Broken Symmetry in Curved Spacetime and Gravity

Modern physics rests on a foundation of two fundamental theories: General Relativity (GR) and the Standard Model (SM). Each theory agrees extremely well with experiments in a certain domain. However, the predictions of the theories disagree with each other in certain situations. Therefore, GR and the SM are likely to be low-energy approximations to some more fundamental theory. A major current goal in physics is to determine the nature of this more fundamental theory.

The most natural approach to learning about the fundamental theory is to look for situations where GR and the SM strongly disagree; in such situations, at least one of these theories must make predictions that are clearly wrong. Unfortunately, all known situations where the theories strongly disagree are untenable to study experimentally. This leads us to consider an alternate approach—suppose that one or both of these theories is slightly wrong in a situation where we can perform experiments with extremely high precision. Careful study of these high-precision experiments could reveal a violation of one of the current theories. This is the approach taken in studies of spacetime symmetry violation.