On operators satisfying the generalized Cauchy-Schwarz inequality

Abstract

In this paper, we introduce the generalized Cauchy-Schwarz inequality for an operator T ∈ L(H) and investigate various properties of operators which satisfy the generalized Cauchy-Schwarz inequality. In particular, every p-hyponormal operator satisfies this inequality. We also prove that if T ∈ L(H) satisfies the generalized Cauchy-Schwarz inequality, then T is paranormal. As an application, we show that if both T and T∗ in L(H) satisfy the generalized Cauchy-Schwarz inequality, then T is normal. © 2017 American Mathematical Society.