Entropy production during reheating after inflation and General Relativistic Entropic Acceleration
Abstract
Preheating transforms the coherent, low-entropy energy of the post-inflationary inflaton condensate into a far-from-equilibrium bath of field quanta, and is therefore an intrinsically irreversible process. We quantify that irreversibility directly, by computing the coarse-grained phase-space entropy of the field fluctuations from classical-statistical lattice simulations performed with CosmoLattice. For each field we reconstruct the mode occupation numbers nk and evaluate S=∑k[(1+nk)ln(1+nk)−nkln nk], following its growth through the different stages of reheating in a self-consistently expanding Friedmann-Lemaître-Robertson-Walker background. We study three canonical models coupled to a daughter scalar χ through g2ϕ2χ2. We discuss the ultraviolet vacuum floor intrinsic to the lattice initial conditions and argue that the produced entropy ΔS is the physically robust diagnostic. The phase-space entropy thus provides a compact, dynamical measure that cleanly separates the resonance-dominated, turbulence-dominated, and spinodal regimes of preheating. We couple this entropy production back into the expansion through the general relativistic entropic acceleration (GREA) framework, modifying the self-consistent scale-factor evolution of CosmoLattice to include the entropic force. The resulting acceleration tracks the heat (the energy transferred to particles) rather than the entropy itself: it is substantial in the tachyonic and quartic-turbulent cases, where an 𝒪(1) fraction of the coherent energy fragments into radiation, but negligible in the resonant m2ϕ2 model despite its copious entropy production. The slow perturbative reheating that follows generates the bulk of the cosmic entropy (S0 ∼1088) yet drives no appreciable acceleration and shuts off entirely at thermalization.
Related
- Radiative Corrections and Reheating in Supergravity Models of Inflation
- Reheating surface volume renormalization and eternal inflation under broken scale invariance
- Einstein-Cartan pseudoscalaron inflation, reheating and nonthermal leptogenesis
- Effective reheating in Gauss–Bonnet inflation with μ (ϕ ,X) coupling
- Reheating Bounds from Thermal GUT Monopole Production
BibTeX
@misc{garciabellido2026entropy,
title = {{Entropy production during reheating after inflation and General Relativistic Entropic Acceleration}},
author = {Juan Garcia-Bellido},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.20242},
eprint = {2609.20242},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.20242},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Entropy production during reheating after inflation and General Relativistic Entropic Acceleration
AU - Juan Garcia-Bellido
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.20242
UR - https://arxiv.org/abs/2609.20242
AB - Preheating transforms the coherent, low-entropy energy of the post-inflationary inflaton condensate into a far-from-equilibrium bath of field quanta, and is therefore an intrinsically irreversible process. We quantify that irreversibility directly, by computing the coarse-grained phase-space entropy of the field fluctuations from classical-statistical lattice simulations performed with CosmoLattice. For each field we reconstruct the mode occupation numbers n_k and evaluate S=∑_k[(1+n_k)ln(1+n_k)−n_kln n_k], following its growth through the different stages of reheating in a self-consistently expanding Friedmann-Lemaître-Robertson-Walker background. We study three canonical models coupled to a daughter scalar χ through g^2ϕ^2χ^2. We discuss the ultraviolet vacuum floor intrinsic to the lattice initial conditions and argue that the produced entropy ΔS is the physically robust diagnostic. The phase-space entropy thus provides a compact, dynamical measure that cleanly separates the resonance-dominated, turbulence-dominated, and spinodal regimes of preheating. We couple this entropy production back into the expansion through the general relativistic entropic acceleration (GREA) framework, modifying the self-consistent scale-factor evolution of CosmoLattice to include the entropic force. The resulting acceleration tracks the heat (the energy transferred to particles) rather than the entropy itself: it is substantial in the tachyonic and quartic-turbulent cases, where an 𝒪(1) fraction of the coherent energy fragments into radiation, but negligible in the resonant m^2ϕ^2 model despite its copious entropy production. The slow perturbative reheating that follows generates the bulk of the cosmic entropy (S_0 ∼10^88) yet drives no appreciable acceleration and shuts off entirely at thermalization.
ER -