Border Rank Lower Bounds of the Matrix Multiplication Tensor - Part 1

Learn advanced techniques for establishing lower bounds on the border rank of matrix multiplication tensors in this mathematical lecture. Explore two primary methods that have proven successful for analyzing matrix multiplication complexity: Koszul flattenings, which associate matrices to tensors of interest and relate their respective ranks, and border apolarity, which refutes the existence of auxiliary data required for border rank decompositions. Discover how these approaches leverage the natural symmetry properties of matrix multiplication tensors, with border apolarity particularly benefiting from the large symmetry group that enables normalization of auxiliary data. Understand the connection between border rank analysis and the fundamental question of matrix multiplication complexity, building on foundational results from Strassen and Bini that demonstrate how understanding tensor rank and border rank is sufficient for determining the matrix multiplication exponent omega.