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Perturbations in generalized multi-field inflation

David Langlois 1 S. Renaux-Petel 2
Institut für theoretische Physik, APC (UMR_7164) - AstroParticule et Cosmologie
Abstract : We study the linear perturbations of multi-field inflationary models governed by a Lagrangian which is a general function of the scalar fields and of a global kinetic term combining their spacetime gradients with an arbitrary field space metric. Our analysis includes k-inflation, DBI inflation and its multi-field extensions which have been recently studied. For this general class of models, we calculate the action to second order in the linear perturbations. We decompose the perturbations into an (instantaneous) adiabatic mode, parallel to the background trajectory, and entropy modes. We show that all the entropy modes propagate with the speed of light whereas the adiabatic mode propagates with an effective speed of sound. We also identify the specific combination of entropy modes which sources the curvature perturbation on large scales. We then study in some detail the case of two scalar fields: we write explicitly the equations of motion for the adiabatic and entropy modes in a compact form and discuss their quantum fluctuations and primordial power spectra.
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Submitted on : Thursday, July 10, 2008 - 11:14:18 AM
Last modification on : Wednesday, October 21, 2020 - 4:32:14 PM

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David Langlois, S. Renaux-Petel. Perturbations in generalized multi-field inflation. Journal of Cosmology and Astroparticle Physics, Institute of Physics (IOP), 2008, 04, pp.017. ⟨10.1088/1475-7516/2008/04/017⟩. ⟨in2p3-00294677⟩



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