Removing Nondeterminism in Constant Height Pushdown Automata

Regulated Nondeterminism in PDAs: The Non-Regular Case

In this paper, we discuss pushdown automata which can make a nondeterministic decision only if the pushdown content forms a string that belongs to a given control language. We prove that if the control language is linear and non-regular, then the computational power of pushdown automata regulated in this way is increased to the power of Turing machines. Naturally, from the practical point of vi...

The Size-Cost of Boolean Operations on Constant Height Deterministic Pushdown Automata

We study the size-cost of boolean operations on constant height deterministic pushdown automata. We prove an asymptotically optimal exponential blow-up for union and intersection, as well as polynomial blow-up for complement.

Boolean Language Operations on Nondeterministic Automata with a Pushdown of Constant Height

We study the size-cost of Boolean operations on constant height nondeterministic pushdown automata, i.e. on pushdown automata with a constant limit on the size of the pushdown. For intersection, we show an exponential simulation and prove that the exponential blowup is necessary. For union, instead, we provide a linear trade-off while, for complement, we show a double-exponential simulation and...

Regulated Nondeterminism in Pushdown Automata

Symmetry Coincides with Nondeterminism for Time-Bounded Auxiliary Pushdown Automata1

We show that every language accepted by a nondeterministic auxiliary pushdown automaton in polynomial time (that is, every language in SAC 1 = Log(CFL)) can be accepted by a symmetric auxiliary pushdown automaton in polynomial time. Keywords-Symmetric Computation, Auxiliary Pushdown Automata, LogCFL, Reversible Computation