On the Power of One-Way Globally Deterministic Synchronized Alternating Turing Maschines and Multihead Automata

The alternating model augmented by a special simple form of communication among parallel processes-the so-called synchronized alternating (SA) model, provides (besides others) nice characterizations of the space complexity classes deened by nondeterministic Turing machines. The model investigated in this paper { globally deterministic synchronized alternating (GDSA) model, is obtained by a feasible restriction of nondeterminism in SA. It is known that it characterizes the deterministic counterparts of the nondeterministic space classes characterized by the SA model. In the paper we resume in the investigation of GDSA solving the open questions about the computational power of the one-way GDSA models. It is known that in the case of space{bounded Turing machine and multihead automata, the one-way SA models are equivalent to their two-way counterparts. We show that the same holds for GDSA models. The results contribute to the knowledge about the model and imply new characterizations of the deterministic space complexity classes.