本文提出了一个新的与模型无关的距离-对偶关系的宇宙学检验，η= D_{L}（z）（1+z）^{-2}/ D_{A}（z）=1，其中D_{L}和D_{A}分别是光度和角直径距离。对于$D_L$，我们考虑从Constitution数据（2009）中获取的两个Ia型SNe子样本，而$D_A$距离由De Fillipis等人（2005）和Bonamente等人（2006）通过结合Sunyaev-Zeldovich效应（SZE）和X射线表面亮度编制的两个星系团样本提供。每个子样本的超新星Ia红移都经过仔细选择，以与相关星系团样本的红移相一致（Δz<0.005），从而可以直接测试DD关系。由于对于非常低的红移，D_{A}（z）\approxeq D_{L}（z），我们通过假设$η$是由两个不同表达式参数化的红移的函数来测试DD关系：η（z）= 1 + η_{0}z和η（z）= 1 + η_{0}z/（1+z），其中η_0是量化可能偏离互易关系的严格有效性的恒定参数（η_0=0）。在最好的情况下（线性参数化），我们得到η_{0} =-0.28 ^{+ 0.44}_{-0.44}（2σ $, statistical + systematic errors) for de Fillipis et al. sample (eliptical geometry), a result only marginally compatible with the DD relation. However, for Bonamente et al. sample (spherical geometry) the constraint is η_{0} = -0.42^{+ 0.34}_{- 0.34} (3σ$，统计+系统误差），这显然与对偶距离关系不相容。
英文摘要：
In this letter we propose a new and model-independent cosmological test for the distance-duality (DD) relation, η=D_{L}(z)(1+z)^{-2}/D_{A}(z)=1, where D_{L} and D_{A} are, respectively, the luminosity and angular diameter distances. For $D_L$ we consider two sub-samples of SNe type Ia taken from Constitution data (2009) whereas $D_A$ distances are provided by two samples of galaxy clusters compiled by De Fillipis et al. (2005) and Bonamente et al. (2006) by combining Sunyaev-Zeldovich effect (SZE) and X-ray surface brightness. The SNe Ia redshifts of each sub-sample were carefully chosen to coincide with the ones of the associated galaxy cluster sample (Δz<0.005) thereby allowing a direct test of DD relation. Since for very low redshifts, D_{A}(z) \approxeq D_{L}(z), we have tested the DD relation by assuming that $η$ is a function of the redshift parametrized by two different expressions: η(z) = 1 + η_{0}z and η(z) = 1 + η_{0}z/(1+z), where η_0 is a constant parameter quantifying a possible departure from the strict validity of the reciprocity relation (η_0=0). In the best scenario (linear parametrization) we obtain η_{0} = -0.28^{+ 0.44}_{- 0.44} (2σ$, statistical + systematic errors) for de Fillipis et al. sample (eliptical geometry), a result only marginally compatible with the DD relation. However, for Bonamente et al. sample (spherical geometry) the constraint is η_{0} = -0.42^{+ 0.34}_{- 0.34} (3σ$, statistical + systematic errors) which is clearly incompatible with the duality-distance relation.
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An important problem in precision cosmology is the determination of the effects of averaging and backreaction on observational predictions, particularly in view of the wealth of new observational data and improved statistical techniques. In this paper, we discuss the observational viability of a class of averaged cosmologies which consist of a simple parametrized phenomenological two-scale backreaction model with decoupled spatial curvature parameters. We perform a Bayesian model selection analysis and find that this class of averaged phenomenological cosmological models is favored with respec…
The large-number hypothesis conjectures that fundamental constants may vary. Accordingly, the spacetime variation of fundamental constants has been an active subject of research for decades. Recently, using data obtained with large telescopes a phenomenological model in which the fine structure constant might vary spatially has been proposed. We test whether this hypothetical spatial variation of α, which follows a dipole law, is compatible with the data of distant thermonuclear supernovae. Unlike previous works, in our calculations we consider not only the variation of the luminosity distance…
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The distance-duality relation (DDR) between the luminosity distance $D_L$ and the angular diameter distance $D_A$ is viewed as a powerful tool for testing for the opacity of the Universe, being independent of any cosmological model. It was applied by many authors, who mostly confirm its validity and report a negligible opacity of the Universe. Nevertheless, a thorough analysis reveals that applying the DDR in cosmic opacity tests is tricky. Its applicability is strongly limited because of a non-unique interpretation of the $D_L$ data in terms of cosmic opacity and a rather low accuracy and def…
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Since Dirac stated his Large Number Hypothesis the space-time variation of fundamental constants has been an active subject of research. Here we analyze the possible spatial variation of two fundamental constants: the fine structure constant α and the speed of light c. We study the effects of such variations on the luminosity distance and on the peak luminosity of Type Ia supernovae (SNe Ia). For this, we consider the change of each fundamental constant separately and discuss a dipole model for its variation. Elaborating upon our previous work, we take into account the variation of the peak lu…
In the upcoming decade cadenced wide-field imaging surveys will increase the number of identified $z<0.3$ Type~Ia supernovae (SNe~Ia) from the hundreds to the hundreds of thousands. The increase in the number density and solid-angle coverage of SNe~Ia, in parallel with improvements in the standardization of their absolute magnitudes, now make them competitive probes of the growth of structure and hence of gravity. The peculiar velocity power spectrum is sensitive to the growth index $γ$, which captures the effect of gravity on the linear growth of structure through the relation $f=Ω_M^γ$. We p…
Testing the Distance Duality Relation with Cosmological Observations at high Redshift using Artificial Neural Network
Guizhou Normal University（贵州师范大学）；Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；Hunan Normal University（湖南师范大学）；Hunan University of Science and Technology（湖南科技大学）
In modern cosmology, an important task is investigating whether there exists a signal of modified gravity in the universe. Due to the limited resolutions and sensitivities of facilities, current observations can not detect any signal of modified gravity. As a consequence, it is urgent to predict the constraining power of future cosmological surveys on modified gravity. We constrain the Hu-Sawicki $f(R)$ gravity with eight future mainstream probes encompassing 21 cm intensity mapping, HI galaxy, cosmic microwave background, optical galaxy, weak lensing, galaxy clustering, type Ia supernovae and…
The Hubble law (HL) governs the low-redshift (low-z) evolution of the distance of an object. However, there is a lack of an investigation of its validity and effective radius for a long time, since the low-z background data with a high precision is scarce. The latest Type Ia supernovae sample Pantheon+ having a significant increase of low-z data provides an excellent opportunity to test the HL. We propose a generalized HL and implement the first modern test of the HL with Pantheon+. We obtain the constraint on the deviation parameter $α=1.00118\pm0.00044$, confirm the validity of linear HL wit…
In this paper, we test the cosmic distance duality (CDD) relation using the luminosity distances from joint light-curve analysis (JLA) type Ia supernovae (SNe Ia) sample and angular diameter distance sample from galaxy clusters. The $R_h=ct$ and $Λ$CDM models are considered. In order to compare the two models, we constrain the CCD relation and the SNe Ia light-curve parameters simultaneously. Considering the effects of Hubble constant, we find that $η\equiv D_A(1+z)^2/D_L=1$ is valid at the 2$σ$ confidence level in both models with $H_0 = 67.8\pm0.9$ km/s/Mpc. However, the CDD relation is vali…
Consistency testing for invariance of the speed of light at different redshifts: the newest results from strong lensing and type Ia supernovae observations
Under very general assumptions of metric theory of spacetime, photons traveling along null geodesics and photon number conservation, two observable concepts of cosmic distance, i.e. the angular diameter and the luminosity distances are related to each other by the so-called distance duality relation (DDR) $D^L=D^A(1+z)^2$. Observational validation of this relation is quite important because any evidence of its violation could be a signal of new physics. In this paper we introduce a new method to test DDR based on strong gravitational lensing systems and type Ia supernovae under a flat universe…
We constrain deviations of the form $T\propto (1+z)^{1+ε}$ from the standard redshift-temperature relation, corresponding to modifying distance duality as $D_L=(1+z)^{2(1+ε)} D_A$. We consider a consistent model, in which both the background and perturbation equations are changed. For this purpose, we introduce a species of dark radiation particles to which photon energy density is transferred, and assume $ε\ge0$. The Planck 2015 release high multipole temperature plus low multipole data give the limit $ε<4.5\times 10^{-3}$ at 95% C.L. The main obstacle to improving this CMB-only result is str…
