A new avenue in the hunt for dark energy

ended

Currently, General Relativity (GR) and the standard model of particles physics are severely challenged by their inability to explain the late-time accelerated expansion of the Universe, known as the “dark energy” problem. The most promising scenarios aiming to explain it are the so--called scalar-tensor theories, corresponding to extensions of GR where gravity is enhanced through a new gravitational force mediated by a scalar field. The quest for phenomenological imprints of new scalar gravitational forces has been a central effort in cosmology and astrophysics over the last decade. My goal is to introduce helioseismology as a test of unprecedented accuracy in the search for new gravitational forces in Nature. The focus will be on the most general scalar-field extensions of GR, known as “DHOST” scalar-tensor theories. The unique ability of solar pulsations to probe the finest details of gravity in the solar interior, combined with the extreme accuracy of helioseismic observations, promises an orders-of-magnitude improvement of previous constraints. I will formulate the theoretical framework for adiabatic stellar pulsations in this context, and with sophisticated numerical techniques, I will model the associated solar pulsation eigenspectrum. A systematic statistical analysis will be devised to confront the predictions against observations making use of powerful helioseismic inversions, and derive the tightest constraints on the most general scalar-tensor theories up to date. The cosmological implications will be predicted, in accordance with ESA’s upcoming Euclid satellite mission. The project will introduce a genuinely novel, interdisciplinary line of research that will strongly impact a broad spectrum of cosmology and astrophysics. The new constraints will be pivotal for our understanding of scalar-gravity interactions in Nature, and are expected to guide the future modelling of dark energy, and scalar field theories in general.