Thermal enhancement of inflationary magnetic fields

Fuente: arXiv
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Main Authors: Berera, Arjun, Brahma, Suddhasattwa, Qiu, Zizang, Ramos, Rudnei O.
Format: Preprint
Published: 2026
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author Berera, Arjun
Brahma, Suddhasattwa
Qiu, Zizang
Ramos, Rudnei O.
author_facet Berera, Arjun
Brahma, Suddhasattwa
Qiu, Zizang
Ramos, Rudnei O.
contents We investigate primordial magnetogenesis by assuming the gauge field is prepared in a thermal state during inflation rather than the standard Bunch-Davies vacuum. The temperature $\mathcal{T}$ introduces a physical scale that breaks conformal invariance at the level of the state while preserving the standard Maxwell action. This modification results in a {\it dissipative boost} that alters the magnetic energy density scaling from $a^{-4}$ to $a^{-3}$, resulting in a present-day magnetic field $B_0$ enhancement that can potentially range from about $10^{8}$ to $10^{16}$ on galactic scales. While this toy model alone does not satisfy observational lower bounds, it demonstrates that thermal initial conditions can significantly mitigate the conformal obstruction. Our results suggest that embedding this mechanism within a fully dynamical warm inflation framework, where dissipation continuously maintains the thermal bath, provides a highly promising path towards successfully realizing a minimal model of inflationary magnetogenesis without the need to invoke non-minimal couplings, anomalous background dynamics or nonlinear extensions of electrodynamics.
format Preprint
id arxiv_https___arxiv_org_abs_2603_10157
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Thermal enhancement of inflationary magnetic fields
Berera, Arjun
Brahma, Suddhasattwa
Qiu, Zizang
Ramos, Rudnei O.
Cosmology and Nongalactic Astrophysics
General Relativity and Quantum Cosmology
High Energy Physics - Theory
We investigate primordial magnetogenesis by assuming the gauge field is prepared in a thermal state during inflation rather than the standard Bunch-Davies vacuum. The temperature $\mathcal{T}$ introduces a physical scale that breaks conformal invariance at the level of the state while preserving the standard Maxwell action. This modification results in a {\it dissipative boost} that alters the magnetic energy density scaling from $a^{-4}$ to $a^{-3}$, resulting in a present-day magnetic field $B_0$ enhancement that can potentially range from about $10^{8}$ to $10^{16}$ on galactic scales. While this toy model alone does not satisfy observational lower bounds, it demonstrates that thermal initial conditions can significantly mitigate the conformal obstruction. Our results suggest that embedding this mechanism within a fully dynamical warm inflation framework, where dissipation continuously maintains the thermal bath, provides a highly promising path towards successfully realizing a minimal model of inflationary magnetogenesis without the need to invoke non-minimal couplings, anomalous background dynamics or nonlinear extensions of electrodynamics.
title Thermal enhancement of inflationary magnetic fields
topic Cosmology and Nongalactic Astrophysics
General Relativity and Quantum Cosmology
High Energy Physics - Theory
url https://arxiv.org/abs/2603.10157