Proceedings of IEEE 9th Annual Conference on Structure in Complexity Theory

28 June-1 July 1994

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Displaying Results 1 - 25 of 38
  • Complexity theory and genetics

    Publication Year: 1994, Page(s):383 - 395
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1082 KB)

    We introduce a population genetics model in which the operators are effectively computable-computable in polynomial time on probabilistic Turing machines. We shall show that in this model a population can encode easily large amount of information from environment into genetic code. Then it can process the information as a parallel computer. More precisely, we show that it can stimulate polynomial ... View full abstract»

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  • Collapsing degrees in subexponential time

    Publication Year: 1994, Page(s):367 - 382
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1253 KB)

    We show that there are subexponential deterministic time classes that have collapsing degrees. In particular, we prove the following: Let t be any effectively superpolynomial time bound. Then there is a set A/spl isin/DTIME(t) such that every set B/spl isin/deg/sub msup p/(A) is p-isomorphic to A.<<ETX>> View full abstract»

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  • Generalized CNF satisfiability problems and non-efficient approximability

    Publication Year: 1994, Page(s):356 - 366
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (901 KB)

    We use variants of the generalized CNF satisfiability problems SAT(S) of T.J. Schhaefer (1978) to characterize the efficient approximability of a number of basic NP and PSPACE-hard optimization problems in the literature. In contrast with the recent results, none of our proofs make use of interactive proof systems or of probabilistically checkable debate systems. In particular assuming P/spl ne/NP... View full abstract»

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  • On the isomorphism problem for weak reducibilities

    Publication Year: 1994, Page(s):338 - 355
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1902 KB)

    The isomorphism conjecture states that all NP-complete sets are polynomial-time isomorphic while the encrypted complete set conjecture states that there is a p-one-way function f and an NP-complete set A such that A and f(A) are not polynomial-time isomorphic. We investigate these two conjectures for reducibilities weaker than polynomial-time. We show that: 1. Relative to reductions computed by on... View full abstract»

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  • The complexity of learning with queries

    Publication Year: 1994, Page(s):324 - 337
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1181 KB)

    We survey recent research concerning the qualitative complexity of Angluin's (1993) model of learning with queries. In this model, there is a learner that tries to identify a target concept by means of queries to a teacher. Thus, the process can be naturally formulated as an oracle computation. Among the results we review there are: characterizations of the power of different learning protocols by... View full abstract»

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  • The complexity of optimal queueing network control

    Publication Year: 1994, Page(s):318 - 322
    Cited by:  Papers (11)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (607 KB)

    We consider the classical problem of optimal control (routing and sequencing) of a network of queues. We prove that this problem is EXP-complete and, therefore, provably intractable. Similar results are established for restricted versions of the problem. A weaker result is also established for the restless bandit problem.<<ETX>> View full abstract»

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  • Multi-prover encoding schemes and three-prover proof systems

    Publication Year: 1994, Page(s):308 - 317
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (961 KB)

    Suppose two provers agree in a polynomial p and want to reveal a single value y=p(x) to a verifier where m is chosen arbitrarily by the verifier. Whereas honest provers should be able to agree on any polynomial p the verifier wants to be sure that with any (cheating) pair of provers the value y he receives is a polynomial function of x. We formalize this question and introduce multi-prover (quasi-... View full abstract»

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  • Towards the parallel repetition conjecture

    Publication Year: 1994, Page(s):304 - 307
    Cited by:  Papers (6)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (269 KB)

    We consider the behavior of the error probability of a two-prover one-round interactive protocol repeated n times in parallel. We point out the connection of this problem with the density form of Hales-Jewett's theorem in Ramsey theory. This allows us to show that the error probability converges to 0 as n/spl rarrspl infin/.<<ETX>> View full abstract»

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  • Alternation in interaction

    Publication Year: 1994, Page(s):294 - 303
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (903 KB)

    We study competing-prover one-round interactive proof systems. We show that one-round proof systems in which the first prover is trying to convince a verifier to accept and the second prover is trying to make the verifier reject recognized languages in NEXPTIME, and, with restrictions on communication and randomness, languages in NP. We extended the restricted model to an alternating sequence of k... View full abstract»

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  • Random debaters and the hardness of approximating stochastic functions

    Publication Year: 1994, Page(s):280 - 293
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1386 KB)

    A random probabilistically checkable debate system (RPCDS) for a language L consists of a probabilistic polynomial-time verifier V and a debate between Player 1, who aims to prove that the input x is in L, and Player 0, who selects a move uniformly at random from the set of legal moves. This model is a natural restriction of the PCDS model (Condon et al., Proc. 25th ACM Symposium on Theory of Comp... View full abstract»

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  • Relationships among PL, #L, and the determinant

    Publication Year: 1994, Page(s):267 - 278
    Cited by:  Papers (14)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1021 KB)

    Results by Toda (1991), Vinay (1991), Damm (1991), and Valiant (1992) have shown that the complexity of the determinant is characterized by the complexity of counting the number of accepting computations of a nondeterministic logspace-bounded machine. (This class of functions is known as L.) By using that characterization and by establishing a few elementary closure properties, we give a very simp... View full abstract»

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  • Logical definability of counting functions

    Publication Year: 1994, Page(s):255 - 266
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1070 KB)

    The relationship between counting functions and logical expressibility is explored. The most well studied class of counting functions is P, which consists of the functions counting the accepting computation paths of a nondeterministic polynomial-time Turing machine. For a logic L, L is the class of functions on finite structures (of a fixed signature) counting the tuples (T~, c~) satisfying a give... View full abstract»

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  • Logspace and logtime leaf languages

    Publication Year: 1994, Page(s):242 - 254
    Cited by:  Papers (8)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1213 KB)

    Leaf languages were used in the context of polynomial time computation to capture complexity classes and to study machine-independent relativizations. In this paper, the expressibility of the leaf language mechanism is investigated in the contexts of logarithmic space and of logarithmic time computation.<<ETX>> View full abstract»

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  • Predicate classes and promise classes

    Publication Year: 1994, Page(s):235 - 241
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (545 KB)

    Considering computation trees produced by polynomial time nondeterministic computations one can define a complexity class by any predicate on computation trees, such classes will be called predicate classes. It will be shown that these classes are exactly the principal ideals of the polynomial time many-one reducibility. Additionally, the set of classes-which are called promise classes-definable b... View full abstract»

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  • Complexity classes defined via k-valued functions

    Publication Year: 1994, Page(s):224 - 234
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (832 KB)

    A lot of complexity classes can be characterized by posing some global acceptance condition on the computation trees produced by nondeterministic polynomial time machines. If the acceptance condition can be performed by a tree automaton, we obtain the concept of locally definable acceptance types (U. Hertrampf, 1992). This concept can be varied in different ways: if the acceptance condition depend... View full abstract»

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  • Random strings make hard instances

    Publication Year: 1994, Page(s):217 - 222
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (477 KB)

    We establish the truth of the "instance complexity conjecture" in the case of DEXT-complete sets w.r.t. polynomial time computations, and r.e. complete sets w.r.t. recursive computations. Specifically, we obtain for every DEXT-complete set A an exponentially dense subset C such that for every nondecreasing polynomial t(n)=/spl omega/(n log n), ic/sup t/(x:A)/spl ges/K/sup t/(x)-c holds for some co... View full abstract»

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  • Test instance generation for promised NP search problems

    Publication Year: 1994, Page(s):205 - 216
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (936 KB)

    We discuss the problem of generating test instances for promised NP search problems. A technical framework is proposed for studying this problem, and it is shown that all known distNP-hard search problems are "complete" for test instance generation problems.<<ETX>> View full abstract»

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  • Constructive separation of classes of indistinguishable ensembles

    Publication Year: 1994, Page(s):198 - 204
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (557 KB)

    We construct ensembles that separate the classes of algorithmically, circuit, statistically, and perfect indistinguishable ensembles without cryptographic assumptions and present a generally usable technique for efficient deterministic simulation of resource bounded probabilistic Turing machines.<<ETX>> View full abstract»

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  • Space lower-bounds for pseudorandom-generators

    Publication Year: 1994, Page(s):186 - 197
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (910 KB)

    Pseudorandom generation is a fundamental notion with many applications such as cryptography and deterministic simulation of random computation. A strong pseudorandom generator w.r.t. a tester class C is one that will "fool" any Turing-test in C to "believe" its output is truly random. We establish the first lower-bounds on the space complexity of general pseudorandom generators (namely, generators... View full abstract»

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  • Time, hardware, and uniformity

    Publication Year: 1994, Page(s):176 - 185
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (835 KB)

    We describe three orthogonal complexity measures: parallel time, amount of hardware, and degree of non-uniformity, which together parametrize most complexity classes. We show that the descriptive complexity framework neatly captures these measures using the parameters: quantifier depth, number of variable bits, and type of numeric predicates respectively. A fairly simple picture arises in which th... View full abstract»

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  • Relative to a random oracle, NP is not small

    Publication Year: 1994, Page(s):162 - 174
    Cited by:  Papers (6)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (998 KB)

    The resource-bounded measure (J. Lutz, 1992) is an extension of classical measure theory which provides a probabilistic means of describing the relative sizes of complexity classes. Lutz proposed the hypothesis that NP does not have measure zero in the class E/sub 2/=DTIME(2/sup polynomial/), meaning loosely that NP contains a non-negligible subset of exponential time. This hypothesis implies a st... View full abstract»

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  • Weakly hard problems

    Publication Year: 1994, Page(s):146 - 161
    Cited by:  Papers (7)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1036 KB)

    A weak completeness phenomenon is investigated in the complexity class E=DTIME(2/sup linear/). According to standard terminology, a language H is /spl lessub msup P/-hard for E if the set P/sub m/(H), consisting of all languages A/spl lessub msup P/H, contains the entire class E. A language C is /spl lessub msup P/-complete for E if it is /spl lessub msup P/-hard for E and is also an element of E.... View full abstract»

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  • Generic separations

    Publication Year: 1994, Page(s):139 - 145
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (525 KB)

    M. Blum and R. Impagliazzo (Proc. 28th IEEE Symposium on Foundations of Computer Science, pp. 118-126, 1987), using techniques of Hartmanis and Hemachandra (1991) and Rackoff (1982), showed that if P = NP then P(G) = NP(G)/spl cap/co-NP(G) = UP(G), where G is a generic oracle. They left open the question as to whether these collapses occur at higher levels of the polynomial-time hierarchy. We give... View full abstract»

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  • Downward separation fails catastrophically for limited nondeterminism classes

    Publication Year: 1994, Page(s):134 - 138
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (443 KB)

    The /spl beta/ hierarchy consists of sets /spl betasub k/=NP[log/sup k/ n]/spl sube/NP. Unlike collapses in the polynomial hierarchy and the Boolean hierarchy, collapses in the /spl beta/ hierarchy do not seem to translate up, nor does closure under complement seem to cause the hierarchy to collapse. For any consistent set of collapses and separations of levels of the hierarchy that respects P=/sp... View full abstract»

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  • On the structure of complete sets

    Publication Year: 1994, Page(s):118 - 133
    Cited by:  Papers (10)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1343 KB)

    The many types of resource-bounded reductions that are both an object of study and a research tool in structural complexity theory have given rise to a large variety of completeness notions. A complete set in a complexity class is a manageable object that represents the structure of the entire class. The study of its structure can reveal properties that are general in that the complexity class, an... View full abstract»

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