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arXiv 0908.3623math.FAmath.CAmath.CVmath.SP
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算子在$\bS_p$类扰动下的函数

Functions of operators under perturbations of class $\bS_p$

A. B. Aleksandrov, V. V. Peller

摘要:

这是我们的论文\cite{AP2}的继续。证明了对于Hölder类$Ł_\a(\R)$和$1<p<\be$中的函数$f$,只要$A$和$B$是具有$A-B\in\bS_p$的自伴算子,则算子$f(A)-f(B)$属于$\bS_{p/\a}$.我们还获得了尖锐的估计Schatten-冯诺依曼规范$\big\|f(A)-f(B)\big\|_{\bS_{p/\a}}$的$\|A-B\|_{\bS_p}$和其他运营商的理想建立类似的结果。我们还估计了高阶差分$\sum\limits_{j=0}^m(-1)^{m-j}(m\j)f\big(A+jK\big)$的Schatten-von Neumann范数。我们证明了类似的结果适用于单位圆上的函数和酉算子,以及单位圆上的解析函数和压缩。然后在假设$A-B\in\bS_p$为$f(A)-f(B)$的情况下,得到了$f$上$f(A)-f(B)$属于$\bS_q$的必要条件.我们还得到了拟交换子$f(A)Q-Qf(B)$的Schatten-von Neumann估计,并引入了谱移函数,找到了$f(A-K)-2f(A)+f(A+K)$形式的算子的迹公式.

英文摘要:

This is a continuation of our paper \cite{AP2}. We prove that for functions $f$ in the Hölder class $Ł_\a(\R)$ and $1<p<\be$, the operator $f(A)-f(B)$ belongs to $\bS_{p/\a}$, whenever $A$ and $B$ are self-adjoint operators with $A-B\in\bS_p$. We also obtain sharp estimates for the Schatten--von Neumann norms $\big\|f(A)-f(B)\big\|_{\bS_{p/\a}}$ in terms of $\|A-B\|_{\bS_p}$ and establish similar results for other operator ideals. We also estimate Schatten--von Neumann norms of higher order differences $\sum\limits_{j=0}^m(-1)^{m-j}(m\j)f\big(A+jK\big)$. We prove that analogous results hold for functions on the unit circle and unitary operators and for analytic functions in the unit disk and contractions. Then we find necessary conditions on $f$ for $f(A)-f(B)$ to belong to $\bS_q$ under the assumption that $A-B\in\bS_p$. We also obtain Schatten--von Neumann estimates for quasicommutators $f(A)Q-Qf(B)$, and introduce a spectral shift function and find a trace formula for operators of the form $f(A-K)-2f(A)+f(A+K)$.

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