Signatures of Primordial Gravitational Waves on the Large-Scale Structure of the Universe.

We study the generation and evolution of second-order energy-density perturbations arising from primordial gravitational waves. Such "tensor-induced scalar modes" approximately evolve as standard linear matter perturbations and may leave observable signatures in the large-scale structure of the Universe. We study the imprint on the matter power spectrum of some primordial models which predict a large gravitational-wave signal at high frequencies.

Mild quasilocal non-Gaussianity as a signature of modified gravity during inflation.

We show that modifications of Einstein gravity during inflation could leave potentially measurable imprints on cosmological observables in the form of non-Gaussian perturbations. This is due to the fact that these modifications appear in the form of an extra field that could have nontrivial interactions with the inflaton. We show it explicitly for the case R+αR(2), where nearly scale-invariant non-Gaussianity at the level of f(NL) ≈ - (1 to 30) can be obtained, in a quasilocal configuration.

Can sterile neutrinos be ruled out as warm dark matter candidates?

We present constraints on the mass of warm dark matter (WDM) particles from a combined analysis of the matter power spectrum inferred from the Sloan Digital Sky Survey Lyman-alpha flux power spectrum at 2.2 View Article and Find Full Text PDF

Gauge-invariant temperature anisotropies and primordial non-Gaussianity.

We provide the gauge-invariant expression for large-scale cosmic microwave background temperature fluctuations at second-order perturbation theory. This enables us to define unambiguously the nonlinearity parameter f(NL), which is used by experimental collaborations to pin down the level of non-Gaussianity in the temperature fluctuations. Furthermore, it contains a primordial term encoding all the information about the non-Gaussianity generated at primordial epochs and about the mechanism which gave rise to cosmological perturbations, thus neatly disentangling the primordial contribution to non-Gaussianity from the one caused by the postinflationary evolution.

A reconstruction of the initial conditions of the universe by optimal mass transportation.

Reconstructing the density fluctuations in the early Universe that evolved into the distribution of galaxies we see today is a challenge to modern cosmology. An accurate reconstruction would allow us to test cosmological models by simulating the evolution starting from the reconstructed primordial state and comparing it to observations. Several reconstruction techniques have been proposed, but they all suffer from lack of uniqueness because the velocities needed to produce a unique reconstruction usually are not known.