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A Class of Norm Inequalities for Operator Monotone Functions and Hyponormal Operators

  • Katarina Bogdanović

摘要

Let \(\Psi \) Ψ , \(\Phi \) Φ be s.n. functions, \(p\ge 2,\) p 2 , and let \(\varphi \) φ be an operator monotone function on \([0,\infty )\) [ 0 , ) such that \(\varphi (0)=0.\) φ ( 0 ) = 0 . If are such that A and B are strictly accretive and then also and \(\begin{aligned}{} & {} \vert {\;\!\!\vert {AX\varphi {(B)}-\varphi {(A)}XB}\vert \;\!\!}\vert _\Psi \\{} & {} \qquad \le \left\| \,\!\sqrt{\varphi \Bigl ({\tfrac{A+A^*}{2}}\Bigr )-\tfrac{A+A^*}{2}\varphi ^\prime \Bigl ({\tfrac{A+A^*}{2}}\Bigr )} \Bigl ({\tfrac{A+A^*}{2}}\Bigr )^{-1}\!A(AX-XB)B\Bigl ({\tfrac{B+B^*}{2}}\Bigr )^{-1}\!\!\right. \\{} & {} \qquad \quad \left. \sqrt{\varphi \Bigl ({\tfrac{B+B^*}{2}}\Bigr )-\tfrac{B+B^*}{2}\varphi ^\prime \Bigl ({\tfrac{B+B^*}{2}}\Bigr )}\,\right\| _\Psi \,\!\!. \end{aligned}\) | | A X φ ( B ) - φ ( A ) X B | | Ψ φ ( A + A 2 ) - A + A 2 φ ( A + A 2 ) ( A + A 2 ) - 1 A ( A X - X B ) B ( B + B 2 ) - 1 φ ( B + B 2 ) - B + B 2 φ ( B + B 2 ) Ψ . under any of the following conditions: (a)

Both A and B are normal,

(b)

A is cohyponormal, B is hyponormal and at least one of them is normal, and \(\Psi \!:=\Phi ^{(p)^*}\!,\) Ψ : = Φ ( p ) ,

(c)

A is cohyponormal, B is hyponormal and \(\vert {\;\!\!\vert {\cdot }\vert \;\!\!}\vert _\Psi \) | | · | | Ψ is the trace norm \(\vert {\;\!\!\vert {\cdot }\vert \;\!\!}\vert _1.\) | | · | | 1 .

Alternative inequalities for \(\vert {\;\!\!\vert {\cdot }\vert \;\!\!}\vert _{\Phi ^{(p)}}\) | | · | | Φ ( p ) norms are also obtained.