Relaxation of the Cosmological Constant

Understand

We present a model that naturally tunes a large positive cosmological constant to a small cosmological constant.

• A slowly rolling scalar field decreases the cosmological constant to a small negative value, causing the universe to contract, thus reheating it.
• An expanding universe with a small positive cosmological constant can be obtained, respectively, by coupling this solution to any model of a cosmological bounce and coupling the scalar field to a sector that undergoes a technically natural phase transition at the meV scale.
• A robust prediction of this model is a rolling scalar field today with some coupling to the standard model.