TY - JOUR

T1 - Particle production from oscillating scalar field and consistency of Boltzmann equation

AU - Moroi, Takeo

AU - Yin, Wen

N1 - Publisher Copyright:
© 2021, The Author(s).

PY - 2021/3

Y1 - 2021/3

N2 - Boltzmann equation plays important roles in particle cosmology in studying the evolution of distribution functions (also called as occupation numbers) of various particles. For the case of the decay of a scalar condensation ϕ into a pair of scalar particles (called χ), we point out that the system may not be well described by the Boltzmann equation when the occupation number of χ becomes large even in the so-called narrow resonance regime. We study the particle production including the possible enhancement due to a large occupation number of the final state particle, known as the stimulated emission or the parametric resonance. Based on the quantum field theory (QFT), we derive a set of equations which directly govern the evolution of the distribution function of χ. Comparing the results of the QFT calculation and those from the Boltzmann equation, we find non-agreements in some cases. In particular, in the expanding Universe, the occupation number of χ based on the QFT may differ by many orders of magnitude from that from the Boltzmann equation. We also discuss a possible relation between the evolution equations based on the QFT and the Boltzmann equation.

AB - Boltzmann equation plays important roles in particle cosmology in studying the evolution of distribution functions (also called as occupation numbers) of various particles. For the case of the decay of a scalar condensation ϕ into a pair of scalar particles (called χ), we point out that the system may not be well described by the Boltzmann equation when the occupation number of χ becomes large even in the so-called narrow resonance regime. We study the particle production including the possible enhancement due to a large occupation number of the final state particle, known as the stimulated emission or the parametric resonance. Based on the quantum field theory (QFT), we derive a set of equations which directly govern the evolution of the distribution function of χ. Comparing the results of the QFT calculation and those from the Boltzmann equation, we find non-agreements in some cases. In particular, in the expanding Universe, the occupation number of χ based on the QFT may differ by many orders of magnitude from that from the Boltzmann equation. We also discuss a possible relation between the evolution equations based on the QFT and the Boltzmann equation.

KW - Beyond Standard Model

KW - Cosmology of Theories beyond the SM

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U2 - 10.1007/JHEP03(2021)296

DO - 10.1007/JHEP03(2021)296

M3 - Article

AN - SCOPUS:85107377270

SN - 1126-6708

VL - 2021

JO - Journal of High Energy Physics

JF - Journal of High Energy Physics

IS - 3

M1 - 296

ER -