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New degree bounds for polynomial threshold functions

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Abstract

A real multivariate polynomial p(x 1, …, x n ) is said to sign-represent a Boolean function f: {0,1}n→{−1,1} if the sign of p(x) equals f(x) for all inputs x∈{0,1}n. We give new upper and lower bounds on the degree of polynomials which sign-represent Boolean functions. Our upper bounds for Boolean formulas yield the first known subexponential time learning algorithms for formulas of superconstant depth. Our lower bounds for constant-depth circuits and intersections of halfspaces are the first new degree lower bounds since 1968, improving results of Minsky and Papert. The lower bounds are proved constructively; we give explicit dual solutions to the necessary linear programs.

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Correspondence to Rocco A. Servedio.

Additional information

A preliminary version of these results appeared as [24].

This work was done while at the Department of Mathematics, MIT, Cambridge, MA, and while supported by NSF grant 99-12342.

Supported by an NSF Mathematical Sciences Postdoctoral Research Fellowship and by NSF grant CCR-98-77049. This work was done while at the Division of Engineering and Applied Sciences, Harvard University, Cambridge, MA.

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O’Donnell, R., Servedio, R.A. New degree bounds for polynomial threshold functions. Combinatorica 30, 327–358 (2010). https://doi.org/10.1007/s00493-010-2173-3

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  • DOI: https://doi.org/10.1007/s00493-010-2173-3

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