Radiative symmetry breaking in scalar-tensor theories of gravity

Scalar-tensor theories of gravity offer an alternative to Einstein's general theory of relativity. These modified theories of gravity may play a role in addressing challenging problems in modern physics, such as the nature of dark matter, which is needed, e.g., to explain the formation of structure in the Universe; or the origin of dark energy, which drives the accelerated expansion of the Universe.

Scalar-tensor theories of gravity often lead to so-called fifth forces, which are heavily constrained by precise tests of gravity performed within the Solar System. However, these constraints can be evaded if the nature of the fifth force changes in regions of high ambient density (such as the Solar System) due to screening mechanisms. The fifth force can then give rise to observable effects in regions of lower ambient density elsewhere in the Universe.

There are a variety of screening mechanisms, and some are driven by the spontaneous breaking of symmetries, akin to the famous Higgs mechanism of the Standard Model of particle physics.

This PhD project will critically analyse spontaneous symmetry breaking in scalar-tensor theories of gravity. The aims are to construct robust fifth-force models with screening driven by quantum effects and to investigate the consequences of these models for experiment and observation.