scholarly journals Defying the laws of gravity I: model-independent reconstruction of the Universe expansion from growth data

2020 ◽  
Vol 494 (1) ◽  
pp. 819-826 ◽  
Author(s):  
Benjamin L’Huillier ◽  
Arman Shafieloo ◽  
David Polarski ◽  
Alexei A Starobinsky
Keyword(s):  
Type Ia Supernovae ◽  
Growth Data ◽  
Growth History ◽  
Type Ia ◽  
History Of ◽  
Space Distortion ◽  
Model Independent ◽  
Ia Supernovae ◽  
The Universe

ABSTRACT Using redshift space distortion data, we perform model-independent reconstructions of the growth history of matter inhomogeneity in the expanding Universe using two methods: crossing statistics and Gaussian processes. We then reconstruct the corresponding history of the Universe background expansion and fit it to Type Ia supernovae data, putting constraints on (Ωm, 0, σ8, 0). The results obtained are consistent with the concordance flat-ΛCDM model and General Relativity as the gravity theory given the current quality of the inhomogeneity growth data.

scholarly journals Model-independent reconstruction of the expansion history of the Universe from Type Ia supernovae

2011 ◽  
Vol 419 (1) ◽  
pp. 513-521 ◽  
Author(s):  
S. Benitez-Herrera ◽  
F. Röpke ◽  
W. Hillebrandt ◽  
C. Mignone ◽  
M. Bartelmann ◽  
...  
Keyword(s):  
Type Ia Supernovae ◽  
Type Ia ◽  
History Of ◽  
Model Independent ◽  
Ia Supernovae ◽  
The Universe

scholarly journals Model-independent cosmic acceleration and redshift-dependent intrinsic luminosity in type-Ia supernovae

2019 ◽  
Vol 625 ◽  
pp. A15 ◽  
Author(s):  
I. Tutusaus ◽  
B. Lamine ◽  
A. Blanchard
Keyword(s):  
Spline Interpolation ◽  
High Redshift ◽  
Cosmic Acceleration ◽  
Expansion Rate ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Model Independent ◽  
Ia Supernovae ◽  
The Universe ◽  
Intrinsic Luminosity

Context. The cosmological concordance model (ΛCDM) is the current standard model in cosmology thanks to its ability to reproduce the observations. The first observational evidence for this model appeared roughly 20 years ago from the type-Ia supernovae (SNIa) Hubble diagram from two different groups. However, there has been some debate in the literature concerning the statistical treatment of SNIa, and their stature as proof of cosmic acceleration. Aims. In this paper we relax the standard assumption that SNIa intrinsic luminosity is independent of redshift, and examine whether it may have an impact on our cosmological knowledge and more precisely on the accelerated nature of the expansion of the universe. Methods. To maximise the scope of this study, we do not specify a given cosmological model, but we reconstruct the expansion rate of the universe through a cubic spline interpolation fitting the observations of the different cosmological probes: SNIa, baryon acoustic oscillations (BAO), and the high-redshift information from the cosmic microwave background (CMB). Results. We show that when SNIa intrinsic luminosity is not allowed to vary as a function of redshift, cosmic acceleration is definitely proven in a model-independent approach. However, allowing for redshift dependence, a nonaccelerated reconstruction of the expansion rate is able to fit, at the same level of ΛCDM, the combination of SNIa and BAO data, both treating the BAO standard ruler rd as a free parameter (not entering on the physics governing the BAO), and adding the recently published prior from CMB observations. We further extend the analysis by including the CMB data. In this case we also consider a third way to combine the different probes by explicitly computing rd from the physics of the early universe, and we show that a nonaccelerated reconstruction is able to nicely fit this combination of low- and high-redshift data. We also check that this reconstruction is compatible with the latest measurements of the growth rate of matter perturbations. We finally show that the value of the Hubble constant (H0) predicted by this reconstruction is in tension with model-independent measurements. Conclusions. We present a model-independent reconstruction of a nonaccelerated expansion rate of the universe that is able to fit all the main background cosmological probes nicely. However, the predicted value of H0 is in tension with recent direct measurements. Our analysis points out that a final reliable and consensual value for H0 is critical to definitively prove cosmic acceleration in a model-independent way.

scholarly journals Testing the isotropy of the Universe with Type Ia supernovae in a model-independent way

2017 ◽  
Vol 474 (3) ◽  
pp. 3516-3522 ◽  
Author(s):  
Yu-Yang Wang ◽  
F Y Wang
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Light Curve ◽  
Type Ia Supernovae ◽  
Anisotropic Universe ◽  
Preferred Direction ◽  
Type Ia ◽  
Model Independent ◽  
Ia Supernovae ◽  
The Universe

Abstract In this paper, we study an anisotropic universe model with Bianchi-I metric using Joint light-curve analysis (JLA) sample of Type Ia supernovae (SNe Ia). Because light-curve parameters of SNe Ia vary with different cosmological models and SNe Ia samples, we fit the SNe Ia light-curve parameters and cosmological parameters simultaneously employing Markov chain Monte Carlo method. Therefore, the results on the amount of deviation from isotropy of the dark energy equation of state (δ), and the level of anisotropy of the large-scale geometry (Σ0) at present, are totally model-independent. The constraints on the skewness and cosmic shear are −0.101 < δ < 0.071 and −0.007 < Σ0 < 0.008. This result is consistent with a standard isotropic universe (δ = Σ0 = 0). However, a moderate level of anisotropy in the geometry of the Universe and the equation of state of dark energy, is allowed. Besides, there is no obvious evidence for a preferred direction of anisotropic axis in this model.

Probing the nature of dark energy

2015 ◽  
Vol 30 (28n29) ◽  
pp. 1545010
Author(s):  
Yun Wang
Keyword(s):  
Dark Energy ◽  
Large Scale ◽  
Structure Type ◽  
Type Ia Supernovae ◽  
Galaxy Clustering ◽  
Growth History ◽  
Type Ia ◽  
History Of ◽  
Expansion Of The Universe ◽  
Ia Supernovae

The cause for the observed acceleration in the expansion of the Universe is unknown, and referred to as “dark energy” for convenience. Dark energy could be an unknown energy component, or a modification of Einstein’s general relativity. This dictates the measurements that are optimal in unveiling the nature of dark energy: the cosmic expansion history, and the growth history of cosmic large scale structure. Type Ia supernovae, galaxy clustering, and weak lensing are generally considered the most powerful observational probes of dark energy. I will examine Type Ia supernovae and galaxy clustering as dark energy probes, and discuss the recent results and future prospects.

scholarly journals SNe Ia as a cosmological probe

2015 ◽  
Vol 24 (14) ◽  
pp. 1530029 ◽  
Author(s):  
Xiangcun Meng ◽  
Yan Gao ◽  
Zhanwen Han
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
High Redshift ◽  
Type Ia Supernovae ◽  
Analysis Techniques ◽  
Type Ia ◽  
History Of ◽  
Acceleration Of The Universe ◽  
Ia Supernovae ◽  
The Universe

Type Ia supernovae (SNe Ia) luminosities can be corrected in order to render them useful as standard candles that are able to probe the expansion history of the universe. This technique was successfully applied to discover the present acceleration of the universe. As the number of SNe Ia observed at high redshift increases and analysis techniques are perfected, people aim to use this technique to probe the equation-of-state of the dark energy (EOSDE). Nevertheless, the nature of SNe Ia progenitors remains controversial and concerns persist about possible evolution effects that may be larger and harder to characterize than the more obvious statistical uncertainties.

scholarly journals Imprint of modified Einstein’s gravity on white dwarfs: Unifying Type Ia supernovae

2015 ◽  
Vol 24 (12) ◽  
pp. 1544026 ◽  
Author(s):  
Upasana Das ◽  
Banibrata Mukhopadhyay
Keyword(s):  
White Dwarfs ◽  
Evolutionary History ◽  
Type Ia Supernovae ◽  
Single Model ◽  
Model Parameter ◽  
Type Ia ◽  
History Of ◽  
Ia Supernovae ◽  
First Time ◽  
The Universe

We establish the importance of modified Einstein’s gravity (MG) in white dwarfs (WDs) for the first time in the literature. We show that MG leads to significantly sub- and super-Chandrasekhar limiting mass WDs, depending on a single model parameter. However, conventional WDs on approaching Chandrasekhar’s limit are expected to trigger Type Ia supernovae (SNeIa), a key to unravel the evolutionary history of the universe. Nevertheless, observations of several peculiar, under- and over-luminous SNeIa argue for the limiting mass widely different from Chandrasekhar’s limit. Explosions of MG induced sub- and super-Chandrasekhar limiting mass WDs explain under- and over-luminous SNeIa respectively, thus unifying these two apparently disjoint sub-classes. Our discovery questions both the global validity of Einstein’s gravity and the uniqueness of Chandrasekhar’s limit.

scholarly journals Windowing artefacts likely account for recent claimed detection of oscillating cosmic scale factor

2020 ◽  
Vol 498 (4) ◽  
pp. 5512-5516
Author(s):  
Sasha R Brownsberger ◽  
Christopher W Stubbs ◽  
Daniel M Scolnic
Keyword(s):  
Type Ia Supernovae ◽  
Data Sets ◽  
Analysis Method ◽  
Data Set ◽  
Statistical Fluctuations ◽  
Data Analyses ◽  
Type Ia ◽  
History Of ◽  
Ia Supernovae ◽  
The Universe

ABSTRACT Using the Pantheon data set of Type Ia supernovae, a recent publication (R20 in this work) reports a  2σ detection of oscillations in the expansion history of the Universe. The study conducted by R20 is wholly worthwhile. However, we demonstrate that there is a $\gt 10{{\ \rm per\ cent}}$ chance of statistical fluctuations in the Pantheon data producing a false oscillatory signal larger than the oscillatory signal that R20 report. Their results are a less than 2σ detection. Applying the R20 methodology to simulated Pantheon data, we determine that these oscillations could arise due to analysis artefacts. The uneven spacing of Type Ia supernovae in redshift space and the complicated analysis method of R20 impose a structured throughput function. When analysed with the R20 prescription, about $11{{\ \rm per\ cent}}$ of artificial ΛCDM data sets produce a stronger oscillatory signal than the actual Pantheon data. Our results underscore the importance of understanding the false ‘signals’ that can be introduced by complicated data analyses.

The Berkeley-AAO Distant Supernova Search

1991 ◽  
Vol 9 (2) ◽  
pp. 261-265 ◽  
Author(s):  
W. J. Couch ◽  
S. Perlmutter ◽  
H. J. M. Newburg ◽  
C. Pennypacker ◽  
G. Goldhaber ◽  
...  
Keyword(s):  
Mass Density ◽  
Type Ia Supernovae ◽  
Standard Candle ◽  
Type Ia ◽  
Ia Supernovae ◽  
The Universe

AbstractA search for Type Ia supernovae at cosmological distances is being undertaken in an attempt to exploit their standard candle property to constrain the mass density of the universe. We describe the rationale for such a program, the observational approach and strategy taken, and the progress made to date. The science that is being generated by the project in additional to supernova detection is also discussed briefly.

scholarly journals Do Type Ia Supernovae Provide Direct Evidence for Past Deceleration of the Universe?

2002 ◽  
Vol 569 (1) ◽  
pp. 18-22 ◽  
Author(s):  
Michael S. Turner ◽  
Adam G. Riess
Keyword(s):  
Direct Evidence ◽  
Type Ia Supernovae ◽  
Type Ia ◽  
Ia Supernovae ◽  
The Universe

scholarly journals RECONSTRUCTION OF 5D COSMOLOGICAL MODELS FROM RECENT OBSERVATIONS

2007 ◽  
Vol 16 (10) ◽  
pp. 1573-1579
Author(s):  
CHENGWU ZHANG ◽  
LIXIN XU ◽  
YONGLI PING ◽  
HONGYA LIU
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Solution ◽  
Type Ia Supernovae ◽  
Shift Parameter ◽  
Type Ia ◽  
Ia Supernovae ◽  
Best Fit ◽  
The Universe

We use a parameterized equation of state (EOS) of dark energy to a 5D Ricci-flat cosmological solution and suppose the universe contains two major components: dark matter and dark energy. Using the recent observational datasets: the latest 182 type Ia Supernovae Gold data, the three-year WMAP CMB shift parameter and the SDSS baryon acoustic peak, we obtain the best fit values of the EOS and two major components' evolution. We find that the best fit EOS crosses -1 in the near past where z ≃ 0.07, the present best fit value of wx(0) < -1 and for this model, the universe experiences the acceleration at about z ≃ 0.5.

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