The Dark Dimension and its interplay with DESI data

In this talk, I will review the motivation for considering an extra mesoscopic Dark Dimension of length l ~ 1 - 10 microns, taking into account theoretical and observational arguments. This scenario leads, by the universal coupling of the Standard Model sector to bulk gravitons, to massive spin 2 KK excitations of the graviton in the Dark Dimension (the “dark gravitons”) as an unavoidable dark matter candidate. I will then consider the natural possibility that the radius of the dark dimension varies as the dark energy decreases, leading to the variation of the dark matter mass. This model is in excellent agreement with recent experimental data from DESI DR2 combined with SN measurements (from DES, Union3 or Pantheon+) and reproduces the same significance as CPL parametrization with the added benefit of providing an explanation for the apparent phantom behavior. Finally, the model also provides a prediction for a fifth force in the dark sector that is consistent with current experimental bounds.