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Journal of Cosmology and Astroparticle Physics 08 (2010) 033
Spherical collapse in chameleon models
P. Brax, R. Rosenfeld, D.A. Steer1
(08/2010)

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 field, 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 in principle depends on the initial comoving size of the inhomogeneity.
1 :  APC - UMR 7164 - AstroParticule et Cosmologie
APC - THEORIE
Physique/Physique des Hautes Energies - Théorie
Lien vers le texte intégral : 
http://fr.arXiv.org/abs/1005.2051