Juan Carlos Hidalgo

Non-Gaussian initial conditions in ΛCDM: Newtonian, relativistic, and primordial contributions

The goal of the present paper is to set initial conditions for structure formation at nonlinear order, consistent with general relativity, while also allowing for primordial non-Gaussianity. We use the nonlinear continuity and Raychaudhuri equations, which together with the nonlinear 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 ΛCDM universe, identifying nonlinear contributions coming from the Newtonian growing mode, primordial non-Gaussianity and intrinsic non-Gaussianity, due to the essential nonlinearity 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 nonlinear parameter f NL.

Einstein's signature in cosmological large-scale structure

We show how the nonlinearity of general relativity generates a characteristic nonGaussian signal in cosmological large-scale structure that we calculate at all perturbative orders in a large-scale limit. Newtonian gravity and general relativity provide complementary theoretical frameworks for modeling large-scale structure in ΛCDM cosmology; a relativistic approach is essential to determine initial conditions, which can then be used in Newtonian simulations studying the nonlinear evolution of the matter density. Most inflationary models in the very early universe predict an almost Gaussian distribution for the primordial metric perturbation, ζ. However, we argue that it is the Ricci curvature of comoving-orthogonal spatial hypersurfaces, R, that drives structure formation at large scales. We show how the nonlinear relation between the spatial curvature, R, and the metric perturbation, ζ, translates into a specific nonGaussian contribution to the initial comoving matter density that we calculate for the simple case of an initially Gaussian ζ. Our analysis shows the nonlinear signature of Einsteins gravity in large-scale structure.

Tachyon inflation in the large-N formalism

We study tachyon inflation within the large-

Testing Hybrid Natural Inflation with BICEP2

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Formation of subhorizon black holes from preheating

formalism, which takes a prescription for the small Hubble flow slow--roll parameter

Collapse threshold for a cosmological Klein Gordon field

\epsilon_1

Second-order cosmological perturbation theory and initial conditions for

as a function of the large number of

N

e

-body simulations

-folds

Canonical single field slow-roll inflation with a non-monotonic tensor-to-scalar ratio

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