Séminaire

Constraining gravity with the future Roman Space Telescope and Simons Observatory

This talk will discuss synergies between the Nancy Grace Roman Space Telescope and CMB lensing data to constrain dark energy and modified gravity scenarios. We will present a simulated likelihood analysis of the galaxy clustering and weak lensing data from the Roman Space Telescope High Latitude Survey combined with CMB lensing data from the Simons Observatory, marginalizing over important astrophysical effects and calibration uncertainties.

Transforming gas-rich low-mass disky galaxies into ultra-diffuse galaxies by ram pressure

Faint extended elliptically shaped ultra-diffuse galaxies and slightly brighter and more compact dwarf elliptical and lenticular stellar systems are common in galaxy clusters. Their poorly constrained evolutionary paths can be studied by identifying young ultra-diffuse galaxy and dwarf elliptical analogues populated with bright, massive stars. Using data mining we identified 11 such low-mass (2 × 10^8 M⊙ < M* < 2 × 10^9 M⊙) galaxies with large half-light radii (2.0 kpc < re < 5 kpc) and recently quenched star formation in the Coma and Abell 2147 galaxy clusters.

Dark matter at the crossroads of two standard models

In a recent publication (Gilles Cohen-Tannoudji and Jean-Pierre Gazeau https://www.mdpi.com/2218-1997/7/11/402, ArXiv https://arxiv.org/abs/2111.01130v2), we have shown that a cosmological standard model consisting of dark matter interpreted as a gluonic Bose-Einstein condensate in anti-de Sitter spacetime, and dark energy related to the cosmological constant, is fully compatible with the standard model of particle physics based of quantum field theory, without the need of involving any

Baryonic effects in the Effective Field Theory of Large-Scale Structure and an analytic recipe for lensing in CMB-S4

Upcoming Large-Scale Structure surveys will likely become the next leading sources of cosmological information, making it crucial to have a precise understanding of the influence of baryons on cosmological observables. The Effective Field Theory of Large-Scale Structure (EFTofLSS) provides a consistent way to predict the clustering of dark matter and baryons on large scales, where their leading corrections in perturbation theory are given by a simple and calculable functional form even after the onset of baryonic processes.

Probing inflation at small scales with the stochastic gravitational wave background

Departures of inflation from the single-field slow-roll paradigm, also known as “features”, are common in ultraviolet completions of inflation. These departures can be significant at small scales where Cosmic Microwave Background data is not constraining. I will explain how such features during inflation can be tested through their gravitational wave signal. In particular, I will show that features lead to a characteristic oscillation in the stochastic gravitational wave background.

Cosmological observables and their combinatorial origin

QFT in nearly dS space-times and, more generally, in FRW backgrounds allows us to describe correlations at the end of inflation. However, how to extract fundamental physics out of them is still a challange: we do not even know how fundamental pillars such as causality and unitarity of time evolution constrain them. In this talk I will report on a recent program that aims to construct quantum mechanical observables in cosmology directly from first principles without making any reference to time evolution.

Results and open questions on two coasting cosmological models

The ΛCDM Model accurately reproduces most cosmological observations, including primordial nucleosynthesis, the cosmic microwave background radiation, and baryonic acoustic oscillations. However, standard baryonic matter constitutes only 5% of the total content of the ΛCDM universe, while the dominant components – cold dark matter (≈25%) and dark energy (≈70%) – are yet unobserved.

Séminaire