The goal of my work was to estimate the Hubble constant $H_0$ through the study of the quadruply lensed, variable QSO SDSSJ1433+6007. I combined multi-filter, archival HST data for lens modelling with a dedicated 3-year long time-delay monitoring campaign using the 2.1 m Fraunhofer telescope at the Wendelstein Observatory.\\
The lens modelling was performed with the public lenstronomy Python package individually for the infrared data, utilizing the higher resolution of the optical data to constrain image positions a priori. This approach revealed two luminous contaminants in one of the near-infrared exposures, which would bias the lensing potentials and cosmological inference if not accounted for. After masking these contaminants, I repeated the modelling and combined the lens posteriors, obtaining a constraint on the Fermat potential with a precision of $\sim 3.3\,\%$.\\
The g'-band Wendelstein light-curve data was reduced and then analyzed using a free-knot spline fitting method implemented in the public Python PyCS3 tools, accounting for microlensing correction. I obtained a precision of $\sim6.6\%$ for the time delays between the QSO images.
By combining the posteriors for the Fermat potential differences and time delays, and assuming a flat $\Lambda$CDM cosmology, I inferred a Hubble constant of $ H_0 = 73.7^{+4.3}_{-3.9}\frac{\text{km}}{\text{s Mpc}}$ achieving $\sim 6\,\%$ uncertainty for this single system.

The Standard Model (SM) of particle physics, despite its remarkable success in explaining a vast array of phenomena, remains incomplete. Crucially, it fails to account for Dark Matter (DM) and the Baryon Asymmetry of the Universe (BAU), highlighting the need for physics Beyond the Standard Model (BSM).

A necessary ingredient to dynamically generate the observed baryon–antibaryon asymmetry is the presence of additional sources of CP violation beyond those present in the SM. As a result, precision measurements of CP-odd observables serve as powerful probes of BSM scenarios. Among these, Electric Dipole Moments (EDMs) stand out as exceptionally sensitive tests of new CP-violating physics.

In this talk, I will discuss how EDM searches can probe dark sectors, which offer rich scenarios for viable DM candidates and may also introduce the necessary ingredients for successful baryogenesis. I will focus on the phenomenology of a CP violating portal between the Dark Sector and SM, possible if the Dark Sector interactions stem from a non-abelian gauge symmetry.

Finally, I will describe EDM searches in a model independent framework, using Effective Field Theories (EFT). I will discuss how, including loop effects in the EFT, EDM experiments can test a wide variety of CP-odd operators.

Between its formation stage as an active accreting seed and today, the Sun underwent large structural changes as well as variation in magnetic activity, rotation rate and its relation to the surrounding environment. I will go through the different processes that are responsible for these changes and present our latest results on the subject. I will talk about the early interaction between the star and its proto-planetary disc bathing in UV radiations emitted from the massive neighbours, but also about the way red giant stars are able to generate their magnetic field, and I will try to summarise our understanding of the internal mixing happening in the stable layers of solar-like stars which can be probed by asteroseismology.
Finally, I will to review the possible implications of this work for other types of stars at different stages of the evolution in the context of the current or future surveys.

The temperature and polarization anisotropies of the cosmic microwave background (CMB) have been used to set constraints on decaying dark matter models down to keV masses. In this talk, I will discuss recent work to extend these limits down into the sub-keV mass range. I will show how we used principal component analysis to estimate the lower bound on the decay lifetime for a basis of different dark matter masses and Standard Model final states, and then how we validated our principal component analysis using Markov chain Monte Carlo methods and Planck 2018 data. I will then show a separate analysis for models decaying into photons below the hydrogen ionization threshold, where the redshift dependence of the effect on the CMB is entirely different. This work constitutes a step towards a complete understanding of the CMB as a probe of exotic energy injection.

Long-range attractive interactions between dark matter particles can significantly enhance their annihilation, particularly at low velocities. However, the standard method of computing this "Sommerfeld enhancement" is known to break down at special points in parameter space, where it predicts cross sections exceeding general bounds from unitarity. I will show how this issue can be resolved within the framework of non-relativistic quantum mechanics, in the case where the physics relevant to annihilation corresponds to a parametrically shorter distance scale (higher energy scale) compared with the long-range potential, by using the short-range annihilation to modify the boundary conditions for the long-range scattering problem. I will present the resulting prescription for the corrected Sommerfeld enhancement, valid for all partial waves and for systems where multiple states are coupled by the long-range potential, and briefly discuss the phenomenological implications.

TBA

C’est avec beaucoup d'excitation et un immense plaisir que je vous invite à ma soutenance de thèse qui se déroulera le vendredi 29 novembre à 14h00, dans l'amphithéâtre du bâtiment 20.

Le titre est : "Photométrie de haute précision pour les grands relevés cosmologiques ZTF et LSST : caractérisation des transmissions instrumentales et atmosphériques".

La soutenance se déroulera en français et sera suivie d'un pot / goûter.

En espérant vous y voir nombreux !

Interacting fluid models are a natural candidate for modified cosmological models with an array of interesting phenomenology. For example, cosmologies with an interacting dark sector have seen particular interest recently in relation to the current observational tensions. However, a Lagrangian description is preferable to phenomenological models for a number of reasons (e.g., for unambiguous cosmological perturbations, or identifying pathologies such as ghosts). In this talk, I will give an overview of the perfect fluid Lagrangian approaches for interacting cosmological models, comparing different formulations in the literature. I will then discuss recent extensions from my own work, which allow for interesting physical processes such as particle creation/annihilation. Lastly, I will mention how even more exotic modifications can be implemented in these Lagrangian formulations.

One of the most outstanding problem in today's understanding of the Universe is the nature of the elusive dark-matter (DM) that dominates the matter content. Rotation curves (RC) have been used to put forward the concept of DM as it was difficult to hide that the RC of massive galaxies remain flat at large galactocentric radii. RC have since revealed a potential problem, for the standard CDM model, on small scales (<1kpc) where DM profiles are too flat (cored) compared to predictions. Alternative DM models have been proposed to produce cores naturally. Hence, rotation curves are dark-matter laboratory given that the shape of RC on intermediate scales (1-5kpc) is a measure of the shape of the inner DM profiles. Measuring the shape of DM profiles in distant marginally resolved galaxies (with z>0) was deemed impossible, but recently, thanks to recent innovations, it has become possible to study the shape of RCs of hundreds of distant galaxies. I will present the most recent innovations, and recent results from our large program using the MUSE 3D spectrograph.