On some mathematical problems for open quantum systems with varying particle number

Fuente: arXiv
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Auteurs principaux: Reible, Benedikt M., Site, Luigi Delle
Format: Preprint
Publié: 2026
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author Reible, Benedikt M.
Site, Luigi Delle
author_facet Reible, Benedikt M.
Site, Luigi Delle
contents We derive the effective Hamiltonian $H - μN$ for open quantum systems with varying particle number from first principles within the framework of non-relativistic quantum statistical mechanics. We prove that under physically motivated assumptions regarding the size of the system and the range of the interaction, this form of the Hamiltonian is unique up to a constant. Our argument relies firstly on establishing a rigorous version of the surface-to-volume ratio approximation, which is routinely used in an empirical form in statistical mechanics, and secondly on showing that the Hilbert space for systems with varying particle number must be isomorphic to Fock space. Together, these findings provide a rigorous mathematical justification for the standard grand canonical formalism employed in statistical physics.
format Preprint
id arxiv_https___arxiv_org_abs_2602_21781
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On some mathematical problems for open quantum systems with varying particle number
Reible, Benedikt M.
Site, Luigi Delle
Mathematical Physics
Statistical Mechanics
Quantum Physics
We derive the effective Hamiltonian $H - μN$ for open quantum systems with varying particle number from first principles within the framework of non-relativistic quantum statistical mechanics. We prove that under physically motivated assumptions regarding the size of the system and the range of the interaction, this form of the Hamiltonian is unique up to a constant. Our argument relies firstly on establishing a rigorous version of the surface-to-volume ratio approximation, which is routinely used in an empirical form in statistical mechanics, and secondly on showing that the Hilbert space for systems with varying particle number must be isomorphic to Fock space. Together, these findings provide a rigorous mathematical justification for the standard grand canonical formalism employed in statistical physics.
title On some mathematical problems for open quantum systems with varying particle number
topic Mathematical Physics
Statistical Mechanics
Quantum Physics
url https://arxiv.org/abs/2602.21781