In this second lecture in my series on asymptotic spectra we will focus on one application: the matrix multiplication problem. We will use the asymptotic spectrum of tensors to prove that a very general method (that includes the methods used to obtain the currently best algorithms) cannot give faster matrix multiplication algorithms. Keywords are Shannon entropy, representation theory and moment polytopes, but prior knowledge of these is not assumed.
I'll show a graphical user interface I wrote which explores the problem of inscribing rectangles in Jordan loops. The motivation behind this is the notorious Square Peg Conjecture of Toeplitz, from 1911.
I did not manage to solve this problem, but I did get the result that at most 4 points of any Jordan loop are vertices of inscribed rectangles. I will sketch a proof of this result, mostly through visual demos, and also I will explain two other theorems about inscribed rectangles which at least bear a resemblance to theorems in symplectic geometry.