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Electronic Colloquium on Computational Complexity

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REPORTS > 1997:
All reports in year 1997:
TR97-001 | 8th January 1997
Marco Cesati, Luca Trevisan

On the Efficiency of Polynomial Time Approximation Schemes

A polynomial time approximation scheme (PTAS) for an optimization
problem $A$ is an algorithm that on input an instance of $A$ and
$\epsilon > 0$ finds a $(1+\epsilon)$-approximate solution in time
that is polynomial for each fixed $\epsilon$. Typical running times
are $n^{O(1/\epsilon)}$ or $2^{1/\epsilon^{O(1)}} ... more >>>


TR97-002 | 28th January 1997
Richard Beigel, Alexis Maciel

Upper and Lower Bounds for Some Depth-3 Circuit Classes

We investigate the complexity of depth-3 threshold circuits
with majority gates at the output, possibly negated AND
gates at level two, and MODm gates at level one. We show
that the fan-in of the AND gates can be reduced to O(log n)
in the case where ... more >>>


TR97-003 | 29th January 1997
Sanjeev Arora, Madhu Sudan

Improved low-degree testing and its applications


NP = PCP(log n, 1) and related results crucially depend upon
the close connection between the probability with which a
function passes a ``low degree test'' and the distance of
this function to the nearest degree d polynomial. In this
paper we study a test ... more >>>


TR97-004 | 19th February 1997
Marek Karpinski, Alexander Zelikovsky

Approximating Dense Cases of Covering Problems

Comments: 1

We study dense instances of several covering problems. An instance of
the set cover problem with $m$ sets is dense if there is $\epsilon>0$
such that any element belongs to at least $\epsilon m$ sets. We show
that the dense set cover problem can be approximated with ... more >>>


TR97-005 | 17th February 1997
Moni Naor, Omer Reingold

On the Construction of Pseudo-Random Permutations: Luby-Rackoff Revisited

Luby and Rackoff showed a method for constructing a pseudo-random
permutation from a pseudo-random function. The method is based on
composing four (or three for weakened security) so called Feistel
permutations each of which requires the evaluation of a pseudo-random
function. We reduce somewhat the complexity ... more >>>


TR97-006 | 31st January 1997
Marco Cesati, Miriam Di Ianni

Parameterized Parallel Complexity

Comments: 1

We consider the framework of Parameterized Complexity, and we
investigate the issue of which problems do admit efficient fixed
parameter parallel algorithms by introducing two different
degrees of efficiently parallelizable parameterized problems, PNC
and FPP. We sketch both some FPP-algorithms solving natural
parameterized problems and ... more >>>


TR97-007 | 21st February 1997
Stasys Jukna

Exponential Lower Bounds for Semantic Resolution


In a semantic resolution proof we operate with clauses only
but allow {\em arbitrary} rules of inference:

C_1 C_2 ... C_m
__________________
C

Consistency is the only requirement. We prove a very simple
exponential lower bound for the size ... more >>>


TR97-008 | 16th March 1997
Noam Nisan, Ziv Bar-Yossef

Pointer Jumping Requires Concurrent Read

We consider the well known problem of determining the k'th
vertex reached by chasing pointers in a directed graph of
out-degree 1. The famous "pointer doubling" technique
provides an O(log k) parallel time algorithm on a
Concurrent-Read Exclusive-Write (CREW) PRAM. We prove that ... more >>>


TR97-009 | 12th March 1997
Jonathan F. Buss, Gudmund Skovbjerg Frandsen, Jeffrey O. Shallit

The Computational Complexity of Some Problems of Linear Algebra

We consider the computational complexity of some problems
dealing with matrix rank. Let E,S be subsets of a
commutative ring R. Let x_1, x_2, ..., x_t be variables.
Given a matrix M = M(x_1, x_2, ..., x_t) with entries
chosen from E union {x_1, x_2, ..., ... more >>>


TR97-010 | 2nd April 1997
Marcos Kiwi

Testing and Weight Distributions of Dual Codes


We study the testing problem, that is, the problem of determining (maybe
probabilistically) if a function to which we have oracle access
satisfies a given property.

We propose a framework in which to formulate and carry out the analyzes
of several known tests. This framework establishes a connection between
more >>>


TR97-011 | 7th April 1997
Alexander E. Andreev, Andrea E. F. Clementi, Jose' D.P. Rolim and Trevisan

Weak Random Sources, Hitting Sets, and BPP Simulations

We show how to simulate any BPP algorithm in polynomial time
using a weak random source of min-entropy $r^{\gamma}$
for any $\gamma >0$.
This follows from a more general result about {\em sampling\/}
with weak random sources.
Our result matches an information-theoretic lower bound ... more >>>


TR97-012 | 19th March 1997
Luca Trevisan

On Local versus Global Satisfiability

We prove an extremal combinatorial result regarding
the fraction of satisfiable clauses in boolean CNF
formulae enjoying a locally checkable property, thus
solving a problem that has been open for several years.

We then generalize the problem to arbitrary constraint
satisfaction ... more >>>


TR97-013 | 13th February 1997
Bernd Borchert, Dietrich Kuske, Frank Stephan

On Existentially First-Order Definable Languages and their Relation to NP

Pin & Weil [PW95] characterized the automata of existentially
first-order definable languages. We will use this result for the following
characterization of the complexity class NP. Assume that the
Polynomial-Time Hierarchy does not collapse. Then a regular language
L characterizes NP as an unbalanced polynomial-time leaf language
if and ... more >>>


TR97-014 | 25th April 1997
Klaus Reinhardt, Eric Allender

Making Nondeterminism Unambiguous

We show that in the context of nonuniform complexity,
nondeterministic logarithmic space bounded computation can be made
unambiguous. An analogous result holds for the class of problems
reducible to context-free languages. In terms of complexity classes,
this can be stated as:
NL/poly = UL/poly
LogCFL/poly ... more >>>


TR97-015 | 21st April 1997
Jan Krajicek

Interpolation by a game

We introduce a notion of a "real game"
(a generalization of the Karchmer - Wigderson game),
and "real communication complexity",
and relate them to the size of monotone real formulas
and circuits. We give an exponential lower bound
for tree-like monotone protocols of small real
communication complexity ... more >>>


TR97-016 | 29th April 1997
Manindra Agrawal, Eric Allender, Samir Datta

On TC^0, AC^0, and Arithmetic Circuits

Continuing a line of investigation that has studied the
function classes #P, #SAC^1, #L, and #NC^1, we study the
class of functions #AC^0. One way to define #AC^0 is as the
class of functions computed by constant-depth polynomial-size
arithmetic circuits of unbounded fan-in addition ... more >>>


TR97-017 | 5th May 1997
Marek Karpinski, Juergen Wirtgen, Alexander Zelikovsky

An Approximation Algorithm for the Bandwidth Problem on Dense Graphs

The bandwidth problem is the problem of numbering the vertices of a
given graph $G$ such that the maximum difference between the numbers
of adjacent vertices is minimal. The problem has a long history and
is known to be NP-complete Papadimitriou [Pa76]. Only few special
cases ... more >>>


TR97-018 | 8th May 1997
Oded Goldreich, Shai Halevi

Eliminating Decryption Errors in the Ajtai-Dwork Cryptosystem.

Following Ajtai's lead, Ajtai and Dwork have recently introduced a
public-key encryption scheme which is secure under the assumption
that a certain computational problem on lattices is hard on the
worst-case. Their encryption method may cause decryption errors,
though with small probability (i.e., inversely proportional to the
more >>>


TR97-019 | 5th May 1997
Martin Sauerhoff

A Lower Bound for Randomized Read-k-Times Branching Programs

In this paper, we are concerned with randomized OBDDs and randomized
read-k-times branching programs. We present an example of a Boolean
function which has polynomial size randomized OBDDs with small,
one-sided error, but only non-deterministic read-once branching
programs of exponential size. Furthermore, we discuss a lower bound
technique for randomized ... more >>>


TR97-020 | 15th May 1997
Oded Goldreich

A Sample of Samplers -- A Computational Perspective on Sampling (survey).


We consider the problem of estimating the average of a huge set of values.
That is,
given oracle access to an arbitrary function $f:\{0,1\}^n\mapsto[0,1]$,
we need to estimate $2^{-n} \sum_{x\in\{0,1\}^n} f(x)$
upto an additive error of $\epsilon$.
We are allowed to employ a randomized algorithm which may ... more >>>


TR97-021 | 16th May 1997
Farid Ablayev

Randomization and nondeterminsm are incomparable for ordered read-once branching programs


In the manuscript F. Ablayev and M. Karpinski, On the power of
randomized branching programs (generalization of ICALP'96 paper
results for the case of pure boolean function, available at
http://www.ksu.ru/~ablayev) we exhibited a simple boolean functions
$f_n$ in $n$ variables such that:

1) $f_{n}$ can be computed ... more >>>


TR97-023 | 3rd June 1997
S. Jukna, A. Razborov, Petr Savicky, Ingo Wegener

On P versus NP \cap co-NP for Decision Trees and Read-Once Branching Programs

It is known that if a Boolean function f in n variables
has a DNF and a CNF of size at most N then f also has a
(deterministic) decision tree of size $\exp(O(\log n\log^2 N)$.
We show that this simulation {\em cannot} be ... more >>>


TR97-024 | 9th June 1997
Marek Karpinski

Polynomial Time Approximation Schemes for Some Dense Instances of NP-Hard Optimization Problems

We survey recent results on the existence of polynomial time
approximation schemes for some dense instances of NP-hard
optimization problems. We indicate further some inherent limits
for existence of such schemes for some other dense instances of
the optimization problems.

more >>>

TR97-025 | 26th May 1997
Harald Hempel, Gerd Wechsung

The Operators min and max on the Polynomial Hierarchy

We define a general maximization operator max and a general minimization
operator min for complexity classes and study the inclusion structure of
the classes max.P, max.NP, max.coNP, min.P, min.NP, and min.coNP.
It turns out that Krentel's class OptP fits naturally into this frame-
work (it can be ... more >>>


TR97-026 | 18th June 1997
Jochen Me\3ner, Jacobo Toran

Optimal proof systems for Propositional Logic and complete sets

A polynomial time computable function $h:\Sigma^*\to\Sigma^*$ whose range
is the set of tautologies in Propositional Logic (TAUT), is called
a proof system. Cook and Reckhow defined this concept
and in order to compare the relative strenth of different proof systems,
they considered the notion ... more >>>


TR97-027 | 29th April 1997
Johannes Merkle, Ralph Werchner

On the Security of Server aided RSA protocols

Revisions: 1

In this paper we investigate the security of the server aided
RSA protocols RSA-S1 and RSA-S1M proposed by Matsumoto, Kato and Imai
resp. Matsumoto, Imai, Laih and Yen. We prove lower bounds for the
complexity of attacks on these protocols and show that the bounds are
sharp by describing attacks ... more >>>


TR97-028 | 12th July 1997
Scott E. Decatur, Oded Goldreich, Dana Ron

Computational Sample Complexity


In a variety of PAC learning models, a tradeoff between time and
information seems to exist: with unlimited time, a small amount of
information suffices, but with time restrictions, more information
sometimes seems to be required.
In addition, it has long been known that there are
concept classes ... more >>>


TR97-029 | 20th August 1997
Pavol Duris, Juraj Hromkovic, Jose' D. P. Rolim, Georg Schnitger

On the Power of Las Vegas for One-way Communication Complexity, Finite Automata, and Polynomial-time Computations

The study of the computational power of randomized
computations is one of the central tasks of complexity theory. The
main goal of this paper is the comparison of the power of Las Vegas
computation and deterministic respectively nondeterministic
computation. We investigate the power of Las Vegas computation for ... more >>>


TR97-030 | 25th August 1997
Martin Sauerhoff

On Nondeterminism versus Randomness for Read-Once Branching Programs

Randomized branching programs are a probabilistic model of computation
defined in analogy to the well-known probabilistic Turing machines.
In this paper, we present complexity theoretic results for randomized
read-once branching programs.
Our main result shows that nondeterminism can be more powerful than
randomness for read-once branching programs. We present a ... more >>>


TR97-031 | 9th September 1997
Oded Goldreich

On the Limits of Non-Approximability of Lattice Problems

Revisions: 2

We show simple constant-round interactive proof systems for
problems capturing the approximability, to within a factor of $\sqrt{n}$,
of optimization problems in integer lattices; specifically,
the closest vector problem (CVP), and the shortest vector problem (SVP).
These interactive proofs are for the ``coNP direction'';
that is, ... more >>>


TR97-032 | 11th July 1997
Jan Johannsen

Lower Bounds for Monotone Real Circuit Depth and Formula Size and Tree-like Cutting Planes

Using a notion of real communication complexity recently
introduced by J. Krajicek, we prove a lower bound on the depth of
monotone real circuits and the size of monotone real formulas for
st-connectivity. This implies a super-polynomial speed-up of dag-like
over tree-like Cutting Planes proofs.

more >>>

TR97-033 | 1st August 1997
Meena Mahajan, Venkatesh Raman

Parametrizing Above Guaranteed Values: MaxSat and MaxCut

In this paper we investigate the parametrized
complexity of the problems MaxSat and MaxCut using the
framework developed by Downey and Fellows.

Let $G$ be an arbitrary graph having $n$ vertices and $m$
edges, and let $f$ be an arbitrary CNF formula with $m$
clauses on $n$ variables. We improve ... more >>>


TR97-034 | 3rd September 1997
Jui-Lin Lee

Counting in uniform $TC^0$

In this paper we first give a uniform $AC^0$ algorithm which uses
partial sums to compute multiple addition. Then we use it to show
that multiple addition is computable in uniform $TC^0$ by using
$count$ only once sequentially. By constructing bit matrix for
multiple addition, ... more >>>


TR97-035 | 31st July 1997
Richard Chang

Bounded Queries, Approximations and the Boolean Hierarchy

Revisions: 1

This paper introduces a new model of computation for describing the
complexity of NP-approximation problems. The results show that the
complexity of NP-approximation problems can be characterized by classes of
multi-valued functions computed by nondeterministic polynomial time Turing
machines with a bounded number of oracle queries to an NP-complete
language. ... more >>>


TR97-036 | 1st August 1997
Meena Mahajan, V. Vinay

Determinant: Combinatorics, Algorithms, and Complexity

We prove a new combinatorial characterization of the
determinant. The characterization yields a simple
combinatorial algorithm for computing the
determinant. Hitherto, all (known) algorithms for
determinant have been based on linear algebra. Our
combinatorial algorithm requires no division and works over
arbitrary commutative rings. It also lends itself to
more >>>


TR97-039 | 11th September 1997
Pierluigi Crescenzi, Luca Trevisan

MAX NP-Completeness Made Easy

We introduce a simple technique to obtain reductions
between optimization constraint satisfaction problems. The
technique uses the probabilistic method to reduce the size of
disjunctions. As a first application, we prove the
MAX NP-completeness of MAX 3SAT without using the PCP theorem
(thus solving an open ... more >>>


TR97-040 | 17th September 1997
Dorit Dor, Shay Halperin, Uri Zwick

All Pairs Almost Shortest Paths

Let G=(V,E) be an unweighted undirected graph on n vertices. A simple
argument shows that computing all distances in G with an additive
one-sided error of at most 1 is as hard as Boolean matrix
multiplication. Building on recent work of Aingworth, Chekuri and
Motwani, we describe an \tilde{O}(min{n^{3/2}m^{1/2},n^{7/3}) time
more >>>


TR97-041 | 18th September 1997
Marek Karpinski, Juergen Wirtgen

On Approximation Hardness of the Bandwidth Problem

The bandwidth problem is the problem of enumerating
the vertices of a given graph $G$ such that the maximum
difference between the numbers of
adjacent vertices is minimal. The problem has a long
history and a number of applications
and is ... more >>>


TR97-042 | 22nd September 1997
Russell Impagliazzo, Pavel Pudlak, Jiri Sgall

Lower Bounds for the Polynomial Calculus and the Groebner Basis Algorithm

Razborov~\cite{Razborov96} recently proved that polynomial
calculus proofs of the pigeonhole principle $PHP_n^m$ must have
degree at least $\ceiling{n/2}+1$ over any field. We present a
simplified proof of the same result. The main
idea of our proof is the same as in the original proof
of Razborov: we want to describe ... more >>>


TR97-043 | 25th September 1997
Bruno Codenotti, Pavel Pudlak, Giovanni Resta

Some structural properties of low rank matrices related to computational complexity

Revisions: 1 , Comments: 1

We consider the conjecture stating that a matrix with rank
$o(n)$ and ones on the main diagonal must contain nonzero
entries on a $2\times 2$ submatrix with one entry on the main
diagonal. We show that a slightly stronger conjecture implies
that ... more >>>


TR97-044 | 26th September 1997
David Mix Barrington, Chi-Jen Lu, Peter Bro Miltersen, Sven Skyum

Searching constant width mazes captures the AC^0 hierarchy


We show that searching a width k maze is complete for \Pi_k, i.e., for
the k'th level of the AC^0 hierarchy. Equivalently, st-connectivity
for width k grid graphs is complete for \Pi_k. As an application,
we show that there is a data structure solving dynamic st-connectivity
for constant ... more >>>


TR97-045 | 29th September 1997
Oded Goldreich, David Zuckerman

Another proof that BPP subseteq PH (and more).

Comments: 1


We provide another proof of the Sipser--Lautemann Theorem
by which $BPP\subseteq MA$ ($\subseteq PH$).
The current proof is based on strong
results regarding the amplification of $BPP$, due to Zuckerman.
Given these results, the current proof is even simpler than previous ones.
Furthermore, extending the proof leads ... more >>>


TR97-046 | 3rd October 1997
Alexander Barg

Complexity Issues in Coding Theory

This is a research-expository paper. It deals with
complexity issues in the theory of linear block codes. The main
emphasis is on the theoretical performance limits of the
best known codes. Therefore, the main subject of the paper are
families of asymptotically good codes, i.e., codes whose rate and
relative ... more >>>


TR97-047 | 20th October 1997
Miklos Ajtai

The Shortest Vector Problem in L_2 is NP-hard for Randomized Reductions.

Revisions: 1

We show that the shortest vector problem in lattices
with L_2 norm is NP-hard for randomized reductions. Moreover we
also show that there is a positive absolute constant c, so that to
find a vector which is longer than the shortest non-zero vector by no
more than a factor of ... more >>>


TR97-048 | 13th October 1997
Soren Riis, Meera Sitharam

Non-constant Degree Lower Bounds imply linear Degree Lower Bounds

The semantics of decision problems are always essentially independent of the
underlying representation. Thus the space of input data (under appropriate
indexing) is closed
under action of the symmetrical group $S_n$ (for a specific data-size)
and the input-output relation is closed under the action of $S_n$.
more >>>


TR97-049 | 22nd October 1997
Michael Schmitt

On the Complexity of Learning for Spiking Neurons with Temporal Coding

Spiking neurons are models for the computational units in
biological neural systems where information is considered to be encoded
mainly in the temporal pattern of their activity. In a network of
spiking neurons a new set of parameters becomes relevant which has no
counterpart in traditional ... more >>>


TR97-050 | 27th October 1997
Stanislav Zak

A subexponential lower bound for branching programs restricted with regard to some semantic aspects

Branching programs (b.p.s) or binary decision diagrams are a
general graph-based model of sequential computation. The b.p.s of
polynomial size are a nonuniform counterpart of LOG. Lower bounds
for different kinds of restricted b.p.s are intensively
investigated. The restrictions based on the number of tests of
more >>>


TR97-051 | 11th November 1997
Pekka Orponen

On the Effect of Analog Noise in Discrete-Time Analog Computations

We introduce a model for analog computation with discrete
time in the presence of analog noise
that is flexible enough to cover the most important concrete
cases, such as noisy analog neural nets and networks of spiking neurons.
This model subsumes the classical ... more >>>


TR97-052 | 11th November 1997
Eduardo D. Sontag

Analog Neural Nets with Gaussian or other Common Noise Distributions cannot Recognize Arbitrary Regular Languages

We consider recurrent analog neural nets where the output of each
gate is subject to Gaussian noise, or any other common noise
distribution that is nonzero on a large set.
We show that many regular languages cannot be recognized by
networks of this type, and
more >>>


TR97-053 | 10th November 1997
Alexander E. Andreev, J. L. Baskakov, Andrea E. F. Clementi, Jose' D. P. Rolim

Small Random Sets for Affine Spaces and Better Explicit Lower Bounds for Branching Programs

Revisions: 2

We show the following Reduction Lemma: any
$\epsilon$-biased sample space with respect to (Boolean) linear
tests is also $2\epsilon$-biased with respect to
any system of independent linear tests. Combining this result with
the previous constructions of $\epsilon$-biased sample space with
respect to linear tests, we obtain the first efficient
more >>>


TR97-054 | 17th November 1997
Ran Raz, Gábor Tardos, Oleg Verbitsky, Nikolay Vereshchagin

Arthur-Merlin Games in Boolean Decision Trees

It is well known that probabilistic boolean decision trees
cannot be much more powerful than deterministic ones (N.~Nisan, SIAM
Journal on Computing, 20(6):999--1007, 1991). Motivated by a question
if randomization can significantly speed up a nondeterministic
computation via a boolean decision tree, we address structural
properties of Arthur-Merlin games ... more >>>


TR97-055 | 22nd September 1997
Bruce Edward Litow

A Decision Method for the Rational Sequence Problem

We give a method to decide whether or not an
ordinary finite order linear recurrence with constant, rational
coefficients ever generates zero.

more >>>

TR97-056 | 1st December 1997
Oded Goldreich

Combinatorial Property Testing (a survey).

Comments: 1

We consider the question of determining whether
a given object has a predetermined property or is ``far'' from any
object having the property.
Specifically, objects are modeled by functions,
and distance between functions is measured as the fraction
of the domain on which the functions differ.
We ... more >>>


TR97-057 | 3rd November 1997
Petr Savicky

Complexity and Probability of some Boolean Formulas

For any Boolean function $f$ let $L(f)$ be its formula size
complexity in the basis $\{\land,\oplus,1\}$. For every $n$ and
every $k\le n/2$, we describe a probabilistic distribution
on formulas in the basis $\{\land,\oplus,1\}$ in some given set of
$n$ variables and of the ... more >>>


TR97-058 | 2nd December 1997
Oded Goldreich

Notes on Levin's Theory of Average-Case Complexity.


In 1984, Leonid Levin has initiated a theory of average-case complexity.
We provide an exposition of the basic definitions suggested by Levin,
and discuss some of the considerations underlying these definitions.

more >>>

TR97-059 | 22nd December 1997
Jin-Yi Cai, Ajay Nerurkar

Approximating the SVP to within a factor $\left(1 + \frac{1}{\mathrm{dim}^\epsilon}\right)$ is NP-hard under randomized reductions

Recently Ajtai showed that
to approximate the shortest lattice vector in the $l_2$-norm within a
factor $(1+2^{-\mbox{\tiny dim}^k})$, for a sufficiently large
constant $k$, is NP-hard under randomized reductions.
We improve this result to show that
to approximate a shortest lattice vector within a
factor $(1+ \mbox{dim}^{-\epsilon})$, for any
$\epsilon>0$, ... more >>>


TR97-060 | 2nd December 1997
Manindra Agrawal, Thomas Thierauf

The Satisfiability Problem for Probabilistic Ordered Branching Programs

We show that the satisfiability problem for
bounded error probabilistic ordered branching programs is NP-complete.
If the error is very small however
(more precisely,
if the error is bounded by the reciprocal of the width of the branching program),
then we have a polynomial-time algorithm for the satisfiability problem.
more >>>


TR97-061 | 12th November 1997
Eli Biham, Dan Boneh, Omer Reingold

Generalized Diffie-Hellman Modulo a Composite is not Weaker than Factoring

The Diffie-Hellman key-exchange protocol may naturally be
extended to k>2 parties. This gives rise to the generalized
Diffie-Hellman assumption (GDH-Assumption).
Naor and Reingold have recently shown an efficient construction
of pseudo-random functions and reduced the security of their
construction to the GDH-Assumption.
In this note, we ... more >>>




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