Screened Theories of Gravity in 3D - Galaxy Clustering and Weak Lensing

The London Relativity and Cosmology Seminar
Geraint Pratten (Sussex)
October 21st, 2015 at 16:30
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Numerous observations have firmly established the accelerated expansion of the Universe with the simplest explanation being a finely tuned cosmological constant. To date, there is no concrete theoretical explanation and numerous candidates have been proposed. Simple extensions include a single scalar field with a sufficiently flat potential that drives the expansion. This scalar could arise from a new form of matter or, as considered here, as an additional scalar gravitational degree of freedom that gives rise to an additional fifth force. 
Such a fifth force is strongly constrained by solar system observations meaning that we need to screen the effects of the scalar on small scales whilst allowing for cosmologically interesting dynamics on large scales. We outline three different mechanisms and how they can be parameterised in a tomographic approach. These models are then studied within the spherical Fourier-Bessel framework - a natural basis for upcoming future surveys that promise to yield both wide angle and deep radial coverage. In particular we discuss constraints on screened theories arising from weak lensing and galaxy clustering results.