Published: 2015-09-30

Inequalities of Lipschitz type for power series in Banach algebras

Sever S. Dragomir

Abstract

Let f(z) = Σn=0αnzn be a function defined by power series with complex coefficients and convergent on the open disk D(0,R)⊂ℂ, R>0. For any x,y∈????, a Banach algebra, with ‖x‖,‖y‖<R we show among others that
f(y)-f(x)‖ ≤ ‖y-x‖∫01f'a(‖(1-t)x+ty‖)dt
where fa(z) = Σn=0n|zn. Inequalities for the commutator such as
‖f(x)f(y) - f(y)f(x)‖ ≤ 2fa(M)f'a(M)‖y-x‖,
if ‖x‖,‖y‖≤M<R, as well as some inequalities of Hermite–Hadamard type are also provided.

Domyślna okładka

Vol. 29 (2015)
Published: 2015-09-30


ISSN: 0860-2107
eISSN: 2391-4238
Ikona DOI 10.2478/amsil

Publisher
University of Silesia Press

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