We look at stateless multihead finite automata in their two-way and one-way, deterministic and nondeterministic variations. The transition of a k-head automaton depends solely on the symbols currently scanned by its k heads, and every such transition moves each head one cell left or right, or instructs it to stay. We show that stateless (k + 4)-head two-way automata are more powerful than stateless k-head two-way automata. In the one-way case, we prove a tighter result: stateless (k + 1)-head one-way automata are more powerful than stateless k-head one-way automata. Finally, we show that the emptiness problem for stateless 2-head two-way automata is undecidable.

Original languageEnglish
Pages (from-to)581-593
Number of pages13
JournalTheoretical Computer Science
Volume411
Issue number3
DOIs
StatePublished - 6 Jan 2010

    Research areas

  • Multihead automata, Stateless automata

    Scopus subject areas

  • Theoretical Computer Science
  • Computer Science(all)

ID: 41141806