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REPORTS > 2002:
All reports in year 2002:
TR02-001 | 8th January 2002
Cynthia Dwork, Moni Naor

Zaps and Their Applications

A zap is a two-round, witness-indistinguishable protocol in which
the first round, consisting of a message from the verifier to the
prover, can be fixed ``once-and-for-all" and applied to any instance,
and where the verifier does not use any private coins.
We present a zap for every language in NP, ... more >>>

TR02-002 | 3rd January 2002
Howard Barnum, Michael Saks

A lower bound on the quantum query complexity of read-once functions

We establish a lower bound of $\Omega{(\sqrt{n})}$ on the bounded-error quantum query complexity of read-once Boolean functions, providing evidence for the conjecture that $\Omega(\sqrt{D(f)})$ is a lower bound for all Boolean functions.Our technique extends a result of Ambainis, based on the idea that successful computation of a function requires ``decoherence'' ... more >>>

TR02-003 | 24th December 2001
Eli Ben-Sasson, Yonatan Bilu

A Gap in Average Proof Complexity

We present the first example of a natural distribution on instances
of an NP-complete problem, with the following properties.
With high probability a random formula from this
distribution (a) is unsatisfiable,
(b) has a short proof that can be found easily, and (c) does not have a short
(general) resolution ... more >>>

TR02-004 | 2nd November 2001
Till Tantau

A Note on the Power of Extra Queries to Membership Comparable Sets

A language is called k-membership comparable if there exists a
polynomial-time algorithm that excludes for any k words one of
the 2^k possibilities for their characteristic string.
It is known that all membership comparable languages can be
reduced to some P-selective language with polynomially many
adaptive queries. We show however ... more >>>

TR02-005 | 3rd January 2002
A. Pavan, Alan L. Selman

Bi-Immunity Separates Strong NP-Completeness Notions

We prove that if for some epsilon > 0 NP contains a set that is
DTIME(2^{n^{epsilon}})-bi-immune, then NP contains a set that 2-Turing
complete for NP but not 1-truth-table complete for NP. Lutz and Mayordomo
(LM96) and Ambos-Spies and Bentzien (AB00) previously obtained the
same consequence using strong ... more >>>

TR02-006 | 8th November 2001
Philippe Moser

Random nondeterministic real functions and Arthur Merlin games

Revisions: 1

We construct a nondeterministic analogue to \textbf{APP}, denoted
\textbf{NAPP}; which is the set of all real valued functions
$f: \{ 0,1 \}^{*} \rightarrow [0,1]$, that are approximable within 1/$k$,
by a probabilistic nondeterministic transducer, in time poly($n,1^{k}$).
We show that the subset of all Boolean ... more >>>

TR02-007 | 14th January 2002
Pavel Pudlak

Monotone complexity and the rank of matrices

Comments: 1

The rank of a matrix has been used a number of times to prove lower
bounds on various types of complexity. In particular it has been used
for the size of monotone formulas and monotone span programs. In most
cases that this approach was used, there is not a single ... more >>>

TR02-008 | 11th January 2002
Valentine Kabanets

Derandomization: A Brief Overview

This survey focuses on the recent (after 1998) developments in
the area of derandomization, with the emphasis on the derandomization of
time-bounded randomized complexity classes.

more >>>

TR02-009 | 17th January 2002
Petr Savicky

On determinism versus unambiquous nondeterminism for decision trees

Let $f$ be a Boolean function. Let $N(f)=\dnf(f)+\dnf(\neg f)$ be the
sum of the minimum number of monomials in a disjunctive normal form
for $f$ and $\neg f$. Let $p(f)$ be the minimum size of a partition
of the Boolean cube into disjoint subcubes such that $f$ is constant on
more >>>

TR02-010 | 21st January 2002
Albert Atserias, Maria Luisa Bonet

On the Automatizability of Resolution and Related Propositional Proof Systems

Having good algorithms to verify tautologies as efficiently as possible
is of prime interest in different fields of computer science.
In this paper we present an algorithm for finding Resolution refutations
based on finding tree-like Res(k) refutations. The algorithm is based on
the one of Beame and Pitassi \cite{BP96} ... more >>>

TR02-011 | 14th October 2001
Boris Ryabko

The nonprobabilistic approach to learning the best prediction.

The problem of predicting a sequence $x_1, x_2,.... $ where each $x_i$ belongs
to a finite alphabet $A$ is considered. Each letter $x_{t+1}$ is predicted
using information on the word $x_1, x_2, ...., x_t $ only. We use the game
theoretical interpretation which can be traced to Laplace where there ... more >>>

TR02-012 | 3rd February 2002
Ran Raz

On the Complexity of Matrix Product

We prove a lower bound of $\Omega(m^2 \log m)$ for the size of
any arithmetic circuit for the product of two matrices,
over the real or complex numbers, as long as the circuit doesn't
use products with field elements of absolute value larger than 1
(where $m \times m$ is ... more >>>

TR02-013 | 30th January 2002
Chris Pollett, Farid Ablayev, Cristopher Moore, Chris Pollett

Quantum and Stochastic Programs of Bounded Width

Revisions: 1

We prove upper and lower bounds on the power of quantum and stochastic
branching programs of bounded width. We show any NC^1 language can
be accepted exactly by a width-2 quantum branching program of
polynomial length, in contrast to the classical case where width 5 is
necessary unless \NC^1=\ACC. ... more >>>

TR02-014 | 10th December 2001
Klaus Weihrauch

Computational Complexity on Computable Metric Spaces

Revisions: 1

We introduce a new Turing machine based concept of time complexity for functions on computable metric spaces. It generalizes the ordinary complexity of word functions and the complexity of real functions studied by Ko \cite{Ko91} et al. Although this definition of ${\rm TIME}$ as the maximum of a generally infinite ... more >>>

TR02-015 | 13th February 2002
Philippe Moser

ZPP is hard unless RP is small

Revisions: 1

We use Lutz's resource bounded measure theory to prove that either \tbf{RP} is
small or \tbf{ZPP} is hard. More precisely we prove that if \tbf{RP} has not p-measure zero, then \tbf{EXP} is contained
in $\mbf{ZPP}/n$.
We also show that if \tbf{RP} has not p-measure zero,
\tbf{EXP} equals ... more >>>

TR02-016 | 30th January 2002
Alina Beygelzimer, Mitsunori Ogihara

On the Enumerability of the Determinant and the Rank

We investigate the complexity of enumerative approximation of
two elementary problems in linear algebra, computing the rank
and the determinant of a matrix. In particular, we show that
if there exists an enumerator that, given a matrix, outputs a
list of constantly many numbers, one of which is guaranteed to
more >>>

TR02-017 | 12th March 2002
Aggelos Kiayias, Moti Yung

Cryptographic Hardness based on the Decoding of Reed-Solomon Codes with Applications

We investigate the decoding problem of Reed-Solomon Codes (aka: the Polynomial Reconstruction Problem -- PR) from a cryptographic hardness perspective. First, following the standard methodology for constructing cryptographically strong primitives, we formulate a decisional intractability assumption related to the PR problem. Then, based on this assumption we show: (i) hardness ... more >>>

TR02-018 | 22nd March 2002
Piotr Berman, Marek Karpinski, Yakov Nekrich

Approximating Huffman Codes in Parallel

In this paper we present some new results on the approximate parallel
construction of Huffman codes. Our algorithm achieves linear work
and logarithmic time, provided that the initial set of elements
is sorted. This is the first parallel algorithm for that problem
with the optimal time and ... more >>>

TR02-019 | 20th March 2002
Nader Bshouty, Lynn Burroughs

On the proper learning of axis parallel concepts

We study the proper learnability of axis parallel concept classes
in the PAC learning model and in the exact learning model with
membership and equivalence queries. These classes include union of boxes,
DNF, decision trees and multivariate polynomials.

For the {\it constant} dimensional axis parallel concepts $C$
we ... more >>>

TR02-020 | 13th March 2002
Elizaveta Okol'nishnikova

On one lower bound for branching programs

The method of obtaining lower bounds on the complexity
of Boolean functions for nondeterministic branching programs
is proposed.
A nonlinear lower bound on the complexity of characteristic
functions of Reed--Muller codes for nondeterministic
branching programs is obtained.

more >>>

TR02-021 | 11th April 2002
Andreas Jakoby, Maciej Liskiewicz, Rüdiger Reischuk

Space Efficient Algorithms for Directed Series-Parallel Graphs

The subclass of directed series-parallel graphs plays an important role in
computer science. Whether a given graph is series-parallel is a
well studied problem in algorithmic graph theory, for which fast sequential and
parallel algorithms have been developed in a sequence of papers.
Also methods are known to solve ... more >>>

TR02-022 | 12th April 2002
Henry Markram

On the Computational Power of Recurrent Circuits of Spiking Neurons

Understanding the structure of real-time neural computation in
highly recurrent neural microcircuits that consist of complex
heterogeneous components has remained a serious challenge for
computational modeling. We propose here a new conceptual framework
that strongly differs from all previous approaches based on
computational models inspired ... more >>>

TR02-023 | 16th April 2002
Josh Buresh-Oppenheim, Paul Beame, Ran Raz, Ashish Sabharwal

Bounded-depth Frege lower bounds for weaker pigeonhole principles

Revisions: 1

We prove a quasi-polynomial lower bound on the size of bounded-depth
Frege proofs of the pigeonhole principle $PHP^{m}_n$ where
$m= (1+1/{\polylog n})n$.
This lower bound qualitatively matches the known quasi-polynomial-size
bounded-depth Frege proofs for these principles.
Our technique, which uses a switching lemma argument like other lower bounds
for ... more >>>

TR02-024 | 24th April 2002
Piotr Indyk

List-decoding in Linear Time

Spielman showed that one can construct error-correcting codes capable
of correcting a constant fraction $\delta << 1/2$ of errors,
and that are encodable/decodable in linear time.
Guruswami and Sudan showed that it is possible to correct
more than $50\%$ of errors (and thus exceed the ``half of the ... more >>>

TR02-025 | 26th April 2002
Wenceslas Fernandez de la Vega, Marek Karpinski, Claire Kenyon, Yuval Rabani

Polynomial Time Approximation Schemes for Metric Min-Sum Clustering

We give polynomial time approximation schemes for the problem
of partitioning an input set of n points into a fixed number
k of clusters so as to minimize the sum over all clusters of
the total pairwise distances in a cluster. Our algorithms work
for arbitrary metric spaces as well ... more >>>

TR02-026 | 7th April 2002
Boaz Barak, Yehuda Lindell

Strict Polynomial-time in Simulation and Extraction

Revisions: 2

The notion of efficient computation is usually identified in cryptography and complexity with probabilistic polynomial time. However, until recently, in order to obtain \emph{constant-round} zero-knowledge proofs and proofs of knowledge, one had to allow simulators and knowledge-extractors to run in time which is only polynomial {\em on the average} (i.e., ... more >>>

TR02-027 | 30th April 2002
Irit Dinur, Venkatesan Guruswami, Subhash Khot

Vertex Cover on k-Uniform Hypergraphs is Hard to Approximate within Factor (k-3-\epsilon)

Given a $k$-uniform hypergraph, the E$k$-Vertex-Cover problem is
to find a minimum subset of vertices that ``hits'' every edge. We
show that for every integer $k \geq 5$, E$k$-Vertex-Cover is
NP-hard to approximate within a factor of $(k-3-\epsilon)$, for
an arbitrarily small constant $\epsilon > 0$.

This almost matches the ... more >>>

TR02-028 | 15th May 2002
Eric Allender, Harry Buhrman, Michal Koucky, Detlef Ronneburger, Dieter van Melkebeek

Power from Random Strings

Revisions: 1 , Comments: 1

We consider sets of strings with high Kolmogorov complexity, mainly
in resource-bounded settings but also in the traditional
recursion-theoretic sense. We present efficient reductions, showing
that these sets are hard and complete for various complexity classes.

In particular, in addition to the usual Kolmogorov complexity measure
K, ... more >>>

TR02-029 | 3rd June 2002
Marek Karpinski, Yakov Nekrich

Parallel Construction of Minimum Redundancy Length-Limited Codes

This paper presents new results on parallel constructions of the
length-limited prefix-free codes with the minimum redundancy.
We describe an algorithm for the construction of length-limited codes
that works in $O(L)$ time with $n$ processors for $L$ the
maximal codeword length.
We also describe an algorithm for a construction ... more >>>

TR02-030 | 3rd June 2002
Lars Engebretsen, Jonas Holmerin, Alexander Russell

Inapproximability Results for Equations over Finite Groups

Revisions: 1

An equation over a finite group G is an expression of form
w_1 w_2...w_k = 1_G, where each w_i is a variable, an inverted
variable, or a constant from G; such an equation is satisfiable
if there is a setting of the variables to values in G ... more >>>

TR02-031 | 30th April 2002
Vikraman Arvind, Venkatesh Raman

Approximate Counting small subgraphs of bounded treewidth and related problems

Revisions: 1

We give a randomized approximation algorithm taking
$O(k^{O(k)}n^{b+O(1)})$ time to count the number of copies of a
$k$-vertex graph with treewidth at most $b$ in an $n$ vertex graph
$G$ with approximation ratio $1/k^{O(k)}$ and error probability
inverse exponential in $n$. This algorithm is based on ... more >>>

TR02-032 | 17th April 2002
Andrei Bulatov

Tractable Constraint Satisfaction Problems on a 3-element set

The Constraint Satisfaction Problem (CSP) provides a common framework for many combinatorial problems. The general CSP is known to be NP-complete; however, certain restrictions on a possible form of constraints may affect the complexity, and lead to tractable problem classes. There is, therefore, a fundamental research direction, aiming to separate ... more >>>

TR02-033 | 11th June 2002
Beate Bollig

A very simple function that requires exponential size nondeterministic graph-driven read-once branching programs

Branching programs are a well-established computation
model for boolean functions, especially read-once
branching programs (BP1s) have been studied intensively.
A very simple function $f$ in $n^2$ variables is
exhibited such that both the function $f$ and its negation
$\neg f$ can be computed by $\Sigma^3_p$-circuits,
the ... more >>>

TR02-034 | 18th April 2002
Andrei Bulatov

Mal'tsev constraints are tractable

A wide variety of combinatorial problems can be represented in the form of the Constraint Satisfaction Problem (CSP). The general CSR is known to be NP-complete, however, some restrictions on the possible form of constraints may lead to a tractable subclass. Jeavons and coauthors have shown that the complexity of ... more >>>

TR02-035 | 27th May 2002
Albert Atserias, Víctor Dalmau

A Combinatorial Characterization of Resolution Width

We provide a characterization of the resolution
width introduced in the context of Propositional Proof Complexity
in terms of the existential pebble game introduced
in the context of Finite Model Theory. The characterization
is tight and purely combinatorial. Our
first application of this result is a surprising
proof that the ... more >>>

TR02-036 | 30th May 2002
Stephen A. Fenner

PP-lowness and a simple definition of AWPP

We show that the counting classes AWPP and APP [Li 1993] are more robust
than previously thought. Our results identify asufficient condition for
a language to be low for PP, and we show that this condition is at least
as weak as other previously studied criteria. Our results imply that
more >>>

TR02-037 | 21st May 2002
Vikraman Arvind, Piyush Kurur

Graph Isomorphism is in SPP

We show that Graph Isomorphism is in the complexity class
SPP, and hence it is in $\ParityP$ (in fact, it is in $\ModkP$ for
each $k\geq 2$). We derive this result as a corollary of a more
general result: we show that a {\em generic problem} $\FINDGROUP$ has
an $\FP^{\SPP}$ ... more >>>

TR02-038 | 5th June 2002
Rahul Santhanam

Resource Tradeoffs and Derandomization

Revisions: 1

We consider uniform assumptions for derandomization. We provide
intuitive evidence that BPP can be simulated non-trivially in
deterministic time by showing that (1) P \not \subseteq i.o.i.PLOYLOGSPACE
implies BPP \subseteq SUBEXP (2) P \not \subseteq SUBPSPACE implies BPP
= P. These results extend and complement earlier work of ... more >>>

TR02-039 | 30th June 2002
Oded Goldreich, Avi Wigderson

Derandomization that is rarely wrong from short advice that is typically good

Comments: 1

For every $\epsilon>0$,
we present a {\em deterministic}\/ log-space algorithm
that correctly decides undirected graph connectivity
on all but at most $2^{n^\epsilon}$ of the $n$-vertex graphs.
The same holds for every problem in Symmetric Log-space (i.e., $\SL$).

Making no assumptions (and in particular not assuming the ... more >>>

TR02-040 | 20th June 2002
Lars Engebretsen, Jonas Holmerin

Three-Query PCPs with Perfect Completeness over non-Boolean Domains

We study non-Boolean PCPs that have perfect completeness and read
three positions from the proof. For the case when the proof consists
of values from a domain of size d for some integer constant d
>= 2, we construct a non-adaptive PCP with perfect completeness
more >>>

TR02-041 | 2nd July 2002
Wenceslas Fernandez de la Vega, Marek Karpinski, Claire Kenyon

A Polynomial Time Approximation Scheme for Metric MIN-BISECTION

We design a polynomial time approximation scheme (PTAS) for
the problem of Metric MIN-BISECTION of dividing a given finite metric
space into two halves so as to minimize the sum of distances across
that partition. The method of solution depends on a new metric placement
partitioning ... more >>>

TR02-042 | 7th June 2002
Dima Grigoriev

Public-key cryptography and invariant theory

Public-key crypto
Contact: dima@maths.univ-rennes1.fr
Author: Dima Grigoriev
Title: Public-key cryptography and invariant theory
Abstract: Public-key cryptosystems are suggested based on invariants of group

more >>>

TR02-043 | 11th July 2002
Dalit Naor, Moni Naor, Jeff Lotspiech

Revocation and Tracing Schemes for Stateless Receivers

We deal with the problem of a center sending a secret message to
a group of users such that some subset of the users is considered
revoked and should not be able to obtain the content of the
message. We concentrate on the stateless receiver case, where
the users do ... more >>>

TR02-044 | 16th July 2002
Wenceslas Fernandez de la Vega, Marek Karpinski

A Polynomial Time Approximation Scheme for Subdense MAX-CUT

We prove that the subdense instances of MAX-CUT of average
degree Omega(n/logn) posses a polynomial time approximation scheme (PTAS).
We extend this result also to show that the instances of general 2-ary
maximum constraint satisfaction problems (MAX-CSP) of the same average
density have PTASs. Our results ... more >>>

TR02-045 | 8th July 2002
Daniele Micciancio, Erez Petrank

Efficient and Concurrent Zero-Knowledge from any public coin HVZK protocol

We show how to efficiently transform any public coin honest verifier
zero knowledge proof system into a proof system that is concurrent
zero-knowledge with respect to any (possibly cheating) verifier via
black box simulation. By efficient we mean that our transformation
incurs only an additive overhead, ... more >>>

TR02-046 | 16th July 2002
Marek Karpinski

On Approximability of Minimum Bisection Problem

We survey some recent results on the complexity of computing
approximate solutions for instances of the Minimum Bisection problem
and formulate some intriguing and still open questions about the
approximability status of that problem. Some connections to other
optimization problems are also indicated.

more >>>

TR02-047 | 3rd August 2002
Oded Goldreich

The GGM Construction does NOT yield Correlation Intractable Function Ensembles.

We consider the function ensembles emerging from the
construction of Goldreich, Goldwasser and Micali (GGM),
when applied to an arbitrary pseudoramdon generator.
We show that, in general, such functions
fail to yield correlation intractable ensembles.
Specifically, it may happen that, given a description of such a ... more >>>

TR02-048 | 31st July 2002
Noga Alon, Oded Goldreich, Yishay Mansour

Almost $k$-wise independence versus $k$-wise independence

We say that a distribution over $\{0,1\}^n$
is almost $k$-wise independent
if its restriction to every $k$ coordinates results in a
distribution that is close to the uniform distribution.
A natural question regarding almost $k$-wise independent
distributions is how close they are to some $k$-wise
independent distribution. We show ... more >>>

TR02-049 | 4th August 2002
Oded Goldreich, Vered Rosen

On the Security of Modular Exponentiation with Application to the Construction of Pseudorandom Generators

Assuming the inractability of factoring, we show that
the output of the exponentiation modulo a composite function
$f_{N,g}(x)=g^x\bmod N$ (where $N=P\cdot Q$) is pseudorandom,
even when its input is restricted to be half the size.
This result is equivalent to the simultaneous hardness of the upper
half of the bits ... more >>>

TR02-050 | 5th August 2002
Oded Goldreich, Madhu Sudan

Locally Testable Codes and PCPs of Almost-Linear Length

Locally testable codes are error-correcting codes that admit
very efficient codeword tests. Specifically, using a constant
number of (random) queries, non-codewords are rejected with
probability proportional to their distance from the code.

Locally testable codes are believed to be the combinatorial
core of PCPs. However, the relation is ... more >>>

TR02-051 | 16th July 2002
Chris Pollett

Nepomnjascij's Theorem and Independence Proofs in Bounded Arithmetic

The use of Nepomnjascij's Theorem in the proofs of independence results
for bounded arithmetic theories is investigated. Using this result and similar ideas, the following statements are proven: (1) At least one of S_1 or TLS does not prove the Matiyasevich-Davis-Robinson-Putnam Theorem and (2) TLS does not prove Sigma^b_{1,1}=Pi^b_{1,1}. Here ... more >>>

TR02-052 | 3rd September 2002
Vince Grolmusz

Computing Elementary Symmetric Polynomials with a Sub-Polynomial Number of Multiplications

Revisions: 1

Elementary symmetric polynomials $S_n^k$ are used as a
benchmark for the bounded-depth arithmetic circuit model of computation.
In this work we prove that $S_n^k$ modulo composite numbers $m=p_1p_2$
can be computed with much fewer multiplications than over any field, if
the coefficients of monomials $x_{i_1}x_{i_2}\cdots x_{i_k}$ ... more >>>

TR02-053 | 20th July 2002
Lars Engebretsen, Venkatesan Guruswami

Is Constraint Satisfaction Over Two Variables Always Easy?

By the breakthrough work of Håstad, several constraint satisfaction
problems are now known to have the following approximation resistance
property: satisfying more clauses than what picking a random
assignment would achieve is NP-hard. This is the case for example for
Max E3-Sat, Max E3-Lin and Max E4-Set Splitting. A notable ... more >>>

TR02-054 | 5th September 2002
Detlef Sieling

Minimization of Decision Trees is Hard to Approximate

Decision trees are representations of discrete functions with widespread applications in, e.g., complexity theory and data mining and exploration. In these areas it is important to obtain decision trees of small size. The minimization problem for decision trees is known to be NP-hard. In this paper the problem is shown ... more >>>

TR02-055 | 13th September 2002
Valentine Kabanets, Russell Impagliazzo

Derandomizing Polynomial Identity Tests Means Proving Circuit Lower Bounds

Revisions: 1

We show that derandomizing Polynomial Identity Testing is,
essentially, equivalent to proving circuit lower bounds for
NEXP. More precisely, we prove that if one can test in polynomial
time (or, even, nondeterministic subexponential time, infinitely
often) whether a given arithmetic circuit over integers computes an
identically zero polynomial, then either ... more >>>

TR02-056 | 19th September 2002
Todd Ebert, Wolfgang Merkle, Heribert Vollmer

On the Autoreducibility of Random Sequences

A binary sequence A=A(0)A(1).... is called i.o. Turing-autoreducible if A is reducible to itself via an oracle Turing machine that never queries its oracle at the current input, outputs either A(x) or a don't-know symbol on any given input x, and outputs A(x) for infinitely many x. If in addition ... more >>>

TR02-057 | 19th September 2002
Richard J. Lipton, Anastasios Viglas

Non-uniform Depth of Polynomial Time and Space Simulations

We discuss some connections between polynomial time and non-uniform, small depth circuits. A connection is shown with simulating deterministic time in small space. The well known result of Hopcroft, Paul and Valiant showing that space is more powerful than time can be improved, by making an assumption about the connection ... more >>>

TR02-058 | 25th September 2002
Philippe Moser

A generalization of Lutz's measure to probabilistic classes

We extend Lutz's measure to probabilistic classes, and obtain notions of measure on probabilistic complexity classes
such as BPP , BPE and BPEXP. Unlike former attempts,
all our measure notions satisfy all three Lutz's measure axioms, that is
every singleton {L} has measure zero ... more >>>

TR02-059 | 9th August 2002
Iordanis Kerenidis, Ronald de Wolf

Exponential Lower Bound for 2-Query Locally Decodable Codes

We prove exponential lower bounds on the length of 2-query
locally decodable codes. Goldreich et al. recently proved such bounds
for the special case of linear locally decodable codes.
Our proof shows that a 2-query locally decodable code can be decoded
with only 1 quantum query, and then ... more >>>

TR02-060 | 15th July 2002
Ke Yang

New Lower Bounds for Statistical Query Learning

We prove two lower bounds on the Statistical Query (SQ) learning
model. The first lower bound is on weak-learning. We prove that for a
concept class of SQ-dimension $d$, a running time of
$\Omega(d/\log d)$ is needed. The SQ-dimension of a concept class is
defined to be the maximum number ... more >>>

TR02-061 | 14th November 2002
Miklos Ajtai

A conjectured 0-1 law about the polynomial time computable properties of random lattices, I.

A measure $\mu_{n}$ on $n$-dimensional lattices with
determinant $1$ was introduced about fifty years ago to prove the
existence of lattices which contain points from certain sets. $\mu_{n}$
is the unique probability measure on lattices with determinant $1$ which
is invariant under linear transformations with determinant $1$, where a
more >>>

TR02-062 | 19th November 2002
Andrew Chi-Chih Yao

Classical Physics and the Church-Turing Thesis

Would physical laws permit the construction of computing machines
that are capable of solving some problems much faster than the
standard computational model? Recent evidence suggests that this
might be the case in the quantum world. But the question is of
great interest even in the realm of classical physics. ... more >>>

TR02-063 | 3rd December 2002
Oded Goldreich

Zero-Knowledge twenty years after its invention

Zero-knowledge proofs are proofs that are both convincing and yet
yield nothing beyond the validity of the assertion being proven.
Since their introduction about twenty years ago,
zero-knowledge proofs have attracted a lot of attention
and have, in turn, contributed to the development of other
areas of cryptography and complexity ... more >>>

TR02-064 | 14th November 2002
Andrej Bogdanov, Luca Trevisan

Lower Bounds for Testing Bipartiteness in Dense Graphs

We consider the problem of testing bipartiteness in the adjacency
matrix model. The best known algorithm, due to Alon and Krivelevich,
distinguishes between bipartite graphs and graphs that are
$\epsilon$-far from bipartite using $O((1/\epsilon^2)polylog(1/epsilon)$
queries. We show that this is optimal for non-adaptive algorithms,
up to the ... more >>>

TR02-065 | 26th November 2002
Olivier Powell

Measure on P revisited

We revisit the problem of generalising Lutz's resource bounded measure
(rbm) to small complexity classes.
We propose a definition of a perfect rbm on P,
and give sufficient and necessary conditions for such a measure to exist.
We also revisit $\mu_\tau$, an rbm for P
defined in previous articles (c.f. ... more >>>

TR02-066 | 24th October 2002
Kristoffer Arnsfelt Hansen, Peter Bro Miltersen, V Vinay

Circuits on Cylinders

We consider the computational power of constant width polynomial
size cylindrical circuits and nondeterministic branching programs.
We show that every function computed by a Pi2 o MOD o AC0 circuit
can also be computed by a constant width polynomial size cylindrical
nondeterministic branching program (or cylindrical circuit) and
that ... more >>>

TR02-067 | 5th October 2002
Marco Cadoli, Francesco Donini, Paolo Liberatore, Marco Schaerf

k-Approximating Circuits

In this paper we study the problem of approximating a boolean
function using the Hamming distance as the approximation measure.
Namely, given a boolean function f, its k-approximation is the
function f^k returning true on the same points in which f does,
plus all points whose Hamming distance from the ... more >>>

TR02-068 | 10th December 2002
Tobias Riege, Jörg Rothe

Complexity of the Exact Domatic Number Problem and of the Exact Conveyor Flow Shop Problem

Revisions: 2

We prove that the exact versions of the domatic number problem are complete
for the levels of the boolean hierarchy over NP. The domatic number
problem, which arises in the area of computer networks, is the problem of
partitioning a given graph into a maximum number ... more >>>

TR02-069 | 14th November 2002
Luca Trevisan

A Note on Deterministic Approximate Counting for k-DNF

Revisions: 1

We describe a deterministic algorithm that, for constant k,
given a k-DNF or k-CNF formula f and a parameter e, runs in time
linear in the size of f and polynomial in 1/e and returns an
estimate of the fraction of satisfying assignments for f up to ... more >>>

TR02-070 | 13th December 2002
Wenceslas Fernandez de la Vega, Marek Karpinski

9/8-Approximation Algorithm for Random MAX-3SAT

Revisions: 1

We prove that MAX-3SAT can be approximated in polynomial time
within a factor 9/8 on random instances.

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TR02-071 | 6th June 2002
Bruno Codenotti, Igor E. Shparlinski

Non-approximability of the Permanent of Structured Matrices over Finite Fields

We show that for several natural classes of ``structured'' matrices, including symmetric, circulant, Hankel and Toeplitz matrices, approximating the permanent modulo a prime $p$ is as hard as computing the exact value. Results of this kind are well known for the class of arbitrary matrices; however the techniques used do ... more >>>

TR02-072 | 12th November 2002
Scott Aaronson

Quantum Lower Bound for Recursive Fourier Sampling

We revisit the oft-neglected 'recursive Fourier sampling' (RFS) problem, introduced by Bernstein and Vazirani to prove an oracle separation between BPP and BQP. We show that the known quantum algorithm for RFS is essentially optimal, despite its seemingly wasteful need to uncompute information. This implies that, to place BQP outside ... more >>>

TR02-073 | 12th December 2002
Janka Chlebíková, Miroslav Chlebik

Approximation Hardness for Small Occurrence Instances of NP-Hard Problem

The paper contributes to the systematic study (started by Berman and
Karpinski) of explicit approximability lower bounds for small occurrence optimization
problems. We present parametrized reductions for some packing and
covering problems, including 3-Dimensional Matching, and prove the best
known inapproximability results even for highly restricted versions of ... more >>>

TR02-074 | 26th December 2002
Andrew Chi-Chih Yao

On the Power of Quantum Fingerprinting

In the simultaneous message model, two parties holding $n$-bit integers
$x,y$ send messages to a third party, the {\it referee}, enabling
him to compute a boolean function $f(x,y)$. Buhrman et al
[BCWW01] proved the remarkable result that, when $f$ is the
equality function, the referee can solve this problem by ... more >>>

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