Towards constraining the pillars of our cosmological model using combined probes

ongoing

Despite the observational successes of the Lambda Cold Dark Matter (ΛCDM) cosmological model, a number of its key ingredients remain unknown. Imminent surveys promise to yield unprecedented constraints on these components, thus making precision tests of ΛCDM a first-time reality. In PiCo, my team and I will focus on two fundamental questions in modern physics that can only be answered through cosmological observations: What mechanism gave rise to the primordial fluctuations seeding all the structures seen in the Universe today? What is the cause for the Universe’s late-time accelerated expansion? We will address these by developing novel analysis techniques built on the complementarity of cosmological probes and advanced statistical methods. These are designed to harness the rich information contained in non-Gaussian, small-scale features of cosmic fields, while enabling precise constraints on ΛCDM, robust to systematic uncertainties dominating high-precision data. Focusing on two of the most powerful probes of the next decade, galaxy clustering and galaxy clusters, we will constrain the mechanisms driving the accelerated expansion through the first joint simulation-based inference analysis of galaxy clusters selected through the Cosmic Microwave Background (CMB) and weak lensing. In addition, we will derive constraints on primordial fluctuations in a combined analysis of galaxy clustering and CMB lensing angular two- and three-point statistics. Capitalizing on my past work, we will develop these methods using simulations and current data, before applying them to galaxy data from the Rubin Observatory Legacy Survey of Space and Time and CMB data from the Simons Observatory, two upcoming high-precision experiments I am deeply involved in. PiCo will deliver tight constraints on the key ingredients of ΛCDM and will thus contribute to understanding if this model provides a complete description of our Universe, or if it is time for a paradigm shift in cosmology.