Influence functionals, decoherence and conformally coupled scalars

Understand

Some of the simplest modifications to general relativity involve the coupling of additional scalar fields to the scalar curvature.

• By making a Weyl rescaling of the metric, these theories can be mapped to Einstein gravity with the additional scalar fields instead being coupled universally to matter.
• The resulting couplings to matter give rise to scalar fifth forces, which can evade the stringent constraints from local tests of gravity by means of so-called screening mechanisms.
• In this talk, we derive evolution equations for the matrix elements of the reduced density operator of a toy matter sector by means of the Feynman-Vernon influence functional.