Understanding the Dyer-Roeder approximation as a consequence of local cancellations of projected shear and expansion rate fluctuations

  title={Understanding the Dyer-Roeder approximation as a consequence of local cancellations of projected shear and expansion rate fluctuations},
  author={Sofie Marie Koksbang},
  journal={Physical Review D},
It is shown with several concrete examples that the Dyer-Roeder approximation is valid in spacetimes which fulfill the condition that fluctuations in the expansion rate along a light ray locally cancels with the shear contribution to the redshift. This is the case for standard cosmological scenarios including perturbed FLRW spacetimes, N-body simulations and Swiss-cheese models. With another concrete example it is then illustrated that it is possible to construct statistically homogeneous and… Expand


Swiss-cheese models and the Dyer-Roeder approximation
In view of interpreting the cosmological observations precisely, especially when they involve narrow light beams, it is crucial to understand how light propagates in our statistically homogeneous,Expand
Weak lensing and the Dyer–Roeder approximation
The distance-redshift relation plays an important role in cosmology. In the standard approach to cosmology, it is assumed that this relation is the same as in a homogeneous universe. As the realExpand
Average expansion rate and light propagation in a cosmological Tardis spacetime
We construct the first exact statistically homogeneous and isotropic cosmological solution in which inhomogeneity has a significant effect on the expansion rate. The universe is modelled as a SwissExpand
Ricci focusing, shearing, and the expansion rate in an almost homogeneous Universe
The Universe is inhomogeneous, and yet it seems to be incredibly well-characterised by a homogeneous relativistic model. One of the current challenges is to accurately characterise the properties ofExpand
Light propagation and the average expansion rate in near-FRW universes
We consider universes that are close to Friedmann-Robertson-Walker in the sense that metric perturbations, their time derivatives and first spatial derivatives are small, but second spatialExpand
Interpretation of the Hubble diagram in a nonhomogeneous universe
In the standard cosmological framework, the Hubble diagram is interpreted by assuming that the light emitted by standard candles propagates in a spatially homogeneous and isotropic spacetime.Expand
The Dyer-Roeder distance-redshift relation in inhomogeneous universes
Using Monte-Carlo methods, we determine the best-fit value of the homogeneity parameter a in the Dyer-Roeder distance-redshift relation for a variety of redshifts, inhomogeneity models andExpand
Observations in statistically homogeneous, locally inhomogeneous cosmological toy models without FLRW backgrounds
Observations are studied in toy-models constituting exact cosmological solutions to the Einstein equation which are statistically homogeneous but locally inhomogeneous, without an a priori introducedExpand
Inhomogeneous cosmology with numerical relativity
We perform three-dimensional numerical relativity simulations of homogeneous and inhomogeneous expanding spacetimes, with a view towards quantifying non-linear effects from cosmologicalExpand
Effects of Nonlinear Inhomogeneity on the Cosmic Expansion with Numerical Relativity.
It is found that collapsing perturbations reach the turnaround point much earlier than expected from the reference spherical top-hat collapse model and that the local deviation of the expansion rate from the homogeneous one can be as high as 28% at an underdensity, for an initial density contrast of 10^{-2}. Expand