Multi-scale perturbation theory. Part I. Methodology and leading-order bispectrum corrections in the matter-dominated era
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Date
2020
Journal Title
Journal ISSN
Volume Title
Publisher
IOP Publishing Ltd
Abstract
Two-parameter perturbation theory is a scheme tailor-made to consistently include nonlinear density contrasts on small scales (< 100 Mpc), whilst retaining a traditional
approach to cosmological perturbations in the long-wavelength universe. In this paper we
study the solutions that arise from this theory in a spatially-flat dust-filled cosmology, and
what these imply for the bispectrum of matter. This is achieved by using Newtonian perturbation theory to model the gravitational fields of nonlinear structures in the quasi-linear
regime, and then using the resulting solutions as source terms for the cosmological equations.
We find that our approach results in the leading-order part of the cosmological gravitational
potentials being identical to those that result from standard cosmological perturbation theory
at second-order, while the dark matter bispectrum itself yields some differences on Hubble
scales. This demonstrates that our approach is sufficient to capture most leading-order relativistic effects, but within a framework that is far easier to generalize. We expect this latter
property to be particularly useful for calculating leading-order relativistic corrections to the
matter power spectrum, as well as for deriving predictions for relativistic effects in alternative
theories of gravity.
Description
Keywords
Cosmological perturbation theory, Gravity, Non-gaussianity, Power spectrum, Nonlinear density
Citation
Clarksona, C. et al. (2020). Multi-scale perturbation theory. Part I. Methodology and leading-order bispectrum corrections in the matter-dominated era. Journal of Cosmology and Astroparticle Physics ,2020(03)