Subpercent accurate fitting of modified gravity growth

Constraining Modified Gravity and Growth with Weak Lensing ⋆

The idea that we live in a Universe undergoing a period of acceleration is a new, yet strongly held, notion in cosmology. As this can, potentially, be explained with a modification to General Relativity we look at current cosmological data with the purpose of testing aspects of gravity. Firstly we constrain a phenomenological model (mDGP) motivated by a possible extra dimension. This is charact...

Performance Evaluation of Accurate Ellipse Fitting

This paper studies numerical schemes for fitting an ellipse to points in an image. First, the problem is posed as maximum likelihood, and the relationship to the KCR lower bound is stated. Then, the algorithms of FNS, HEIV, renormalization, and Gauss-Newton iterations are described. Using simulated and real image data, their convergence properties are compared, and their dependence on the shape...

Modified gravity and cosmology

Viscosity in Modified Gravity

A bulk viscosity is introduced in the formalism of modified gravity. It is shown that, based on a natural scaling law for the viscosity, a simple solution can be found for quantities such as the Hubble parameter and the energy density. These solutions may incorporate a viscosity-induced Big Rip singularity. By introducing a phase transition in the cosmic fluid, the future singularity can nevert...

Observational Tests of Modified Gravity

Modifications of general relativity provide an alternative explanation to dark energy for the observed acceleration of the Universe. Modified gravity theories have richer observational consequences for large scale structures than conventional dark energy models, in that different observables are not described by a single growth factor even in the linear regime. We examine the relationships betw...