Cosmology of Ricci-tensor-squared gravity in the Palatini variational approach
- Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
- Institute of Theoretical Physics, University of Heidelberg, 69120 Heidelberg (Germany)
We consider the cosmology of the Ricci-tensor-squared gravity in the Palatini variational approach. The gravitational action of standard general relativity is modified by adding a function f(R{sup ab}R{sub ab}) to the Einstein-Hilbert action, and the Palatini variation is used to derive the field equations. A general method of obtaining the background and first-order covariant and gauge-invariant perturbation equations is outlined. As an example, we consider the cosmological constraints on such theories arising from the supernova type Ia and cosmic microwave background observations. We find that the best fit to the data is a non-null leading-order correction to Einstein gravity, but the current data exhibit no significant preference over the concordance model. The growth of nonrelativistic matter density perturbations at late times is also analyzed, and we find that a scale-dependent (positive or negative) sound-speed-squared term generally appears in the growth equation for small-scale density perturbations. We also estimate the observational bound imposed by the matter power spectrum for the model with f(R{sup ab}R{sub ab})={alpha}(R{sup ab}R{sub ab}){sup {beta}} to be roughly |{beta}| < or approx. O(10{sup -5}) so long as the dark matter does not possess compensating anisotropic stresses.
- OSTI ID:
- 21027873
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 76, Issue 10; Other Information: DOI: 10.1103/PhysRevD.76.104047; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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ACTION INTEGRAL
ANISOTROPY
CORRECTIONS
COSMOLOGY
DENSITY
DISTURBANCES
FIELD EQUATIONS
GAUGE INVARIANCE
GENERAL RELATIVITY THEORY
GRAVITATION
NONLUMINOUS MATTER
PERTURBATION THEORY
RELICT RADIATION
RICCI TENSOR
SOUND WAVES
STRESSES
SUPERNOVAE
VARIATIONAL METHODS