Benedetta Rosatello, Gen Ye, Maria Berti, Isaac Tutusaus, Nastassia Grimm, Camille Bonvin

Measurements from the Dark Energy Survey (DES) Year 3 data have shown that the Weyl potential -- the sum of the spatial and temporal distortions of the geometry -- evolves more slowly than predicted by General Relativity, assuming a $Λ$CDM background evolution. An evolving dark energy with a phantom crossing, as preferred by the Dark Energy Spectroscopic Instrument (DESI), is expected to decrease the depth of the gravitational potentials through a stronger acceleration than in $Λ$CDM, potentially solving the tension with General Relativity. In this paper, we show that $w_0w_a$CDM models indeed reduce the tension with respect to $Λ$CDM, down to a level of $1.6-2.2σ$, depending on the treatment of CMB lensing. This reduction is not due to an increase in the Weyl potential's uncertainties, but truly to the impact of the evolving background on the theoretical predictions in General Relativity. More data are needed to robustly determine if evolving dark energy fully explains the low value of the Weyl potential at intermediate redshifts, or if modifications of gravity or interactions in the dark sector are needed, which could simultaneously stabilize the phantom crossing indicated by DESI.