Hubble Data Research Articles

Isotropization of symmetric teleparallel gravity with observational constraints

In this paper, we examine the homogeneous and isotropic flat Universe in the frame of symmetric teleparallel gravity say [Formula: see text] gravity (where [Formula: see text] is the nonmetricity scalar). In this work, we parametrized the field equations with the help of Hubble’s parameter defined as [Formula: see text], where [Formula: see text] and [Formula: see text] are model/free parameters which are constrained with updated 57 data points of the Hubble data set within the redshift range [Formula: see text]. For this, we have used a Markov Chain Monte Carlo Technique (MCMCT). Some physical parameters of the model are discussed. In addition, we analyze the jerk parameter and the statefinder parameters and we also study the energy conditions to assess the compatibility of our model with dark energy models; we determine that the Strong Energy Condition (SEC) is violated due to the fact that the Universe is currently accelerating.

A possible role for the merger of clusters/voids in the cosmological expansion

ABSTRACT In this study, we use the merger process of clusters/voids in the role of variable dark energy fluid to alleviate the Hubble tension, which can lead to a balance in the cosmological expansion rate. To reach this target, we will introduce a modified form of energy density for cosmic fluid with the quadratic equation of state, and then we obtain Hubble, deceleration parameters, and luminosity distance for this fluid. To obtain the merger factor and other parameters of our model, we utilize the NONLINEARMODELFIT function within MATHEMATICA. By consideration of the local and global measurements of $\rm H_0$, and the equation of state parameter w as the priory values, and fitting our model with observational Hubble data measurements, we will show that the merger of clusters/voids plays the role of balancing the cosmic expansion rate. Also, it will be shown that the model is more compatible than wCDM with the standard model to describe the accelerating Universe

F(T, B) gravity with statistically fitting of H(z)

Some recent developments (accelerated expansion) in the Universe cannot be explained by the conventional formulation of general relativity. We apply the recently proposed f(T, B) gravity to investigate the accelerated expansion of the Universe. By parametrizing the Hubble parameter and estimating the best fit values of the model parameters b 0, b 1, and b 2 imposed from Supernovae type Ia, Cosmic Microwave Background, Baryon Acoustic Oscillation, and Hubble data using the Markov Chain Monte Carlo method, we propose a method to determine the precise solutions to the field equations. We then observe that the model appears to be in good agreement with the observations. A change from the deceleration to the acceleration phase of the Universe is shown by the evolution of the deceleration parameter. In addition, we investigate the behavior of the statefinder analysis, equation of state (EoS) parameters, along with the energy conditions. Furthermore, to discuss other cosmological parameters, we consider some well-known f(T, B) gravity models, specifically, f(T, B) = aT b + cB d . Lastly, we find that the considered f(T, B) gravity models predict that the present Universe is accelerating and the EoS parameter behaves like the ΛCDM model.

Observational constraints in modified Chaplygin gas cosmological model

Bianchi type-V cosmological model with modified Chaplygin gas having the equation of state p=γρ−Cρα, where C is a positive constant and 0≤α,γ≤1, has been investigated. To find the deterministic solution, we have considered power-law and intermediate expansions which predicts the decelerating and accelerating phases of expansion of the Universe. Here, we have also constructed cosmographic parameters like H,j,l,s∗ and studied their evolution in the background of Bianchi type-V Universe with modified Chaplygin gas. The geometric diagnostics, the state-finder (r,s) in our cosmological model to discriminate from the ΛCDM model are studied. We have performed the statistical analysis and obtained best fit values of the parameters using MCMC technique for intermediate model. We have also compared our models with observed Hubble data for both scenarios. We have noted some new and interesting cosmological solutions which is relevant for the model building, including present accelerating phase of the Universe.

Constraints on the transition redshift from the calibrated gamma-ray burst Ep–Eiso correlation

ABSTRACT We constrain the deceleration–acceleration epoch, namely the transition redshift ztr, adopting model-independent techniques that utilize a calibrated Ep–Eiso correlation for gamma-ray bursts (GRBs). To do so, in addition to real data points, we employ up to 1000 simulated observational Hubble data (OHD) points. We then calibrate the Ep–Eiso correlation by means of the well-consolidate Bézier polynomial technique, interpolating OHD up to the second order. Once GRB data have been calibrated, we consider two strategies of cosmographic expansions, i.e. first we take a direct Hubble rate expansion around ztr, and second the expansion of the deceleration parameter around the same redshift, but with a different order. Employing Type Ia supernovae, baryonic acoustic oscillations and GRB data sets, from Monte Carlo analyses we infer tight constraints on ztr and the jerk parameters at z = ztr, namely jtr. Our results are extremely compatible with previous outcomes and confirm the Lambda cold dark matter predictions, being slightly different in terms of the jerk parameter. In this respect, we conjecture which extensions of the concordance paradigm are possible and we compare our findings with expectations provided by generic dark energy models.

Evidence of a decreasing trend for the Hubble constant

The current discrepancy between the Hubble constant, H0, derived from the local distance ladder and from the cosmic microwave background is one of the most crucial issues in cosmology, as it may possibly indicate unknown systematics or new physics. Here, we present a novel non-parametric method to estimate the Hubble constant as a function of redshift. We establish independent estimates of the evolution of Hubble constant by diagonalizing the covariance matrix. From type Ia supernovae, baryon acoustic oscillation data and the observed Hubble parameter data, a decreasing trend in the Hubble constant with a significance of a 5.6σ confidence level is found. At low redshift, its value is dramatically consistent with that measured from the local distance ladder and it drops to the value measured from the cosmic microwave background at high redshift. Our results may relieve the Hubble tension, with a preference for recent solutions, especially with respect to novel physics.

Effective dark energy through spin-gravity coupling

We investigate cosmological scenarios with spin-gravity coupling. In particular, due to the spin of the baryonic and dark matter particles and its coupling to gravity, they probe an effective spin-dependent metric, which can be calculated semi-classically in the Mathisson-Papapetrou-Tulczyjew-Dixon formalism. Hence, the usual field equations give rise to modified Friedmann equations, in which the extra terms can be identified as an effective dark-energy sector. Additionally, we obtain an effective interaction between the matter and dark-energy sectors. In the case where the spin-gravity coupling switches off, we recover standard ΛCDM cosmology. We perform a dynamical system analysis and we find a matter-dominated point that can describe the matter era, and a stable late-time solution corresponding to acceleration and dark-energy domination. For small values of the spin coupling parameter, deviations from ΛCDM concordance scenario are small, however for larger values they can be brought to the desired amount, leading to different dark-energy equation-of-state parameter behavior, as well as to different transition redshift from acceleration to deceleration. Finally, we confront the model predictions with Hubble function data.

Revisiting cosmography via Gaussian process

In this paper, we revisit the kinematical state of our Universe via the cosmographic approach by using Gaussian process, where the minimum assumption is the cosmological principle, i.e. the Friedmann–Lemaître–Robertson–Walker metric. A obviously distinguished feature is that these cosmography parameters are free of any gravity theories and cosmological models. And Gaussian process is independent of any specific parameterized forms of function. Thus by transformations these generic cosmography parameters can be used to constrain a cosmological model and dark energy model directly at the kinematics level of our Universe. As a result, a series of cosmography parameters up to the fifth oder, i.e. the Hubble parameter H(z), the deceleration parameter q(z), the jerk parameter j(z), the snap parameter s(z) and the lerk parameter l(z), evolve with respect to the redshift z are reconstructed from the cosmic observations which include the recently released Pantheon+ SN Ia samples and the observational Hubble data H(z), also dubbed as cosmic chronometers. The result shows the transition redshift from a decelerated expansion to an accelerated expansion z_t=0.652^{+0.054}_{-0.043} which is consistent with the previous results.

Spatial curvature and thermodynamics

ABSTRACTReasonable parametrizations of the current Hubble data set of the expansion rate of our homogeneous and isotropic universe, after suitable smoothing of these data, strongly suggest that the area of the apparent horizon increases irrespective of whether the spatial curvature of the metric is open, flat, or closed. Put in another way, any sign of the spatial curvature appears consistent with the second law of thermodynamics.

Null test for cosmic curvature using Gaussian process* *Supported by the National SKA Program of China (2022SKA0110200, 2022SKA0110203) and the National Natural Science Foundation of China (11975072, 11835009, 11875102)

The cosmic curvature , which determines the spatial geometry of the universe, is an important parameter in modern cosmology. Any deviation from would have a profound impact on the primordial inflation paradigm and fundamental physics. In this work, we adopt a cosmological model-independent method to test whether deviates from zero. We use the Gaussian process to reconstruct the reduced Hubble parameter and the derivative of the distance from observational data and then determine with a null test relation. The cosmic chronometer (CC) Hubble data, baryon acoustic oscillation (BAO) Hubble data, and supernovae Pantheon sample are considered. Our result is consistent with a spatially flat universe within the domain of reconstruction , at the confidence level. In the redshift interval , the result favors a flat universe, while at , it tends to favor a closed universe. In this sense, there is still a possibility for a closed universe. We also carry out the null test of the cosmic curvature at using the simulated gravitational wave standard sirens, CC+BAO, and redshift drift Hubble data. The result indicates that in the future, with the synergy of multiple high-quality observations, we can tightly constrain the spatial geometry or exclude the flat universe.

Constant sound speed and its thermodynamical interpretation in f(Q) gravity

On the basis of homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) geometry, solutions to the issues of cosmic acceleration and dark energy are being put forth within the context of f(Q) gravity. We take into account a power law f(Q) model using f(Q)=αQn, where α and n are free model parameters. In the current scenario, we may establish the energy density and pressure for our f(Q) cosmic model by applying the constant sound speed parameterizations, i.e., ϑs2=β, where a barotropic cosmic fluid is described in terms of β. The field equations are then derived, and their precise solutions are established. We obtain the constraints on the model parameters using the updated Hubble (Hz) data sets consisting of 31 data points, the recently published Pantheon samples (SNe) with 1048 points, and Baryon acoustic oscillations (BAO) data sets. We also examine the physical behavior of the deceleration parameter, the equation of state (EoS) parameter, the statefinder diagnostic, and the Om diagnostic. We conclude that our f(Q) cosmic model predicts a transition in the universe from deceleration to acceleration. Further, to investigate the feasibility of the model, we discussed some of its thermodynamic aspects.

Testing dark energy models with gamma-ray bursts calibrated from the observationalH(z) data through a Gaussian process

ABSTRACTWe use a cosmology-independent method to calibrate gamma-ray burst (GRB) from the observational Hubble data (OHD) with the cosmic chronometer method. By using Gaussian process to reconstruct OHD, we calibrate the Amati relation (Ep–Eiso) to construct a GRB Hubble diagram with the A118 data set, and constrain dark energy models in a flat space with the Markov chain Monte Carlo numerical method. With the cosmology-independent GRBs at 1.4 < z ≤ 8.2 in the A118 data set and the Pantheon sample of Type Ia supernovae at 0.01 < z ≤ 2.3, we obtained Ωm = $0.379^{+0.033}_{-0.024}$, h = $0.701^{+0.0035}_{-0.0035}$, w = $-1.25^{+0.14}_{-0.12}$, and wa = $-0.84^{+0.81}_{-0.38}$ for the flat Chevallier–Polarski–Linder model at the 1σ confidence level. We find no significant evidence supporting deviations from the standard Lambda cold dark matter model.

The reconstruction of constant jerk parameter with f(R,T) gravity

In this work, we have developed an FLRW type model of a universe which displays transition from deceleration in the past to the acceleration at the present. For this, we have considered field equations of f(R,T) gravity and have taken f(R,T)=R+2λT, λ being an arbitrary constant. We have estimated the λ parameter in such a way that the transition red shift is found similar in the deceleration parameter, pressure and the equation of state parameter ω. The present value of Hubble parameter is estimated on the basis of the three types of observational data set: latest compilation of 46 Hubble data set, SNe Ia 580 data sets of distance modulus and 66 Pantheon data set of apparent magnitude which comprised of 40 SN Ia bined and 26 high redshift data's in the range 0.014≤z≤2.26. These data are compared with theoretical results through the χ2 statistical test. Interestingly, the model satisfies all the three weak, strong and dominant energy conditions. The model fits well with observational findings. We have discussed some of the physical aspects of the model, in particular the age of the universe.

Test of artificial neural networks in likelihood-free cosmological constraints: A comparison of information maximizing neural networks and denoising autoencoder

In the procedure of constraining the cosmological parameters with the observational Hubble data and the type Ia supernova data, the combination of Masked Autoregressive Flow and Denoising Autoencoder can perform a good result. The above combination extracts the features from OHD with DAE, and estimates the posterior distribution of cosmological parameters with MAF. We ask whether we can find a better tool to compress large data in order to gain better results while constraining the cosmological parameters. Information maximising neural networks, a kind of simulation-based machine learning technique, was proposed at an earlier time. In a series of numerical examples, the results show that IMNN can find optimal, non-linear summaries robustly. In this work, we mainly compare the dimensionality reduction capabilities of IMNN and DAE. We use IMNN and DAE to compress the data into different dimensions and set different learning rates for MAF to calculate the posterior. Meanwhile, the training data and mock OHD are generated with a simple Gaussian likelihood, the spatially flat {\Lambda}CDM model and the real OHD data. To avoid the complex calculation in comparing the posterior directly, we set different criteria to compare IMNN and DAE.

The study of hypersurface-homogeneous space-time in Renyi holographic dark energy

The investigation of this work is carried on the hypersurface-homogeneous space-time in the presence of two fluids, one being the pressureless matter and the other being the Renyi holographic dark energy (RHDE). Eventually, this work solves the cosmological model with Renyi HDE by taking the Hubble horizon as an infrared (IR) cutoff ([Formula: see text]). The geometrical and matter parts of space-time are solved within the Saez–Ballester scalar-tensor theory of gravitation. Interestingly, this study obtains a time-varying deceleration parameter ([Formula: see text]) that exhibits a transition from deceleration to acceleration phase. For the configurations of parameter [Formula: see text] emerging in space-time, three physically plausible cosmological hypotheses of the cosmos are outlined in this work. The kinematical properties were obtained and discussed for the three values of [Formula: see text]. The study of cosmic expansion in the accelerated phase of this work is done through various cosmological parameters like EoS, deceleration parameter, statefinder parameter, etc. The Hubble parameter is derived in terms of cosmic time and redshift both. The present value of this parameter is estimated by taking [Formula: see text] point data sets of observational Hubble data (OHD). The stability of the model is verified through the analysis of squared speed of sound ([Formula: see text]) parameter. In this work, the obtained results match with recent observational data.

Cosmology with viscous generalized Chaplygin gas in [formula omitted] gravity

We use the hybrid model of bulk viscosity and generalized chaplygin gas (GCG), named the viscous generalized chaplygin gas (VGCG) model, which is thought to be an alternate dark fluid of the universe. We explore the dynamics of the VGCG model in the framework of the non-metricity f(Q) gravity using the functional form f(Q)=βQn, where β and n are arbitrary constants. For the purpose of constraining model parameters, we use recent observational datasets such as Observational Hubble data, Baryon Acoustic Oscillations, and Type Ia supernovae data. According to our study, the evolution of the deceleration parameter q and the equation of state (EoS) parameter w shows a transition from deceleration to an acceleration phase and its deviation from the ΛCDM model.

Multi-probe analysis of the galaxy cluster CL J1226.9+3332

The precise estimation of the mass of galaxy clusters is a major issue for cosmology. Large galaxy cluster surveys rely on scaling laws that relate cluster observables to their masses. From the high-resolution observations of ∼45 galaxy clusters with the NIKA2 and XMM-Newton instruments, the NIKA2 Sunyaev-Zel’dovich Large Program should provide an accurate scaling relation between the thermal Sunyaev-Zel’dovich effect and the hydrostatic mass. In this paper we present an exhaustive analysis of the hydrostatic mass of the well-known galaxy cluster CL J1226.9+3332, the highest-redshift cluster in the NIKA2 Sunyaev-Zel’dovich Large Program at z = 0.89. We combined the NIKA2 observations with thermal Sunyaev-Zel’dovich data from the NIKA, Bolocam, and MUSTANG instruments and XMM-Newton X-ray observations, and tested the impact of the systematic effects on the mass reconstruction. We conclude that slight differences in the shape of the mass profile can be crucial when defining the integrated mass at R500, which demonstrates the importance of the modelling in the mass determination. We prove the robustness of our hydrostatic mass estimates by showing the agreement with all the results found in the literature. Another key factor for cosmology is the bias of the masses estimated assuming the hydrostatic equilibrium hypothesis. Based on the lensing convergence maps from the Cluster Lensing And Supernova survey with Hubble (CLASH) data, we obtain the lensing mass estimate for CL J1226.9+3332. From this we are able to measure the hydrostatic-to-lensing mass bias for this cluster, which spans from 1 − bHSE/lens ∼ 0.7 to 1, presenting the impact of data sets and mass reconstruction models on the bias.

On the homogeneity of SnIa absolute magnitude in the Pantheon+ sample

ABSTRACT We have analysed the Pantheon+ sample using a new likelihood model that replaces the single Type Ia supernovae (SnIa) absolute magnitude parameter M used in the standard likelihood model of Brout et. al. with two absolute magnitude parameters (M< and M>) and a transition distance (dcrit) that determines the distance at which M changes from M< to M>. The use of this likelihood dramatically changes the quality of fit to the Pantheon+ sample for a Lambda cold dark matter background by Δχ2 = −19.6. The tension between the M< and M> best-fitting values is at a level more than 3σ with a best-fitting dcrit very close to $20\, \mathrm{Mpc}$. The origin of this improvement of fit and M<–M> tension is that the new likelihood model successfully models two signals hidden in the data: (1) the volumetric redshift scatter bias systematic and (2) a mild signal for a change of intrinsic SnIa luminosity at about $20\, \mathrm{Mpc}$. This interpretation of the results is confirmed by truncating the z < 0.01 Hubble diagram data from the Pantheon+ data where the above systematic is dominant and showing that the M<–M> tension decreases from above 3σ to a little less than 2σ. It is also confirmed by performing a Monte Carlo simulation, which shows that the maximum significance of the SnIa luminosity transition ($\Sigma \equiv \frac{|M_{\gt} -M_{\lt} |}{\sqrt{\sigma _{M_{\gt} }^2+\sigma _{M_{\lt} }^2}}$) as obtained from the real SH0ES data is larger than the corresponding maximum significance of $94{{\ \rm per\ cent}}$ of the corresponding homogeneous simulated samples.

Cosmological tests of the osculating Barthel–Kropina dark energy model

We further investigate the dark energy model based on the Finsler geometry inspired osculating Barthel–Kropina cosmology. The Barthel–Kropina cosmological approach is based on the introduction of a Barthel connection in an osculating Finsler geometry, with the connection having the property that it is the Levi-Civita connection of a Riemannian metric. From the generalized Friedmann equations of the Barthel–Kropina model, obtained by assuming that the background Riemannian metric is of the Friedmann–Lemaitre–Robertson–Walker type, an effective geometric dark energy component can be generated, with the effective, geometric type pressure, satisfying a linear barotropic type equation of state. The cosmological tests, and comparisons with observational data of this dark energy model are considered in detail. To constrain the Barthel–Kropina model parameters, and the parameter of the equation of state, we use 57 Hubble data points, and the Pantheon Supernovae Type Ia data sample. The st statistical analysis is performed by using Markov Chain Monte Carlo (MCMC) simulations. A detailed comparison with the standard Lambda CDM model is also performed, with the Akaike information criterion (AIC), and the Bayesian information criterion (BIC) used as the two model selection tools. The statefinder diagnostics consisting of jerk and snap parameters, and the Om(z) diagnostics are also considered for the comparative study of the Barthel–Kropina and Lambda CDM cosmologies. Our results indicate that the Barthel–Kropina dark energy model gives a good description of the observational data, and thus it can be considered a viable alternative of the Lambda CDM model.

The interaction of extended Bose–Einstein condensate dark matter with viscous f(T,B) gravity

In this paper, we study the viscous $f(T, B)$ gravity model as a source of dark energy, and the Extended Bose-Einstein Condensate (EBEC) as a source of dark matter, in a flat-FRW metric. In the presence of bulk viscosity, we obtain Friedmann equations and write two continuity equations of dark energy and dark matter by interacting them. Using the generalized Gross-Pitaeveskii equation, we earn Equation of State (EoS) of dark matter by EBEC regime as $p_m = \alpha \rho_{m} + \beta \rho_{m}^2$ in which the both of terms are respectively introduced as normal dark matter and dark matter halo. The innovation of the work is that we can simultaneously describe the nature of the dark parts of the universe with the viscous $f(T, B)$ gravity and the EBEC regime, which leads to a deep understanding of the different epochs of the universe from early to late times. In what follows, the energy density and the pressure of dark energy are reconstructed in terms of the redshift parameter, and then we fit the obtained results with 53 supernova data from the Hubble data constraints. Next, we plot the cosmological parameters in terms of the redshift parameter and conclude that the current universe is in an accelerated phase. Finally, we analyze the stability and instability of the current model with the sound speed parameter as well as we draw the density parameter values for dark energy in terms of the redshift parameter.