Journal
JOURNAL OF HIGH ENERGY PHYSICS
Volume -, Issue 3, Pages -Publisher
SPRINGER
DOI: 10.1007/JHEP03(2016)013
Keywords
Cosmology of Theories beyond the SM; Classical Theories of Gravity
Categories
Funding
- MICINN (Spain) [FIS2011-23000, FPA2011-27853-01, FIS2014-52837-P]
- Consolider-Ingenio MULTIDARK [CSD2009-00064]
- Complutense University [CT4/14]
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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(phi) = lambda vertical bar phi vertical bar(n)/n. At leading order in the wavenumber expansion, a simple expression for the effective sound speed of perturbations is obtained c(eff)(2) = omega = (n - 2)/(n + 2) with omega the effective equation of state. We also obtain the first order correction in k(2)/omega(2)(eff), when the wavenumber k of the perturbations is much smaller than the background oscillation frequency, omega(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 delta phi; and for sub-Hubble modes, exploiting Floquet's theorem.
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