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Hardness of Solving Sparse Overdetermined Linear Systems: A 3-Query PCP over Integers

Published:01 September 2009Publication History
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Abstract

A classic result due to Håstad established that for every constant ε > 0, given an overdetermined system of linear equations over a finite field Fq where each equation depends on exactly 3 variables and at least a fraction (1 − ε) of the equations can be satisfied, it is NP-hard to satisfy even a fraction (1/q + ε) of the equations.

In this work, we prove the analog of Håstad’s result for equations over the integers (as well as the reals). Formally, we prove that for every ε, δ > 0, given a system of linear equations with integer coefficients where each equation is on 3 variables, it is NP-hard to distinguish between the following two cases: (i) there is an assignment of integer values to the variables that satisfies at least a fraction (1 − ε) of the equations, and (ii) no assignment even of real values to the variables satisfies more than a fraction δ of the equations.

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  1. Hardness of Solving Sparse Overdetermined Linear Systems: A 3-Query PCP over Integers

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