A NOTE ON REBOUND TURING MACHINES

Abstract

This paper continues the investigation of rebound Turing machines (RTM's). We first investigate a relationship between the accepting powers of simple one-way 2-head finite automata and simultaneously space-bounded and leaf-size bounded alternating RTM's, and show that for any functions L(n) and Z(n) such that L(n)Z(n)=o( log n) and [Formula: see text], simple one-way 2-head finite automata are incomparable with simultaneously L(n) space-bounded and Z(n) leaf-size bounded alternating RTM's. We then investigate a relationship between Las Vegas and determinism for space-bounded RTM's, and show that there is a language accepted by a Las Vegas rebound automaton, but not accepted by any weakly o( log log n) space-bounded deterministic RTM. This is the first separation result between Las Vegas and determinism for space-bounded computing models over strings.