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REPORTS > AUTHORS > PRATIK WORAH:
All reports by Author Pratik Worah:

TR13-146 | 20th October 2013
Subhash Khot, Madhur Tulsiani, Pratik Worah

A Characterization of Approximation Resistance

Revisions: 1

A predicate $f:\{-1,1\}^k \mapsto \{0,1\}$ with $\rho(f) = \frac{|f^{-1}(1)|}{2^k}$ is called {\it approximation resistant} if given a near-satisfiable instance of CSP$(f)$, it is computationally hard to find an assignment that satisfies at least $\rho(f)+\Omega(1)$ fraction of the constraints.

We present a complete characterization of approximation resistant predicates under the ... more >>>


TR13-075 | 23rd May 2013
Subhash Khot, Madhur Tulsiani, Pratik Worah

A Characterization of Strong Approximation Resistance

For a predicate $f:\{-1,1\}^k \mapsto \{0,1\}$ with $\rho(f) = \frac{|f^{-1}(1)|}{2^k}$, we call the predicate strongly approximation resistant if given a near-satisfiable instance of CSP$(f)$, it is computationally hard to find an assignment such that the fraction of constraints satisfied is outside the range $[\rho(f)-\Omega(1), \rho(f)+\Omega(1)]$.

We present a characterization of ... more >>>


TR13-017 | 23rd January 2013
Pratik Worah

A Short Excursion into Semi-Algebraic Hierarchies

This brief survey gives a (roughly) self-contained overview of some complexity theoretic results about semi-algebraic proof systems and related hierarchies and the strong connections between them. The article is not intended to be a detailed survey on "Lift and Project" type optimization hierarchies (cf. Chlamtac and Tulsiani) or related proof ... more >>>


TR12-151 | 6th November 2012
Subhash Khot, Madhur Tulsiani, Pratik Worah

The Complexity of Somewhat Approximation Resistant Predicates

Revisions: 1

A boolean predicate $f:\{0,1\}^k\to\{0,1\}$ is said to be {\em somewhat approximation resistant} if for some constant $\tau > \frac{|f^{-1}(1)|}{2^k}$, given a $\tau$-satisfiable instance of the MAX-$k$-CSP$(f)$ problem, it is NP-hard to find an assignment that {\it strictly beats} the naive algorithm that outputs a uniformly random assignment. Let $\tau(f)$ denote ... more >>>


TR12-105 | 17th August 2012
Madhur Tulsiani, Pratik Worah

$LS_+$ Lower Bounds from Pairwise Independence

We consider the complexity of LS$_+$ refutations of unsatisfiable instances of Constraint Satisfaction Problems (CSPs) when the underlying predicate supports a pairwise independent distribution on its satisfying assignments. This is the most general condition on the predicates under which the corresponding MAX-CSP problem is known to be approximation resistant.

We ... more >>>


TR12-003 | 13th December 2011
Pratik Worah

Rank Bounds for a Hierarchy of Lov\'{a}sz and Schrijver

Lov\'{a}sz and Schrijver introduced several lift and project methods for $0$-$1$ integer programs, now collectively known as Lov\'{a}sz-Schrijver ($LS$) hierarchies. Several lower bounds have since been proven for the rank of various linear programming relaxations in the $LS$ and $LS_+$ hierarchies. In this paper we investigate rank bounds in the ... more >>>




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