Indian Journal of Pure and Applied Mathematics ( IF 0.4 ) Pub Date : 2021-06-22 , DOI: 10.1007/s13226-021-00126-4 Longfa Sun
Let X, Y be Banach spaces, W be a closed wedge of X, and \(f:W\cup -W\rightarrow Y\) be a symmetric \(\varepsilon \)-isometry. We firstly establish a weak stability formula about the symmetric isometry f. Making use of it, we prove a series of new stability theorems for the symmetric isometries defined on the positive cones W of C(K)-spaces. For example, if \(f(W\cup -W)\) contains a reproducing wedge of Y, then there exists a linear surjective isometry \(U:C(K)\rightarrow Y\) such that \(f-U\) is uniformly bounded by \(\frac{3}{2}\varepsilon \) on \(W\cup -W\); and if \(\overline{\mathrm{co}}f(W\cup -W)\) contains a reproducing wedge P of Y, then there exists a bounded linear operator \(T:Y\rightarrow C(K)\) with \(\Vert T\Vert =1\) such that
$$\begin{aligned} \Vert Tf(x)-x\Vert \le \frac{3}{2}\varepsilon ,~~{\mathrm{for\;\; all\;}}~ x\in W\cup -W. \end{aligned}$$中文翻译:
楔上对称 $$\varepsilon $$ ε -isometries 的稳定性
设X , Y是 Banach 空间,W是X 的一个封闭楔形,并且\(f:W\cup -W\rightarrow Y\)是一个对称的\(\varepsilon \) -等距。我们首先建立了关于对称等距f的弱稳定性公式。利用它,我们证明了在C ( K ) 空间的正锥W上定义的对称等距的一系列新的稳定性定理。例如,如果\(f(W\cup -W)\)包含Y的再现楔形,则存在线性满射等距\(U:C(K)\rightarrow Y\)使得\(fU\)在\(W\cup -W\)上由\(\frac{3}{2}\varepsilon \)统一限定;如果\(\划线{\ mathrm {共}} F到(W \杯-W)\)包含再现楔P的ÿ,则存在的线性算子\(T:Y \ RIGHTARROW C(K)\ )与\(\Vert T\Vert =1\)使得
$$\begin{aligned} \Vert Tf(x)-x\Vert \le \frac{3}{2}\varepsilon ,~~{\mathrm{for\;\; 所有\;}}~ x\in W\cup -W。\end{对齐}$$