Presentation of the Institut Pascal, Yves Balkanski Room: Amphitheater + Cathedrale + Offices

Presentation of the program Room: Amphitheater + Cathedrale + Offices

Flah presentation of participants Room: Amphitheater + Cathedrale + Offices

"Le big-bang, un siècle de cosmologie", Public talk in French, Jean-Philippe Uzan, Room: Amphitheater + Cathedrale + Offices Le modèle du Big-bang, cette théorie qui se fixe pour objectif de décrire l’Univers et son histoire, est un extraordinaire échafaudage qui a bouleversé notre représentation du cosmos, de l’espace et du temps. Selon les mots de Georges Lemaître, « une cosmogonie vraiment complète devrait expliquer les atomes comme les soleils ». Trouvant ses racines dans la relativité générale d'Einstein, la cosmologie a peu à peu incorporé toute la physique du XXe siècle - physique atomique, nucléaire et quantique - et les idées spéculatives du XXe siècle afin de comprendre la diversité et la structuration de la matière. Elle se positionne ainsi comme un terrain de jeu permettant de tester les nouvelles théories de la physique. Cette conférence exposera la structure du modèle du big-bang en détaillant ses hypothèses et les observations qui les sous-tendent. Il discutera pour finir ses problèmes ouverts et ses évolutions possibles.

Presentation of the Institut Pascal, Yves Balkanski Room: Amphitheater + Cathedrale + Offices

Presentation of the week Room: Amphitheater + Cathedrale + Offices

Flash presentation of new participants Room: Amphitheater + Cathedrale + Offices

Zhong-Zhi Xianyu Room: Amphitheater + Cathedrale + Offices

Bowei Zhang Room: Amphitheater + Cathedrale + Offices

Shuntaro Aoki Room: Amphitheater + Cathedrale + Offices

Flavio Riccardi, Probing de Sitter from the horizon Room: Amphitheater + Cathedrale + Offices In a QFT on de Sitter background, one can study correlators between fields pushed to the future and past horizons of a comoving observer. This is a neat probe of the physics in the observer’s causal diamond (known as the static patch). This setup highlights how the analytic structure of de Sitter correlators encodes a generalized quasinormal spectrum, even in interacting theories, using the analyticity properties of the spectral density that appears in the Källén-Lehmann expansion of dS correlators. I will also show how the low-frequency behaviour is captured by a finite-temperature EFT with boundary couplings, leading to unitarity constraints on the EFT parameters. Understanding these analytic properties offers new tools for going beyond conventional perturbation theory in the study of inflationary correlators.

Arthur Poisson Room: Amphitheater + Cathedrale + Offices

Fabian Schmidt, Connecting field-level inference with n-point functions Room: Amphitheater + Cathedrale + Offices

Thomas Flöss Room: Amphitheater + Cathedrale + Offices

Massimo Pietroni Room: Amphitheater + Cathedrale + Offices

Antonis Kalogirou Room: Amphitheater + Cathedrale + Offices

Zachary Slepian Room: Amphitheater + Cathedrale + Offices

Koki Tokeshi Room: Amphitheater + Cathedrale + Offices

Guillermo Ballesteros Room: Amphitheater + Cathedrale + Offices

Jesus Gambin Egea Room: Amphitheater + Cathedrale + Offices

Jinn-Ouk Gong, Classicality of cosmological perturbations Room: Amphitheater + Cathedrale + Offices

Alejandro Perez Rodriguez Room: Amphitheater + Cathedrale + Offices

Sebastian Cespedes Room: Amphitheater + Cathedrale + Offices

Perseas Christodoulidis Room: Amphitheater + Cathedrale + Offices

Giovanni Tambalo, Inflation Beyond Perturbation Theory Room: Amphitheater + Cathedrale + Offices

Siméon Vareilles, Cosmological Perturbations: A Wheeler–DeWitt Quantum-Gravity Perspective Room: Amphitheater + Cathedrale + Offices

Shi Pi Room: Amphitheater + Cathedrale + Offices

Laura Iacconi, Mapping inflationary loop corrections to boundary terms Room: Amphitheater + Cathedrale + Offices Both single- and multi-field models of inflation might lead to enhanced scalar fluctuations on scales much smaller than those seeding the large-scale structure formation. In these scenarios, it is possible that the spike of power at high wavenumber might induce large corrections to the scalar power spectrum, e.g. in the form of loop corrections, potentially endangering the perturbativity of the underlying models. In this talk we discuss recent developments in the calculation of the 1-loop correction to a large-scale adiabatic mode. We demonstrate that non-volume-suppressed corrections only contribute at the boundaries of the momentum integral. To achieve this we employ expansion methods, such as the $\delta N$ formalism, as well as more general expansions that do not rely on assumption of validity of the separate universe picture.

Colloquium, Ben Wandelt Room: Amphitheater + Cathedrale + Offices

Diederik Roest Room: Amphitheater + Cathedrale + Offices

Yoann Launay, Stochastic inflation beyond the lamppost with general and numerical relativity Room: Amphitheater + Cathedrale + Offices The absence of general non-perturbative methods in quantum field theory on curved spacetimes has highlighted the importance of numerical studies in classical regimes. This work presents an overview of our recent advances in solving the equations of general relativity (GR) for inhomogeneous inflation, driven by vacuum quantum fluctuations. A key contribution of this work is the transition from a cosmological framework—such as knowledge of curvature perturbations on comoving hypersurfaces—to a numerical relativity (NR) framework. This transition introduces a consistent method for incorporating perturbative initial conditions that satisfy GR constraints. Moreover, it naturally defines a coarse-graining procedure for an inflating spacetime, enabling the construction of a stochastic model for inflation in full GR. We explain the subtlety between an initial input of perturbations and stochastic sources, which relates to the concept of quantum diffusion. Finally, our latest results are presented and include non-perturbative phenomena arising from perturbative sources, highlighting the potential of NR to probe these regimes.

Yurino Mizuguchi Room: Amphitheater + Cathedrale + Offices

Olli Väisänen Room: Amphitheater + Cathedrale + Offices

Presentation of the week and flash presentation of new participants Room: Amphitheater + Cathedrale + Offices

Jens Jasche Room: Amphitheater + Cathedrale + Offices

Emanuele Fondi Room: Amphitheater + Cathedrale + Offices

Hugo Simon Room: Amphitheater + Cathedrale + Offices

Francis Bernardeau, Large Deviation Principle in Large-scale structure cosmology Room: Amphitheater + Cathedrale + Offices

Denis Karateev Room: Amphitheater + Cathedrale + Offices

Harry Goodhew, Geometry of kinematic flow Room: Amphitheater + Cathedrale + Offices

Zhehan Qin Room: Amphitheater + Cathedrale + Offices

Dong-Gang Wang Room: Amphitheater + Cathedrale + Offices

Gonzalo Palma Room: Amphitheater + Cathedrale + Offices

Lucas Pinol Room: Amphitheater + Cathedrale + Offices

Enrico Pajer Room: Amphitheater + Cathedrale + Offices

Thomas Colas, The Open Effective Field Theory of Single-Clock Cosmology Room: Amphitheater + Cathedrale + Offices Friction and noise naturally emerge when light and gravitational waves propagate through unknown environments. In this talk, I will present recent developments in a systematic effective field theory framework that captures dissipation and noise in a controlled, model-independent way. Building on fundamental principles such as symmetries, locality, and unitarity, I will show how these constraints shape the possible forms of dissipative dynamics. I will then explore the phenomenological implications for the tensor sector in the early universe and for scalar perturbations in the late universe, highlighting potential observational signatures.

Ana Achúcarro Room: Amphitheater + Cathedrale + Offices

Luca Santoni, Dissipative Inflation via Scalar Production Room: Amphitheater + Cathedrale + Offices

Chiara Animali Room: Amphitheater + Cathedrale + Offices

Pierre Auclair Room: Amphitheater + Cathedrale + Offices

Eemeli Tomberg Room: Amphitheater + Cathedrale + Offices