Non-Gaussianity from the second-order cosmological perturbation
- Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)
Several conserved and/or gauge-invariant quantities described as the second-order curvature perturbation have been given in the literature. We revisit various scenarios for the generation of second-order non-Gaussianity in the primordial curvature perturbation {zeta}, employing for the first time a unified notation and focusing on the normalization f{sub NL} of the bispectrum. When {zeta} first appears a few Hubble times after horizon exit, |f{sub NL}| is much less than 1 and is, therefore, negligible. Thereafter {zeta} (and hence f{sub NL}) is conserved as long as the pressure is a unique function of energy density (adiabatic pressure). Nonadiabatic pressure comes presumably only from the effect of fields, other than the one pointing along the inflationary trajectory, which are light during inflation ('light noninflaton fields'). During single-component inflation f{sub NL} is constant, but multicomponent inflation might generate vertical bar f{sub NL} vertical bar {approx}1 or bigger. Preheating can affect f{sub NL} only in atypical scenarios where it involves light noninflaton fields. The simplest curvaton scenario typically gives f{sub NL}<<-1 or f{sub NL}=+5/4. The inhomogeneous reheating scenario can give a wide range of values for f{sub NL}. Unless there is a detection, observation can eventually provide a limit vertical bar f{sub NL} vertical bar or approx. 1, at which level it will be crucial to calculate the precise observational limit using second-order theory.
- OSTI ID:
- 20709523
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 71, Issue 12; Other Information: DOI: 10.1103/PhysRevD.71.123508; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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