Quasi Grüss Type Inequalities for Complex Functions Defined on Unit Circle with Applications for Unitary Operators in Hilbert Spaces

Abstract

Some quasi Grüss type inequalities for the Riemann-Stieltjes integral of continuous complex valued integrands defined on the complex unit circle C(0, 1) and various subclasses of integrators are given. Natural applications for functions of unitary operators in Hilbert spaces are provided.

Keywords

• Grüss type inequalities
• Riemann-Stieltjes integral inequalities
• Unitary operators in Hilbert spaces
• Spectral theory
• Quadrature rules