Last summer, early observations from the James Webb Space Telescope (JWST) caused quite a stir due to their discovery of a puzzlingly abundant population of extremely massive galaxies at too high redshift, too many to have been in place if the ΛCDM model as we understand it is correct. In today’s new preprint with Shahnawaz Adil, Upala Mukhopadhyay, and Anjan Sen (all three from JMI, and kudos to Shahnawaz and Upala who did all the heavy-lifting!) we study whether these results could be explained by a dark energy model beyond the cosmological constant. In particular we consider a model featuring a negative cosmological constant (anti de Sitter vacuum) with an evolving component (whose energy density is of course positive) on top - this model is phenomenologically motivated from string theory considerations, particularly the swampland program, and the difficulty in constructing consistent de Sitter string vacua. We show that such a model can dramatically alter structure formation and potentially explain how the galaxies seen by JWST could have been in place much earlier than is allowed within ΛCDM. You can read our results in the preprint we just posted on arXiv: 2307.12763.
