Orateur
Description
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 primarily as perturbations around an FLRW spacetime, model gravitational lensing through layers of approximations and idealized matter distributions, and run most cosmological simulations using Newtonian or weak-field gravity rather than solving the full Einstein equations. In this talk, I will discuss whether our ever-growing statistical and computational sophistication has been matched by a comparable evolution of the physical description of the Universe itself. I will review possible paths beyond the standard modeling framework, from both theoretical and numerical perspectives, and highlight the rich landscape of well-defined problems they open up across physics, mathematics, and computational cosmology. I will argue that, as tensions and anomalies persist and datasets enter an entirely new regime, the time may have come to rethink cosmological modeling from the ground up, taking general relativity in its full generality as the natural foundation. In practice, I will revisit several critical steps in cosmological modeling from a general-relativistic perspective, from the construction of initial conditions and the choice of cosmic topology to non-perturbative spacetime evolution and light propagation, and examine how the assumptions built into our standard framework may constrain the questions we can ask and, ultimately, the conclusions we can draw about the evolution of the Universe.