Stability of the Exponential Functional Equation in Riesz Algebras

We deal with the stability of the exponential Cauchy functional equation F(x+y)=F(x)F(y) in the class of functions F:G→L mapping a group (G, +) into a Riesz algebra L. The main aim of this paper is to prove that the exponential Cauchy functional equation is stable in the sense of Hyers-Ulam and is not superstable in the sense of Baker. To prove the stability we use the Yosida Spectral Representation Theorem.