2022-02-18 11:00  P5A-1

The cosmological constant problem, Fab Four, and well-tempered cosmology

Reginald Christian Bernardo

The cosmological constant problem remains to be physics’ biggest tension between theory and observation. Conceding to this means accepting an uncomfortable fine-tuning of at least fifty orders of magnitude. Instead, we briefly review Steven Weinberg’s no-go theorem and how this paved the direction to self-tuning fields. We then recognize two ways of realizing a self-tuning mechanism in scalar-tensor theories: through Fab Four models and well-tempered cosmology. We discuss the core property “degeneracy” shared by such models which works to admit a low energy vacuum state independent of an arbitrarily large cosmological constant. We end with the recent progress in both Fab Four and well-tempered models, and draw future directions.