Relations among simultaneous complexity classes of nondeterministic and alternating Turing machines

Shigeki Iwata, Takumi Kasai, Etsuro Moriya

Research output: Contribution to journalArticle


Ruzzo [Tree-size bounded alternation, J. Comput. Syst. Sci. 21] introduced the notion of tree-size for alternating Turing machines (ATMs) and showed that it is a reasonable measure for classification of complexity classes. We establish in this paper that computations by tree-size and space simultaneously bounded ATMs roughly correspond to computations by time and space simultaneously bounded nondeterministic TMs (NTMs). We also show that not every polynomial time bounded and sublinear space simultaneously bounded NTM can be simulated by any deterministic TM with a slightly increased time bound and a slightly decreased space bound simultaneously.

Original languageEnglish
Pages (from-to)267-278
Number of pages12
JournalActa Informatica
Issue number3
Publication statusPublished - 1993 Mar
Externally publishedYes


ASJC Scopus subject areas

  • Information Systems

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