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

This workshop will be the fifth in the PTChat series devoted to analytic approaches to the large-scale structure (LSS) of the Universe in the subject of cosmology. Previous PTChat meetings (Saclay 2011; Cargèse 2013; IAP 2016; YITP 2019) successfully fostered active discussions on perturbation theory and nonlinear structure formation.

After a several-year interval, the field is now entering a new phase driven by major forthcoming datasets. Euclid’s first data release (DR1) is scheduled for 2026, followed by DR2 in 2028, and complemented by recent and upcoming data from DESI (DR2), KiDS-Legacy, HSC, PFS, Rubin, Roman, and SPHEREx. These Stage-IV surveys demand significant advances in theoretical modeling, statistical methodology, and cross-survey analysis. Renewed discussions among theorists are therefore essential to keep pace with observational progress.

The proposed PTChat workshop aims to bring together leading researchers to exchange recent developments, identify key challenges, and stimulate collaborations that can respond to this rapidly evolving landscape.
The scientific program will focus on two broad and complementary directions:

A. Challenges from Stage-IV cosmological surveys
● Methods to fully exploit high-precision data from Euclid, DESI, Rubin, and other next-generation surveys.
● Cross-correlation strategies for heterogeneous datasets (galaxy clustering, weak lensing, CMB lensing, intensity mapping).
● Observational signature of modified gravity and clustering dark energy.
● Detecting subtle signatures of beyond-standard cosmology, including primordial non-Gaussianity (f_NL, g_NL), parity violation, cosmic birefringence, statistical anisotropies

B. New theoretical and methodological developments
● Advances in renormalized and resummed perturbation theory (PT); opportunity for extended presentations on Vlasov PT.
● Applications of large-deviation theory to nonlinear statistics.
● Field- and simulation-based inference: assessing their performance and future potential.
● Links to early-Universe physics, including primordial black hole formation and related statistics.