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Title: Introduction to the effective field theory of large-scale structure.

In this T^3, I will present the paradigm of the effective field theory of large-scale structure (EFTofLSS), a semi-analytical method which provides an accurate description of the galaxy power spectrum and aims at improving cosmological constraints from large-scale structure surveys, a major challenge in the context of the forthcoming data from DESI and Euclid. First, I will show how it is possible to describe the matter overdensity field in the non-linear regime with the standard perturbation theory (up one-loop order). Second, I will deal with the inconsistencies of the standard perturbation theory and show how the EFTofLSS, which remains a perturbative method, overcomes them by providing an appropriate renormalizable formalism.
Note that there is no need for (many) pre-requisites to follow this T^3.

The LambdaCDM model, together with its linear and higher
order perturbations, constitute the roots of contemporary cosmology
allowing us to understand roughly the evolution and the geometry of
our Universe. The following thoughts inspire us to go further. First,
The Universe homogeneity and isotropy are only averaged properties
valid at scales which grow as structures with larger redshifts are
discovered. The advent of precision cosmology results in the emerging
or in the increasing of tensions, even of anomalies, owing to the
mismatch between predictions extrapolated since the early Universe and
observations of the late Universe realized with increased precision.
General Relativity offers a mean to solve these inconsistencies. The
Szekeres model is an exact solution of Einstein's equations,
inhomogeneous and without symmetry, able to represent the
matter/cosmological constant dominated region of our Universe, since
its gravitational source is a pressureless fluid and since the
cosmological constant can be incorporated in its equations. One among
its main advantages is that it includes the homogeneous and isotropic
Friedmann solution as a limiting case. It is therefore able to
reproduce naturally the homogeneity/inhomogeneity transition at the
scale where its defining functions reach the values of the standard
cosmological parameters. The most robust predictions of the early
Universe cosmology are therefore maintained. During this seminar, the
Szekeres solution will be presented together with its main properties
necessary for a cosmological use. The different observations which
will be of use to constrain the parameter-functions determining the
Szekeres model of Universe valid at a given precision will de
described and commented. The perspectives opened by neural networks to
complete this analysis of huge data sets will be discussed.

Astrophysicien et auteur d’un livre sur le James Webb Space Telescope, Éric Lagadec est une figure incontournable en médiation scientifique, avec une présence remarquée dans les médias. À travers cette conférence, il partagera son parcours et ses stratégies pour rendre la science accessible à tous, tout en naviguant dans l’univers médiatique.

Que vous soyez chercheur·euse, médiateur·rice scientifique, communicant·e ou simplement curieux·se de découvrir comment mieux valoriser votre travail auprès du grand public, cette rencontre vous offrira des pistes concrètes et inspirantes. Une opportunité unique d’échanger avec un scientifique passionné, à la croisée des mondes de la recherche et de la vulgarisation.

Public ciblé : toutes les personnes intéressées par la diffusion des savoirs et la médiation scientifique

TBA

The classical picture of protoplanetary discs being smooth, continuous structures of gas and dust has been questioned by a decade of spatially resolved observations, primarily with SPHERE and ALMA. These observations have shown the widespread presence of rings, gaps, and large-scale asymmetries like spirals or arcs in the emission of protoplanetary discs. I will discuss whether such structures may be interpreted as signatures of the presence of unseen planets. Recent VLTI observations probing the innermost regions of protoplanetary discs might tell us a rather similar story, and I will present ongoing work on interpreting asymmetries in the discs emission inferred from near-infrared VLTI observations, based on on hydrodynamical simulations post-processed by dust radiative transfer calculations. If time allows, I will also report the finding of a new instability that we have recently found in protoplanetary discs.

The interpretation of high-precision Galactic Cosmic-Ray data (~3%) is strongly limited by nuclear cross-section uncertainties (~20%). In this talk, I will provide a brief introduction to Cosmic-Ray transport in the Galaxy, with several illustrations of the issue of cross-sections. I will then present recent results aiming at sorting the most important reactions to improve. Synergies between different communities (cosmic-ray, astro-particle, high-energy, and nuclear physics) are actually needed to tackle these issues, and I will show and illustrate our 'community' strategy to engage in a long term programme to measure these cross-sections.