Probing dark Energy and Gravity through Analysis of the growth of Structure Using Supernovae

Understanding the nature of dark energy, which drive the accelerated expansion of the universe, is one of the greatest questions in modern cosmology. Today, the rise of persistent tensions in observational data is challenging the standard description of dark energy as a cosmological constant, urging the need for new, independent cosmological measurements. Constraints on the growth of cosmic structure (GoS) constitute a key path to address these tensions by probing both dark energy and gravity. My MSCA fellowship proposes to develop a novel approach to constrain GoS using Type Ia Supernovae (SNe Ia). SNe Ia are one of the main probe of modern cosmology, enabling precise distance measurement across the universe. However, the number of SNe Ia available for cosmological analysis has remained relatively low, reaching about 2 000 SNe Ia in the most recent dataset. The Rubin Observatory's Legacy Survey of Space and Time (Rubin-LSST), starting in fall 2025, will revolutionize the field by delivering ~200 000 cosmological-grade SNe Ia. This unprecedented sample will, for the first time, unlock precise constraints of the GoS from SNe Ia only.In this fellowship, I will (1) lead the first pre-LSST measurement of the GoS using the SN Ia data from the Asteroid Terrestrial-impact Last Alert System survey; (2) scale up the methodology developed in the analysis of ATLAS data for Rubin-LSST, delivering a robust GoS analysis pipeline validated on realistic simulations and first-year data; (3) establish synergies between Rubin-LSST probes by extending the pipeline to a joint analysis of GoS using SNe Ia and Weak Lensing data, and deliver a proof-of-concept measurement with first-year data. By laying the essential groundwork for these novel analyses in the Rubin-LSST era, this project will open new avenues to understand the nature of dark energy and gravity.