Cosmological perturbations in coherent oscillating scalar field models



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Ruiz Cembranos, José Alberto and López Maroto, Antonio and Nuñez Jareño, Santos José (2016) Cosmological perturbations in coherent oscillating scalar field models. Journal of high energy physics, 3 . ISSN 1029-8479

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The fact that fast oscillating homogeneous scalar fields behave as perfect fluids in average and their intrinsic isotropy have made these models very fruitful in cosmology. In this work we will analyse the perturbations dynamics in these theories assuming general power law potentials V(ϕ) = λ|ϕ|^n /n. At leading order in the wavenumber expansion, a simple expression for the effective sound speed of perturbations is obtained c_eff^ 2  = ω = (n − 2)/(n + 2) with ω the effective equation of state. We also obtain the first order correction in k^ 2/ω_eff^ 2 , when the wavenumber k of the perturbations is much smaller than the background oscillation frequency, ω_eff. For the standard massive case we have also analysed general anharmonic contributions to the effective sound speed. These results are reached through a perturbed version of the generalized virial theorem and also studying the exact system both in the super-Hubble limit, deriving the natural ansatz for δϕ; and for sub-Hubble modes, exploiting Floquet’s theorem.

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Open Access, © The Authors.
© Springer Verlag, A. G.
Article funded by SCOAP3.
This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.
This work has been supported by MICINN (Spain) project numbers FIS2011-23000, FPA2011-27853-01, FIS2014-52837-P and Consolider-Ingenio MULTIDARK CSD2009- 00064. S.J.N.J. acknowledge support from Complutense University under grant CT4/14. We would like to thank Alberto Díez Tejedor for his useful comments.

Uncontrolled Keywords:Cosmology of theories beyond the SM; Classical theories of gravity
Subjects:Sciences > Physics
ID Code:37973
Deposited On:01 Jun 2016 16:22
Last Modified:01 Jun 2016 16:22

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