Extended Chameleons

Abstract

We extend the chameleon models by considering Scalar-Fluid theories where the coupling between matter and the scalar field can be represented by a quadratic effective potential with density-dependent minimum and mass. In this context, we study the effects of the scalar field on Solar System tests of gravity and show that models passing these stringent constraints can still induce large modifications of Newton's law on galactic scales. On these scales we analyse models which could lead to a percent deviation of Newton's law outside the virial radius. We then model the dark matter halo as a Navarro-Frenk-White profile and explicitly find that the fifth force can give large contributions around the galactic core in a particular model where the scalar field mass is constant and the minimum of its potential varies linearly with the matter density. At cosmological distances, we find that this model does not alter the growth of large scale structures and therefore would be best tested on galactic scales, where interesting signatures might arise in the galaxy rotation curves.

21 pages, 8 figures; v2: acknowledgements added

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Cited by in corpus (6)

• Dynamical systems applied to cosmology: dark energy and modified gravity
• Scalar-Fluid interacting dark energy: cosmological dynamics beyond the exponential potential
• Dark energy with a gradient coupling to the dark matter fluid: cosmological dynamics and structure formation
• Post-Newtonian parameters and cosmological constant of screened modified gravity
• Lagrangian description of cosmic fluids: mapping dark energy into unified dark energy
• On-shell Lagrangian of an ideal gas