Abstract
Linear cosmological perturbations of a large class of modified gravity
and dark energy models can be unified in the effective field theory of
cosmic acceleration, encompassing Horndeski scalar-tensor theories and
beyond. The fully available model space inherent to this formalism
cannot be constrained by measurements in the quasistatic small-scale
regime alone. To facilitate the analysis of modifications from the
concordance model beyond this limit, we introduce a semi-dynamical
treatment extrapolated from the evolution of perturbations at a pivot
scale of choice. At small scales, and for Horndeski theories, the
resulting modifications recover a quasistatic approximation but account
for corrections to it near the Hubble scale. For models beyond Horndeski
gravity, we find that the velocity field and time derivative of the
spatial metric potential can generally not be neglected, even in the
small-scale limit. We test the semi-dynamical approximation against the
linear perturbations of a range of dark energy and modified gravity
models, finding good agreement between the two.
Original language | English |
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Pages (from-to) | 40 |
Journal | Journal of Cosmology and Astroparticle Physics (JCAP) |
Volume | 11 |
Issue number | 11 |
DOIs | |
Publication status | Published - 24 Nov 2015 |