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oai:drops-oai.dagstuhl.de:5826 2024-03-06T10:37:12Z ddc:004 open_access

Functional Lower Bounds for Arithmetic Circuits and Connections to Boolean Circuit Complexity Forbes, Michael A. Kumar, Mrinal Saptharishi, Ramprasad boolean circuits arithmetic circuits lower bounds functional computation We say that a circuit C over a field F {functionally} computes a polynomial P in F[x_1, x_2, ..., x_n] if for every x in {0,1}^n we have that C(x) = P(x). This is in contrast to syntactically computing P, when C = P as formal polynomials. In this paper, we study the question of proving lower bounds for homogeneous depth-3 and depth-4 arithmetic circuits for functional computation. We prove the following results: 1. Exponential lower bounds for homogeneous depth-3 arithmetic circuits for a polynomial in VNP. 2. Exponential lower bounds for homogeneous depth-4 arithmetic circuits with bounded individual degree for a polynomial in VNP. Our main motivation for this line of research comes from our observation that strong enough functional lower bounds for even very special depth-4 arithmetic circuits for the Permanent imply a separation between #P and ACC0. Thus, improving the second result to get rid of the bounded individual degree condition could lead to substantial progress in boolean circuit complexity. Besides, it is known from a recent result of Kumar and Saptharishi [Kumar/Saptharishi, ECCC 2015] that over constant sized finite fields, strong enough {average case} functional lower bounds for homogeneous depth-4 circuits imply superpolynomial lower bounds for homogeneous depth-5 circuits. Our proofs are based on a family of new complexity measures called shifted evaluation dimension, and might be of independent interest. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Michael A. Forbes and Mrinal Kumar and Ramprasad Saptharishi 2016 Is Part Of LIPIcs, Volume 50, 31st Conference on Computational Complexity (CCC 2016) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.CCC.2016.33 urn:nbn:de:0030-drops-58266 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CCC.2016.33 eng https://creativecommons.org/licenses/by/3.0/legalcode