upper bound (n3n)/6(n^3-n)/6 was found almost 30 years ago. We reduce the upper bound on the length of the minimal synchronizing word to n(7n2+6n16)/48n(7n^2+6n-16)/48. An implemented algorithm for finding synchronizing word with restricted upper bound is described. The work presents the distribution of all synchronizing automata of small size according to the length of an almost minimal synchronizing word.

Keywords

Cite

@article{arxiv.1104.2409,
  title  = {Modifying the upper bound on the length of minimal synchronizing word},
  author = {A. N. Trahtman},
  journal= {arXiv preprint arXiv:1104.2409},
  year   = {2014}
}

Comments

This paper has been withdrawn by the author. Key Lemma 3 is wrong, the statement of the paper was not proved