La possibilité que la constante de gravitation évolue dans le temps est une éventualité qui a été explorée par le passé. Je présenterais quelques résultats récents sur cette possibilité en Cosmologie et la façon dont cela peut être une alternative au modèle standard.

The future large galaxy surveys will allow for precise cosmological analyses using the clustering of galaxies and cosmic shear. The cross-correlation between these probes can tighten constraints and it is therefore important to quantify its impact for future surveys. In this talk I will present the latest results of the Euclid Collaboration quantifying the role of the cross-correlation between...

To exploit the power of next-generation large-scale structure surveys, ensembles of numerical simulations are necessary to give accurate theoretical predictions of the statistics of observables. High-fidelity simulations come at a towering computational cost. Therefore, approximate but fast simulations, *surrogates*, are widely used to gain speed at the price of introducing model error. We...

I will present a theoretical description of the weak-lensing Aperture-mass field with large deviation theory. I will highlight the difficulty I encountered comparing the formalism to ray-tracing numerical simulations and emphasize the need for accurate tests of non gaussian statistics in such numerical suites if we are to correctly use them in future large surveys.

Du Vide trans-Planckian à l'Energie Noire dans le Modele Standard de l'Univers

Le Résummé sera envoyé plus tard pour inclure plus des résultats récents

Merci pour votre comprehension !

A bientot et bien amicalement à vous,

## NS

The observed galaxy distribution via galaxy redshift surveys appears distorted due to redshift-space distortions (RSD). While one dominant contribution to RSD comes from the Doppler effect induced by the peculiar velocity of galaxies, the relativistic effects, including the gravitational redshift effect, are recently recognized to give small but important contributions. Such contributions lead...

I will first introduce a new, perfectly parallel approach to simulate cosmic structure formation, based on the spatial COmoving Lagrangian Acceleration (sCOLA) framework. Building upon a hybrid analytical and numerical description of particles' trajectories, sCOLA allows an efficient tiling of a cosmological volume, where the dynamics within each tile is computed independently. I will show...

The feedback mechanisms that regulate galaxy formation, exploding stars and accretion onto supermassive black holes, are poorly understood. This results in an order unity uncertainty in the distribution of the gas inside halos, the ``missing baryon problem''. Because baryons are 15% of the total mass in the universe, this baryonic uncertainty is also the largest theoretical systematics for...

I will present the clustering analysis of quasars of the final data release (DR16) of eBOSS. The sample contains $343\,708$ quasars between redshifts $0.8\leq z\leq2.2$ over $4699\,\mathrm{deg}^2$. We calculate the Legendre multipoles (0,2,4) of the anisotropic power spectrum and perform a BAO and a Full-Shape (FS) analysis at the effective redshift $z{\rm eff}=1.480$. The errors include...

Mergers of compact objects have been nicknamed *standard sirens*, by analogy with electromagnetic standard candles, because their waveform directly gives access to their distance. When an electromagnetic counterpart is observed, such sources thus allow us to construct a Hubble diagram, just as supernovae. Recently, the gravitational-wave Hubble diagram has been argued to be a key probe of...

Mise en évidence de perturbations adversaires d'un modèle de CNN pour le photo-z, recherche de robustesse.

In this talk I present novel cosmological constraints obtained from cosmic voids in the final BOSS DR12 dataset. I briefly introduce voids as a tool for cosmology, and focus on illustrating how to get constraints from the void-galaxy cross-correlation function, relying on measurements of the Alcock-Paczynski effect and of the redshift-space distortions pattern around voids. I discuss...

Next generation experiments such as the Vera Rubin Observatory Legacy Survey of Space and Time (LSST) will provide an unprecedented volume of time-domain data opening a new era of optical big data in astronomy. To fully harness the power of these surveys, new methods must be developed to deal with large data volumes and to coordinate resources for follow-up of promising candidates. In this...

The two-point clustering analysis of the eBOSS DR16 QSO sample provides our best cosmological measurements at an effective redshift z ~ 1.5. As part of the final analysis, we performed an N-body mock challenge using HOD mocks constructed from the OuterRim simulation. The aim of this was to validate the RSD models used in the analysis, and to measure the modelling systematic uncertainties. This...

I will present some results from the past 2-3 years of cosmic shear analyses. Current surveys (KiDS, DES, HSC) focus on understanding the recent tension on the structure growth parameter S8 found between the CMB and the weak-lensing probes. This is done by testing cosmological models beyond Lambda CDM, carefully studying every possible systematic bias, and re-analyzing and combining the...

Preliminary

Next generation of large cosmological survey with a huge (10^9-10^10) statistics of sources (Galaxy, Clusters and Supernova) requires sub-percent photometric accuracy or better to improve systematic errors at similar level of the statistical errors on cosmological parameters.

Ground observatories are very sensitive to atmospheric conditions due to the fluctuations on clouds...