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Electronic Colloquium on Computational Complexity
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REPORTS > 2007:
All reports in year 2007:
TR07-001 | 19th November 2006
Stefan S. Dantchev, Barnaby Martin, Stefan Szeider

Parameterized Proof Complexity: a Complexity Gap for Parameterized Tree-like Resolution

Revisions: 2

We propose a proof-theoretic approach for gaining evidence that certain parameterized problems are not fixed-parameter tractable. We consider proofs that witness that a given propositional formula cannot be satisfied by a truth assignment that sets at most k variables to true, considering k as the parameter. One could separate the ... more >>>


TR07-002 | 8th November 2006
Moti Yung, Yunlei Zhao

Concurrent Knowledge-Extraction in the Public-Key Model

Comments: 2

Knowledge extraction is a fundamental notion, modeling knowledge possession in a computational complexity sense. The notion provides a tool for cryptographic protocol design and analysis, enabling one to argue about the internal state of protocol players. We define and
investigate the relative power of the notion of ``concurrent knowledge-extraction'' ... more >>>


TR07-003 | 5th January 2007
Jin-Yi Cai, Pinyan Lu

Bases Collapse in Holographic Algorithms

Holographic algorithms are a novel approach to design polynomial time computations using linear superpositions. Most holographic algorithms are designed with basis vectors of dimension 2. Recently Valiant showed that a basis of dimension 4 can be used to solve in P an interesting (restrictive SAT) counting problem mod 7. This ... more >>>


TR07-004 | 12th January 2007
Lance Fortnow, Rahul Santhanam

Time Hierarchies: A Survey

We survey time hierarchies, with an emphasis on recent attempts to prove hierarchies for semantic classes.

more >>>

TR07-005 | 17th January 2007
Rahul Santhanam

Circuit Lower Bounds for Merlin-Arthur Classes

We show that for each k > 0, MA/1 (MA with 1 bit of advice) does not have circuits of size n^k. This implies the first superlinear circuit lower bounds for the promise versions of the classes MA, AM and ZPP_{||}^{NP}.

We extend our main result in several ways. For ... more >>>


TR07-006 | 12th January 2007
David P. Woodruff

New Lower Bounds for General Locally Decodable Codes

For any odd integer q > 1, we improve the lower bound for general q-query locally decodable codes C: {0,1}^n -> {0,1}^m from m = Omega(n/log n)^{(q+1)/(q-1)} to m = Omega(n^{(q+1)/(q-1)})/log n. For example, for q = 3 we improve the previous bound from Omega(n^2/log^2 n) to Omega(n^2/log n). For ... more >>>


TR07-007 | 17th January 2007
Jan Krajicek

An exponential lower bound for a constraint propagation proof system based on ordered binary decision diagrams

We prove an exponential lower bound on the size of proofs
in the proof system operating with ordered binary decision diagrams
introduced by Atserias, Kolaitis and Vardi. In fact, the lower bound
applies to semantic derivations operating with sets defined by OBDDs.
We do not assume ... more >>>


TR07-008 | 27th November 2006
Philipp Weis, Neil Immerman

Structure Theorem and Strict Alternation Hierarchy for FO^2 on Words

It is well-known that every first-order property on words is expressible
using at most three variables. The subclass of properties expressible with
only two variables is also quite interesting and well-studied. We prove
precise structure theorems that characterize the exact expressive power of
first-order logic with two variables on words. ... more >>>


TR07-009 | 8th January 2007
Nathan Segerlind

Nearly-Exponential Size Lower Bounds for Symbolic Quantifier Elimination Algorithms and OBDD-Based Proofs of Unsatisfiability

Revisions: 1 , Comments: 1

We demonstrate a family of propositional formulas in conjunctive normal form
so that a formula of size $N$ requires size $2^{\Omega(\sqrt[7]{N/logN})}$
to refute using the tree-like OBDD refutation system of
Atserias, Kolaitis and Vardi
with respect to all variable orderings.
All known symbolic quantifier elimination algorithms for satisfiability
generate ... more >>>


TR07-010 | 4th January 2007
Arist Kojevnikov

Improved Lower Bounds for Resolution over Linear Inequalities

Revisions: 1

We continue a study initiated by Krajicek of
a Resolution-like proof system working with clauses of linear
inequalities, R(CP). For all proof systems of this kind
Krajicek proved an exponential lower bound that depends
on the maximal absolute value of coefficients in the given proof and
the maximal clause width.

... more >>>

TR07-011 | 19th December 2006
Bodo Manthey

On Approximating Restricted Cycle Covers

A cycle cover of a graph is a set of cycles such that every vertex is
part of exactly one cycle. An L-cycle cover is a cycle cover in which
the length of every cycle is in the set L. The weight of a cycle cover
of an edge-weighted graph ... more >>>


TR07-012 | 22nd January 2007
Shachar Lovett, Sasha Sodin

Almost Euclidean sections of the N-dimensional cross-polytope using O(N) random bits

Revisions: 1

It is well known that $\R^N$ has subspaces of dimension
proportional to $N$ on which the $\ell_1$ norm is equivalent to the
$\ell_2$ norm; however, no explicit constructions are known.
Extending earlier work by Artstein--Avidan and Milman, we prove that
such a subspace can be generated using $O(N)$ random bits.

... more >>>

TR07-013 | 6th February 2007
Andris Ambainis, Joseph Emerson

Quantum t-designs: t-wise independence in the quantum world

A t-design for quantum states is a finite set of quantum states with the property of simulating the Haar-measure on quantum states w.r.t. any test that uses at most t copies of a state. We give efficient constructions for approximate quantum t-designs for arbitrary t.

We then show that an ... more >>>


TR07-014 | 23rd January 2007
Amit Chakrabarti

Lower Bounds for Multi-Player Pointer Jumping

We consider the $k$-layer pointer jumping problem in the one-way
multi-party number-on-the-forehead communication model. In this problem,
the input is a layered directed graph with each vertex having outdegree
$1$, shared amongst $k$ players: Player~$i$ knows all layers {\em
except} the $i$th. The players must communicate, in the order
$1,2,\ldots,k$, ... more >>>


TR07-015 | 1st March 2007
Oded Goldreich, Or Sheffet

On the randomness complexity of property testing

We initiate a general study of the randomness complexity of
property testing, aimed at reducing the randomness complexity of
testers without (significantly) increasing their query complexity.
One concrete motovation for this study is provided by the
observation that the product of the randomness and query complexity
of a tester determine ... more >>>


TR07-016 | 13th February 2007
Prasad Raghavendra

A Note on Yekhanin's Locally Decodable Codes

Revisions: 1

Locally Decodable codes(LDC) support decoding of any particular symbol of the input message by reading constant number of symbols of the codeword, even in presence of constant fraction of errors.

In a recent breakthrough, Yekhanin designed $3$-query LDCs that hugely improve over earlier constructions. Specifically, for a Mersenne prime $p ... more >>>


TR07-017 | 18th January 2007
Ashish Rastogi, Richard Cole

Indivisible Markets with Good Approximate EquilibriumPrices

Revisions: 1

This paper considers the tradeoff between divisibility and the hardness of approximating
equilibrium prices. Tight bounds are obtained for smooth Fisher markets that obey a relaxed
weak gross substitutes property (WGS). A smooth market is one in which small changes in
prices cause only proportionately small changes ... more >>>


TR07-018 | 1st March 2007
Christian Glaßer, Alan L. Selman, Liyu Zhang

The Informational Content of Canonical Disjoint NP-Pairs

We investigate the connection between propositional proof systems and their canonical pairs. It is known that simulations between proof systems translate to reductions between their canonical pairs. We focus on the opposite direction and study the following questions.

Q1: Where does the implication [can(f) \le_m can(g) => f \le_s ... more >>>


TR07-019 | 10th March 2007
Jin-Yi Cai, Pinyan Lu

On Block-wise Symmetric Signatures for Matchgates

We give a classification of block-wise symmetric signatures
in the theory of matchgate computations. The main proof technique
is matchgate identities, a.k.a. useful Grassmann-Pl\"{u}cker
identities.

more >>>

TR07-020 | 11th March 2007
Jin-Yi Cai, Pinyan Lu

Holographic Algorithms: The Power of Dimensionality Resolved

Valiant's theory of holographic algorithms is a novel methodology
to achieve exponential speed-ups in computation. A fundamental
parameter in holographic algorithms is the dimension of the linear basis
vectors.
We completely resolve the problem of the power of higher dimensional
bases. We prove that 2-dimensional bases are universal for
holographic ... more >>>


TR07-021 | 5th March 2007
Brett Hemenway, Rafail Ostrovsky

Public Key Encryption Which is Simultaneously a Locally-Decodable Error-Correcting Code

Revisions: 3

In this paper, we introduce the notion of a Public-Key Encryption (PKE) Scheme that is also a Locally-Decodable Error-Correcting Code.
In particular, our construction simultaneously satisfies all of the following properties:
\begin{itemize}
\item
Our Public-Key Encryption is semantically secure under a certain number-theoretic hardness assumption
... more >>>


TR07-022 | 20th February 2007
Rafail Ostrovsky, William Skeith

Algebraic Lower Bounds for Computing on Encrypted Data

In cryptography, there has been tremendous success in building
primitives out of homomorphic semantically-secure encryption
schemes, using homomorphic properties in a black-box way. A few
notable examples of such primitives include items like private
information retrieval schemes and collision-resistant hash functions. In this paper, we illustrate a general
methodology for ... more >>>


TR07-023 | 26th February 2007
Heribert Vollmer, Michael Bauland, Elmar Böhler, Nadia Creignou, Steffen Reith, Henning Schnoor

The Complexity of Problems for Quantified Constraints

In this paper we will look at restricted versions of the evaluation problem, the model checking problem, the equivalence problem, and the counting problem for quantified propositional formulas, both with and without bound on the number of quantifier alternations. The restrictions are such that we consider formulas in conjunctive normal-form ... more >>>


TR07-024 | 5th March 2007
Laszlo Egri, Benoit Larose, Pascal Tesson

Symmetric Datalog and Constraint Satisfaction Problems in Logspace

We introduce symmetric Datalog, a syntactic restriction of linear
Datalog and show that its expressive power is exactly that of
restricted symmetric monotone Krom SNP. The deep result of
Reingold on the complexity of undirected
connectivity suffices to show that symmetric Datalog queries can be
evaluated in logarithmic space. We ... more >>>


TR07-025 | 5th March 2007
Benoit Larose, Pascal Tesson, Pascal Tesson

Universal Algebra and Hardness Results for Constraint Satisfaction Problems

We present algebraic conditions on constraint languages \Gamma
that ensure the hardness of the constraint satisfaction problem
CSP(\Gamma) for complexity classes L, NL, P, NP and Mod_pL.
These criteria also give non-expressibility results for various
restrictions of Datalog. Furthermore, we show that if
CSP(\Gamma) is not first-order definable then it ... more >>>


TR07-026 | 21st November 2006
Dana Moshkovitz, Ran Raz

Sub-Constant Error Probabilistically Checkable Proof of Almost Linear Size

We show a construction of a PCP with both sub-constant error and
almost-linear size. Specifically, for some constant alpha in (0,1),
we construct a PCP verifier for checking satisfiability of
Boolean formulas that on input of size n uses log n + O((log
n)^{1-alpha}) random bits to query a constant ... more >>>


TR07-027 | 2nd February 2007
Tobias Friedrich, Jun He, Nils Hebbinghaus, Frank Neumann, Carsten Witt

Approximating Covering Problems by Randomized Search Heuristics Using Multi-Objective Models

The main aim of randomized search heuristics is to produce good approximations of optimal solutions within a small amount of time. In contrast to numerous experimental results, there are only a few theoretical results on this subject.
We consider the approximation ability of randomized search for the class of ... more >>>


TR07-028 | 12th February 2007
Daniel Sawitzki

Implicit Simulation of FNC Algorithms

Implicit algorithms work on their input's characteristic functions and should solve problems heuristically by as few and as efficient functional operations as possible. Together with an appropriate data structure to represent the characteristic functions they yield heuristics which are successfully applied in numerous areas. It is known that implicit algorithms ... more >>>


TR07-029 | 20th January 2007
Kazuhisa Makino, Suguru Tamaki, Masaki Yamamoto

A Dichotomy Theorem within Schaefer for the Boolean Connectivity Problem

Revisions: 1

P. Gopalan, P. G. Kolaitis, E. N. Maneva and C. H. Papadimitriou
studied in [Gopalan et al., ICALP2006] connectivity properties of the
solution-space of Boolean formulas, and investigated complexity issues
on connectivity problems in Schaefer's framework [Schaefer, STOC1978].
A set S of logical relations is Schaefer if all relations in ... more >>>


TR07-030 | 29th March 2007
Kai-Min Chung, Omer Reingold, Salil Vadhan

S-T Connectivity on Digraphs with a Known Stationary Distribution

We present a deterministic logspace algorithm for solving s-t connectivity on directed graphs if (i) we are given a stationary distribution for random walk on the graph and (ii) the random walk which starts at the source vertex $s$ has polynomial mixing time. This result generalizes the recent deterministic logspace ... more >>>


TR07-031 | 26th March 2007
Yael Tauman Kalai, Ran Raz

Interactive PCP

An interactive-PCP (say, for the membership $x \in L$) is a
proof that can be verified by reading only one of its bits, with the
help of a very short interactive-proof.
We show that for membership in some languages $L$, there are
interactive-PCPs that are significantly shorter than the known
more >>>


TR07-032 | 27th March 2007
Pavel Pudlak

Quantum deduction rules

We define propositional quantum Frege proof systems and compare it
with classical Frege proof systems.

more >>>

TR07-033 | 14th February 2007
Michael Navon, Alex Samorodnitsky

Linear programming bounds for codes via a covering argument

We recover the first linear programming bound of McEliece, Rodemich, Rumsey, and Welch for binary error-correcting codes and designs via a covering argument. It is possible to show, interpreting the following notions appropriately, that if a code has a large distance, then its dual has a small covering radius and, ... more >>>


TR07-034 | 29th March 2007
Anup Rao

An Exposition of Bourgain's 2-Source Extractor

A construction of Bourgain gave the first 2-source
extractor to break the min-entropy rate 1/2 barrier. In this note,
we write an exposition of his result, giving a high level way to view
his extractor construction.

We also include a proof of a generalization of Vazirani's XOR lemma
that seems ... more >>>


TR07-035 | 3rd April 2007
Mark Braverman, Raghav Kulkarni, Sambuddha Roy

Parity Problems in Planar Graphs

We consider the problem of counting the number of spanning trees in planar graphs. We prove tight bounds on the complexity of the problem, both in general and especially in the modular setting. We exhibit the problem to be complete for Logspace when the modulus is 2^k, for constant k. ... more >>>


TR07-036 | 6th April 2007
Ryan Williams

Time-Space Tradeoffs for Counting NP Solutions Modulo Integers

We prove the first time-space tradeoffs for counting the number of solutions to an NP problem modulo small integers, and also improve upon the known time-space tradeoffs for Sat. Let m be a positive integer, and define MODm-Sat to be the problem of determining if a given Boolean formula has ... more >>>


TR07-037 | 2nd February 2007
Leonid Gurvits

Polynomial time algorithms to approximate mixed volumes within a simply exponential factor

Revisions: 1

We study in this paper randomized algorithms to approximate the mixed volume of well-presented convex compact sets.
Our main result is a poly-time algorithm which approximates $V(K_1,...,K_n)$ with multiplicative error $e^n$ and
with better rates if the affine dimensions of most of the sets $K_i$ are small.\\
Our approach is ... more >>>


TR07-038 | 23rd April 2007
Iftach Haitner, Jonathan J. Hoch, Omer Reingold, Gil Segev

Finding Collisions in Interactive Protocols -- A Tight Lower Bound on the Round Complexity of Statistically-Hiding Commitments

We study the round complexity of various cryptographic protocols. Our main result is a tight lower bound on the round complexity of any fully-black-box construction of a statistically-hiding commitment scheme from one-way permutations, and even from trapdoor permutations. This lower bound matches the round complexity of the statistically-hiding commitment scheme ... more >>>


TR07-039 | 27th March 2007
Bodo Manthey, Till Tantau

Smoothed Analysis of Binary Search Trees and Quicksort Under Additive Noise

Revisions: 1

Binary search trees are a fundamental data structure and their height
plays a key role in the analysis of divide-and-conquer algorithms like
quicksort. Their worst-case height is linear; their average height,
whose exact value is one of the best-studied problems in average-case
complexity, is logarithmic. We analyze their smoothed height ... more >>>


TR07-040 | 12th April 2007
Kiran Kedlaya, Sergey Yekhanin

Locally Decodable Codes From Nice Subsets of Finite Fields and Prime Factors of Mersenne Numbers

A k-query Locally Decodable Code (LDC) encodes an n-bit message x as an N-bit codeword C(x), such that one can probabilistically recover any bit x_i of the message by querying only k bits of the codeword C(x), even after some constant fraction of codeword bits has been corrupted. The major ... more >>>


TR07-041 | 20th April 2007
Nicola Galesi, Massimo Lauria

Extending Polynomial Calculus to $k$-DNF Resolution

Revisions: 1

We introduce an algebraic proof system Pcrk, which combines together {\em Polynomial Calculus} (Pc) and {\em $k$-DNF Resolution} (Resk).
This is a natural generalization to Resk of the well-known {\em Polynomial Calculus with Resolution} (Pcr) system which combines together Pc and Resolution.

We study the complexity of proofs in such ... more >>>


TR07-042 | 7th May 2007
Zohar Karnin, Amir Shpilka

Black Box Polynomial Identity Testing of Depth-3 Arithmetic Circuits with Bounded Top Fan-in

Revisions: 2 , Comments: 1

In this paper we consider the problem of determining whether an
unknown arithmetic circuit, for which we have oracle access,
computes the identically zero polynomial. Our focus is on depth-3
circuits with a bounded top fan-in. We obtain the following
results.

1. A quasi-polynomial time deterministic black-box identity testing algorithm ... more >>>


TR07-043 | 7th May 2007
Uriel Feige, Guy Kindler, Ryan O'Donnell

Understanding Parallel Repetition Requires Understanding Foams

Motivated by the study of Parallel Repetition and also by the Unique
Games Conjecture, we investigate the value of the ``Odd Cycle Games''
under parallel repetition. Using tools from discrete harmonic
analysis, we show that after $d$ rounds on the cycle of length $m$,
the value of the game is ... more >>>


TR07-044 | 23rd April 2007
Philipp Hertel

Black-White Pebbling is PSPACE-Complete

The complexity of the Black-White Pebbling Game has remained an open problem for 30 years. It was devised to capture the power of non-deterministic space bounded computation. Since then it has been continuously studied and applied to problems in diverse areas of computer science including VLSI design and more recently ... more >>>


TR07-045 | 24th April 2007
Heribert Vollmer

The complexity of deciding if a Boolean function can be computed by circuits over a restricted basis

We study the complexity of the following algorithmic problem: Given a Boolean function $f$ and a finite set of Boolean functions $B$, decide if there is a circuit with basis $B$ that computes $f$. We show that if both $f$ and all functions in $B$ are given by their truth-table, ... more >>>


TR07-046 | 23rd April 2007
Philipp Hertel

An Exponential Time/Space Speedup For Resolution

Comments: 1

Satisfiability algorithms have become one of the most practical and successful approaches for solving a variety of real-world problems, including hardware verification, experimental design, planning and diagnosis problems. The main reason for the success is due to highly optimized algorithms for SAT based on resolution. The most successful of these ... more >>>


TR07-047 | 15th May 2007
Dan Gutfreund, Alexander Healy, Tali Kaufman, Guy Rothblum

A (De)constructive Approach to Program Checking

Program checking, program self-correcting and program self-testing
were pioneered by [Blum and Kannan] and [Blum, Luby and Rubinfeld] in
the mid eighties as a new way to gain confidence in software, by
considering program correctness on an input by input basis rather than
full program verification. Work in ... more >>>


TR07-048 | 3rd April 2007
Alexandr Andoni, Piotr Indyk, Robert Krauthgamer

Earth Mover Distance over High-Dimensional Spaces

The Earth Mover Distance (EMD) between two equal-size sets
of points in R^d is defined to be the minimum cost of a
bipartite matching between the two pointsets. It is a natural metric
for comparing sets of features, and as such, it has received
significant interest in computer vision. Motivated ... more >>>


TR07-049 | 1st June 2007
Beate Bollig, Niko Range, Ingo Wegener

Exact OBDD Bounds for some Fundamental Functions

Ordered binary decision diagrams (OBDDs) are nowadays the most common
dynamic data structure or representation type for Boolean functions.
Among the many areas of application are verification, model checking,
computer aided design, relational algebra, and symbolic graph algorithms.
Although many even exponential lower bounds on the OBDD size of Boolean ... more >>>


TR07-050 | 25th May 2007
Arkadev Chattopadhyay

Discrepancy and the power of bottom fan-in in depth-three circuits

We develop a new technique of proving lower bounds for the randomized communication complexity of boolean functions in the multiparty 'Number on the Forehead' model. Our method is based on the notion of voting polynomial degree of functions and extends the Degree-Discrepancy Lemma in the recent work of Sherstov (STOC'07). ... more >>>


TR07-051 | 18th April 2007
Pilar Albert, Elvira Mayordomo, Philippe Moser

Bounded Pushdown dimension vs Lempel Ziv information density

In this paper we introduce a variant of pushdown dimension called bounded pushdown (BPD) dimension, that measures the density of information contained in a sequence, relative to a BPD automata, i.e. a finite state machine equipped with an extra infinite memory stack, with the additional requirement that every input symbol ... more >>>


TR07-052 | 7th May 2007
Li Chen, Bin Fu

Linear and Sublinear Time Algorithms for the Basis of Abelian Groups

Revisions: 2

It is well known that every finite Abelian group $G$ can be
represented as a product of cyclic groups: $G=G_1\times
G_2\times\cdots G_t$, where each $G_i$ is a cyclic group of size
$p^j$ for some prime $p$ and integer $j\ge 1$. If $a_i$ is the
generator of the cyclic group of ... more >>>


TR07-053 | 27th April 2007
Jens Groth, Amit Sahai

Efficient Non-interactive Proof Systems for Bilinear Groups

Non-interactive zero-knowledge proofs and non-interactive witness-indistinguishable proofs have played a significant role in the theory of cryptography. However, lack of efficiency has prevented them from being used in practice. One of the roots of this inefficiency is that non-interactive zero-knowledge proofs have been constructed for general NP-complete languages such as ... more >>>


TR07-054 | 25th May 2007
Shirley Halevy, Oded Lachish, Ilan Newman, Dekel Tsur

Testing Properties of Constraint-Graphs

We study a model of graph related formulae that we call
the \emph{Constraint-Graph model}. A
constraint-graph is a labeled multi-graph (a graph where loops
and parallel edges are allowed), where each edge $e$ is labeled
by a distinct Boolean variable and every vertex is
associate with a Boolean function over ... more >>>


TR07-055 | 22nd May 2007
Oliver Kullmann

Constraint satisfaction problems in clausal form: Autarkies and minimal unsatisfiability

Revisions: 1

We consider the next step from boolean conjunctive normal forms to
arbitrary constraint satisfaction problems (with arbitrary constraints), namely "generalised clause-sets" (or "sets of no-goods"), which allow negative literals "v <> e" for variables v and values e --- this level of generality appears to be the right level for ... more >>>


TR07-056 | 10th July 2007
Zeev Dvir, Ariel Gabizon, Avi Wigderson

Extractors and Rank Extractors for Polynomial Sources

In this paper we construct explicit deterministic extractors from polynomial sources, namely from distributions sampled by low degree multivariate polynomials over finite fields. This naturally generalizes previous work on extraction from affine sources (which are degree 1 polynomials). A direct consequence is a deterministic extractor for distributions sampled by polynomial ... more >>>


TR07-057 | 11th July 2007
Oded Goldreich

On the Average-Case Complexity of Property Testing

Revisions: 1

Motivated by a recent study of Zimand (22nd CCC, 2007),
we consider the average-case complexity of property testing
(focusing, for clarity, on testing properties of Boolean strings).
We make two observations:

1) In the context of average-case analysis with respect to
the uniform distribution (on all strings of ... more >>>


TR07-058 | 9th June 2007
Dmitry Gavinsky

Classical Interaction Cannot Replace a Quantum Message

Revisions: 1

We demonstrate a two-player communication problem that can be solved in the one-way quantum model by a 0-error protocol of cost O(log n) but requires exponentially more communication in the classical interactive (two-way) model.

more >>>

TR07-059 | 6th July 2007
Shankar Kalyanaraman, Chris Umans

Algorithms for Playing Games with Limited Randomness

We study multiplayer games in which the participants have access to
only limited randomness. This constrains both the algorithms used to
compute equilibria (they should use little or no randomness) as well
as the mixed strategies that the participants are capable of playing
(these should be sparse). We frame algorithmic ... more >>>


TR07-060 | 11th July 2007
Tali Kaufman, Madhu Sudan

Sparse Random Linear Codes are Locally Decodable and Testable

We show that random sparse binary linear codes are locally testable and locally decodable (under any linear encoding) with constant queries (with probability tending to one). By sparse, we mean that the code should have only polynomially many codewords. Our results are the first to show that local decodability and ... more >>>


TR07-061 | 12th July 2007
Or Meir

On the Rectangle Method in proofs of Robustness of Tensor Products

Revisions: 4

Given linear two codes R,C, their tensor product $R \otimes C$
consists of all matrices whose rows are codewords of R and whose
columns are codewords of C. The product $R \otimes C$ is said to
be robust if for every matrix M that is far from $R \otimes C$
more >>>


TR07-062 | 15th July 2007
Oded Goldreich, Or Meir

The Tensor Product of Two Good Codes Is Not Necessarily Robustly Testable

Revisions: 2

Given two codes R,C, their tensor product $R \otimes C$ consists of all matrices whose rows are codewords of R and whose columns are codewords of C. The product $R \otimes C$ is said to be robust if for every matrix M that is far from $R \otimes C$ it ... more >>>


TR07-063 | 2nd July 2007
Tomas Feder, Carlos Subi

Nearly Tight Bounds on the Number of Hamiltonian Circuits of the Hypercube and Generalizations

We conjecture that for every perfect matching $M$ of the $d$-dimensional
$n$-vertex hypercube, $d\geq 2$, there exists a second perfect matching $M'$
such that the union of $M$ and $M'$ forms a Hamiltonian circuit of the
$d$-dimensional hypercube. We prove this conjecture in the case where there are
two dimensions ... more >>>


TR07-064 | 19th June 2007
Rahul Jain, Hartmut Klauck, Ashwin Nayak

Direct Product Theorems for Communication Complexity via Subdistribution Bounds

A basic question in complexity theory is whether the computational
resources required for solving k independent instances of the same
problem scale as k times the resources required for one instance.
We investigate this question in various models of classical
communication complexity.

We define a new measure, the subdistribution bound, ... more >>>


TR07-065 | 13th July 2007
Jonathan Katz

Which Languages Have 4-Round Zero-Knowledge Proofs?

We show that if a language $L$ has a 4-round, black-box, computational zero-knowledge proof system with negligible soundness error, then $\bar L \in MA$. Assuming the polynomial hierarchy does not collapse, this means, in particular, that $NP$-complete languages do not have 4-round zero-knowledge proofs (at least with respect to black-box ... more >>>


TR07-066 | 24th April 2007
Maciej Liskiewicz, Christian Hundt

A Combinatorial Geometric Approach to Linear Image Matching

The problem of image matching is to find for two given digital images $A$ and $B$
an admissible transformation that converts image $A$ as close as possible to $B$.
This problem becomes hard if the space of admissible transformations is too complex.
Consequently, in many real applications, like the ones ... more >>>


TR07-067 | 22nd May 2007
Paul Spirakis, haralampos tsaknakis

Computing 1/3-approximate Nash equilibria of bimatrix games in polynomial time.

Revisions: 2

In this paper we propose a methodology for determining approximate Nash equilibria of non-cooperative bimatrix games and, based on that, we provide a polynomial time algorithm that computes $\frac{1}{3} + \frac{1}{p(n)} $ -approximate equilibria, where $p(n)$ is a polynomial controlled by our algorithm and proportional to its running time. The ... more >>>


TR07-068 | 24th July 2007
Thomas Thierauf, Fabian Wagner

The Isomorphism Problem for Planar 3-Connected Graphs is in Unambiguous Logspace

The isomorphism problem for planar graphs is known to be efficiently solvable. For planar 3-connected graphs, the isomorphism problem can be solved by efficient parallel algorithms, it is in the class AC^1.

In this paper we improve the upper bound for planar 3-connected graphs to unambiguous logspace, in fact to ... more >>>


TR07-069 | 29th July 2007
Ronen Shaltiel, Chris Umans

Low-end uniform hardness vs. randomness tradeoffs for AM

In 1998, Impagliazzo and Wigderson proved a hardness vs. randomness tradeoff for BPP in the {\em uniform setting}, which was subsequently extended to give optimal tradeoffs for the full range of possible hardness assumptions by Trevisan and Vadhan (in a slightly weaker setting). In 2003, Gutfreund, Shaltiel and Ta-Shma proved ... more >>>


TR07-070 | 11th June 2007
Nir Ailon, Edo Liberty

Fast Dimension Reduction Using Rademacher Series on Dual BCH Codes

\begin{abstract}
The Fast Johnson-Lindenstrauss Transform was recently discovered by
Ailon and Chazelle as a technique for performing fast dimension
reduction from $\ell_2^d$ to $\ell_2^k$ in time $O(\max\{d\log d,
k^3\})$, where $k$ is the target lower dimension. This beats the
naive $O(dk)$ achieved by multiplying by random dense matrices, as
noticed ... more >>>


TR07-071 | 1st August 2007
Jacobo Toran

Reductions to Graph Isomorphism

We show that several reducibility notions coincide when applied to the
Graph Isomorphism (GI) problem. In particular we show that if a set is
many-one logspace reducible to GI, then it is in fact many-one AC^0
reducible to GI. For the case of Turing reducibilities we show that ... more >>>


TR07-072 | 2nd July 2007
Alexander A. Sherstov

Communication Complexity under Product and Nonproduct Distributions

We solve an open problem of Kushilevitz and Nisan
(1997) in communication complexity. Let $R_{eps}(f)$
and $D^{mu}_{eps}(f)$ denote the randomized and
$mu$-distributional communication complexities of
f, respectively ($eps$ a small constant). Yao's
well-known Minimax Principle states that
R_{eps}(f) = max_{mu} { D^{mu}_{eps}(f) }.
Kushilevitz and Nisan (1997) ask whether ... more >>>


TR07-073 | 3rd August 2007
Parikshit Gopalan, Subhash Khot, Rishi Saket

Hardness of Reconstructing Multivariate Polynomials over Finite Fields

We study the polynomial reconstruction problem for low-degree
multivariate polynomials over finite fields. In the GF[2] version of this problem, we are given a set of points on the hypercube and target values $f(x)$ for each of these points, with the promise that there is a polynomial over GF[2] of ... more >>>


TR07-074 | 7th August 2007
Dmitry Gavinsky, Pavel Pudlak

Exponential Separation of Quantum and Classical Non-Interactive Multi-Party Communication Complexity

We give the first exponential separation between quantum and
classical multi-party
communication complexity in the (non-interactive) one-way and
simultaneous message
passing settings.
For every k, we demonstrate a relational communication problem
between k parties
that can be solved exactly by a quantum simultaneous message passing
protocol of
cost ... more >>>


TR07-075 | 9th August 2007
Shachar Lovett

Unconditional pseudorandom generators for low degree polynomials

We give an explicit construction of pseudorandom
generators against low degree polynomials over finite fields. We
show that the sum of $2^d$ small-biased generators with error
$\epsilon^{2^{O(d)}}$ is a pseudorandom generator against degree $d$
polynomials with error $\epsilon$. This gives a generator with seed
length $2^{O(d)} \log{(n/\epsilon)}$. Our construction follows ... more >>>


TR07-076 | 25th July 2007
Satyen Kale, C. Seshadhri

Testing Expansion in Bounded Degree Graphs

Revisions: 1

We consider the problem of testing graph expansion in the bounded degree model. We give a property tester that given a graph with degree bound $d$, an expansion bound $\alpha$, and a parameter $\epsilon > 0$, accepts the graph with high probability if its expansion is more than $\alpha$, and ... more >>>


TR07-077 | 7th August 2007
Ilias Diakonikolas, Homin Lee, Kevin Matulef, Krzysztof Onak, Ronitt Rubinfeld, Rocco Servedio, Andrew Wan

Testing for Concise Representations

We describe a general method for testing whether a function on n input variables has a concise representation. The approach combines ideas from the junta test of Fischer et al. with ideas from learning theory, and yields property testers that make poly(s/epsilon) queries (independent of n) for Boolean function classes ... more >>>


TR07-078 | 11th August 2007
Ran Raz, Iddo Tzameret

Resolution over Linear Equations and Multilinear Proofs

We develop and study the complexity of propositional proof systems of varying strength extending resolution by allowing it to operate with disjunctions of linear equations instead of clauses. We demonstrate polynomial-size refutations for hard tautologies like the pigeonhole principle, Tseitin graph tautologies and the clique-coloring tautologies in these proof systems. ... more >>>


TR07-079 | 11th August 2007
Emanuele Viola, Avi Wigderson

One-way multi-party communication lower bound for pointer jumping with applications

In this paper we study the one-way multi-party communication model,
in which every party speaks exactly once in its turn. For every
fixed $k$, we prove a tight lower bound of
$\Omega{n^{1/(k-1)}}$ on the probabilistic communication
complexity of pointer jumping in a $k$-layered tree, where the
pointers of the $i$-th ... more >>>


TR07-080 | 7th August 2007
Chris Peikert, Brent Waters

Lossy Trapdoor Functions and Their Applications

We propose a new general primitive called lossy trapdoor
functions (lossy TDFs), and realize it under a variety of different
number theoretic assumptions, including hardness of the decisional
Diffie-Hellman (DDH) problem and the worst-case hardness of
standard lattice problems.

Using lossy TDFs, we develop a new approach for constructing ... more >>>


TR07-081 | 10th August 2007
Andrej Bogdanov, Emanuele Viola

Pseudorandom bits for polynomials

We present a new approach to constructing pseudorandom generators that fool low-degree polynomials over finite fields, based on the Gowers norm. Using this approach, we obtain the following main constructions of explicitly computable generators $G : \F^s \to \F^n$ that fool polynomials over a prime field $\F$:
\begin{enumerate}
\item a ... more >>>


TR07-082 | 27th July 2007
Christian Borgs, Jennifer Chayes, Nicole Immorlica, Adam Kalai, Vahab Mirrokni, Christos H. Papadimitriou

The Myth of the Folk Theorem

The folk theorem suggests that finding Nash Equilibria
in repeated games should be easier than in one-shot games. In
contrast, we show that the problem of finding any (epsilon) Nash
equilibrium for a three-player infinitely-repeated game is
computationally intractable (even when all payoffs are in
{-1,0,-1}), unless all of PPAD ... more >>>


TR07-083 | 23rd August 2007
Artur Czumaj, Asaf Shapira, Christian Sohler

Testing Hereditary Properties of Non-Expanding Bounded-Degree Graphs


We study property testing in the model of bounded degree graphs. It
is well known that in this model many graph properties cannot be
tested with a constant number of queries and it seems reasonable to
conjecture that only few are testable with o(sqrt{n}) queries.
Therefore in this paper ... more >>>


TR07-084 | 4th September 2007
Brendan Juba, Madhu Sudan

Universal Semantic Communication I

Is it possible for two intelligent beings to communicate meaningfully, without any common language or background? This question has interest on its own, but is especially relevant in the context of modern computational infrastructures where an increase in the diversity of computers is making the task of inter-computer interaction increasingly ... more >>>


TR07-085 | 2nd September 2007
Ran Raz, Amir Yehudayoff

Multilinear Formulas, Maximal-Partition Discrepancy and Mixed-Sources Extractors

We study multilinear formulas, monotone arithmetic circuits, maximal-partition discrepancy, best-partition communication complexity and extractors constructions. We start by proving lower bounds for an explicit polynomial for the following three subclasses of syntactically multilinear arithmetic formulas over the field C and the set of variables {x1,...,xn}:

1. Noise-resistant. A syntactically multilinear ... more >>>


TR07-086 | 7th September 2007
Venkatesan Guruswami, James R. Lee, Alexander Razborov

Almost Euclidean subspaces of $\ell_1^N$ via expander codes

We give an explicit (in particular, deterministic polynomial time)
construction of subspaces $X
\subseteq \R^N$ of dimension $(1-o(1))N$ such that for every $x \in X$,
$$(\log N)^{-O(\log\log\log N)} \sqrt{N}\, \|x\|_2 \leq \|x\|_1 \leq \sqrt{N}\, \|x\|_2.$$
If we are allowed to use $N^{1/\log\log N}\leq N^{o(1)}$ random bits
and ... more >>>


TR07-087 | 11th July 2007
Nutan Limaye, Meena Mahajan, B. V. Raghavendra Rao

Arithmetizing classes around NC^1 and L

The parallel complexity class NC^1 has many equivalent models such as
polynomial size formulae and bounded width branching
programs. Caussinus et al. \cite{CMTV} considered arithmetizations of
two of these classes, #NC^1 and #BWBP. We further this study to
include arithmetization of other classes. In particular, we show that
counting paths ... more >>>


TR07-088 | 7th September 2007
Elad Hazan, C. Seshadhri

Adaptive Algorithms for Online Decision Problems

Revisions: 1

We study the notion of learning in an oblivious changing environment. Existing online learning algorithms which minimize regret are shown to converge to the average of all locally optimal solutions. We propose a new performance metric, strengthening the standard metric of regret, to capture convergence to locally optimal solutions, and ... more >>>


TR07-089 | 13th September 2007
Parikshit Gopalan, Venkatesan Guruswami

Deterministic Hardness Amplification via Local GMD Decoding

We study the average-case hardness of the class NP against
deterministic polynomial time algorithms. We prove that there exists
some constant $\mu > 0$ such that if there is some language in NP
for which no deterministic polynomial time algorithm can decide L
correctly on a $1- (log n)^{-\mu}$ fraction ... more >>>


TR07-090 | 11th September 2007
Shachar Lovett

Tight lower bounds for adaptive linearity tests

Revisions: 1 , Comments: 1

Linearity tests are randomized algorithms which have oracle access to the truth table of some function $f$,
which are supposed to distinguish between linear functions and functions which are far from linear. Linearity tests were first introduced by Blum, Luby and Rubenfeld in \cite{BLR93}, and were later used in the ... more >>>


TR07-091 | 10th September 2007
Martin Grohe

Logic, Graphs, and Algorithms

Algorithmic meta theorems are algorithmic results that apply to whole families of combinatorial problems, instead of just specific problems. These families are usually defined in terms of logic and graph theory. An archetypal algorithmic meta theorem is Courcelle's Theorem, which states that all graph properties definable in monadic second-order logic ... more >>>


TR07-092 | 10th July 2007
Piotr Berman, Bhaskar DasGupta

Approximating the Online Set Multicover Problems Via Randomized Winnowing

In this paper, we consider the weighted online set k-multicover problem. In this problem, we have an universe V of elements, a family SS of subsets of V with a positive real cost for every S\in SS, and a ``coverage factor'' (positive integer) k. A subset \{i_0,i_1,\ldots\ \subseteq V of ... more >>>


TR07-093 | 27th July 2007
Andrei A. Bulatov

The complexity of the counting constraint satisfaction problem

Revisions: 1

The Counting Constraint Satisfaction Problem (#CSP(H)) over a finite
relational structure H can be expressed as follows: given a
relational structure G over the same vocabulary,
determine the number of homomorphisms from G to H.
In this paper we characterize relational structures H for which
#CSP(H) can be solved in ... more >>>


TR07-094 | 3rd August 2007
Christian Glaßer, Heinz Schmitz, Victor Selivanov

Efficient Algorithms for Membership in Boolean Hierarchies of Regular Languages

The purpose of this paper is to provide efficient algorithms that decide membership for classes of several Boolean hierarchies for which efficiency (or even decidability) were previously not known. We develop new forbidden-chain characterizations for the single levels of these hierarchies and obtain the following results:

1. The classes of ... more >>>


TR07-095 | 13th July 2007
Vikraman Arvind, Partha Mukhopadhyay

The Ideal Membership Problem and Polynomial Identity Testing

Revisions: 2

\begin{abstract}
Given a monomial ideal $I=\angle{m_1,m_2,\cdots,m_k}$ where $m_i$
are monomials and a polynomial $f$ as an arithmetic circuit the
\emph{Ideal Membership Problem } is to test if $f\in I$. We study
this problem and show the following results.
\begin{itemize}
\item[(a)] If the ideal $I=\angle{m_1,m_2,\cdots,m_k}$ for a
more >>>


TR07-096 | 8th October 2007
Lance Fortnow, Rahul Santhanam

Infeasibility of Instance Compression and Succinct PCPs for NP

We study the notion of "instance compressibility" of NP problems [Harnik-Naor06], closely related to the notion of kernelization in parameterized complexity theory [Downey-Fellows99, Flum-Grohe06, Niedermeier06]. A language $L$ in NP is instance compressible if there
is a polynomial-time computable function $f$ and a set $A$ such that
for each instance ... more >>>


TR07-097 | 8th October 2007
Miklos Ajtai, Cynthia Dwork

The First and Fourth Public-Key Cryptosystems with Worst-Case/Average-Case Equivalence.

We describe a public-key cryptosystem with worst-case/average case
equivalence. The cryptosystem has an amortized plaintext to
ciphertext expansion of $O(n)$, relies on the hardness of the
$\tilde O(n^2)$-unique shortest vector problem for lattices, and
requires a public key of size at most $O(n^4)$ bits. The new
cryptosystem generalizes a conceptually ... more >>>


TR07-098 | 2nd October 2007
Tali Kaufman, Simon Litsyn, Ning Xie

Breaking the $\epsilon$-Soundness Bound of the Linearity Test over GF(2)

For Boolean functions that are $\epsilon$-far from the set of linear functions, we study the lower bound on the rejection probability (denoted $\textsc{rej}(\epsilon)$) of the linearity test suggested by Blum, Luby and Rubinfeld. The interest in this problem is partly due to its relation to PCP constructions and hardness of ... more >>>


TR07-099 | 30th September 2007
Dieter van Melkebeek

A Survey of Lower Bounds for Satisfiability and Related Problems

Ever since the fundamental work of Cook from 1971, satisfiability has been recognized as a central problem in computational complexity. It is widely believed to be intractable, and yet till recently even a linear-time, logarithmic-space algorithm for satisfiability was not ruled out. In 1997 Fortnow, building on earlier work by ... more >>>


TR07-100 | 25th September 2007
Alexander A. Sherstov

The Pattern Matrix Method for Lower Bounds on Quantum Communication

In a breakthrough result, Razborov (2003) gave optimal
lower bounds on the communication complexity of every function f
of the form f(x,y)=D(|x AND y|) for some D:{0,1,...,n}->{0,1}, in
the bounded-error quantum model with and without prior entanglement.
This was proved by the _multidimensional_ discrepancy method. We
give an entirely ... more >>>


TR07-101 | 10th September 2007
Patrick Briest, Martin Hoefer, Piotr Krysta

Stackelberg Network Pricing Games

Revisions: 1

We study a multi-player one-round game termed Stackelberg Network Pricing Game, in which a leader can set prices for a subset of m pricable edges in a graph. The other edges have a fixed cost. Based on the leader's decision one or more followers optimize a polynomial-time solvable combinatorial minimization ... more >>>


TR07-102 | 4th October 2007
Andrej Bogdanov, Muli Safra

Hardness amplification for errorless heuristics

An errorless heuristic is an algorithm that on all inputs returns either the correct answer or the special symbol "I don't know." A central question in average-case complexity is whether every distributional decision problem in NP has an errorless heuristic scheme: This is an algorithm that, for every &delta; > ... more >>>


TR07-103 | 28th September 2007
Emanuele Viola

Selected Results in Additive Combinatorics: An Exposition

We give a self-contained exposition of selected results in additive
combinatorics over the group {0,1}^n. In particular, we prove the
celebrated theorems known as the Balog-Szemeredi-Gowers theorem ('94 and '98) and
the
Freiman-Ruzsa theorem ('73 and '99), leading to the remarkable result
by Samorodnitsky ('07) that linear transformations are efficiently ... more >>>


TR07-104 | 15th September 2007
Moses Charikar, Konstantin Makarychev, Yury Makarychev

On the Advantage over Random for Maximum Acyclic Subgraph

In this paper we present a new approximation algorithm for the MAX ACYCLIC SUBGRAPH problem. Given an instance where the maximum acyclic subgraph contains (1/2 + delta) fraction of all edges, our algorithm finds an acyclic subgraph with (1/2 + Omega(delta/ log n)) fraction of all edges.

more >>>

TR07-105 | 21st September 2007
Jelani Nelson

A Note on Set Cover Inapproximability Independent of Universe Size

Revisions: 1

In the set cover problem we are given a collection of $m$ sets whose union covers $[n] = \{1,\ldots,n\}$ and must find a minimum-sized subcollection whose union still covers $[n]$. We investigate the approximability of set cover by an approximation ratio that depends only on $m$ and observe that, for ... more >>>


TR07-106 | 10th September 2007
Yijia Chen, Martin Grohe, Magdalena Grüber

On Parameterized Approximability

Combining classical approximability questions with parameterized complexity, we introduce a theory of parameterized approximability.
The main intention of this theory is to deal with the efficient approximation of small cost solutions for optimisation problems.

more >>>

TR07-107 | 26th October 2007
Nathan Segerlind

Exponential lower bounds and integrality gaps for tree-like Lovasz-Schrijver procedures

The matrix cuts of Lov{\'{a}}sz and Schrijver are methods for tightening linear relaxations of zero-one programs by the addition of new linear inequalities. We address the question of how many new inequalities are necessary to approximate certain combinatorial problems with strong guarantees, and to solve certain instances of Boolean satisfiability.

... more >>>

TR07-108 | 27th October 2007
Moses Charikar, Konstantin Makarychev, Yury Makarychev

Local Global Tradeoffs in Metric Embeddings

Suppose that every k points in a n point metric space X are D-distortion embeddable into l_1. We give upper and lower bounds on the distortion required to embed the entire space X into l_1. This is a natural mathematical question and is also motivated by the study of relaxations ... more >>>


TR07-109 | 7th October 2007
Venkatesan Guruswami, Atri Rudra

Better Binary List-Decodable Codes via Multilevel Concatenation

We give a polynomial time construction of binary codes with the best
currently known trade-off between rate and error-correction
radius. Specifically, we obtain linear codes over fixed alphabets
that can be list decoded in polynomial time up to the so called
Blokh-Zyablov bound. Our work ... more >>>


TR07-110 | 24th October 2007
Beate Bollig

The Optimal Read-Once Branching Program Complexity for the Direct Storage Access Function

Branching programs are computation models
measuring the space of (Turing machine) computations.
Read-once branching programs (BP1s) are the
most general model where each graph-theoretical path is the computation
path for some input. Exponential lower bounds on the size of read-once
branching programs are known since a long time. Nevertheless, there ... more >>>


TR07-111 | 1st November 2007
Tali Kaufman, Madhu Sudan

Algebraic Property Testing: The Role of Invariance

We argue that the symmetries of a property being tested play a
central role in property testing. We support this assertion in the
context of algebraic functions, by examining properties of functions
mapping a vector space $\K^n$ over a field $\K$ to a subfield $\F$.
We consider $\F$-linear properties that ... more >>>


TR07-112 | 25th September 2007
Alexander A. Sherstov

Unbounded-Error Communication Complexity of Symmetric Functions

The sign-rank of a real matrix M is the least rank
of a matrix R in which every entry has the same sign as the
corresponding entry of M. We determine the sign-rank of every
matrix of the form M=[ D(|x AND y|) ]_{x,y}, where
D:{0,1,...,n}->{-1,+1} is given and ... more >>>


TR07-113 | 15th November 2007
Matthew Andrews, Julia Chuzhoy, Venkatesan Guruswami, Sanjeev Khanna, Kunal Talwar, Lisa Zhang

Inapproximability of edge-disjoint paths and low congestion routing on undirected graphs

In the undirected Edge-Disjoint Paths problem with Congestion
(EDPwC), we are given an undirected graph with $V$ nodes, a set of
terminal pairs and an integer $c$. The objective is to route as many
terminal pairs as possible, subject to the constraint that at most
$c$ demands can be routed ... more >>>


TR07-114 | 28th September 2007
Jakob Nordström

A Simplified Way of Proving Trade-off Results for Resolution

We present a greatly simplified proof of the length-space
trade-off result for resolution in Hertel and Pitassi (2007), and
also prove a couple of other theorems in the same vein. We point
out two important ingredients needed for our proofs to work, and
discuss possible conclusions to be drawn regarding ... more >>>


TR07-115 | 19th November 2007
Or Meir

Combinatorial Construction of Locally Testable Codes

An error correcting code is said to be locally testable if there is a test that checks whether a given string is a codeword, or rather far from the code, by reading only a constant number of symbols of the string. Locally Testable Codes (LTCs) were first systematically studied by ... more >>>


TR07-116 | 25th September 2007
Alexander A. Sherstov

Approximate Inclusion-Exclusion for Arbitrary Symmetric Functions

Comments: 1

Let A_1,...,A_n be events in a probability space. The
approximate inclusion-exclusion problem, due to Linial and
Nisan (1990), is to estimate Pr[A_1 OR ... OR A_n] given
Pr[AND_{i\in S}A_i] for all |S|<=k. Kahn et al. (1996) solve
this problem optimally for each k. We study the following more
general question: ... more >>>


TR07-117 | 8th November 2007
Edward Hirsch, Dmitry Itsykson

An infinitely-often one-way function based on an average-case assumption

We assume the existence of a function f that is computable in polynomial time but its inverse function is not computable in randomized average-case polynomial time. The cryptographic setting is, however, different: even for a weak one-way function, every possible adversary should fail on a polynomial fraction of inputs. Nevertheless, ... more >>>


TR07-118 | 27th November 2007
Asaf Nachmias, Asaf Shapira

Testing the Expansion of a Graph

We study the problem of testing the expansion of
graphs with bounded degree d in sublinear time. A graph is said to
be an \alpha-expander if every vertex set U \subset V of size at
most |V|/2 has a neighborhood of size at least \alpha|U|.

We show that the algorithm ... more >>>


TR07-119 | 5th December 2007
Piotr Berman, Bhaskar DasGupta, Marek Karpinski

Approximating Transitive Reductions for Directed Networks

We consider <i>minimum equivalent digraph</i> (<i>directed network</i>) problem (also known as the <i>strong transitive reduction</i>), its maximum optimization variant, and some extensions of those two types of problems. We prove the existence of polynomial time approximation algorithms with ratios 1.5 for all the minimization problems and 2 for all the ... more >>>


TR07-120 | 5th October 2007
Sharon Feldman, Guy Kortsarz, Zeev Nutov

Improved approximation algorithms for directed Steiner forest

We consider the k-Directed Steiner Forest} (k-dsf) problem:
given a directed graph G=(V,E) with edge costs, a collection D subseteq V \times V
of ordered node pairs, and an integer k leq |D|, find a minimum cost subgraph
H of G
that contains an st-path for (at least) k ... more >>>


TR07-121 | 21st November 2007
Zeev Dvir, Amir Shpilka, Amir Yehudayoff

Hardness-Randomness Tradeoffs for Bounded Depth Arithmetic Circuits

In this paper we show that lower bounds for bounded depth arithmetic circuits imply derandomization of polynomial identity testing for bounded depth arithmetic circuits. More formally, if there exists an explicit polynomial f(x_1,...,x_m) that cannot be computed by a depth d arithmetic circuit of small size then there exists ... more >>>


TR07-122 | 22nd November 2007
Zeev Dvir, Amir Shpilka

Towards Dimension Expanders Over Finite Fields

In this paper we study the problem of explicitly constructing a
{\em dimension expander} raised by \cite{BISW}: Let $\mathbb{F}^n$
be the $n$ dimensional linear space over the field $\mathbb{F}$.
Find a small (ideally constant) set of linear transformations from
$\F^n$ to itself $\{A_i\}_{i \in I}$ such that for every linear
more >>>


TR07-123 | 21st November 2007
Shachar Lovett, Roy Meshulam, Alex Samorodnitsky

Inverse Conjecture for the Gowers norm is false

Revisions: 2


Let $p$ be a fixed prime number, and $N$ be a large integer.
The 'Inverse Conjecture for the Gowers norm' states that if the "$d$-th Gowers norm" of a function $f:\F_p^N \to \F_p$ is non-negligible, that is larger than a constant independent of $N$, then $f$ can be non-trivially ... more >>>


TR07-124 | 23rd November 2007
Nitin Saxena

Diagonal Circuit Identity Testing and Lower Bounds

In this paper we give the first deterministic polynomial time algorithm for testing whether a {\em diagonal} depth-$3$ circuit $C(\arg{x}{n})$ (i.e. $C$ is a sum of powers of linear functions) is zero. We also prove an exponential lower bound showing that such a circuit will compute determinant or permanent only ... more >>>


TR07-125 | 11th October 2007
Ali Juma, Valentine Kabanets, Charles Rackoff, Amir Shpilka

The black-box query complexity of polynomial summation

For any given Boolean formula $\phi(x_1,\dots,x_n)$, one can
efficiently construct (using \emph{arithmetization}) a low-degree
polynomial $p(x_1,\dots,x_n)$ that agrees with $\phi$ over all
points in the Boolean cube $\{0,1\}^n$; the constructed polynomial
$p$ can be interpreted as a polynomial over an arbitrary field
$\mathbb{F}$. The problem ... more >>>


TR07-126 | 5th November 2007
Nathan Segerlind

On the relative efficiency of resolution-like proofs and ordered binary decision diagram proofs

We show that tree-like OBDD proofs of unsatisfiability require an exponential increase ($s \mapsto 2^{s^{\Omega(1)}}$) in proof size to simulate unrestricted resolution, and that unrestricted OBDD proofs of unsatisfiability require an almost-exponential increase ($s \mapsto 2^{ 2^{\left( \log s \right)^{\Omega(1)}}}$) in proof size to simulate $\Res{O(\log n)}$. The ``OBDD proof ... more >>>


TR07-127 | 22nd November 2007
Arie Matsliah, Eli Ben-Sasson, Prahladh Harsha, Oded Lachish

Sound 3-query PCPPs are Long

We initiate the study of the tradeoff between the {\em length} of a
probabilistically checkable proof of proximity (PCPP) and the
maximal {\em soundness} that can be guaranteed by a $3$-query
verifier with oracle access to the proof. Our main observation is
that a verifier limited to querying a short ... more >>>


TR07-128 | 10th November 2007
Kevin Matulef, Ryan O'Donnell, Ronitt Rubinfeld, Rocco Servedio

Testing Halfspaces

This paper addresses the problem of testing whether a Boolean-valued function f is a halfspace, i.e. a function of the form f(x)=sgn(w &#8901; x - &#952;). We consider halfspaces over the continuous domain R^n (endowed with the standard multivariate Gaussian distribution) as well as halfspaces over the Boolean cube {-1,1}^n ... more >>>


TR07-129 | 25th October 2007
Jeffrey C. Jackson, Homin Lee, Rocco Servedio, Andrew Wan

Learning Random Monotone DNF

We give an algorithm that with high probability properly learns random monotone t(n)-term
DNF under the uniform distribution on the Boolean cube {0, 1}^n. For any polynomially bounded function t(n) <= poly(n) the algorithm runs in time poly(n, 1/eps) and with high probability outputs an eps accurate monotone DNF ... more >>>


TR07-130 | 3rd December 2007
Ronen Shaltiel, Emanuele Viola

Hardness amplification proofs require majority

Hardness amplification is the fundamental task of
converting a $\delta$-hard function $f : {0,1}^n ->
{0,1}$ into a $(1/2-\eps)$-hard function $Amp(f)$,
where $f$ is $\gamma$-hard if small circuits fail to
compute $f$ on at least a $\gamma$ fraction of the
inputs. Typically, $\eps,\delta$ are small (and
$\delta=2^{-k}$ captures the case ... more >>>


TR07-131 | 16th November 2007
Satyen Kale

Boosting and hard-core set constructions: a simplified approach

We revisit the connection between boosting algorithms and hard-core set constructions discovered by Klivans and Servedio. We present a boosting algorithm with a certain smoothness property that is necessary for hard-core set constructions: the distributions it generates do not put too much weight on any single example. We then use ... more >>>


TR07-132 | 8th December 2007
Emanuele Viola

The sum of d small-bias generators fools polynomials of degree d

We prove that the sum of $d$ small-bias generators $L
: \F^s \to \F^n$ fools degree-$d$ polynomials in $n$
variables over a prime field $\F$, for any fixed
degree $d$ and field $\F$, including $\F = \F_2 =
{0,1}$.

Our result improves on both the work by Bogdanov and
Viola ... more >>>


TR07-133 | 20th November 2007
Craig Gentry, Chris Peikert, Vinod Vaikuntanathan

Trapdoors for Hard Lattices and New Cryptographic Constructions

We show how to construct a variety of ``trapdoor'' cryptographic tools
assuming the worst-case hardness of standard lattice problems (such as
approximating the shortest nonzero vector to within small factors).
The applications include trapdoor functions with \emph{preimage
sampling}, simple and efficient ``hash-and-sign'' digital signature
schemes, universally composable oblivious transfer, ... more >>>


TR07-134 | 14th December 2007
Jeff Kinne, Dieter van Melkebeek

Space Hierarchy Results for Randomized and Other Semantic Models

Revisions: 1

We prove space hierarchy and separation results for randomized and other semantic models of computation with advice. Previous works on hierarchy and separation theorems for such models focused on time as the resource. We obtain tighter results with space as the resource. Our main theorems are the following.

Let <i>s</i>(<i>n</i>) ... more >>>


TR07-135 | 26th December 2007
Paul Valiant, Paul Valiant

Testing Symmetric Properties of Distributions

We introduce the notion of a Canonical Tester for a class of properties, that is, a tester strong and
general enough that ``a property is testable if and only if the
Canonical Tester tests it''. We construct a Canonical Tester
for the class of symmetric properties of one or two
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TR07-136 | 28th November 2007
Felix Brandt, Felix Fischer, Markus Holzer

Equilibria of Graphical Games with Symmetries

We study graphical games where the payoff function of each player satisfies one of four types of symmetries in the actions of his neighbors. We establish that deciding the existence of a pure Nash equilibrium is NP-hard in graphical games with each of the four types of symmetry. Using a ... more >>>


TR07-137 | 6th November 2007
Yijia Chen, Jörg Flum, Moritz Müller

Lower Bounds for Kernelizations

Among others, refining the methods of [Fortnow and Santhanam, ECCC Report TR07-096] we improve a result of this paper and show for any parameterized problem with a ``linear weak OR'' and with NP-hard underlying classical problem that there is no polynomial reduction from the problem to itself that assigns to ... more >>>




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