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All reports by Author Ran Raz:

TR17-121 | 31st July 2017
Sumegha Garg, Ran Raz, Avishay Tal

Extractor-Based Time-Space Lower Bounds for Learning

A matrix $M: A \times X \rightarrow \{-1,1\}$ corresponds to the following learning problem: An unknown element $x \in X$ is chosen uniformly at random. A learner tries to learn $x$ from a stream of samples, $(a_1, b_1), (a_2, b_2) \ldots$, where for every $i$, $a_i \in A$ is chosen ... more >>>

TR17-020 | 12th February 2017
Ran Raz

A Time-Space Lower Bound for a Large Class of Learning Problems

We prove a general time-space lower bound that applies for a large class of learning problems and shows that for every problem in that class, any learning algorithm requires either a memory of quadratic size or an exponential number of samples.

Our result is stated in terms of the norm ... more >>>

TR16-113 | 22nd July 2016
Gillat Kol, Ran Raz, Avishay Tal

Time-Space Hardness of Learning Sparse Parities

We define a concept class ${\cal F}$ to be time-space hard (or memory-samples hard) if any learning algorithm for ${\cal F}$ requires either a memory of size super-linear in $n$ or a number of samples super-polynomial in $n$, where $n$ is the length of one sample.

A recent work shows ... more >>>

TR16-019 | 5th February 2016
Ran Raz

Fast Learning Requires Good Memory: A Time-Space Lower Bound for Parity Learning

We prove that any algorithm for learning parities requires either a memory of quadratic size or an exponential number of samples. This proves a recent conjecture of Steinhardt, Valiant and Wager and shows that for some learning problems a large storage space is crucial.

More formally, in the problem of ... more >>>

TR15-088 | 31st May 2015
Anat Ganor, Gillat Kol, Ran Raz

Exponential Separation of Communication and External Information

We show an exponential gap between communication complexity and external information complexity, by analyzing a communication task suggested as a candidate by Braverman [Bra13]. Previously, only a separation of communication complexity and internal information complexity was known [GKR14,GKR15].

More precisely, we obtain an explicit example of a search problem with ... more >>>

TR14-170 | 10th December 2014
Yael Tauman Kalai, Ran Raz

On the Space Complexity of Linear Programming with Preprocessing

Revisions: 1

Linear Programs are abundant in practice, and tremendous effort has been put into designing efficient algorithms for such problems, resulting with very efficient (polynomial time) algorithms. A fundamental question is: what is the space complexity of Linear Programming?

It is widely believed that (even approximating) Linear Programming requires a large ... more >>>

TR14-113 | 27th August 2014
Anat Ganor, Gillat Kol, Ran Raz

Exponential Separation of Information and Communication for Boolean Functions

We show an exponential gap between communication complexity and information complexity for boolean functions, by giving an explicit example of a partial function with information complexity $\leq O(k)$, and distributional communication complexity $\geq 2^k$. This shows that a communication protocol for a partial boolean function cannot always be compressed to ... more >>>

TR14-049 | 11th April 2014
Anat Ganor, Gillat Kol, Ran Raz

Exponential Separation of Information and Communication

Revisions: 1

We show an exponential gap between communication complexity and information complexity, by giving an explicit example for a communication task (relation), with information complexity $\leq O(k)$, and distributional communication complexity $\geq 2^k$. This shows that a communication protocol cannot always be compressed to its internal information. By a result of ... more >>>

TR14-023 | 19th February 2014
Gil Cohen, Anat Ganor, Ran Raz

Two Sides of the Coin Problem

Revisions: 1

In the Coin Problem, one is given n independent flips of a coin that has bias $\beta > 0$ towards either Head or Tail. The goal is to decide which side the coin is biased towards, with high confidence. An optimal strategy for solving the coin problem is to apply ... more >>>

TR13-183 | 22nd December 2013
Yael Tauman Kalai, Ran Raz, Ron Rothblum

How to Delegate Computations: The Power of No-Signaling Proofs

Revisions: 1

We construct a 1-round delegation scheme (i.e., argument-system) for every language computable in time t=t(n), where the running time of the prover is poly(t) and the running time of the verifier is n*polylog(t). In particular, for every language in P we obtain a delegation scheme with almost linear time verification. ... more >>>

TR13-107 | 7th August 2013
Gil Cohen, Ivan Bjerre Damgard, Yuval Ishai, Jonas Kolker, Peter Bro Miltersen, Ran Raz, Ron Rothblum

Efficient Multiparty Protocols via Log-Depth Threshold Formulae

We put forward a new approach for the design of efficient multiparty protocols:

1. Design a protocol for a small number of parties (say, 3 or 4) which achieves
security against a single corrupted party. Such protocols are typically easy
to construct as they may employ techniques that do not ... more >>>

TR13-064 | 22nd April 2013
Anat Ganor, Ran Raz

Space Pseudorandom Generators by Communication Complexity Lower Bounds

Revisions: 1

In 1989, Babai, Nisan and Szegedy [BNS92] gave a construction of a pseudorandom generator for logspace, based on lower bounds for multiparty communication complexity. The seed length of their pseudorandom generator was $2^{\Theta(\sqrt n)}\,\,\,$, because the best lower bounds for multiparty communication complexity are relatively weak. Subsequently, pseudorandom generators for ... more >>>

TR13-058 | 5th April 2013
Ilan Komargodski, Ran Raz, Avishay Tal

Improved Average-Case Lower Bounds for DeMorgan Formula Size

Revisions: 2

We give a function $h:\{0,1\}^n\to\{0,1\}$ such that every deMorgan formula of size $n^{3-o(1)}/r^2$ agrees with $h$ on at most a fraction of $\frac{1}{2}+2^{-\Omega(r)}$ of the inputs. This improves the previous average-case lower bound of Komargodski and Raz (STOC, 2013).

Our technical contributions include a theorem that shows that the ``expected ... more >>>

TR13-020 | 2nd February 2013
Tom Gur, Ran Raz

Arthur-Merlin Streaming Complexity

We study the power of Arthur-Merlin probabilistic proof systems in the data stream model. We show a canonical $\mathcal{AM}$ streaming algorithm for a wide class of data stream problems. The algorithm offers a tradeoff between the length of the proof and the space complexity that is needed to verify it.

... more >>>

TR13-001 | 2nd January 2013
Gillat Kol, Ran Raz

Interactive Channel Capacity

Revisions: 1

We study the interactive channel capacity of an $\epsilon$-noisy channel. The interactive channel capacity $C(\epsilon)$ is defined as the minimal ratio between the communication complexity of a problem (over a non-noisy channel), and the communication complexity of the same problem over the binary symmetric channel with noise rate $\epsilon$, where ... more >>>

TR12-174 | 12th December 2012
Anat Ganor, Ilan Komargodski, Ran Raz

The Spectrum of Small DeMorgan Formulas

Revisions: 1

We show a connection between the deMorgan formula size of a Boolean function and the noise stability of the function. Using this connection, we show that the Fourier spectrum of any balanced Boolean function computed by a deMorgan formula of size $s$ is concentrated on coefficients of degree up to ... more >>>

TR12-062 | 17th May 2012
Ilan Komargodski, Ran Raz

Average-Case Lower Bounds for Formula Size

Revisions: 2

We give an explicit function $h:\{0,1\}^n\to\{0,1\}$ such that any deMorgan formula of size $O(n^{2.499})$ agrees with $h$ on at most $\frac{1}{2} + \epsilon$ fraction of the inputs, where $\epsilon$ is exponentially small (i.e. $\epsilon = 2^{-n^{\Omega(1)}}$). Previous lower bounds for formula size were obtained for exact computation.

The same ... more >>>

TR11-122 | 14th September 2011
Gillat Kol, Ran Raz

Competing Provers Protocols for Circuit Evaluation

Let $C$ be a (fan-in $2$) Boolean circuit of size $s$ and depth $d$, and let $x$ be an input for $C$. Assume that a verifier that knows $C$ but doesn't know $x$ can access the low degree extension of $x$ at one random point. Two competing provers try to ... more >>>

TR11-096 | 2nd July 2011
Gil Cohen, Ran Raz, Gil Segev

Non-Malleable Extractors with Short Seeds and Applications to Privacy Amplification

Motivated by the classical problem of privacy amplification, Dodis and Wichs (STOC '09) introduced the notion of a non-malleable extractor, significantly strengthening the notion of a strong extractor. A non-malleable extractor is a function $nmExt : \{0,1\}^n \times \{0,1\}^d \rightarrow \{0,1\}^m$ that takes two inputs: a weak source $W$ and ... more >>>

TR10-142 | 18th September 2010
Ran Raz, Ricky Rosen

A Strong Parallel Repetition Theorem for Projection Games on Expanders

The parallel repetition theorem states that for any Two
Prover Game with value at most $1-\epsilon$ (for $\epsilon<1/2$),
the value of the game repeated $n$ times in parallel is at most
$(1-\epsilon^3)^{\Omega(n/s)}$, where $s$ is the length of the
answers of the two provers. For Projection
Games, the bound on ... more >>>

TR10-035 | 7th March 2010
Mark Braverman, Anup Rao, Ran Raz, Amir Yehudayoff

Pseudorandom Generators for Regular Branching Programs

We give new pseudorandom generators for \emph{regular} read-once branching programs of small width.
A branching program is regular if the in-degree of every vertex in it is (0 or) $2$.
For every width $d$ and length $n$,
our pseudorandom generator uses a seed of length $O((\log d + \log\log n ... more >>>

TR10-002 | 4th January 2010
Ran Raz

Tensor-Rank and Lower Bounds for Arithmetic Formulas

We show that any explicit example for a tensor $A:[n]^r \rightarrow \mathbb{F}$ with tensor-rank
$\geq n^{r \cdot (1- o(1))}$,
(where $r = r(n) \leq \log n / \log \log n$), implies an explicit super-polynomial lower bound for the size of general arithmetic formulas over $\mathbb{F}$. This shows that strong enough ... more >>>

TR09-138 | 14th December 2009
Gillat Kol, Ran Raz

Bounds on 2-Query Locally Testable Codes with Affine Tests

We study Locally Testable Codes (LTCs) that can be tested by making two queries to the tested word using an affine test. That is, we consider LTCs over a finite field F, with codeword testers that only use tests of the form $av_i + bv_j = c$, where v is ... more >>>

TR09-128 | 29th November 2009
Gillat Kol, Ran Raz

Locally Testable Codes Analogues to the Unique Games Conjecture Do Not Exist

The Unique Games Conjecture (UGC) is possibly the most important open problem in the research of PCPs and hardness of approximation. The conjecture is a strengthening of the PCP Theorem, predicting the existence of a special type of PCP verifiers: 2-query verifiers that only make unique tests. Moreover, the UGC ... more >>>

TR08-071 | 6th August 2008
Dana Moshkovitz, Ran Raz

Two Query PCP with Sub-Constant Error

We show that the NP-Complete language 3Sat has a PCP
verifier that makes two queries to a proof of almost-linear size
and achieves sub-constant probability of error $o(1)$. The
verifier performs only projection tests, meaning that the answer
to the first query determines at most one accepting answer to the
more >>>

TR08-018 | 28th February 2008
Ran Raz

A Counterexample to Strong Parallel Repetition

The parallel repetition theorem states that for any two-prover game,
with value $1- \epsilon$ (for, say, $\epsilon \leq 1/2$), the value of
the game repeated in parallel $n$ times is at most
$(1- \epsilon^c)^{\Omega(n/s)}$, where $s$ is the answers' length
(of the original game) and $c$ is a universal ... more >>>

TR08-006 | 18th January 2008
Ran Raz, Amir Yehudayoff

Lower Bounds and Separations for Constant Depth Multilinear Circuits

We prove an exponential lower bound for the size of constant depth multilinear arithmetic circuits computing either the determinant or the permanent (a circuit is called multilinear, if the polynomial computed by each of its gates is multilinear). We also prove a super-polynomial separation between the size of product-depth $d$ ... more >>>

TR08-001 | 5th January 2008
Ran Raz

Elusive Functions and Lower Bounds for Arithmetic Circuits

A basic fact in linear algebra is that the image of the curve
$f(x)=(x^1,x^2,x^3,...,x^m)$, say over $C$, is not contained in any
$m-1$ dimensional affine subspace of $C^m$. In other words, the image
of $f$ is not contained in the image of any polynomial-mapping
$G:C^{m-1} ---> C^m$ ... 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 >>>

TR07-078 | 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 >>>

TR07-031 | 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 >>>

TR07-026 | 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 >>>

TR06-087 | 25th July 2006
Iordanis Kerenidis, Ran Raz

The one-way communication complexity of the Boolean Hidden Matching Problem

We give a tight lower bound of Omega(\sqrt{n}) for the randomized one-way communication complexity of the Boolean Hidden Matching Problem [BJK04]. Since there is a quantum one-way communication complexity protocol of O(log n) qubits for this problem, we obtain an exponential separation of quantum and classical one-way communication complexity for ... more >>>

TR06-060 | 4th May 2006
Ran Raz, Amir Shpilka, Amir Yehudayoff

A Lower Bound for the Size of Syntactically Multilinear Arithmetic Circuits

We construct an explicit polynomial $f(x_1,...,x_n)$, with
coefficients in ${0,1}$, such that the size of any syntactically
multilinear arithmetic circuit computing $f$ is at least
$\Omega( n^{4/3} / log^2(n) )$. The lower bound holds over any field.

more >>>

TR06-001 | 1st January 2006
Ran Raz, Iddo Tzameret

The Strength of Multilinear Proofs

We introduce an algebraic proof system that manipulates multilinear arithmetic formulas. We show that this proof system is fairly strong, even when restricted to multilinear arithmetic formulas of a very small depth. Specifically, we show the following:

1. Algebraic proofs manipulating depth 2 multilinear arithmetic formulas polynomially simulate Resolution, Polynomial ... more >>>

TR05-109 | 28th September 2005
Ariel Gabizon, Ran Raz, Ronen Shaltiel

Deterministic Extractors for Bit-fixing Sources by Obtaining an Independent Seed

An $(n,k)$-bit-fixing source is a distribution $X$ over $\B^n$ such that
there is a subset of $k$ variables in $X_1,\ldots,X_n$ which are uniformly
distributed and independent of each other, and the remaining $n-k$ variables
are fixed. A deterministic bit-fixing source extractor is a function $E:\B^n
\ar \B^m$ which on ... more >>>

TR05-108 | 28th September 2005
Ariel Gabizon, Ran Raz

Deterministic Extractors for Affine Sources over Large Fields

An $(n,k)$-affine source over a finite field $F$ is a random
variable $X=(X_1,...,X_n) \in F^n$, which is uniformly
distributed over an (unknown) $k$-dimensional affine subspace of $
F^n$. We show how to (deterministically) extract practically all
the randomness from affine sources, for any field of size larger
than $n^c$ (where ... more >>>

TR05-086 | 14th August 2005
Dana Moshkovitz, Ran Raz

Sub-Constant Error Low Degree Test of Almost Linear Size

Revisions: 1

Given a function f:F^m \rightarrow F over a finite
field F, a low degree tester tests its proximity to
an m-variate polynomial of total degree at most d
over F. The tester is usually given access to an oracle
A providing the supposed restrictions of f to
affine subspaces of ... more >>>

TR05-038 | 10th April 2005
Ran Raz

Quantum Information and the PCP Theorem

We show how to encode $2^n$ (classical) bits $a_1,...,a_{2^n}$
by a single quantum state $|\Psi \rangle$ of size $O(n)$ qubits,
such that:
for any constant $k$ and any $i_1,...,i_k \in \{1,...,2^n\}$,
the values of the bits $a_{i_1},...,a_{i_k}$ can be retrieved
from $|\Psi \rangle$ by a one-round Arthur-Merlin interactive ... more >>>

TR05-025 | 20th February 2005
Zeev Dvir, Ran Raz

Analyzing Linear Mergers

Mergers are functions that transform k (possibly dependent)
random sources into a single random source, in a way that ensures
that if one of the input sources has min-entropy rate $\delta$
then the output has min-entropy rate close to $\delta$. Mergers
have proven to be a very useful tool in ... more >>>

TR04-099 | 11th November 2004
Ran Raz

Extractors with Weak Random Seeds

We show how to extract random bits from two or more independent
weak random sources, in cases where only one source is of linear
min-entropy and all other sources are of logarithmic min-entropy.
We also give improved constructions of mergers and condensers.
In all that comes below, $\delta$ is an ... more >>>

TR04-042 | 21st May 2004
Ran Raz

Multilinear-$NC_1$ $\ne$ Multilinear-$NC_2$

An arithmetic circuit or formula is multilinear if the polynomial
computed at each of its wires is multilinear.
We give an explicit example for a polynomial $f(x_1,...,x_n)$,
with coefficients in $\{0,1\}$, such that over any field:
1) $f$ can be computed by a polynomial-size multilinear circuit
of depth $O(\log^2 ... more >>>

TR03-067 | 14th August 2003
Ran Raz

Multi-Linear Formulas for Permanent and Determinant are of Super-Polynomial Size

An arithmetic formula is multi-linear if the polynomial computed
by each of its sub-formulas is multi-linear. We prove that any
multi-linear arithmetic formula for the permanent or the
determinant of an $n \times n$ matrix is of size super-polynomial
in $n$.

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 >>>

TR02-012 | 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 >>>

TR01-021 | 7th March 2001
Ran Raz

Resolution Lower Bounds for the Weak Pigeonhole Principle

Revisions: 1

We prove that any Resolution proof for the weak
pigeon hole principle, with $n$ holes and any number of
pigeons, is of length $\Omega(2^{n^{\epsilon}})$,
(for some global constant $\epsilon > 0$).

more >>>

TR00-044 | 26th June 2000
Tzvika Hartman, Ran Raz

On the Distribution of the Number of Roots of Polynomials and Explicit Logspace Extractors

Weak designs were defined by Raz, Reingold and Vadhan (1999) and are
used in constructions of extractors. Roughly speaking, a weak design
is a collection of subsets satisfying some near-disjointness
properties. Constructions of weak designs with certain parameters are
given in [RRV99]. These constructions are explicit in the sense that
more >>>

TR00-029 | 30th April 2000
Ran Raz, Amir Shpilka

Lower Bounds for Matrix Product, in Bounded Depth Circuits with Arbitrary Gates

Revisions: 1

We prove super-linear lower bounds for the number of edges
in constant depth circuits with $n$ inputs and up to $n$ outputs.
Our lower bounds are proved for all types of constant depth
circuits, e.g., constant depth arithmetic circuits, constant depth
threshold circuits ... more >>>

TR99-046 | 17th November 1999
Ran Raz, Omer Reingold, Salil Vadhan

Extracting All the Randomness and Reducing the Error in Trevisan's Extractors

We give explicit constructions of extractors which work for a source of
any min-entropy on strings of length n. These extractors can extract any
constant fraction of the min-entropy using O(log^2 n) additional random
bits, and can extract all the min-entropy using O(log^3 n) additional
random bits. Both of these ... more >>>

TR98-066 | 3rd November 1998
Irit Dinur, Eldar Fischer, Guy Kindler, Ran Raz, Shmuel Safra

PCP Characterizations of NP: Towards a Polynomially-Small Error-Probability

This paper strengthens the low-error PCP characterization of NP, coming
closer to the ultimate BGLR conjecture. Namely, we prove that witnesses for
membership in any NP language can be verified with a constant
number of accesses, and with an error probability exponentially
small in the ... 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 >>>

TR10-141 | 18th September 2010 (removed)
Ran Raz

A Strong Parallel Repetition Theorem for Projection Games on Expanders

Reason: This paper has been remove on the author's behalf. Please note that TR10-142 is the corrected version.

ISSN 1433-8092 | Imprint