License: Creative Commons Attribution 3.0 Unported license (CC BY 3.0)
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DOI: 10.4230/LIPIcs.CCC.2020.2
URN: urn:nbn:de:0030-drops-125546
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Chatterjee, Prerona ; Kumar, Mrinal ; She, Adrian ; Volk, Ben Lee

A Quadratic Lower Bound for Algebraic Branching Programs

LIPIcs-CCC-2020-2.pdf (0.5 MB)


We show that any Algebraic Branching Program (ABP) computing the polynomial ∑_{i=1}^n xⁿ_i has at least Ω(n²) vertices. This improves upon the lower bound of Ω(nlog n), which follows from the classical result of Baur and Strassen [Volker Strassen, 1973; Walter Baur and Volker Strassen, 1983], and extends the results of Kumar [Mrinal Kumar, 2019], which showed a quadratic lower bound for homogeneous ABPs computing the same polynomial.
Our proof relies on a notion of depth reduction which is reminiscent of similar statements in the context of matrix rigidity, and shows that any small enough ABP computing the polynomial ∑_{i=1}^n xⁿ_i can be depth reduced to essentially a homogeneous ABP of the same size which computes the polynomial ∑_{i=1}^n xⁿ_i + ε(?), for a structured "error polynomial" ε(?). To complete the proof, we then observe that the lower bound in [Mrinal Kumar, 2019] is robust enough and continues to hold for all polynomials ∑_{i=1}^n xⁿ_i + ε(?), where ε(?) has the appropriate structure.

BibTeX - Entry

  author =	{Prerona Chatterjee and Mrinal Kumar and Adrian She and Ben Lee Volk},
  title =	{{A Quadratic Lower Bound for Algebraic Branching Programs}},
  booktitle =	{35th Computational Complexity Conference (CCC 2020)},
  pages =	{2:1--2:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-156-6},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{169},
  editor =	{Shubhangi Saraf},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{},
  URN =		{urn:nbn:de:0030-drops-125546},
  doi =		{10.4230/LIPIcs.CCC.2020.2},
  annote =	{Keywords: Algebraic Branching Programs, Lower Bound}

Keywords: Algebraic Branching Programs, Lower Bound
Collection: 35th Computational Complexity Conference (CCC 2020)
Issue Date: 2020
Date of publication: 17.07.2020

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