On the Power of Randomized Pushdown Automata
DLT '01 Revised Papers from the 5th International Conference on Developments in Language Theory
On the power of randomized multicounter machines
Theoretical Computer Science - Insightful theory
Pushdown automata and multicounter machines, a comparison of computation modes
ICALP'03 Proceedings of the 30th international conference on Automata, languages and programming
On probabilistic pushdown automata
Information and Computation
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Properties of probabilistic as well as ``probabilistic plus nondeterministic'''' pushdown automata and auxiliary pushdown automata are studied. These models are analogous to their counterparts with nondeterministic and alternating states. Complete characterizations in terms of well-known complexity classes are given for the classes of languages recognized by polynomial time-bounded, logarithmic space-bounded auxiliary pushdown automata with probabilistic states and with ``probabilistic plus nondeterministic'''' states. Also, complexity lower bounds are given for the classes of languages recognized by these automata with unlimited running time. It follows that, by fixing an appropriate mode of computation, the difference between classes of languages such as P and PSPACE, NL and SAC^1, PL and Diff_