Consider two consecutive moves, $m_{1}$ and $m_{2}$ , made by a two-pushdown automaton, M , whose pushdowns are denoted by $\pi_{1}$ and $\pi_{2}$ . If during $m_{1}$ M does not shorten $\pi_{i}$ , for some $i = 1, 2$ , while during $m_{2}$ it shortens $\pi_{i}$ , then M makes a turn in $\pi_{i}$ during $m_{2}$ . If M makes a turn in both $\pi_{1}$ and $\pi_{2}$ during $m_{2}$ , this turn is simultaneous . A two-pushdown automaton is one-turn if it makes no more than one turn in either of its pushdowns during any computation. A two-pushdown automaton is simultaneously one-turn if it makes either no turn or one simultaneous turn in its pushdowns during any computation. This paper demonstrates that every recursively enumerable language is accepted by a simultaneously one-turn two-pushdown automaton. Consequently, every recursively enumerable language is accepted by a one-turn two-pushdown automaton.
Simultaneously One-Turn Two-Pushdown Automata
Reprints and Corporate Permissions
Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?
To request a reprint or corporate permissions for this article, please click on the relevant link below:
Academic Permissions
Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?
Obtain permissions instantly via Rightslink by clicking on the button below:
If you are unable to obtain permissions via Rightslink, please complete and submit this Permissions form. For more information, please visit our Permissions help page.
Related research
People also read lists articles that other readers of this article have read.
Recommended articles lists articles that we recommend and is powered by our AI driven recommendation engine.
Cited by lists all citing articles based on Crossref citations.
Articles with the Crossref icon will open in a new tab.