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Abstract
We propose a method to study and constrain modified gravity theories for dark matter using CMB temperature anisotropies and polarization. We assume that the theories considered here have already passed the matter powerspectrum test of largescale structure. With this requirement met, we show that a modified gravity theory can be specified by parametrizing the time evolution of its darkmatter density contrast, which is completely controlled by the darkmatter stress history. We calculate how the stress history with a given parametrization affects the CMB observables, and a qualitative discussion of the physical effects involved is supplemented with numerical examples. It is found that, in general, alternative gravity theories can be efficiently constrained by the CMB temperature and polarization spectra. There exist, however, special cases where modified gravity cannot be distinguished from the CDM model even by using both CMB and matter power spectrum observations, nor can they be efficiently restricted by other observables in perturbed cosmologies. Our results show how the stress properties of dark matter, which determine the evolutions of both density perturbations and the gravitational potential, can be effectively investigated using just the general conservation equations and without assuming any specific theoretical gravitational theory within a wide class.
Original language  English 

Pages (fromto)  064021 
Number of pages  14 
Journal  Physical review. D, Particles, fields, gravitation, and cosmology 
Volume  78 
Issue number  6 
DOIs  
Publication status  Published  Sept 2008 
Keywords
 MICROWAVE BACKGROUND ANISOTROPIES
 GAUGEINVARIANT APPROACH
 NEWTONIAN DYNAMICS
 GRAVITY
 GALAXIES
 ENERGY
 MODELS
 POLARIZATION
 CONSTRAINTS
 COVARIANT
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 1 Finished

Astrophysics at St Andrews: Astrophysics at St.Andrews
Cameron, A. C. (PI) & Horne, K. D. (CoI)
1/04/06 → 31/03/11
Project: Standard