In this project, we turn our attention to the Equivalence Principle (EP)--which was dramatized by Einstein in his famous "elevator" thought experiment. Despite many physicists holding that the EP is the foundation of our best gravitational theory, various philosophers have argued that the EP is useless or incoherent. This project will defend the EP and shed new light on it by linking it to two fundamental ideas in physics: (i) the covariant phase space (CPS) approach to gauge symmetry and subsystem charges; and (ii) the framework of effective field theory (EFT) and spontaneous symmetry breaking (SSB).
We aim to rigorously show that the EP is both an idealization and at the same time a fundamental principle of the theory. By means of a major international conference and three focused workshops, we will bring together the CPS/EFT community, the General Relativity community, and philosophers working on the status of the EP as well as modeling/idealization. Our team will produce 6 articles in top physics and philosophy journals on how the EP can be fruitfully reconceived using EFT principles. One major impact is ushering in a new phase of applications of the EP, including progress in the problem of self-force and small body motion. Another is conceptual, namely adjudicating the status of the EP in the foundations of gravitation.
