CONCAVITY OF CERTAIN MATRIX TRACE FUNCTIONS
Fumio Hiai · Taiwanese Journal of Mathematics · 2001
We demonstrate how Epstein's method using theory of Pick func-tions improves the existing results and also proves new ones on the joint con-cavity of trace functions of the form Tr (F(A1, . . . ,Ak)), where F(A1, . . .,Ak)is a matrix-valued function of positive semidefinite matrices A1, . . . ,Ak.