Foundations of Double Operator Integrals with a Variant Approach to the Nonseparable Case

Fuente: arXiv
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Hauptverfasser: Ferydouni, Robert, Spiegel, Daniel D.
Format: Preprint
Veröffentlicht: 2025
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author Ferydouni, Robert
Spiegel, Daniel D.
author_facet Ferydouni, Robert
Spiegel, Daniel D.
contents We aim to give a self-contained and detailed yet simplified account of the foundations of the theory of double operator integrals, in order to provide an accessible entry point to the theory. We make two new contributions to these foundations: (1) a new proof of the existence of the product of two projection-valued measures, which allows for the definition of the double operator integral for Hilbert-Schmidt operators, and (2) a variant approach to the integral projective tensor product on arbitrary (not necessarily separable) Hilbert spaces using a somewhat more explicit norm than has previously been given. We prove the Daletskii-Krein formula for strongly differentiable perturbations of a densely-defined self-adjoint operator and conclude by reviewing an application of the theory to quantum statistical mechanics.
format Preprint
id arxiv_https___arxiv_org_abs_2510_25789
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Foundations of Double Operator Integrals with a Variant Approach to the Nonseparable Case
Ferydouni, Robert
Spiegel, Daniel D.
Mathematical Physics
Functional Analysis
Operator Algebras
We aim to give a self-contained and detailed yet simplified account of the foundations of the theory of double operator integrals, in order to provide an accessible entry point to the theory. We make two new contributions to these foundations: (1) a new proof of the existence of the product of two projection-valued measures, which allows for the definition of the double operator integral for Hilbert-Schmidt operators, and (2) a variant approach to the integral projective tensor product on arbitrary (not necessarily separable) Hilbert spaces using a somewhat more explicit norm than has previously been given. We prove the Daletskii-Krein formula for strongly differentiable perturbations of a densely-defined self-adjoint operator and conclude by reviewing an application of the theory to quantum statistical mechanics.
title Foundations of Double Operator Integrals with a Variant Approach to the Nonseparable Case
topic Mathematical Physics
Functional Analysis
Operator Algebras
url https://arxiv.org/abs/2510.25789