Constraints on cosmological anisotropy out to z = 1 from Type Ia supernovae

This article proposes a comprehensive analysis of light propagation in an anisotropic and spatially homogeneous Bianchi I universe. After recalling that null geodesics are easily determined in such a spacetime, we derive the expressions of the redshift and direction drifts of light sources; by solving analytically the Sachs equation, we then obtain an explicit expression of the Jacobi matrix describing the propagation of narrow light beams. As a by-product, we recover the old formula by Saunders for the angular diameter distance in a Bianchi I spacetime, but our derivation goes further since it also provides the optical shear and rotation. These results pave the way to the analysis of both supernovae data and weak lensing by the large-scale structure in Bianchi universes.

show abstract

“…(6.11); its trace reads 18) but, on the one hand, remember that Eq. (2.3) implies 19) and, on the other hand, 20) so that finally…”

Section: B Evolution Matrixmentioning

confidence: 99%

Light propagation in a homogeneous and anisotropic universe

2015

View full text Add to dashboard Cite

show abstract

“…This has previously been studied by Kolatt and Lahav [29] and Bochner [30]. Although their approaches were somewhat different, they both looked in essence for evidence of a lack of uniformity in the Hubble flow from a statistical point of view.…”

Section: Introductionmentioning

confidence: 99%

Supernova Hubble diagram for off-center observers in a spherically symmetric inhomogeneous universe

Alnes

Amarzguioui

2007

Phys. Rev. D

View full text Add to dashboard Cite

We have previously shown that spherically symmetric, inhomogeneous universe models can explain both the supernova data and the location of the first peak in the CMB spectrum without resorting to dark energy. In this work, we investigate whether it is possible to get an even better fit to the supernova data by allowing the observer to be positioned away from the origin in the spherically symmetric coordinate system. In such a scenario, the observer sees an anisotropic relation between redshifts and the luminosity distances of supernovae. The level of anisotropy allowed by the data will then constrain how far away from the origin the observer can be located, and possibly even allow for a better fit. Our analysis shows that the fit is indeed improved, but not by a significant amount. Furthermore, it shows that the supernova data do not place a rigorous constraint on how far off-center the observer can be located.

show abstract

“…However, evidence for a non-zero cosmological constant is still controversial, since supernovae might evolve with redshift and/or may be dimmed by intergalactic dust (Aguirre 1999). The fundamental assumption of a homogeneous Universe and its implication for a non-zero cosmological constant are also discussed (Célérier 2000;Kolatt & Lahav 2001). The second constraint is derived from the location of features in the cosmic microwave background (CMB) anisotropy spectrum, particularly the first Doppler peak.…”

Section: Introductionmentioning

confidence: 99%

Constraining the cosmological parameters using strong lensing

Golse

Kneib

Soucail

2002

A&A

View full text Add to dashboard Cite

Abstract. We investigate the potential of using strong lensing clusters to constrain the cosmological parameters Ωm and Ω λ . The existence of a multiple image system with known redshift allows, for a given (Ωm, Ω λ ) cosmology, absolute calibration of the total mass deduced from lens modelling. Recent Hubble Space Telescope (HST) observations of galaxy clusters reveal a large number of multiple images, which are predicted to be at different redshifts. If it is possible to measure spectroscopically the redshifts of many multiple images then one can in principle constrain (Ωm, Ω λ ) through ratios of angular diameter distances, independently of any external assumptions. For a regular/relaxed cluster observed by HST with 3 multiple image systems, each with different spectroscopic redshifts, we show by analytic calculation that the following uncertainties can be expected: Ωm = 0.30 ± 0.11, Ω λ = 0.70 ± 0.23 or Ωm = 1.00 ± 0.17, Ω λ = 0.00 ± 0.48 for the two most popular world models. Numerical tests on simulated data confirm these good constraints, even in the case of more realistic cluster potentials, such as bimodal clusters, or when including perturbations by galaxies. To investigate the sensitivity of the method to different mass profiles, we also use an analytic "pseudo-elliptical" Navarro et al. profile in the simulations. These constraints can be improved if more than 3 multiple images with spectroscopic redshifts are observed, or by combining the results from different clusters. Some prospects on the determination of the cosmological parameters with gravitational lensing are given.

show abstract

Constraints on cosmological anisotropy out to z = 1 from Type Ia supernovae

Cited by 46 publications

References 20 publications

Light propagation in a homogeneous and anisotropic universe

Light propagation in a homogeneous and anisotropic universe

Supernova Hubble diagram for off-center observers in a spherically symmetric inhomogeneous universe

Constraining the cosmological parameters using strong lensing

Contact Info

Product

Resources

About