Kreĭn's trace formula and the spectral shift function

Let A,B be two selfadjoint operators whose difference B−A is trace class. Kreĭn proved the existence of a certain function ξ∈L1(ℝ) such that tr[f(B)−f(A)]=∫ℝf′(x)ξ(x)dx for a large set of functions f. We give here a new proof of this result and discuss the class of admissible functions. Our proof is...

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Main Author: Khristo N. Boyadzhiev
Format: Article
Language:English
Published: Wiley 2001-01-01
Series:International Journal of Mathematics and Mathematical Sciences
Online Access:http://dx.doi.org/10.1155/S0161171201004318
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author Khristo N. Boyadzhiev
author_facet Khristo N. Boyadzhiev
author_sort Khristo N. Boyadzhiev
collection DOAJ
description Let A,B be two selfadjoint operators whose difference B−A is trace class. Kreĭn proved the existence of a certain function ξ∈L1(ℝ) such that tr[f(B)−f(A)]=∫ℝf′(x)ξ(x)dx for a large set of functions f. We give here a new proof of this result and discuss the class of admissible functions. Our proof is based on the integral representation of harmonic functions on the upper half plane and also uses the Baker-Campbell-Hausdorff formula.
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spelling doaj-art-de675f6b1c7d49fd8737d4fb60289e0d2025-02-03T06:08:11ZengWileyInternational Journal of Mathematics and Mathematical Sciences0161-17121687-04252001-01-0125423925210.1155/S0161171201004318Kreĭn's trace formula and the spectral shift functionKhristo N. Boyadzhiev0Department of Mathematics, Ohio Northern University, Ada 45810, Ohio, USALet A,B be two selfadjoint operators whose difference B−A is trace class. Kreĭn proved the existence of a certain function ξ∈L1(ℝ) such that tr[f(B)−f(A)]=∫ℝf′(x)ξ(x)dx for a large set of functions f. We give here a new proof of this result and discuss the class of admissible functions. Our proof is based on the integral representation of harmonic functions on the upper half plane and also uses the Baker-Campbell-Hausdorff formula.http://dx.doi.org/10.1155/S0161171201004318
spellingShingle Khristo N. Boyadzhiev
Kreĭn's trace formula and the spectral shift function
International Journal of Mathematics and Mathematical Sciences
title Kreĭn's trace formula and the spectral shift function
title_full Kreĭn's trace formula and the spectral shift function
title_fullStr Kreĭn's trace formula and the spectral shift function
title_full_unstemmed Kreĭn's trace formula and the spectral shift function
title_short Kreĭn's trace formula and the spectral shift function
title_sort krein s trace formula and the spectral shift function
url http://dx.doi.org/10.1155/S0161171201004318
work_keys_str_mv AT khristonboyadzhiev kreinstraceformulaandthespectralshiftfunction