Colloque national du WG Dark Energy 2026 - 10ème édition

Liste des Contributions

45. welcome

02/11/2026 13:30

30. Pauline Vielzeuf

Pauline VIELZEUF (cppm)

02/11/2026 14:00

27. FOSSIL: Probing the cosmological model with spectral distortions

Nabila Aghanim (Institut d'Astrophysique Spatiale)

02/11/2026 14:30

The Cosmic Microwave Background (CMB) is a pillar of modern cosmology. Since the results of the COBE/FIRAS satellite in the nineties the CMB spectrum is known to be a quasi-perfect blackbody. However, both standard and non-standard physics processes inevitably lead to deviations from blackbody, named spectral distortions.
FOSSIL, proposed to ESA as its 8th medium-class mission, aims at...

41. Euclid

Marc Sauvage (CEA/DRF/Irfu/SAp)

02/11/2026 15:00

38. H0

Louise Breuval (Observatoire de Paris, LESIA)

02/11/2026 16:00

3. From synthetic source injection to simulated mocks: characterizing redshift calibration systematics for Euclid

Tyann Dumerchat (IFAE / Universitat Autonoma de Barcelona)

02/11/2026 16:30

Euclid is an ongoing space-based cosmological survey designed to map the large-scale structure of the Universe by observing billions of galaxies. Its primary goal is to investigate the nature of dark matter and dark energy and to place tight constraints on the cosmological model.
A key probe for Euclid is galaxy weak gravitational lensing, which measures the small distortions induced in the...

5. Field-level Inference for the Joint Analysis of Galaxy Clustering and CMB Lensing

Jonathan Hawla

02/11/2026 16:50

We present our work towards a field-level inference (FLI) pipeline for the joint analysis of DESI galaxy clustering and CMB lensing from Planck and ACT. We demonstrate an end-to-end Bayesian framework that jointly samples the posterior of the initial density field, galaxy bias, and local primordial non-Gaussianity ($f_{\mathrm{NL}}$). Our differentiable forward model propagates initial...

6. Kinessence, phantom crossing and sign-switching dark energy

philippe brax (IPHT Saclay)

02/11/2026 17:10

We introduce Kinessence models where combining K-mouflage and quintessence leads to phantom-
crossing of the dark energy equation of state and sign-switching of the dark energy density. This
is realised by joining a dark scalar sector comprising K-essence kinetic terms and a quintessence
potential together with a Yukawa coupling to matter. We investigate the dynamics of these models
in the...

7. A late universe model designed to fit the cosmological data: the Szekeres exact GR solution

Dr Marie-Noëlle Célérier (Observatoire de Paris)

02/11/2026 17:30

In the current era of precision cosmology, it is well-known that the present standard $\Lambda$CDM model, despite its successes, is an insufficient average of our actual Universe. Given the recorded tensions, it appears that a more precise representation of the local universe is mandatory. The Szekeres exact solution of General Relativity possesses all the nice properties allowing it to...

9. Dark Gravity cosmology: an Upgrade

Frederic HENRY COUANNIER (cppm)

02/11/2026 17:50

Dark Gravity is a natural extension of General Relativity in the presence of a flat, non-dynamical background. We present an upgraded version of the theory in which the transition from the matter-dominated expansion law, a(t)∝t2/3, to the late-time accelerated regime, a(t)∝t2, occurs progressively rather than abruptly.

Compared with the version presented at the MG17 conference, the new...

29. Extracting cosmological parameters from multi-wavelength cross-correlations

johan comparat

02/11/2026 18:10

Galaxy clustering and weak lensing on small scales hold much of the cosmological information in the coming surveys of large scale structure. They also carry the imprint of baryons: gas expelled from haloes by feedback suppresses the matter power spectrum at the level of the statistical errors, and this effect is degenerate with . The same gas is observed directly, in X-rays, through the...

33. Impact of a wCDM cosmology on the tSZ power spectrum

Emma Ayçoberry (IAP)

03/11/2026 09:00

The distribution of matter in the Universe is a powerful probe of cosmology. Measuring the efficiency with which gravity produces clusters against expanding Universe is the key to understanding, e.g. the equation of state of dark energy. The thermal Sunyaev-Zel’dovich (tSZ) effect, being sensitive to the baryonic content of the Universe, also shows sensitivity to dark energy. In this work, I...

10. Impacts of alternative Dark Energy models on the formation of galaxies

Adrian SZPILFIDEL (LUX)

03/11/2026 09:30

Recent cosmological measurements have suggested that the dark energy density might not be constant but evolving. In this study, we explored the interplay between the properties of dark energy and the physical processes responsible for the formation of galaxies which has remained poorly explored. We carried out the analysis on merger trees generated from a semi-analytical approach based on the...

11. Deep Learning Detection of Galaxy Clusters with YOLOv10: From SDSS to Rubin/LSST

Vinh Phat Tran (APC/UPCité)

03/11/2026 09:50

Galaxy clusters are powerful and key cosmological probes that trace the evolution of large-scale structures of the universe and inform models of cosmic evolution, but their identification in the increasingly large imaging datasets produced by current and upcoming surveys requires detection methods that are both accurate and scalable. The Vera C. Rubin Observatory Legacy Survey of Space and...

12. Evolving only the observed spacetime region: fast Euclid-scale lightcones with sCOLA

Mayeul Aubin (PhD student at Institut d'Astrophysique de Paris (IAP))

03/11/2026 10:10

Precision constraints on dark energy from large-scale-structure surveys require large ensembles of cosmological simulations for covariance estimation, forward modelling, and simulation-based inference. Producing such ensembles at Euclid volumes remains computationally challenging with conventional $N$-body methods. We present a fast and scalable framework based on the spatially discretised...

26. Full-Shape Analysis of DESI DR2 and Cross-Correlation with CMB Lensing

Arnaud de Mattia

03/11/2026 11:00

After a brief overview of the DESI survey and its timeline, I will present the full-shape analysis of DESI DR2 galaxy clustering data. This analysis constrains the growth rate of structure from the galaxy power spectrum and, for the first time in a DESI collaboration analysis, the bispectrum. I will highlight the methodological developments underpinning this analysis and the resulting...

8. Cosmology at z>2 with the DESI Lyman-alpha forest

Eric Armengaud (IRFU - CEA)

03/11/2026 11:20

The Lyman-alpha (Lya) forest provides a unique probe of large-scale structure, extending cosmological measurements to redshifts and scales currently inaccessible to other tracers. The new DESI Lya data offer an unprecedented opportunity for precision cosmology at high redshift.

I will present new DESI Lya results: a new z>2 DR2 BAO measurement in three redshift bins, providing a direct...

34. Beyond standard galaxy clustering methods with DESI

Pauline Zarrouk (LPNHE)

03/11/2026 11:40

35. TBD

Alice PISANI (Aix Marseille University, CNRS/IN2P3, CPPM)

03/11/2026 14:00

36. UNIONS: Weak lensing in the Northern sky

Cail Daley (CosmoStat, CEA Paris-Saclay), Calum Murray (CEA)

03/11/2026 14:30

The Ultraviolet Near-Infrared Optical Northern Survey (UNIONS) is the largest deep weak lensing survey in the northern sky, combining multi-band imaging from telescopes on Mauna Kea over more than 5500 deg² at a depth comparable to LSST Year 1. The UNIONS collaboration have improved our understanding of the intrinsic alignments of galaxies, the tidal stripping of satellite galaxies in...

37. Dark energy with supernovae

Nicolas Regnault (LPNHE)

03/11/2026 15:00

32. Euclid meets CMB lensing: first cosmological constraints from the Euclid Quick Data Release

Dr Margherita Lembo (Institut d'Astrophysique de Paris (IAP))

03/11/2026 16:00

The Euclid Quick Data Release (Q1) offers the first opportunity to test the cosmological potential of Euclid on real data. In this talk I will present the first cosmological analysis performed on Euclid data, based on the tomographic clustering of photometric galaxies in the three Euclid Deep Fields and their cross-correlation with CMB lensing from Planck and ACT. Despite covering only about...

15. Growth, geometry, and early-universe split of the matter density parameter Ωm

Felicitas Keil (IRAP Toulouse)

03/11/2026 16:30

While the $\Lambda$CDM model can successfully reproduce the measurements of many cosmological probes, some discrepancies have recently emerged. It is therefore necessary to test the standard cosmological model for consistency.

An important stress test is to separate the effect of different cosmological regimes on the parameter inference. We treat three regimes separately here: geometry,...

16. UNIONS: constraining the galaxy-halo shape connection in 3D for intrinsic alignments studies

Antonin Corinaldi (CEA Paris-Saclay / AIM / CosmoStat)

03/11/2026 16:50

The 3D morphology of galaxies provides direct insights into the processes governing galaxy formation and evolution within the large-scale structures of the Universe. More precisely, the connection between the morphology of galaxies and halos is a key ingredient in cosmology and astrophysics. It is in particular interesting to understand the intrinsic alignments (IA) of galaxies, the...

17. Cosmological dependence of the magnification bias from N-body simulations and relativistic ray-tracing

Fabien Castillo (LUX, Observatoire de Paris)

03/11/2026 17:10

The new generation of galaxy surveys will reach an unprecedented precision, allowing to test cosmology and gravity theories from the relativistic effects on the clustering of matter in the universe. In particular, the magnification bias, the change of observed galaxy density caused by lensing magnification, can be used as a cosmological probe. In this work, we investigate the impact of the...

18. DES: What have we learned about Weak-Lensing analysis within ΛCDM?

William D'Assignies D.

03/11/2026 17:30

The DES collaboration pioneered the combination of cosmic shear, galaxy clustering, and galaxy–galaxy lensing in a 3×2pt cosmological analysis with DES Year 1, and has since performed two more major analyses. In this talk, I will first review the results of the DES Year 6 3×2-point analysis within ΛCDM, together with its combination with other DES probes, which constitutes the final 'standard'...

19. Cheaper neural summary statistics: an ensemble of CNNs trained on low-resolution simulations

Iñigo Sáez-Casares (Università degli Studi di Milano)

03/11/2026 17:50

Machine learning techniques can be used to build near-optimal summary statistics for extracting cosmological information from the large-scale structure of the Universe. Their training, however, requires large numbers of simulated samples, making them expensive to construct. We aim to build a neural summary statistic trained on fast but approximate low-resolution simulations that remains...

28. The ADELINE suite: simulations of massive galaxy clusters in wCDM dark energy models

Félix Tornatore (Observatoire de Paris)

03/11/2026 18:10

Understanding how modifications to the dark energy model affect the formation and evolution of galaxy clusters is of crucial importance to avoid potential biases when interpreting current and upcoming cosmological observations. However, this question remains relatively unexplored, particularly when realistic AGN feedback models are taken into account. In this presentation, I introduce the...

39. Martin Kunz

Martin Kunz

04/11/2026 09:00

40. Clotilde Laigle

04/11/2026 09:30

43. The status of dynamical dark energy after the final Dark Energy Survey results

Agnès Ferté (LPNHE)

04/11/2026 10:00

The Dark Energy Survey had a key role in the potential hints for a dynamical dark energy over the past two years. The collaboration recently released its final analysis on the CPL parametrisation of the equation of state, achieving its goal set 20 years ago to test dark energy with multi-probes. After summarizing the recent progress on constraining dynamical dark energy, I will present DES Y6...

24. From Precision Cosmology to Accurate Spacetimes

Vincent Reverdy (Laboratoire d'Annecy de Physique des Particules)

04/11/2026 11:00

While a new generation of surveys, including LSST and Euclid, is mapping the Universe with unprecedented precision, increasingly sophisticated analysis pipelines are being developed to extract every bit of information from these data. Yet some of the foundational assumptions used to interpret them have, in many respects, remained largely unchanged for decades. We still describe the Universe...

25. Are we correctly estimating uncertainties in cluster analyses ?

Narei Lorenzo Martinez (LAPP)

04/11/2026 11:20

The Legacy Survey of Space and Time (LSST) has now started its ten-year survey. Its promise: detecting of order 100,000 galaxy clusters up to z~1, while providing weak-lensing information for a substantial fraction of them. The weak-lensing measurements will allow us to calibrate the relation between cluster observables, such as richness and halo mass. Combined with complementary Stage IV...

21. Gravitational Lensing Beyond Standard Approximations

M. Laurent MAGRI-STELLA (LAPP)

04/11/2026 11:40

Are the standard approximations used in gravitational lensing still adequate in the era of precision cosmology? If not, how can we move beyond them?

As cosmological tensions sharpen, a new generation of surveys such as Euclid and LSST is set to deliver an unprecedented volume of data, with billions of galaxies analyzed through increasingly sophisticated pipelines, including machine-learning...

23. From 3×2pt to 4×3pt: bispectra as calibrators of non-linear bias and intrinsic alignment

Raphaël Kou (IRAP)

04/11/2026 12:00

Upcoming photometric surveys such as Euclid and LSST will combine galaxy clustering and weak lensing to constrain dark energy, but exploiting mildly non-linear scales requires additional nuisance parameters for galaxy bias and intrinsic alignments, which degrade cosmological constraints. We present a framework combining 1-loop power spectra (3×2pt) with tree-level auto- and cross-bispectra of...

20. Local PNG with DESI DR2: pipeline, validation, and forward modeling of survey selection effects

Domitille Chebat (CEA Saclay - IRFU - DPhP)

04/11/2026 12:20

Primordial non-Gaussianity (PNG) is one of the few accessible windows into inflation: a significant detection of local PNG, $\left\vert f_\mathrm{NL}^\mathrm{loc} \right\vert \gtrsim 1$, would rule out standard single-field slow roll inflation. The tightest current constraints come from the CMB bispectrum, and are close to the cosmic variance limit. Three-dimensional galaxy surveys such as...

42. N-Body Simulations of Luminal Horndeski Theories in the EFTofDE Formalism

Himanish Ganjoo

04/11/2026 12:40

The Effective Field Theory of Dark Energy (EFTofDE) is an efficient framework to describe a wide range of modified gravity theories with a limited number of parameters. To robustly constrain them by comparison with clustering and weak lensing data from upcoming large-scale structure surveys, high-resolution cosmological N-body simulations are required to obtain accurate predictions for the...

47. Euclid meets CMB lensing: first cosmological constraints from the Euclid Quick Data Release

Dr Margherita Lembo (Institut d'Astrophysique de Paris (IAP))

The Euclid Quick Data Release (Q1) offers the first opportunity to test the cosmological potential of Euclid on real data. In this talk I will present the first cosmological analysis performed on Euclid data, based on the tomographic clustering of photometric galaxies in the three Euclid Deep Fields and their cross-correlation with CMB lensing from Planck and ACT. Despite covering only about...

48. N-Body Simulations of Luminal Horndeski Theories in the EFTofDE Formalism

Himanish Ganjoo (LUX, Observatoire de Paris)

The Effective Field Theory of Dark Energy (EFTofDE) is an efficient framework to describe a wide range of modified gravity theories with a limited number of parameters. To robustly constrain them by comparison with clustering and weak lensing data from upcoming large-scale structure surveys, high-resolution cosmological N-body simulations are required to obtain accurate predictions for the...

31. Nabila Aghanim

Nabila Aghanim (Institut d'Astrophysique Spatiale)

44. Natural Phantom Crossing from Axion-WIMP Interactions

Cedric DELAUNAY (LAPTH)

46. Recent Updates from the SH0ES Team on the Cepheid-SNIa Distance Ladder with HST, JWST and Gaia

Dr Louise Breuval (Space Telescope Science Institute)

The current tension between local late-universe measurements of the Hubble Constant (H0) and CMB + Lambda-CDM inferred values suggests growing evidence of new physics beyond the standard model. In this talk, I will review recent developments of the Cepheid and SNIa distance ladder, which has produced the most precise H0 local measurement. The talk will first focus on key improvements in...