The Single Ring Theorem

Manjunath Krishnapur
Abstract
What are the eigenvalues of a typical matrix with a given set of singular values? We make the question precise by considering a random matrix of the form A=UDV, where D is a diagonal matrix and U,V are independent unitary matrices sampled from Haar measure.Under certain assumptions on the distribution of D, we show that A has a limiting spectral distribution, and characterize its properties. In particular, it has the surprising feature that the support of the limit spectral distribution is a connected annulus. This is joint work with Alice Guionnet and Ofer Zeitouni.