Nonperturbative Dynamics Of Reheating After Inflation: A Review (1410.3808v3)

Abstract: Our understanding of the state of the universe between the end of inflation and big bang nucleosynthesis (BBN) is incomplete. The dynamics at the end of inflation are rich and a potential source of observational signatures. Reheating, the energy transfer between the inflaton and Standard Model fields (possibly through intermediaries) and their subsequent thermalization, can provide clues to how inflation fits in with known high-energy physics. We provide an overview of our current understanding of the nonperturbative, nonlinear dynamics at the end of inflation, some salient features of realistic particle physics models of reheating, and how the universe reaches a thermal state before BBN. In addition, we review the analytical and numerical tools available in the literature to study preheating and reheating and discuss potential observational signatures from this fascinating era.

• The paper explains how nonperturbative mechanisms like parametric resonance drive rapid energy transfer from the inflaton field.
• The paper demonstrates that numerical simulations reveal complex nonlinear dynamics, including the formation of oscillons and topological solitons.
• The paper emphasizes the critical role of achieving thermalization before Big Bang Nucleosynthesis to connect early inflationary physics to observable cosmology.

Nonperturbative Dynamics of Reheating After Inflation

The article "Nonperturbative Dynamics of Reheating After Inflation: A Review" by Amin et al. provides a comprehensive examination of the complex dynamics occurring at the end of the cosmic inflation era. This stage, known as reheating, is critical for connecting the ultracool state post-inflation to the hot, thermalized conditions necessary for Big Bang Nucleosynthesis (BBN). Understanding this transition is foundational for reconciling high-energy particle physics with observed cosmological phenomena.

Overview

The review discusses the intricate, nonperturbative interactions between the inflaton field and Standard Model particles, potentially mediated by intermediary fields, to achieve thermalization of the universe. The authors explore a variety of particle physics models and propose various mechanisms by which reheating might occur.

Key Themes

1. Inflaton Energy Transfer: The paper distinguishes between two principal mechanisms of energy transfer from the inflaton field: perturbative and nonperturbative processes. Early models primarily addressed perturbative decays, but later research highlighted nonperturbative phenomena, particularly parametric resonances or preheating.

- Perturbative Decay: Typically modeled through three-point interactions, the decay rate can be estimated using conventional quantum field theory techniques. - Nonperturbative Preheating: The review covers how inflaton oscillations lead to parametric resonance, amplifying certain modes of field fluctuations exponentially, thus facilitating energy transfer.

1. Nonlinear Dynamics: As fluctuations grow during preheating, the universe enters a phase where nonlinear effects dominate. This necessitates the use of numerical simulations to understand the evolution fully and predict the formation of alignable structures such as oscillons or topological solitons.
2. Thermalization: Completing the energy transfer from the inflaton to a thermal bath of particles is crucial for the universe to transition into a radiation-dominated thermal equilibrium state before BBN. The authors detail stages of thermalization, highlighting out-of-equilibrium processes where quantum field theory provides critical insight.
3. Particle Physics Models: The inflaton could couple to a variety of fields, including scalars, fermions, and gauge bosons. This coupling is shown to play a significant role in the preheating dynamics. Models with higher-derivative interactions or those beyond the Standard Model (like supersymmetry) provide intriguing avenues of research.
4. Observational Consequences: While challenging to observe directly, the paper outlines possible modern observational phenomena that might trace back to reheating dynamics, such as the impact on gravitational waves, primordial black holes, and modulated reheating. Observational constraints and implications could refine our understanding of inflationary models.

Numerical Tools and Techniques

The paper also surveys various numerical tools developed to paper the dynamics during the reheating phase. These tools enable simulations of field evolution in dynamic, expanding spacetimes and are essential for analyzing complex phenomena that occur beyond linear approximations.

Implications and Future Prospects

Understanding reheating is vital for mapping the predictions of inflationary models to observable cosmological data accurately. Given the diversity of potential connections to particle physics, further advancements in model-building, simulations, and observational techniques hold promise for uncovering new facets of early universe physics. Theoretical work aligning reheating dynamics with both present cosmic structures and high-energy physics remains an active and promising field of research.

In summary, this review is an invaluable resource for researchers investigating the bridge between early inflationary physics and cosmological observations, offering a detailed portrait of the rich dynamics of reheating that potentially holds keys to deeper insights into the universe's evolution.