ON AN ADDITIVE FUNCTIONAL INEQUALITY IN NORMED MODULES OVER A C*-ALGEBRA

한국수학교육학회지시리즈B:순수및응용수학 / Journal of the Korean Society of Mathematical Education Series B: The Pure and Applied Mathematics, (P)1226-0657; (E)2287-6081

2008, v.15 no.4, pp.393-400

An, Jong-Su (DEPARTMENT OF MATHEMATICS EDUCATION, PUSAN NATIONAL UNIVERSITY)

An, Jong-Su. (2008). ON AN ADDITIVE FUNCTIONAL INEQUALITY IN NORMED MODULES OVER A <TEX>$C^*$</TEX>-ALGEBRA. 한국수학교육학회지시리즈B:순수및응용수학, 15(4), 393-400.

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Abstract

In this paper, we investigate the following additive functional inequality (0.1) ||f(x)+f(y)+f(z)+f(w)||<TEX>${\leq}$</TEX>||f(x+y)+f(z+w)|| in normed modules over a <TEX>$C^*$</TEX>-algebra. This is applied to understand homomor-phisms in <TEX>$C^*$</TEX>-algebra. Moreover, we prove the generalized Hyers-Ulam stability of the functional inequality (0.2) ||f(x)+f(y)+f(z)f(w)||<TEX>${\leq}$</TEX>||f(x+y+z+w)||+<TEX>${\theta}||x||^p||y||^p||z||^p||w||^p$</TEX> in real Banach spaces, where <TEX>${\theta}$</TEX>, p are positive real numbers with <TEX>$4p{\neq}1$</TEX>.

keywords: Jordan-von Neumann functional equation, functional inequality, linear mapping in normed modules over a <tex> $C^*$</tex>-algebra

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논문 상세

Vol.15 No.4

ON AN ADDITIVE FUNCTIONAL INEQUALITY IN NORMED MODULES OVER A <TEX>$C^*$</TEX>-ALGEBRA

ON AN ADDITIVE FUNCTIONAL INEQUALITY IN NORMED MODULES OVER A C*-ALGEBRA

Abstract

한국수학교육학회지시리즈B:순수및응용수학