Reheating as a variational probe of cosmological observables
Jinn-Ouk Gong
astro-ph.CO, gr-qc, hep-ph, hep-th, physics.class-ph
Submitted: 2026-06-17
Comments: 11 pages, 3 figures, 2 tables
License: http://creativecommons.org/licenses/by/4.0/
The gist: We formulate reheating as a constrained variational problem in the space of equation-of-state histories, rather than attempting to describe it through microscopic models.
Terminology
Abstract
We formulate reheating as a constrained variational problem in the space of equation-of-state histories, rather than attempting to describe it through microscopic models. We introduce a regularized functional framework that identifies reheating histories which extremize a given cosmological observable under minimal physical assumptions. As illustrative applications, we consider prompt gravitational waves, induced gravitational waves, and primordial black holes. We find that different observables select qualitatively different regions of reheating-history space. These examples demonstrate that cosmological observables define distinct extremal directions in reheating-history space and can therefore be used to systematically explore the space of post-inflationary expansion histories.
Sources
- Planck 2018 results. VI. Cosmological parameters
- Inflation Dynamics and Reheating
- Reheating in Inflationary Cosmology: Theory and Applications
- Nonperturbative Dynamics Of Reheating After Inflation: A Review
- Observing the Inflationary Reheating
- Teasing bits of information out of the CMB energy spectrum
- Largest temperature of the radiation era and its cosmological implications
- Stochastic Gravitational Wave Production After Inflation
- Perturbative Understanding of Non-Perturbative Processes and Quantumization versus Classicalization
- Reheating constraints to inflationary models
- Reheating predictions in single field inflation
- Thermalization after/during Reheating
- Thermalization Process after Inflation and Effective Potential of Scalar Field
- Weakly model-independent determination of total expansion during inflation
- The cosmological gravitational wave background from primordial density perturbations
- Gravitational Wave Spectrum Induced by Primordial Scalar Perturbations
- Introduction to Effective Field Theory
- Probing reheating temperature of the universe with gravitational wave background
- Minimal Production of Prompt Gravitational Waves during Reheating
- Relic gravitational waves produced after preheating
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