Cosmology Beyond the Analytic Lamppost (CoBALt)

16 juin 2025, 09:00 → 4 juil. 2025, 17:00 Europe/Paris

Amphitheater + Cathedrale + Offices (Institut Pascal )

Cosmology Beyond the Analytic Lamppost  (CoBALt)

Primordial correlations produced in the early inflationary Universe are now within experimental reach and offer a unique window into physics at high energies and on curved spacetime. This 3-week program will capitalise on recently developed numerical algorithms and machine learning techniques to improve our understanding and analysis of these cosmological signals beyond conventional perturbation theory. It will bring together international experts from different niches to share ideas and recent progress, forge new collaborations and set the next targets for this rapidly growing community. The first week will feature lectures and hands-on tutorials aimed at PhD students and newcomers to the field, providing a pedagogical introduction to the key open problems and how to use the numerical tools currently available. The second and third weeks will be of workshop type.

 

There is no registration fee. We will provide accommodation and working day lunches to participants, whose number is hence limited. Registration before May 23.

 

Key questions to be addressed

1. How to extract observable correlation functions from inflationary mechanisms that are not captured by traditional perturbative approaches?

2. How to go beyond n-point correlators and perform an optimal field-level inference of cosmological parameters (including primordial non-Gaussianity)?

3. How to model the tail of the underlying probability distribution and characterise rare events such as the formation of primordial black holes?

4. How to characterise the space of consistent field theories in cosmology and what constraints this places on inflationary phenomenology?

 

Lectures

Lattice simulations of inflation, Angelo Caravano¹

Field-level inference for cosmology, Florent Leclercq¹

Positivity and gravity, Anna Tokareva^2,3,4

The cosmological flow, Denis Werth¹ 

1 Institut d'astrophysique de Paris. 2 HIAS, UCAS, Hangzhou. 3 ICTP-AP, Beijing. 4 Imperial College London

Organisers

Sébastien Renaux Petel - Institut d’astrophysique de Paris, CNRS & Sorbonne Université (renaux@iap.fr)

Scott Melville - Queen Mary University of London (s.melville@qmul.ac.uk)

David J.Mulryne - Queen Mary University of London 

Benjamin D.Wandelt  - Institut d’Astrophysique de Paris, CNRS & Sorbonne Université - Center for Computational Astrophysics

Philippe Brax - Institut de Physique Théorique, Université Paris-Saclay, CEA, CNRS 

Vesna Cupic - Institut Pascal, program manager (vesna.cupic@universite-paris-saclay.fr) 

 

Support

In addition to the essential support of the Institut Pascal, this operation was supported by the « action thématique » Cosmology-Galaxies (ATCG) of the CNRS/INSU PN Astro, and Queen Mary University of London.

 

Conférence grand public: Mardi 17 juin 2025 à 18:00 - Jean-Phillipe UZAN :

Participer à la réunion Zoom https://zoom.us/j/91943762697?pwd=9xRQSYWiXIsnox7bu1K7jVW0ZgZmbJ.1 ID de réunion: 919 4376 2697 Code secret: 770764

 

Colloquium: Jeudi 26 Juin 2025 à 14:00 - Benjamin D. Wandelt 

 

 

lun. 16 juin

09:30 Welcome coffee

1 Presentation of the Institut Pascal, Yves Balkanski

2 Presentation of the program

3 Flah presentation of participants

12:30 Lunch

Lecture, field-level inference for cosmology, Florent Leclercq: Course 1

2025_CoBALt_lecture1.pdf

2025_CoBALt_lecture2.pdf

2025_CoBALt_lecture3.pdf

2025_CoBALt_lecture4.pdf

15:30 Coffee break

Lecture, field-level inference for cosmology, Florent Leclercq: Course 2

2025_CoBALt_lecture1.pdf

2025_CoBALt_lecture2.pdf

2025_CoBALt_lecture3.pdf

2025_CoBALt_lecture4.pdf

18:00 Happy hour

mar. 17 juin

08:30 Welcome coffee

The cosmological flow: Course 1

10:30 Coffee break

The cosmological flow: Course 2

12:30 Buffet Lunch in the Cathedral

Lecture, field-level inference for cosmology, Florent Leclercq: Course 3

2025_CoBALt_lecture1.pdf

2025_CoBALt_lecture2.pdf

2025_CoBALt_lecture3.pdf

2025_CoBALt_lecture4.pdf

15:30 Coffee break

Lecture, field-level inference for cosmology, Florent Leclercq: Course 4

2025_CoBALt_lecture1.pdf

2025_CoBALt_lecture2.pdf

2025_CoBALt_lecture3.pdf

2025_CoBALt_lecture4.pdf

4 "Le big-bang, un siècle de cosmologie", Public talk in French, Jean-Philippe Uzan,

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.

mer. 18 juin

08:30 Welcome coffee

The cosmological flow: Course 3

10:30 Coffee break

The cosmological flow: Course 4

12:30 Lunch

Lattice simulations of inflation: Course 1

15:30 Coffee break

Lattice simulations of inflation: Course 2

jeu. 19 juin

08:30 Welcome coffee

Lattice simulations of inflation: Course 3

10:30 Coffee break

Lattice simulations of inflation: Course 4

12:30 Lunch

Lecture, Positivity and gravity, Anna Tokareva: Course 1

15:30 Coffee break

Lecture, Positivity and gravity, Anna Tokareva: Course 2

19:00 Conference dinner

ven. 20 juin

08:30 Welcome coffee

Lecture, Positivity and gravity, Anna Tokareva: Course 3

10:30 Coffee break

Lecture, Positivity and gravity, Anna Tokareva: Course 4

12:30 Lunch

lun. 23 juin

09:30 Welcome coffee

5 Presentation of the Institut Pascal, Yves Balkanski

6 Presentation of the week

7 Flash presentation of new participants

8 Zhong-Zhi Xianyu

CoBALt_Xianyu.pdf

12:30 Lunch

9 Bowei Zhang

10 Shuntaro Aoki

11 Flavio Riccardi, Probing de Sitter from the horizon

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.

15:30 Coffee break

12 Arthur Poisson

18:30 Happy hour

mar. 24 juin

09:00 Welcome coffee

13 Fabian Schmidt, Connecting field-level inference with n-point functions

14 Thomas Flöss

11:00 Coffee break

15 Massimo Pietroni

16 Antonis Kalogirou

12:30 Buffet Lunch in the Cathedral

17 Zachary Slepian

18 Koki Tokeshi

15:30 Coffee

mer. 25 juin

09:00 Welcome coffee

19 Guillermo Ballesteros

20 Jesus Gambin Egea

11:00 Coffee break

21 Jinn-Ouk Gong, Classicality of cosmological perturbations

22 Alejandro Perez Rodriguez

12:30 Lunch

23 Sebastian Cespedes

24 Perseas Christodoulidis

15:30 Coffee

19:00 Conference dinner

jeu. 26 juin

09:00 Welcome coffee

25 Giovanni Tambalo, Inflation Beyond Perturbation Theory

26 Siméon Vareilles, Cosmological Perturbations: A Wheeler–DeWitt Quantum-Gravity Perspective

Perturbations_in_WDW_Cobalt_June2025.pdf

11:00 Coffee break

27 Shi Pi

28 Laura Iacconi, Mapping inflationary loop corrections to boundary terms

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.

12:30 Lunch

29 Colloquium, Ben Wandelt

18:00 Social event

ven. 27 juin

09:00 Welcome coffee

30 Diederik Roest

31 Yoann Launay, Stochastic inflation beyond the lamppost with general and numerical relativity

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.

11:00 Coffee break

32 Yurino Mizuguchi

33 Olli Väisänen

12:30 Lunch

15:30 Coffee

lun. 30 juin

09:30 Welcome coffee

34 Presentation of the week and flash presentation of new participants

35 Jens Jasche

36 Emanuele Fondi

37 Hugo Simon

12:30 Lunch

38 Francis Bernardeau, Large Deviation Principle in Large-scale structure cosmology

15:30 Coffee break

18:00 Happy hour

mar. 1 juillet

09:00 Welcome coffee

39 Denis Karateev

S-matrix_bootstrap.pdf

40 Harry Goodhew, Geometry of kinematic flow

11:00 Coffee break

41 Zhehan Qin

42 Dong-Gang Wang

12:30 Buffet Lunch in the Cathedral

43 Gonzalo Palma

44 Lucas Pinol

mer. 2 juillet

09:00 Welcome coffee

45 Enrico Pajer

46 Thomas Colas, The Open Effective Field Theory of Single-Clock Cosmology

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.

11:00 Coffee break

47 Ana Achúcarro

48 Luca Santoni, Dissipative Inflation via Scalar Production

12:30 Lunch

jeu. 3 juillet

09:00 Welcome coffee

49 Chiara Animali

50 Pierre Auclair

51 Eemeli Tomberg

11:00 Coffee break

12:30 Lunch

19:00 Conference dinner

ven. 4 juillet

09:00 Welcome coffee

11:00 Coffee break

12:30 Lunch

15:00 Coffee break