Hyers-Ulam stability of homomorphisms and *-homomorphisms on Hilbert C*-modules
Sajjad Khan, Choonkil Park
TL;DR
This paper addresses the Hyers-Ulam stability of homomorphisms and $\ast$-homomorphisms on Hilbert $C^{*}$-modules by employing a fixed-point approach. The authors introduce $\ast$-homomorphisms on Hilbert $C^{*}$-modules and prove the existence and uniqueness of stabilizing maps $H$ under contractive control functions, with explicit error bounds $\|f(x)-H(x)\|\le \frac{1}{2-2L}\varphi(x,x,0)$. They also establish Hyers-Ulam-Rassias stability for the $p$-type controls and provide analogous results for $\ast$-homomorphisms, ensuring that $H$ preserves the module operations and star-structure. The results extend classical stability theory to the setting of Hilbert $C^{*}$-modules and offer quantitative stability criteria via generalized metric spaces and fixed-point theory.
Abstract
In this paper, we introduce the idea of $\ast$-homomorphism on a Hilbert $C^{*}$-module. Furthermore, we prove the Hyers-Ulam stability of homomorphisms and $\ast$-homomorphisms on Hilbert $C^{*}$-modules using the fixed point method.
