Stability of the Jensen-type functional equation in -algebras: a fixed point approach.
The paper deals with the stability of the fundamental equation of information of multiplicative type. It is proved that the equation in question is stable in the sense of Hyers and Ulam under some assumptions. This result is applied to prove the stability of a system of functional equations that characterizes the recursive measures of information of multiplicative type.
In this paper we prove stability-type theorems for functional equations related to spherical functions. Our proofs are based on superstability-type methods and on the method of invariant means.