3 research outputs found
Expansion history and f(R) modified gravity
We attempt to fit cosmological data using modified Lagrangians
containing inverse powers of the Ricci scalar varied with respect to the
metric. While we can fit the supernova data well, we confirm the behaviour at medium to high redshifts reported elsewhere and argue
that the easiest way to show that this class of models are inconsistent with
the data is by considering the thickness of the last scattering surface. For
the best fit parameters to the supernova data, the simplest 1/R model gives
rise to a last scattering surface of thickness , inconsistent
with observations.Comment: accepted in JCAP, presentation clarified, results and conclusions
unchange
Cosmological constraints combining H(z), CMB shift and SNIa observational data
Recently H(z) data obtained from differential ages of galaxies have been
proposed as a new geometrical probe of dark energy. In this paper we use those
data, combined with other background tests (CMB shift and SNIa data), to
constrain a set of general relativistic dark energy models together with some
other models motivated by extra dimensions. Our analysis rests mostly on
Bayesian statistics, and we conclude that LCDM is at least substantially
favoured, and that braneworld models are less favoured than general
relativistic ones.Comment: 17 pages, 11 figures; improved discussion, new figures, updated to
match published versio
Testing the DGP model with ESSENCE
We use the recent supernova data set from the ESSENCE collaboration combined
with data from the Supernova Legacy Survey and nearby supernovae to test the
DGP brane world model and its generalisations. Combination of this data with a
flatness prior and the position of the peak of the CMB disfavours the DGP model
slightly. Inclusion of the baryon acoustic peak from the Sloan Digital Sky
Survey increase the tension of the DGP model with the data, although it is not
clear how self consistent this procedure would be without a re-analysis of the
survey data in the framework of the DGP cosmology. Generalisations of the DGP
model are tested and constraints on relevant parameters obtained.Comment: Minor corrections, clarifications and references added. Published in
JCA