منابع مشابه
Computing LOGCFL certi#cates
The complexity class LOGCFL consists of all languages (or decision problems) which are logspace reducible to a context-free language. Since LOGCFL is included in AC, the problems in LOGCFL are highly parallelizable. By results of Ruzzo (JCSS 21 (1980) 218), the complexity class LOGCFL can be characterized as the class of languages accepted by alternating Turing machines (ATMs) which use logarit...
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Deciding the equivalence of regular expressions is a fundamental problem of theoretical computer science. On one hand, there are several decision procedures to solve this problem. On the other hand, there are several axiomatisations of the equivalence of regular expression. The axiomatisations are proved to be complete and the proofs consists of showing that each steps of a decision procedure c...
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Systems of polynomial equations with coefficients over a field K can be used to concisely model combinatorial problems. In this way, a combinatorial problem is feasible (e.g., a graph is 3colorable, hamiltonian, etc.) if and only if a related system of polynomial equations has a solution over the algebraic closure of the field K. In this paper, we investigate an algorithm aimed at proving combi...
متن کاملThe Descriptive Complexity Approach to LOGCFL
Building upon the known generalized-quantifier-based first-order characterization of LOGCFL, we lay the groundwork for a deeper investigation. Specifically, we examine subclasses of LOGCFL arising from varying the arity and nesting of groupoidal quantifiers. Our work extends the elaborate theory relating monoidal quantifiers to NC and its subclasses. In the absence of the BIT predicate, we reso...
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Today we continue with some additional aspects of quantifier elimination. We will then recall the Positivstellensatz and its relations with semidefinite programming. After introducing copositive matrices, we present Pólya’s theorem on positive forms on the simplex, and the associated relaxations. Finally, we conclude with an important result due to Schmüdgen about representation of positive pol...
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ژورنال
عنوان ژورنال: Theoretical Computer Science
سال: 2002
ISSN: 0304-3975
DOI: 10.1016/s0304-3975(01)00108-6