Francis Bernardeau

RegPT: Direct and fast calculation of regularized cosmological power spectrum at two-loop order

We present a specific prescription for the calculation of cosmological power spectra, exploited here at two-loop order in perturbation theory, based on the multipoint propagator expansion. In this approach, density and velocity power spectra are constructed from the regularized expressions of the propagators that reproduce both the resummed behavior in the high-

Weak lensing predictions at intermediate scales

k

Detection of non-Gaussian signatures in the VIRMOS-DESCART lensing survey

limit and the standard perturbation theory results at low

Lensing at cosmological scales: a test of higher dimensional gravity

k

Source–lens clustering effects on the skewness of the lensing convergence

. With the help of

Cosmic statistics of statistics

N

Power spectra in the eikonal approximation with adiabatic and nonadiabatic modes

-body simulations, we particularly focus on the density field, and show that such a construction gives robust and accurate predictions for both the density power spectrum and the correlation function at percent level in the weakly nonlinear regime. We then present an algorithm that allows accelerated evaluations of all the required diagrams by reducing the computational tasks to one-dimensional integrals. This is achieved by means of precomputed kernel sets defined for appropriately chosen fiducial models. The computational time for two-loop results is then reduced from a few minutes, with the direct method, to a few seconds with the fast one. The robustness and applicability of this method are tested against the power spectrum cosmic emulator from which a wide variety of cosmological models can be explored. The Fortran program with which direct and fast calculations of density power spectra can be done, RegPT, is publicly released as part of this paper.

Constructing regularized cosmic propagators

As pointed out in previous studies, the measurement of the skewness of the convergence field κ will be useful in breaking the degeneracy among the cosmological parameters constrained from weak lensing observations. The combination of shot noise and finite survey volume implies that such a measurement is likely to be performed in a range of intermediate scales (0.5 to 20xa0arcmin) where neither perturbation theory nor the hierarchical ansatz applies. Here we explore the behaviour of the skewness of κ at these intermediate scales, based on results for the non-linear evolution of the mass bispectrum. We combined different ray-tracing simulations to test our predictions, and we find that our calculations describe accurately the transition from the weakly non-linear to the strongly non-linear regime. We show that the single lens-plane approximation remains accurate even in the non-linear regime, and we explicitly calculate the corrections to this approximation. We also discuss the prospects of measuring the skewness in upcoming weak lensing surveys.

Resummed propagators in multi-component cosmic fluids with the eikonal approximation

We have detected non-Gaussian signatures in the VIRMOS-DESCART weak lensing survey from a measurement of the three-point shear correlation function, following the method developed by Bernardeau et al. (2002). We obtain a 2.4-sigma signal over four independent angular bins, or equivalently, a 4.9-sigma confidence level detection with respect to measurements errors on scale of about 2 to 4 arcmin. The amplitude and the shape of the signal are consistent with theoretical expectations obtained from ray-tracing simulations. This result supports the idea that the measure corresponds to a cosmological signal due to the gravitational instability dynamics. Its properties could be used to put constraints on the cosmological parameters, in particular on the density parameter of the Universe, but the error level as well as the cosmic variance are still too large to permit secure conclusions.

Precision modeling of redshift-space distortions from a multipoint propagator expansion

Recent developments in gravitational lensing astronomy have paved the way to genuine mappings of the gravitational potential at cosmological scales. We stress that comparing these data with traditional large scale structure surveys will provide us with a test of gravity at such scales. These constraints could be of great importance in the framework of higher dimensional cosmological models.