Spherical collapse in chameleon models

Ph Brax, R Rosenfeld, D.A Steer
2010 Journal of Cosmology and Astroparticle Physics  
We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon
more » ... eld, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in the presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse depends on the initial comoving size of the inhomogeneity.
doi:10.1088/1475-7516/2010/08/033 fatcat:2vni2aqcfbfwbmsqfwjn6rzrwe