Non-linear dark energy clustering

Abstract

We consider a dark energy fluid with arbitrary sound speed and equation of state and discuss theeffect of its clustering on the cold dark matter distribution at the non-linear level. We writethe continuity, Euler and Poisson equations for the system in the Newtonian approximation.Then, using the time renormalization group method to resum perturbative corrections at all orders, wecompute the total clustering power spectrum and matter power spectrum.At the linear level, a sound speed of dark energy different from that of light modifies the powerspectrum on observationally interesting scales, such as those relevant for baryonic acousticoscillations. We show that the effect of varying the sound speed of dark energy on the non-linear corrections to the matter power spectrum is below the per cent level, and therefore these corrections can be well modelled by their counterpart in cosmological scenarios with smooth dark energy. We also show that the non-linear effects on the matter growth index can be as large as 10–15 per cent for small scales.