Systematic error due to isotropic inhomogeneities

Negishi, Hiroyuki; Nakao, Ken–ichi; Yoo, Chul-Moon; Nishikawa, Ryusuke

doi:10.1103/physrevd.92.103003

Cited by 3 publications

(3 citation statements)

References 35 publications

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“…In contrast, the models with a non-vanishing cosmological constant, namely, ΛLTB models, have been studied not very often although we can find several restricted analyses [10][11][12][13]. In this paper, we assume that the late time behaviour of our universe is well described by a ΛLTB model.…”

Section: Jcap03(2018)033mentioning

confidence: 99%

Observational constraint on spherical inhomogeneity with CMB and local Hubble parameter

Tokutake

Ichiki

Yoo

2018

J. Cosmol. Astropart. Phys.

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We derive an observational constraint on a spherical inhomogeneity of the void centered at our position from the angular power spectrum of the cosmic microwave background(CMB) and local measurements of the Hubble parameter. The late time behaviour of the void is assumed to be well described by the so-called Λ-Lemaître-Tolman-Bondi (ΛLTB) solution. Then, we restrict the models to the asymptotically homogeneous models each of which is approximated by a flat Friedmann-Lemaître-Robertson-Walker model. The late time ΛLTB models are parametrized by four parameters including the value of the cosmological constant and the local Hubble parameter. The other two parameters are used to parametrize the observed distance-redshift relation. Then, the ΛLTB models are constructed so that they are compatible with the given distance-redshift relation. Including conventional parameters for the CMB analysis, we characterize our models by seven parameters in total. The local Hubble measurements are reflected in the prior distribution of the local Hubble parameter. As a result of a Markov-Chains-Monte-Carlo analysis for the CMB temperature and polarization anisotropies, we found that the inhomogeneous universe models with vanishing cosmological constant are ruled out as is expected. However, a significant under-density around us is still compatible with the angular power spectrum of CMB and the local Hubble parameter.

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Section: Jcap03(2018)033mentioning

confidence: 99%

Observational constraint on spherical inhomogeneity with CMB and local Hubble parameter

Tokutake

Ichiki

Yoo

2018

J. Cosmol. Astropart. Phys.

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“…isotropic inhomogeneities may cause systematic errors on the amount of dark energy and its equation of state. Some authors studied systematic errors due to isotropic inhomogeneities and have evaluated the magnitude of them [14][15][16][17][18][19][20][21][22][23][24]. However, nobody has not shown how to remove the systematic errors caused by isotropic inhomogeneities.…”

Section: Introductionmentioning

confidence: 99%

Can we remove the systematic error due to isotropic inhomogeneities?

Negishi

Nakao

2017

Phys. Rev. D

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Usually, we assume that there is no inhomogeneity isotropic in terms of our location in our universe. This assumption has not been observationally confirmed yet in sufficient accuracy, and we need to consider the possibility that there are non-negligible large-scale isotropic inhomogeneities in our universe. The existence of large-scale isotropic inhomogeneities affects the determination of the cosmological parameters. In particular, from only the distance-redshift relation, we can not distinguish the inhomogeneous isotropic universe model from the homogeneous isotropic one, because of the ambiguity in the cosmological parameters. In this paper, in order to avoid such ambiguity, we consider three observables, the distance-redshift relation, the fluctuation spectrum of the cosmic microwave background radiation(CMBR) and the scale of the baryon acoustic oscillation(BAO), and compare these observables in two universe models; One is the inhomogeneous isotropic universe model with the cosmological constant and the other is the homogeneous isotropic universe model with the dark energy other than the cosmological constant. We show that these two universe models can not predict the same observational data of all three observables but the same ones of only two of three, as long as the perturbations are adiabatic. In principle, we can distinguish the inhomogeneous isotropic universe from the homogeneous isotropic one through appropriate three observables, if the perturbations are adiabatic.

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“…The difference between Ω Λ0 and Ω dis Λ0 can be regarded as a systematic error in estimation of Λ due to the spherical inhomogeneity as is discussed in refs. [27,28]. In order to estimate the magnitude of the systematic error due to possible inhomogeneity, we calculate the amplitude of the inhomogeneity for several values of Ω Λ0 /Ω dis Λ0 .…”

Section: Introductionmentioning

confidence: 99%

Inverse construction of the ΛLTB model from a distance-redshift relation

Tokutake

Yoo

2016

J. Cosmol. Astropart. Phys.

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Spherically symmetric dust universe models with a positive cosmological constant Λ, known as Λ-Lemaître-Tolman-Bondi(ΛLTB) models, are considered. We report a method to construct the ΛLTB model from a given distance-redshift relation observed at the symmetry center. The spherical inhomogeneity is assumed to be composed of growing modes. We derive a set of ordinary differential equations for three functions of the redshift, which specify the spherical inhomogeneity. Once a distanceredshift relation is given, with careful treatment of possible singular points, we can uniquely determine the model by solving the differential equations for each value of Λ. As a demonstration, we fix the distance-redshift relation as that of the flat ΛCDM model with (Ω dis m0 , Ω dis Λ0 ) = (0.3, 0.7), where Ω dis m0 and Ω dis Λ0 are the normalized matter density and the cosmological constant, respectively. Then, we construct the ΛLTB model for several values of Ω Λ0 := Λ/(3H 2 0 ), where H 0 is the present Hubble parameter observed at the symmetry center. We obtain void structure around the symmetry center for Ω Λ0 < Ω dis Λ0 . We show the relation between the ratio Ω Λ0 /Ω dis Λ0 and the amplitude of the inhomogeneity. * Electronic address: tokutake@gravity.phys.nagoya-u.ac.jp † Electronic address: yoo@gravity.phys.nagoya-u.ac.jp 2

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Systematic error due to isotropic inhomogeneities

Cited by 3 publications

References 35 publications

Observational constraint on spherical inhomogeneity with CMB and local Hubble parameter

Observational constraint on spherical inhomogeneity with CMB and local Hubble parameter

Can we remove the systematic error due to isotropic inhomogeneities?

Inverse construction of the ΛLTB model from a distance-redshift relation

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