The Equivalence Principle in the Dark Sector in light of DESI

RESUMO

Recent measurements of the distribution of galaxies by the Dark Energy Spectroscopic Instrument (DESI) are in mild tension with a standard $\Lambda$-Cold Dark Matter cosmological model inferred from the anisotropies of the Cosmic Microwave Background (CMB) when extrapolated to low redshifts. Several solutions to explain this discrepancy in terms of new physics have been put forward, notably from new dynamics in a complex Dark Sector. Here we report on a resolution to this discrepancy that postulates that the inertial and gravitational masses of dark matter particles are not the same. Our best fit to CMB data combined either with Baryon Acoustic Oscillation (BAO) and Full Shape (FS) data from DESI DR1 (Data Release 1), or with BAO DR2 data alone, suggests the presence of a new long-range force in the Dark Sector with strength of $\beta \sim 0.5\% $ relative to gravity, at the $\sim 2.5\sigma$ level. A preliminary analysis combining FS DR1 and BAO DR2 data confirms the statistical power of DR2 and raises the evidence for dark forces to $\sim 3\sigma$, albeit ignoring the not yet available cross-correlation between the two datasets.