Abstract and Applied Analysis
Volume 2009 (2009), Article ID 360432, 17 pages
doi:10.1155/2009/360432
Research Article

Stability of the Jensen-Type Functional Equation in C∗-Algebras: A Fixed Point Approach

Choonkil Park1 and John Michael Rassias2

1Department of Mathematics, Hanyang University, Seoul 133-791, South Korea
2Pedagogical Department E.E., National and Capodistrian University of Athens, 4 Agamemnonos Street, Aghia Paraskevi, Athens 15342, Greece

Received 27 November 2008; Accepted 26 January 2009

Academic Editor: Bruce Calvert

Copyright © 2009 Choonkil Park and John Michael Rassias. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Using fixed point methods, we prove the generalized Hyers-Ulam stability of homomorphisms in C∗-algebras and Lie C∗-algebras and also of derivations on C∗-algebras and Lie C∗-algebras for the Jensen-type functional equation f((x+y)/2)+f((x−y)/2)=f(x).