Lower and upper bounds of joint $(f,\delta )$-numerical radius functions

Abstract

In this study, the classical results on the joint numerical radius for $n$-tuples of Hilbert space operators are extended to the setting of the joint $(f,\delta )$-numerical radius. New and diverse contributions to this area are provided, including novel estimates for the lower and upper bounds of the $(f,\delta )$-numerical radius in the context of sectorial operators.