Thermodynamics of a Spherically Symmetric Causal Diamond in Minkowski Spacetime

Fuente: arXiv
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Auteurs principaux: Fransen, Kwinten, He, Temple, Zurek, Kathryn M.
Format: Preprint
Publié: 2025
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author Fransen, Kwinten
He, Temple
Zurek, Kathryn M.
author_facet Fransen, Kwinten
He, Temple
Zurek, Kathryn M.
contents We compute a gravitational on-shell action of a finite, spherically symmetric causal diamond in $(d+2)$-dimensional Minkowski spacetime, finding it is proportional to the area of the bifurcate horizon $A_{\mathcal{B}}$. We then identify the on-shell action with the saddle point of the Euclidean gravitational path integral, which is naturally interpreted as a partition function. This partition function is thermal with respect to a modular Hamiltonian $K$. Consequently, we determine, from the on-shell action using standard thermodynamic identities, both the mean and variance of the modular Hamiltonian, finding $\langle K \rangle = \langle (ΔK)^2 \rangle = \frac{A_{\mathcal{B}}}{4 G_N}$. Finally, we show that modular fluctuations give rise to fluctuations in the geometry, and compute the associated phase shift of massless particles traversing the diamond under such fluctuations.
format Preprint
id arxiv_https___arxiv_org_abs_2507_22977
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Thermodynamics of a Spherically Symmetric Causal Diamond in Minkowski Spacetime
Fransen, Kwinten
He, Temple
Zurek, Kathryn M.
High Energy Physics - Theory
General Relativity and Quantum Cosmology
High Energy Physics - Phenomenology
We compute a gravitational on-shell action of a finite, spherically symmetric causal diamond in $(d+2)$-dimensional Minkowski spacetime, finding it is proportional to the area of the bifurcate horizon $A_{\mathcal{B}}$. We then identify the on-shell action with the saddle point of the Euclidean gravitational path integral, which is naturally interpreted as a partition function. This partition function is thermal with respect to a modular Hamiltonian $K$. Consequently, we determine, from the on-shell action using standard thermodynamic identities, both the mean and variance of the modular Hamiltonian, finding $\langle K \rangle = \langle (ΔK)^2 \rangle = \frac{A_{\mathcal{B}}}{4 G_N}$. Finally, we show that modular fluctuations give rise to fluctuations in the geometry, and compute the associated phase shift of massless particles traversing the diamond under such fluctuations.
title Thermodynamics of a Spherically Symmetric Causal Diamond in Minkowski Spacetime
topic High Energy Physics - Theory
General Relativity and Quantum Cosmology
High Energy Physics - Phenomenology
url https://arxiv.org/abs/2507.22977