An Exponential Lower Bound for Homogeneous Depth Four Arithmetic Formulas

Kayal, Neeraj and Limaye, Nutan and Saha, Chandan and Srinivasan, Srikanth (2014) An Exponential Lower Bound for Homogeneous Depth Four Arithmetic Formulas. In: 55th Annual IEEE Symposium on Foundations of Computer Science (FOCS), OCT 18-21, 2014, Microsoft Res New England, Philadelphia, PA, pp. 61-70.

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Abstract

We show here a 2(Omega(root d.log N)) size lower bound for homogeneous depth four arithmetic formulas. That is, we give an explicit family of polynomials of degree d on N variables (with N = d(3) in our case) with 0, 1-coefficients such that for any representation of a polynomial f in this family of the form f = Sigma(i) Pi(j) Q(ij), where the Q(ij)'s are homogeneous polynomials (recall that a polynomial is said to be homogeneous if all its monomials have the same degree), it must hold that Sigma(i,j) (Number of monomials of Q(ij)) >= 2(Omega(root d.log N)). The above mentioned family, which we refer to as the Nisan-Wigderson design-based family of polynomials, is in the complexity class VNP. Our work builds on the recent lower bound results 1], 2], 3], 4], 5] and yields an improved quantitative bound as compared to the quasi-polynomial lower bound of 6] and the N-Omega(log log (N)) lower bound in the independent work of 7].

Item Type:	Conference Proceedings
Series.:	Annual IEEE Symposium on Foundations of Computer Science
Publisher:	IEEE
Additional Information:	Copy right for this article belongs to the IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA
Keywords:	Arithmetic circuits; shifted partial derivatives; lower bounds
Department/Centre:	Division of Electrical Sciences > Computer Science & Automation
Date Deposited:	06 Jan 2016 05:44
Last Modified:	06 Jan 2016 05:44
URI:	http://eprints.iisc.ac.in/id/eprint/53069

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