scholarly journals Low-redshift tests of Newtonian cosmologies with a time-varying gravitational constant

2020 ◽  
Vol 497 (4) ◽  
pp. 4407-4415
Author(s):  
Ekim Taylan Hanımeli ◽  
Isaac Tutusaus ◽  
Brahim Lamine ◽  
Alain Blanchard
Keyword(s):  
Dark Energy ◽  
Gravitational Constant ◽  
Second Law ◽  
Time Varying ◽  
Acoustic Oscillations ◽  
Cosmological Observations ◽  
Type Ia ◽  
Varying Gravitational Constant ◽  
Ia Supernovae ◽  
Intrinsic Luminosity

ABSTRACT In this work, we investigate Newtonian cosmologies with a time-varying gravitational constant, G(t). We examine whether such models can reproduce the low-redshift cosmological observations without a cosmological constant, or any other sort of explicit dark energy fluid. Starting with a modified Newton’s second law, where G is taken as a function of time, we derive the first Friedmann–Lemaître equation, where a second parameter, G*, appears as the gravitational constant. This parameter is related to the original G from the second law, which remains in the acceleration equation. We use this approach to reproduce various cosmological scenarios that are studied in the literature, and we test these models with low-redshift probes: type-Ia supernovae (SNIa), baryon acoustic oscillations, and cosmic chronometers, taking also into account a possible change in the supernovae intrinsic luminosity with redshift. As a result, we obtain several models with similar χ2 values as the standard ΛCDM cosmology. When we allow for a redshift-dependence of the SNIa intrinsic luminosity, a model with a G exponentially decreasing to zero while remaining positive (model 4) can explain the observations without acceleration. When we assume no redshift-dependence of SNIa, the observations favour a negative G at large scales, while G* remains positive for most of these models. We conclude that these models offer interesting interpretations to the low-redshift cosmological observations, without needing a dark energy term.

scholarly journals COSMIC CONSTRAINT ON RICCI DARK ENERGY MODEL

2009 ◽  
Vol 24 (17) ◽  
pp. 1355-1360 ◽  
Author(s):  
LIXIN XU ◽  
WENBO LI ◽  
JIANBO LU
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Energy Model ◽  
Likelihood Method ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Ricci Dark Energy ◽  
Type Ia ◽  
Ia Supernovae ◽  
Best Fit

In this paper, a holographic dark energy model, dubbed Ricci dark energy, is confronted with cosmological observational data from type Ia Supernovae (SN Ia), baryon acoustic oscillations (BAO) and cosmic microwave background (CMB). By using maximum likelihood method, we found that Ricci dark energy model is a viable candidate of dark energy model with the best fit parameters: Ωm0 = 0.34 ± 0.04, α = 0.38 ± 0.03 with 1σ error. Here, α is a dimensionless parameter related to Ricci dark energy ρR and Ricci scalar R, i.e. ρR ∝ αR.

CONSTRAINTS ON VARIABLE CHAPLYGIN GAS MODEL FROM TYPE IA SUPERNOVAE AND BARYON ACOUSTIC OSCILLATIONS

2010 ◽  
Vol 25 (09) ◽  
pp. 737-747 ◽  
Author(s):  
JIANBO LU ◽  
LIXIN XU
Keyword(s):  
Dark Energy ◽  
Chaplygin Gas ◽  
Model Parameters ◽  
Type Ia Supernovae ◽  
Acoustic Oscillations ◽  
Confidence Levels ◽  
Energy Models ◽  
Type Ia ◽  
Baryon Acoustic Oscillations ◽  
Ia Supernovae

We apply the type Ia supernovae union dataset and the baryon acoustic oscillations data at z = 0.2 and z = 0.35 to constrain variable Chaplygin gas (VCG) model as the unification of dark matter and dark energy. It is shown that the confidence levels for VCG model parameters are [Formula: see text]. And it indicates that the values of transition redshift and current deceleration parameter are: [Formula: see text]. In addition, we plot the evolution trajectory of the VCG model in the statefinder parameter r–s plane and show the discrimination between this scenario and other dark energy models.

scholarly journals Update constraints on neutrino mass and mass hierarchy in light of dark energy models

2020 ◽  
Vol 29 (13) ◽  
pp. 2050088
Author(s):  
Zhenjie Liu ◽  
Haitao Miao
Keyword(s):  
Dark Energy ◽  
Neutrino Masses ◽  
Mass Hierarchy ◽  
Acoustic Oscillations ◽  
Energy Models ◽  
Background Data ◽  
Type Ia ◽  
Model Independent ◽  
Degenerate Neutrino ◽  
Ia Supernovae

Combining cosmic microwave (CMB) background data from Planck satellite data, Baryon Acoustic Oscillations (BAO) measurements and Type Ia supernovae (SNe Ia) data, we obtain the bounds on total neutrino masses [Formula: see text] with the approximation of degenerate neutrino masses and for three dark energy models: the cosmological constant ([Formula: see text]CDM) model, a phenomenological emergent dark energy (PEDE) model and a model-independent quintessential parametrization (HBK). The bounds on the sum of neutrino masses [Formula: see text] depend on the dark energy (DE) models. In the HBK model, we confirm the conclusion from some previous work that the quintessence prior of DE tends to tighten the cosmological constraint on [Formula: see text]. On the other hand, the PEDE model leads to larger [Formula: see text] and a nonzero lower bound. Besides, we also explore the correlation between three different neutrino hierarchies and DE models.

scholarly journals CMB Tensions with Low-Redshift H0 and S8 Measurements: Impact of a Redshift-Dependent Type-Ia Supernovae Intrinsic Luminosity

Symmetry ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 986 ◽  
Author(s):  
Matteo Martinelli ◽  
Isaac Tutusaus
Keyword(s):  
Dark Energy ◽  
Formation Rate ◽  
Type Ia Supernovae ◽  
Late Time ◽  
Systematic Uncertainties ◽  
Type Ia ◽  
Systematic Effects ◽  
Ia Supernovae ◽  
The Impact ◽  
Intrinsic Luminosity

With the recent increase in precision of our cosmological datasets, measurements of Λ CDM model parameter provided by high- and low-redshift observations started to be in tension, i.e., the obtained values of such parameters were shown to be significantly different in a statistical sense. In this work we tackle the tension on the value of the Hubble parameter, H 0 , and the weighted amplitude of matter fluctuations, S 8 , obtained from local or low-redshift measurements and from cosmic microwave background (CMB) observations. We combine the main approaches previously used in the literature by extending the cosmological model and accounting for extra systematic uncertainties. With such analysis we aim at exploring non standard cosmological models, implying deviation from a cosmological constant driven acceleration of the Universe expansion, in the presence of additional uncertainties in measurements. In more detail, we reconstruct the Dark Energy equation of state as a function of redshift, while we study the impact of type-Ia supernovae (SNIa) redshift-dependent astrophysical systematic effects on these tensions. We consider a SNIa intrinsic luminosity dependence on redshift due to the star formation rate in its environment, or the metallicity of the progenitor. We find that the H 0 and S 8 tensions can be significantly alleviated, or even removed, if we account for varying Dark Energy for SNIa and CMB data. However, the tensions remain when we add baryon acoustic oscillations (BAO) data into the analysis, even after the addition of extra SNIa systematic uncertainties. This points towards the need of either new physics beyond late-time Dark Energy, or other unaccounted systematic effects (particulary in BAO measurements), to fully solve the present tensions.

scholarly journals Bayesian comparison of interacting modified holographic Ricci dark energy scenarios

2021 ◽  
Vol 81 (1) ◽  
Author(s):  
Antonella Cid ◽  
Carlos Rodriguez-Benites ◽  
Mauricio Cataldo ◽  
Gonzalo Casanova
Keyword(s):  
Dark Energy ◽  
Hubble Constant ◽  
Joint Analysis ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Ricci Dark Energy ◽  
Type Ia ◽  
Cosmological Data ◽  
Ia Supernovae ◽  
Local Value

AbstractWe perform a Bayesian model selection analysis for interacting scenarios of dark matter and modified holographic Ricci dark energy (MHRDE) with linear interacting terms. We use a combination of some of the latest cosmological data such as type Ia supernovae, cosmic chronometers, the local value of the Hubble constant, baryon acoustic oscillations measurements and cosmic microwave background through the angular scale of the sound horizon at last scattering. We find moderate/strong evidence against all the MHRDE interacting scenarios studied with respect to $$\Lambda $$ Λ CDM when the full joint analysis is considered.

scholarly journals Precise astronomical flux calibration and its impact on studying the nature of the dark energy

2015 ◽  
Vol 30 (40) ◽  
pp. 1530030 ◽  
Author(s):  
Christopher W. Stubbs ◽  
Yorke J. Brown
Keyword(s):  
Dark Energy ◽  
Survey Methodology ◽  
Atmospheric Transmission ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
Accelerating Expansion ◽  
Systematic Uncertainties ◽  
Type Ia ◽  
Ia Supernovae ◽  
Flux Calibration

Measurements of the luminosity of Type Ia supernovae versus redshift provided the original evidence for the accelerating expansion of the Universe and the existence of dark energy. Despite substantial improvements in survey methodology, systematic uncertainty in flux calibration dominates the error budget for this technique, exceeding both statistics and other systematic uncertainties. Consequently, any further collection of Type Ia supernova data will fail to refine the constraints on the nature of dark energy unless we also improve the state of the art in astronomical flux calibration to the order of 1%. We describe how these systematic errors arise from calibration of instrumental sensitivity, atmospheric transmission and Galactic extinction, and discuss ongoing efforts to meet the 1% precision challenge using white dwarf stars as celestial standards, exquisitely calibrated detectors as fundamental metrologic standards, and real-time atmospheric monitoring.

Cosmological constraints on the variable modified Chaplygin gas model by using MCMC approach

2015 ◽  
Vol 24 (08) ◽  
pp. 1550059 ◽  
Author(s):  
Jian-bin Chen ◽  
Zhen-qi Liu ◽  
Lili Xing
Keyword(s):  
Apparent Horizon ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Mean Values ◽  
Cosmological Constraints ◽  
Variable Modified Chaplygin Gas ◽  
Type Ia ◽  
Ia Supernovae

We investigate the cosmological constraints on the variable modified Chaplygin gas (VMCG) model from the latest observational data: Union2 dataset of Type Ia supernovae (SNIa), the observational Hubble data (OHD), the baryon acoustic oscillations (BAO) and the cosmic microwave background (CMB) data. By using the Markov chain Monte Carlo (MCMC) method, we obtain the mean values of parameters in the flat model: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. Furthermore, we investigate the thermodynamical properties of VMCG model at apparent horizon, event horizon and particle horizon respectively.

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.

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