Strongly Coupled Chameleon Fields: New Horizons in Scalar Field Theory

We show that, as a result of nonlinear self-interactions, scalar field theories that couple to matter much more strongly than gravity are not only viable but could well be detected by a number of future experiments provided that they are properly designed to do so.

Figure 1

The whole of the shaded area shows the allowed parameter space with all current bounds. For some values of $M$ and $\lambda$, we need the BeCu sheet to have a thin shell; this results in a region near $\beta \sim O(1)$ being ruled out. Future space-based tests could detect the more lightly shaded regions. The solid horizontal lines indicate the case where the chameleon field behaves like dark energy. Plots for theories with $n<-4$ or $n>0$ are similar to cases $n=-8$ and $n=4$, respectively.