Searching for a cosmological preferred axis in complicated class of cosmological models: case study f (R, T ) model

Salehi, Amin; Aftabi, Sajjad

doi:10.1007/jhep09(2016)140

Cited by 17 publications

(12 citation statements)

References 68 publications

(129 reference statements)

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“…As standard candles, the supernovae of type Ia (SNe Ia) have been used to investigate the accelerating expansion of the Universe (Riess et al 1998;Perlmutter et al 1999), and the possible deviations from the isotropic universe ( Heneka et al 2014;Bengaly et al 2015;Li et al 2015;Javanmardi et al 2015;Lin et al 2016a,b;Salehi & Aftabi 2016;Salehi & Setare 2017;Li & Lin 2017;Ghodsi et al 2017;Wang & Wang 2018;Andrade et al 2018b;Chang et al 2018a;Deng & Wei 2018b), with the datasets given by the Union2 sample (Amanullah et al 2010), the Union2.1 sample (Suzuki et al 2012) and the "Joint Lightcurve Analysis" (JLA) sample (Betoule et al 2014). Antoniou & Perivolaropoulos (2010) first used the hemisphere comparison (HC) method to the Union2 sample and they found a certain cosmological preferred direction with maximum accelerating expansion rate.…”

Section: Introductionmentioning

confidence: 99%

Anisotropy of the Universe via the Pantheon supernovae sample revisited

Zhao

Zhou

Chang

2019

Monthly Notices of the Royal Astronomical Society

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We employ the hemisphere comparison (HC) method and the dipole fitting (DF) method to investigate the cosmic anisotropy in the recently released Pantheon sample of type Ia supernovae (SNe Ia) and five combinations among Pantheon. For the HC method, we find the maximum anisotropy level in the full Pantheon sample is AL max = 0.361 ± 0.070 and corresponding direction (l, b) = (123.05A robust check shows the statistical significance of maximum anisotropy level is about 2.1σ. We also find that the Low-z and SNLS subsamples have decisive impact on the overall anisotropy while other three subsamples have little impact. Moreover, the anisotropy level map significantly rely on the inhomogeneous distribution of SNe Ia in the sky. For the DF method, we find the dipole anisotropy in the Pantheon sample is very weak. The dipole magnitude is constrained to be less than 1.16 × 10 −3 at 95% confidence level. However, the dipole direction is well inferred by MCMC method and it points towards (l, b) = (306.00 •+82.95 • −125.01 • , −34.20 •+16.82 • −54.93 • ). This direction is very close to the axial direction to the plane of SDSS subsample. It may imply that SDSS subsample is the decisive part to the dipole anisotropy in the full Pantheon sample. All these facts imply that the cosmic anisotropy found in Pantheon sample significantly rely on the inhomogeneous distribution of SNe Ia in the sky. More homogeneous distribution of SNe Ia is necessary to search for a more convincing cosmic anisotropy.

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Section: Introductionmentioning

confidence: 99%

Anisotropy of the Universe via the Pantheon supernovae sample revisited

Zhao

Zhou

Chang

2019

Monthly Notices of the Royal Astronomical Society

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“…If such a cosmological axis exists, then universe undergoes an anisotropic expansion and the observed acceleration is maximized in one direction. The Union2 data are widely used as the standard candle to test possible anisotropy of the universe [10,16,17,26,29,32,68,72,[77][78][79][80][81][82][83][84][85][86][87][88][89]. The consensus of these studies is that there is an asymmetry axis pointing in a preferred direction.…”

Section: Discussionmentioning

confidence: 99%

Are Type Ia supernova powerful tool to detect anisotropic expansion of the Universe?

et al. 2020

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In this paper, we present a detailed analysis of the dark energy dipole using Union2, Pantheon and GRB dataset in Chameleon and Teleparallel dark energy models, in comparison with $$\Lambda $$ΛCDM. Both models are extensively studied in recent years and our result shows that with Union2 and Pantheon data, the preferred direction of the anisotropy in both models are very close to each other as well as with those obtained in some studies for $$\Lambda $$ΛCDM. However, when the models fitted with a combination of Union 2 and GRB, the statistical analysis slightly favors the Chameleon cosmology over Teleparallel gravity, with the maximum anisotropic direction of $$(l = 330^{+30}_{-28}$$(l=330-28+30, $$b = -15^{+23}_{-25})$$b=-15-25+23) in galactic coordinate system, comparable with $$\alpha $$α-dipole result in Keck-VLT data and LCDM.

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“…We have also used the relation g αβ R μβαν = −g αβ R βμαν = −R μν in the last step of Eq. (53). Note that the above two identities are valid in both the metric and the Palatini formulations [84].…”

Section: The Divergence Of the Matter Energy-momentum Tensormentioning

confidence: 95%

Palatini formulation of f(R, T) gravity theory, and its cosmological implications

Jimin¹,

Li²,

Harkó³

et al. 2018

Eur. Phys. J. C

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We consider the Palatini formulation of f (R, T ) gravity theory, in which a non-minimal coupling between the Ricci scalar and the trace of the energy-momentum tensor is introduced, by considering the metric and the affine connection as independent field variables. The field equations and the equations of motion for massive test particles are derived, and we show that the independent connection can be expressed as the Levi-Civita connection of an auxiliary, energy-momentum trace dependent metric, related to the physical metric by a conformal transformation. Similar to the metric case, the field equations impose the nonconservation of the energy-momentum tensor. We obtain the explicit form of the equations of motion for massive test particles in the case of a perfect fluid, and the expression of the extra force, which is identical to the one obtained in the metric case. The thermodynamic interpretation of the theory is also briefly discussed. We investigate in detail the cosmological implications of the theory, and we obtain the generalized Friedmann equations of the f (R, T ) gravity in the Palatini formulation. Cosmological models with Lagrangians of the type f = R − α 2 /R + g(T ) and f = R + α 2 R 2 + g(T ) are investigated. These models lead to evolution equations whose solutions describe accelerating Universes at late times.

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Searching for a cosmological preferred axis in complicated class of cosmological models: case study f (R, T ) model

Cited by 17 publications

References 68 publications

Anisotropy of the Universe via the Pantheon supernovae sample revisited

Anisotropy of the Universe via the Pantheon supernovae sample revisited

Are Type Ia supernova powerful tool to detect anisotropic expansion of the Universe?

Palatini formulation of f(R, T) gravity theory, and its cosmological implications

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