Eigenvalue Inequalities and Schubert Calculus
Uwe Helmke, Joachim Rosenthal · Mathematische Nachrichten · 1995
Abstract Using techniques from algebraic topology we derive linear inequalities which relate the spectrum of a set of Hermitian matrices A1,…, Ar ϵ ¢n×n with the spectrum of the sum A1 + … + Ar. These extend eigenvalue inequalities due to Freede‐Thompson and Horn for sums of eigenvalues of two Hermitian matrices.