Explicit lower bounds via geometric complexity theory

  • Authors:
  • Peter Bürgisser;Christian Ikenmeyer

  • Affiliations:
  • University of Paderborn, Paderborn, Germany;University of Paderborn, Paderborn, Germany

  • Venue:
  • Proceedings of the forty-fifth annual ACM symposium on Theory of computing
  • Year:
  • 2013

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Abstract

We prove the lower bound R Mm) ≥ 3/2 m2-2 on the border rank of m x m matrix multiplication by exhibiting explicit representation theoretic (occurence) obstructions in the sense of Mulmuley and Sohoni's geometric complexity theory (GCT) program. While this bound is weaker than the one recently obtained by Landsberg and Ottaviani, these are the first significant lower bounds obtained within the GCT program. Behind the proof is an explicit description of the highest weight vectors in Symd⊗3 (Cn)* in terms of combinatorial objects, called obstruction designs. This description results from analyzing the process of polarization and Schur-Weyl duality.