Scalar Fields with Quadratic Couplings to Matter around Cavities

Ultra-light scalars could explain the observed properties of dark matter. These scalars may couple quadratically to Standard Model fields. From these couplings a scalar gains an effective mass which shifts according to the local density of matter. This change in mass causes the the amplitude of the field to shift in the environment of detection experiments. In our work we show that a cavity-like matter environment around an experiment - such as a vacuum chamber, laboratory room, or the casing of a satellite - can exponentially suppress the amplitude of scalar oscillations in its interior. This substantially weakens constraints on scalars with strong couplings to standard model fields. In light of this fact, we discuss the possibility of using fifth force tests measurements on bodies orbiting the Earth to access regimes of strong coupling, on account of their minimal matter environment.