Structure Formation in the Symmetron Model
  Scalar fields, strongly coupled to matter, can be present in nature and still be invisible to local experiments if they are subject to a screening mechanism. The symmetron is one such mechanism which relies on restoration of a spontaneously broken symmetry in regions of high density to shield the scalar fifth force. We have investigated structure formation in the symmetron model by using N-body simulations and find strong observable signatures in both the linear and nonlinear matter power spectrum and on the halo mass function. The mechanism for suppressing the scalar fifth force in high density regions is also found to work very well. 
Anne-Christine Davis, Baojiu Li, David F. Mota and Hans A. Winther
astro-ph.CO gr-qc hep-ph