New characterizations of operator monotone functions

2018/03/18 by Trung Hoa Dinh, Dinh, Trung Hoa, ‎Raluca Dumitru +5
Computer Science · Mathematics · #Analytic and geometric function theory #Mathematical Inequalities and Applications #Optimization and Variational Analysis #math.FA #math.OA

paper · pdf · doi:10.48550/arxiv.1803.06659

Linear Algebra and Its Applications, 2018

arxiv created 2018/03/18 · arxiv updated 2018/03/20

Abstract

If σ is a symmetric mean and f is an operator monotone function on [0, ∞), then f(2(A^-1+B^-1)^-1)≤ f(AσB)≤ f((A+B)/2). Conversely, Ando and Hiai showed that if f is a function that satisfies either one of these inequalities for all positive operators A and B and a symmetric mean different than the arithmetic and the harmonic mean, then the function is operator monotone. In this paper, we show that the arithmetic and the harmonic means can be replaced by the geometric mean to obtain similar characterizations. Moreover, we give characterizations of operator monotone functions using self-adjoint means and general means subject to a constraint due to Kubo and Ando.

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