Renormalization of the Quantum Stress Tensor Fluctuations and the Limits of Semiclassical Gravity

Fuente: arXiv
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Autores principales: Perez, Alejandro, Sudarsky, Daniel
Formato: Preprint
Publicado: 2025
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author Perez, Alejandro
Sudarsky, Daniel
author_facet Perez, Alejandro
Sudarsky, Daniel
contents We analyze the expectation value of the energy-momentum tensor and its fluctuations in quantum field theory on curved spacetimes $\langle T_{ab} \rangle$. A generally accepeted condition for the conceptual consistency of semiclassical gravity, where $\langle T_{ab} \rangle$ represent the sources of the Einstein equations, is that the fluctuations of the energy momentum tensor remain small compared to its expectation value. We study the renormalization of both the energy-momentum tensor $\langle T_{ab}(x)\rangle_{\rm ren}$ and the fluctuation tensor $\langle T_{ab}(x) T_{cd}(x) \rangle_{\rm ren}$ for suitable Hadamard states, using the operator product expansion for a free scalar field on a fixed curved background. We show that states (usually referred to as `squeezed vacua') -- arising naturally in black hole evaporation and in inflationary cosmology -- fail to satisfy the natural semiclassicality criterion.
format Preprint
id arxiv_https___arxiv_org_abs_2512_17789
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Renormalization of the Quantum Stress Tensor Fluctuations and the Limits of Semiclassical Gravity
Perez, Alejandro
Sudarsky, Daniel
General Relativity and Quantum Cosmology
High Energy Physics - Theory
We analyze the expectation value of the energy-momentum tensor and its fluctuations in quantum field theory on curved spacetimes $\langle T_{ab} \rangle$. A generally accepeted condition for the conceptual consistency of semiclassical gravity, where $\langle T_{ab} \rangle$ represent the sources of the Einstein equations, is that the fluctuations of the energy momentum tensor remain small compared to its expectation value. We study the renormalization of both the energy-momentum tensor $\langle T_{ab}(x)\rangle_{\rm ren}$ and the fluctuation tensor $\langle T_{ab}(x) T_{cd}(x) \rangle_{\rm ren}$ for suitable Hadamard states, using the operator product expansion for a free scalar field on a fixed curved background. We show that states (usually referred to as `squeezed vacua') -- arising naturally in black hole evaporation and in inflationary cosmology -- fail to satisfy the natural semiclassicality criterion.
title Renormalization of the Quantum Stress Tensor Fluctuations and the Limits of Semiclassical Gravity
topic General Relativity and Quantum Cosmology
High Energy Physics - Theory
url https://arxiv.org/abs/2512.17789