Corpus ID: 12027659

Counting and empty alternating pushdown automata ∗

  title={Counting and empty alternating pushdown automata ∗},
  author={K. Reinhardt},
We show that the class of context free languages CFL is not equal to ⊕1−PDA (= ⊕CFL), the class of languages, which are recognized by a nondeterministic oneway push-down automaton equipped with parity acceptance. Furthermore we show that LOG(⊕CFL) = ⊕AuxPDApt contains all languages, which can be recognized by a uniform weak unambiguous AC1-circuit introduced in [LR90a]. Therefore, it contains all languages, which can be recognized by a CREW -PRAM. We show, that L#Aux PDApt is contained in… Expand
Empty Alternation
We introduce the notion of empty alternation by investigating alternating automata which are restricted to empty their storage except for a logarithmically space-bounded tape before making anExpand


Hierarchies over the Context-Free Languages
It is shown, that a hierarchy can be characterized with alternating pushdown automata, which is expected to be strict in contrast to a hierarchy with alternating finite automata or alternating space bounded automata. Expand
Counting auxiliary pushdown automata and semi-unbounded arithmetic circuits
  • V. Vinay
  • Computer Science, Mathematics
  • [1991] Proceedings of the Sixth Annual Structure in Complexity Theory Conference
  • 1991
One of the highlights of the present work is an exact characterization of the important class DET, which is shown that DET is exactly the class of functions that can be computed as the difference between the outputs of two counting logspace machines. Expand
Alternation Bounded Auxiliary Pushdown Automata
The result is used to show that the hierarchy of classes of languages accepted by pushdown automata based on the number of alternations collapses at the second level of the hierarchy. Expand
Two applications of complementation via inductive counting
An errorless probabilistic algorithm is given for the undirected graph s-t connectivity problem that runs in O(log n) space and polynomial expected time, and it is shown that the class LOGCFL is closed under complementation. Expand
Problems Complete for +L
⊕L is the class of languages acceptable by logarithmic space bounded Turing machines that work nondeterministically and are equipped with parity-acceptance, i.e. an input word is accepted if and onlyExpand
On the Tape Complexity of Deterministic Context-Free Languages
A tape hardest deterministic context-free language is described and the best upper bound known on the tape complexity of (deterministic) context- free languages is (log(n) 2). Expand
Alternating Pushdown and Stack Automata
The classes of languages accepted by alternating pushdown automata, alternating stack Automata, and alternating nonerasing stack automata are characterized in terms of complexity classes defined by time bounded deterministic Turing machines. Expand
On Uniform Circuit Complexity
  • W. L. Ruzzo
  • Computer Science, Mathematics
  • J. Comput. Syst. Sci.
  • 1981
It is argued that uniform circuit complexity introduced by Borodin is a reasonable model of parallel complexity and that context-free language recognition is in NC, the class of polynomial size andPolynomial-in-log depth circuits. Expand
A very hard log space counting class
  • C. Àlvarez, Birgit Jenner
  • Mathematics, Computer Science
  • Proceedings Fifth Annual Structure in Complexity Theory Conference
  • 1990
It is demonstrated that span-L-functions can be computed in polynomial time if and only if P=NP=PH=P( Hash P), i.e if the class P(Hash P) and all the classes of thePolynomial-time hierarchy are contained in P. Expand
A Grammatical Characterization of Alternating Pushdown Automata
  • E. Moriya
  • Computer Science
  • Theor. Comput. Sci.
  • 1989
It is shown that the class of alternating context-free languages is equal to theclass of languages accepted by alternating pushdown automata. Expand