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Cauchy-Rassias Stability of Cauchy-Jensen Additive Mappings in Banach Spaces
引用本文:Choonkil BAAK. Cauchy-Rassias Stability of Cauchy-Jensen Additive Mappings in Banach Spaces[J]. 数学学报(英文版), 2006, 22(6): 1789-1796. DOI: 10.1007/s10114-005-0697-z
作者姓名:Choonkil BAAK
作者单位:Department of Mathematics, Chungnam National University, Daejeon 305-764, South Korea
基金项目:Supported by Korea Research Foundation Grant KRF-2005-070-C00009.Acknowledgments The author would like to thank the referee for a number of valuable suggestions regarding a previous version of this paper.
摘    要:
Let X, Y be vector spaces. It is shown that if a mapping f : X → Y satisfies f((x+y)/2+z)+f((x-y)/2+z=f(x)+2f(z),(0.1) f((x+y)/2+z)-f((x-y)/2+z)f(y),(0.2) or 2f((x+y)/2+x)=f(x)+f(y)+2f(z)(0.3)for all x, y, z ∈ X, then the mapping f : X →Y is Cauchy additive. Furthermore, we prove the Cauchy-Rassias stability of the functional equations (0.1), (0.2) and (0.3) in Banach spaces. The results are applied to investigate isomorphisms between unital Banach algebras.

关 键 词:Cauchy附加映射 Jensen附加映射 Cauchy-Rassias稳定性 同构Banach代数
收稿时间:2005-03-18
修稿时间:2005-03-182005-07-29

Cauchy–Rassias Stability of Cauchy–Jensen Additive Mappings in Banach Spaces
Choonkil Baak. Cauchy–Rassias Stability of Cauchy–Jensen Additive Mappings in Banach Spaces[J]. Acta Mathematica Sinica(English Series), 2006, 22(6): 1789-1796. DOI: 10.1007/s10114-005-0697-z
Authors:Choonkil Baak
Affiliation:(1) Department of Mathematics, Chungnam National University, Daejeon 305–764, South Korea
Abstract:
Let X, Y be vector spaces. It is shown that if a mapping f : XY satisfies
$$
f{left( {frac{{x + y}}
{2} + z} right)} + f{left( {frac{{x - y}}
{2} + z} right)} = f{left( x right)} + 2f{left( z right)},
$$
(0.1)
$$
f{left( {frac{{x + y}}
{2} + z} right)} - f{left( {frac{{x - y}}
{2} + z} right)} = f{left( y right)},
$$
(0.2) or
$$
2f{left( {frac{{x + y}}
{2} + z} right)} = f{left( x right)} + f{left( y right)} + 2f{left( z right)}
$$
(0.3) for all x, y, zX, then the mapping f : XY is Cauchy additive. Furthermore, we prove the Cauchy–Rassias stability of the functional equations (0.1), (0.2) and (0.3) in Banach spaces. The results are applied to investigate isomorphisms between unital Banach algebras. Supported by Korea Research Foundation Grant KRF-2005-070-C00009.
Keywords:Cauchy additive mapping   Jensen additive mapping   Cauchy-Rassias stability   isomorphism between Banach algebra
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