DMS Linear Algebra/Algebra Seminar

Speaker:  Tin-Yau Tam

Title: The relation of a nonsingular matrix and its components in polar decomposition

Abstract: Each nonsingular matrix A has the so called polar decomposition A =  PU (or UP) where P is positive definite and U is unitary. The Weyl--Horn Theorem gives a nice relation between the eigenvalues of A and the eigenvalues of P. The relation is known as log majorization and is on the moduli of the eigenvalues of A and P. Kostant extended the result in the context of semisimple Lie groups. The Horn--Steinberg Theorem gives a nice relation between the eigenvalues of A and the eigenvalues of U. The relation is on the arguments of the eigenvalues A and the arguments of the eigenvalues of U. We will review these two theorems and provide some progress toward the extension of Horn--Steinberg Theorem in the context of complex semsimple Lie groups.