Early dark sector, the Hubble tension, and the swampland
Evan McDonough, Mengxiang Lin, J. Colin Hill, Wayne Hu, Shengjia Zhou
Abstract
This work investigates the interplay of the Hubble tension, Early Dark Energy (EDE), and the swampland distance conjecture. The latter predicts a tower of light states for large field excursions, while EDE is a scalar field model to alleviate the Hubble tension which indeed requires Planckian field excursions, but also leads to tensions with large-scale structure (LSS) probes. The authors consider exponentially EDE-dependent masses of dark matter with the distance conjecture constant, which supposedly is a positive constant of O(1), as a free parameter. Using a large set of different catalogs of experiments, fitting also LSS data, a mild tension with the swampland distance conjecture is observed that constrains the constant to be significantly less than one. Modifications of the heuristic EDE potential may resolve this conflict.