TY - JOUR

T1 - Evolution of the curvature perturbation during and after multi-field inflation

AU - Choi, Ki Young

AU - Gong, Jinn Ouk

AU - Jeong, Donghui

PY - 2009

Y1 - 2009

N2 - We study the evolution of the curvature perturbation on the super-horizon scales starting from the inflationary epoch until there remains only a single dynamical degree of freedom, presureless matter, in the universe. We consider the cosmic inflation driven by a multiple number of the inflaton fields, which decay into both radiation and pressureless matter components. We present a complete set of the exact background and perturbation equations which describe the evolution of the universe throughout its history. By applying these equations to the simple but reasonable model of multi-field chaotic inflation, we explicitly show that the total curvature perturbation is continuously varying because of the non-adiabatic components of the curvature perturbation generated by the multiple inflaton fields throughout the whole evolution of the universe. We also provide an useful analytic estimation of the total as well as matter and radiation curvature perturbations, assuming that matter is completely decoupled from radiation from the beginning. The resulting isocurvature perturbation between matter and radiation is at most sub-percent level when the masses of the inflaton fields are distributed between 10 -6m Pl and 10 -5m Pl. We find that this result is robust unless we use non-trivial decay rates, and that thus, in general, it is hard to obtain large matter-radiation isocurvature perturbation. Also, by using the δN formalism, we point out that the inflationary calculation, especially when involving multiple inflaton fields, is likely to lose the potentially important post-inflationary evolution which can modify the resulting curvature perturbation.

AB - We study the evolution of the curvature perturbation on the super-horizon scales starting from the inflationary epoch until there remains only a single dynamical degree of freedom, presureless matter, in the universe. We consider the cosmic inflation driven by a multiple number of the inflaton fields, which decay into both radiation and pressureless matter components. We present a complete set of the exact background and perturbation equations which describe the evolution of the universe throughout its history. By applying these equations to the simple but reasonable model of multi-field chaotic inflation, we explicitly show that the total curvature perturbation is continuously varying because of the non-adiabatic components of the curvature perturbation generated by the multiple inflaton fields throughout the whole evolution of the universe. We also provide an useful analytic estimation of the total as well as matter and radiation curvature perturbations, assuming that matter is completely decoupled from radiation from the beginning. The resulting isocurvature perturbation between matter and radiation is at most sub-percent level when the masses of the inflaton fields are distributed between 10 -6m Pl and 10 -5m Pl. We find that this result is robust unless we use non-trivial decay rates, and that thus, in general, it is hard to obtain large matter-radiation isocurvature perturbation. Also, by using the δN formalism, we point out that the inflationary calculation, especially when involving multiple inflaton fields, is likely to lose the potentially important post-inflationary evolution which can modify the resulting curvature perturbation.

KW - Cosmological perturbation theory

KW - Inflation

KW - Physics of the early universe

UR - http://www.scopus.com/inward/record.url?scp=65649093335&partnerID=8YFLogxK

U2 - 10.1088/1475-7516/2009/02/032

DO - 10.1088/1475-7516/2009/02/032

M3 - Article

AN - SCOPUS:65649093335

VL - 2009

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

SN - 1475-7516

IS - 2

M1 - 032

ER -