On the Koplienko Spectral Shift Function. I. Basics

• Published in: Журнал математической физики, анализа, геометрии
• Date: 2008
• Main Authors: Gesztesy, F., Pushnitski, A., Simon, B.
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2008
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/106495
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: On the Koplienko Spectral Shift Function. I. Basics / F. Gesztesy, A. Pushnitski, B. Simon // Журнал математической физики, анализа, геометрии. — 2008. — Т. 4, № 1. — С. 63-107. — Бібліогр.: 71 назв. — англ.

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) is in I₂, the Hilbert{Schmidt operators, while KrSSF is defined for pairs A,B with (A - B) is in I₁, 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) is in I₂ so det₂((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 I₁-perturbations that uses the KrSSF.