Nonlinear perturbations of cosmological scalar fields with non-standard kinetic terms
- APC (Astroparticules et Cosmologie), UMR 7164 (CNRS, Universite Paris 7, CEA, Observatoire de Paris), 10 rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13 (France)
- Institut fuer Teoretische Physik, Universitaet Heidelberg, Philosophenweg 16 and 19, D-69120 Heidelberg (Germany)
We adopt a covariant formalism to derive exact evolution equations for nonlinear perturbations, in a universe dominated by two scalar fields. These scalar fields are characterized by non-canonical kinetic terms and an arbitrary field space metric, a situation typically encountered in inflationary models inspired by string theory. We decompose the nonlinear scalar perturbations into adiabatic and entropy modes, generalizing the definition adopted in the linear theory, and we derive the corresponding exact evolution equations. We also obtain a nonlinear generalization of the curvature perturbation on uniform density hypersurfaces, showing that on large scales it is sourced only by the nonlinear version of the entropy perturbation. We then expand these equations to second order in the perturbations, using a coordinate based formalism. Our results are relatively compact and elegant and enable one to identify the new effects coming from the non-canonical structure of the scalar fields Lagrangian. We also explain how to analyze, in our formalism, the interesting scenario of multi-field Dirac-Born-Infeld inflation.
- OSTI ID:
- 22156851
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2009, Issue 01; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
Similar Records
Non-Gaussianity of superhorizon curvature perturbations beyond δ N formalism
Cosmological perturbations and noncommutative tachyon inflation