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arXiv · 1307.1478

Non-Gaussian initial conditions in $\Lambda$CDM: Newtonian, relativistic and primordial contributions

Marco Bruni·Juan Carlos Hidalgo·Nikolai Meures·David Wands
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Abstract

The goal of the present paper is to set initial conditions for structure formation at non-linear order, consistent with general relativity, while also allowing for primordial non-Gaussianity. We use the non-linear continuity and Raychauduri equations, which together with the non-linear energy constraint determine the evolution of the matter density fluctuation in general relativity. We solve this equations at first and second order in a perturbative expansion, recovering and extending previous results derived in the matter-dominated limit and in the Newtonian regime. We present a second-order solution for the comoving density contrast in a $\Lambda$CDM universe, identifying non-linear contributions coming from the Newtonian growing mode, primordial non-Gaussianity and intrinsic non-Gaussianity, due to the essential non-linearity of the relativistic constraint equations. We discuss the application of these results to initial conditions in N-body simulations, showing that relativistic corrections mimic a non-zero non-linear parameter $f_{\rm NL}$.

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Marco Bruni, Juan Carlos Hidalgo, Nikolai Meures, David Wands. 2013-07-04. Non-Gaussian initial conditions in $\Lambda$CDM: Newtonian, relativistic and primordial contributions. https://doi.org/10.1088/0004-637x%2F785%2F1%2F2

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