Towards the Theory of Reheating After Inflation

Towards the Theory of Reheating After Inflation

(April 30, 1997) | Lev Kofman, Andrei Linde, Alexei A. Starobinsky
The paper by Kofman, Linde, and Starobinsky explores the theory of reheating after inflation, focusing on the effects beyond perturbation theory. They introduce the concept of *preheating*, which occurs when the initial amplitude of the inflaton field's oscillations is large enough. In this regime, the inflaton field interacts with another scalar field, leading to broad parametric resonance. This resonance occurs in a stochastic manner, with quantum fields experiencing a series of kicks due to the rapid expansion of the universe. Despite the stochastic nature, it results in exponential growth of fluctuations in the interacting field. The authors develop a theory of preheating, considering the expansion of the universe and backreaction of produced particles, including rescattering. They show that the contribution of produced particles to the effective potential is proportional to the absolute value of the inflaton field, not its square. The process is divided into stages, with the first stage being dominated by the backreaction of created particles, followed by an increase in the frequency of oscillations due to the interaction with the interacting field. The effects of rescattering terminate the resonance. The paper calculates the number density and quantum fluctuations of the produced particles, demonstrating that efficient preheating can occur under certain conditions, potentially leading to particles with masses much greater than the inflaton field. The authors also discuss the implications of preheating for nonthermal phase transitions, topological defect production, and baryogenesis.The paper by Kofman, Linde, and Starobinsky explores the theory of reheating after inflation, focusing on the effects beyond perturbation theory. They introduce the concept of *preheating*, which occurs when the initial amplitude of the inflaton field's oscillations is large enough. In this regime, the inflaton field interacts with another scalar field, leading to broad parametric resonance. This resonance occurs in a stochastic manner, with quantum fields experiencing a series of kicks due to the rapid expansion of the universe. Despite the stochastic nature, it results in exponential growth of fluctuations in the interacting field. The authors develop a theory of preheating, considering the expansion of the universe and backreaction of produced particles, including rescattering. They show that the contribution of produced particles to the effective potential is proportional to the absolute value of the inflaton field, not its square. The process is divided into stages, with the first stage being dominated by the backreaction of created particles, followed by an increase in the frequency of oscillations due to the interaction with the interacting field. The effects of rescattering terminate the resonance. The paper calculates the number density and quantum fluctuations of the produced particles, demonstrating that efficient preheating can occur under certain conditions, potentially leading to particles with masses much greater than the inflaton field. The authors also discuss the implications of preheating for nonthermal phase transitions, topological defect production, and baryogenesis.
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