PTchat: Cosmology Perturbation Theory in the Era of Stage IV Surveys

Liste des Contributions

4. Vlasov Perturbation Theory (Part I)

Roman Scoccimarro (NYU)

24/11/2026 10:00

1

I introduce Vlasov Perturbation Theory (VPT), which solves the Vlasov hierarchy for cosmological perturbations due to collisionless particles. VPT takes into account shell-crossing, which enters essentially as a new background characterized by a "dispersion scale". We discuss how VPT incorporates a screening of large-scale modes from UV modes that cross the dispersion scale, suppressing the...

3. Vlasov Perturbation Theory (Part II)

Mathias Garny (Technical University Munich)

24/11/2026 11:30

After the framework of Vlasov Perturbation Theory (VPT) has been introduced in a previous talk by Roman Scoccimarro, I will discuss the application to LCDM cosmology as well as the role of higher order cumulants and the truncation scheme of the coupled hierarchy.

21. Weak Lensing and Tensor Observables from Perturbation Theory

Shi-Fan Chen (Columbia University)

24/11/2026 12:30

The current generation of galaxy surveys, including the Rubin Observatory and Euclid, will make unprecedented measurements of the weak lensing of galaxy shapes. I will discuss some recent progress in modeling weak lensing using analytic methods, particularly the application of purely analytic predictions from the EFT of large-scale structure to cosmic shear analyses. I will also discuss work...

8. Large- and small-scale power spectrum modeling for SPHEREx PNG

Elisabeth Krause (University of Arizona)

24/11/2026 14:30

This talk will review the power spectrum modeling validation for SPHEREx multi-tracer power spectrum PNG analyses, quantifying the impact of relativistic effects on ultra-large scales, and efficient sampling of 1-loop EFT parameters on weakly non-linear scales.

6. Projection of the gravitational dynamics: curl-free Gaussian ansatz

Patrick VALAGEAS (CEA Saclay)

24/11/2026 15:00

We present a new approach to model the gravitational dynamics of large-scale structures. Instead of solving the equations of motion up to a finite perturbative order or building phenomenological models, we follow the evolution of the probability distribution of the displacement and velocity fields within an approximation subspace. Keeping the exact equations of motion with their full...

11. Galaxy-halo connection for DESI tracers

Shun Saito (Missouri University of Science and Technology)

24/11/2026 16:00

To realize a simulation-based cosmology inference, modeling galaxy-halo connection is a key ingredient. In this talk, I plan to summarize galaxy-halo connection study from the most updated sample of galaxies and QSOs in the Dark Energy Spectroscopic Instrument (DESI). If time is allowed, I would like to discuss a possible path to combine the large-scale EFT with the small-scale simulation-based method.

26. Primordial non-Gaussianity and integral constraint on galaxy clustering

Shintaro Nakano

24/11/2026 16:30

14. Linear response approach to dynamical friction.

Vincent Desjacques

25/11/2026 10:00

Dynamical friction, which is a key mechanism governing the merger of astrophysical objects, from (primordial) black holes to galaxies. I will present the approach we have developed for compact eccentric binaries in a variety of astrophysical environments. I will also highlight how nonlinear response, wake self-interaction etc. could modify the linear-response description.

24. Selected topics in the statistics and dynamics of cosmological fields (TBD)

Takahiko Matsubara (KEK High Energy Accelerator Research Organization)

25/11/2026 10:30

I will discuss some recent topics from my research. The specific topics will be decided later.

25. The BAO–CMB Tension and Implications for Inflation

Elisa G. M. Ferreira

25/11/2026 11:30

Combining cosmological probes is one of the most powerful approaches in modern cosmology. However, within the $\Lambda$CDM framework, a discrepancy emerges between the cosmological parameters inferred from certain CMB datasets and those preferred by DESI DR2 BAO measurements. One important consequence is a shift in the inferred scalar spectral index, $n_s$, toward higher values relative to...

19. Galaxy Intrinsic Alignments: Parity Violation and Redshift-Space Modeling

Toshiki Kurita (Max Planck Institute for Astrophysics)

25/11/2026 12:00

In this talk, I will present recent work on perturbative modeling of galaxy intrinsic alignment power spectra. I will first discuss the parity-odd EB power spectrum as a probe of parity-violating primordial non-Gaussianity, complementary to recent analyses of the parity-odd galaxy four-point correlation function. I will then present one-loop modeling of intrinsic alignment power spectra in...

10. Towards a Fingers-of-God resummation

Alejandro Aviles (ICF - UNAM)

25/11/2026 12:30

In redshift space, the usual separation between perturbative dynamics on large scales and nonlinear motions on small scales is blurred by the mapping itself. As a consequence, velocities generated on small scales can enter nonperturbatively even at wavenumbers where the long wavelength dynamics remains under perturbative control. This suggests reorganizing the expansion so that the velocity...

22. PT-Field: a perturbative free energy for field-level inference

Massimo Pietroni (Università di Parma)

25/11/2026 14:30

The field-level posterior of a cosmological density field can be written in terms of the connected correlators of the model, which corresponds to marginalizing over the initial conditions analytically, rather than numerically. The construction is not restricted to the noiseless limit or to identifying k_max with the UV cutoff of the initial conditions. A feasible perturbative expansion,...

17. Density interpolation and adaptive mesh refinement in cosmological N-body codes

Stéphane Colombi

25/11/2026 15:00

We study discreteness effects in cosmological N-body simulations using adaptive mesh refinement (AMR), specifically RAMSES. We perform comparisons between triangular shaped cloud and cloud in cell interpolation techniques and study the effect of changing the refinement strategy of the AMR mesh in terms of the number of particles per cell.

27. photo-3x2-pt: Cosmology from cosmic shear and galaxy clustering with a single photometric galaxy catalog

Takashi Hamana

25/11/2026 16:00

28. FLI and SBI with GridSPT

Ken Osato

25/11/2026 16:30

2. Cosmology from galaxy clustering: field level vs summary statistics

Fabian Schmidt (Max Planck Institute for Astrophysics)

26/11/2026 10:00

The question of how much information on cosmology we can ultimately extract from large-scale structure observations has recently received renewed interest. Focusing on (idealized, spectroscopic) galaxy clustering, I will present results on field-level cosmology inference and compare with the constraints obtained using standard analysis techniques. I will then discuss where the additional...

20. Postcollapse Lagrangian perturbation theory in three dimensions

Shohei Saga

26/11/2026 11:30

The gravitational collapse of collisionless matter produces shell-crossing singularities, beyond which standard perturbation theory breaks down. We present the fully perturbative treatment of the early post-collapse dynamics in three dimensions using Lagrangian coordinates. High-order Lagrangian perturbation theory is used up to the first shell crossing, while the generic pancake-like...

9. The full-sky angular bispectrum of galaxy number counts

Thomas Montandon (Laboratoire Univers et Particule de Montpellier (LUPM))

26/11/2026 12:00

Stage-IV surveys such as Euclid, SKAO and the Rubin Observatory will observe billions of galaxies and deliver a 3D map of the Universe out to $z \gtrsim 2.5$. Photometric surveys are designed primarily for cosmic shear, but their broad radial windows and full-sky coverage make them equally well suited to tomographic angular analyses, which by construction avoid the flat-sky approximation and...

13. PowerFull: fast and accurate computation of the relativistic angular galaxy power spectrum including local primordial non-Gaussianity

Donghui Jeong (Penn State University / KIAS)

26/11/2026 12:30

Current and forthcoming wide-field galaxy surveys, such as SPHEREx and Euclid, provide a unique opportunity to probe the ultra-large scales of structure formation, where primordial non-Gaussianity, often parameterized by fNL, is expected to leave its most detectable imprint. At the same time, these surveys inevitably enter regimes where relativistic and wide-angle effects become significant,...

7. Through the looking glass: Survey geometry effects on the bispectrum

Dr Alexander Eggemeier (Argelander Institut für Astronomie, Universität Bonn)

26/11/2026 14:30

Robust extraction of cosmological information from the galaxy bispectrum requires an accurate understanding of how the survey selection function distorts the measured signal. In Fourier space the selection function couples different scales and multipoles, an effect encoded in a "mixing matrix" used to convolve theoretical predictions before comparison with data. For the power spectrum this...

23. Composite-Field Correlators of Biased Tracers

Azadeh Moradinezhad (Laboratoire d'Annecy de Physique Théorique (LAPTh))

26/11/2026 15:00

Extracting non-Gaussian information from large-scale structure (LSS) is essential to fully exploiting current and upcoming cosmological surveys, but higher-order statistics are challenging to measure and analyse. Composite-field correlators offer an efficient alternative, compressing the bispectrum and trispectrum into one-dimensional skew and kurto spectra through cross-spectra of the density...

29. Probing Gravitational Redshift on Small Scales： From Halos to Subhalos

Takuya Inoue

26/11/2026 16:00

30. TBA

Zehnyuan Wang

26/11/2026 16:30

18. On Measuring Galaxy Clustering on the Largest Scales Accessible to a Galaxy Survey

Masahiro Takada (Kavli IPMU)

27/11/2026 10:00

I will discuss measurements of galaxy clustering on the largest scales accessible to spectroscopic galaxy surveys and the associated uncertainties. If time permits, I will also provide an update on the Subaru Prime Focus Spectrograph (PFS).

31. TBA

Zvonimir Vlah

27/11/2026 10:30

1. BullFrog integrator for large-scale structure: quantum analogue and beyond ΛCDM

Cornelius Rampf (Ruđer Bošković Institute)

27/11/2026 11:30

Upcoming cosmological experiments will deliver unprecedented measurements of the matter distribution on the largest cosmic scales, enabling tests of physics beyond the standard models of cosmology and particle physics. Extracting this information requires accurate and efficient predictions of cosmic structure formation. I present results from classical and semiclassical simulations that use...

32. TBA

Martin Crocce

27/11/2026 12:00

15. Perturbation Theory Applied to Minkowski Tensors in Redshift Space

Dr Stephen Appleby (Korea Institute for Advanced Study)

27/11/2026 12:30

Morphological statistics such as Minkowski functionals and Minkowski tensors capture information beyond the two-point function and are sensitive to redshift-space anisotropies. Applying them to Stage-IV data requires analytic predictions. In this talk, I present the ensemble averages of the translation-invariant rank-2 Minkowski tensors for a matter density field that is perturbatively...

12. New developments in field-level inference

Fabian Schmidt (Max Planck Institute for Astrophysics)

I will present the latest state of field-level cosmology inference using the Lagrangian perturbative forward model developed in our group. Given the rapid development and many new methods that have recently proposed in the field, I will also propose a definition of the term "field-level inference" in distinction with "reconstructions" and summary-based inferences.