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arXiv · 0705.3629

On the Koplienko spectral shift function, I. Basics

Fritz Gesztesy·Alexander Pushnitski·Barry Simon
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Abstract

We study the Koplienko Spectral Shift Function (KoSSF), which is distinct from the one of Krein (KrSSF). KoSSF is defined for pairs $A,B$ with $(A-B)\in\calI_2$, the Hilbert-Schmidt operators, while KrSSF is defined for pairs $A,B$ with $(A-B)\in\calI_1$, the trace class operators. We review various aspects of the construction of both KoSSF and KrSSF. Among our new results are: (i) that any positive Riemann integrable function of compact support occurs as a KoSSF; (ii) that there exist $A,B$ with $(A-B)\in\calI_2$ so $\det_2((A-z)(B-z)^{-1})$ does not have nontangential boundary values; (iii) an alternative definition of KoSSF in the unitary case; and (iv) a new proof of the invariance of the a.c. spectrum under $\calI_1$-perturbations that uses the KrSSF.

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Fritz Gesztesy, Alexander Pushnitski, Barry Simon. 2007-05-24. On the Koplienko spectral shift function, I. Basics. https://arxiv.org/abs/0705.3629

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