Hubble Parameter Measurements Research Articles

Observations Favor the Redshift-evolutionary L X–L UV Relation of Quasars from Copula

We compare, with data from quasars, Hubble parameter measurements, and Pantheon+ type Ia supernova, three different relations between X-ray luminosity (L X) and ultraviolet luminosity (L UV) of quasars. These three relations consist of the standard and two redshift-evolutionary L X–L UV relations, which are constructed, respectively, by considering a redshift-dependent correction to the luminosities of quasars and using the statistical tool copula. By employing the PAge approximation for a cosmological model–independent description of the cosmic background evolution and dividing the quasar data into the low-redshift and high-redshift parts, we find that the constraints on the PAge parameters from the low-redshift and high-redshift data, which are obtained with the redshift-evolutionary relations, are consistent with each other, while they are not when the standard relation is considered. If the data are used to constrain the coefficients of the relations and the PAge parameters simultaneously, then the observations support the redshift-evolutionary relations at more than 3σ. The Akaike and Bayes information criteria indicate that there is strong evidence against the standard relation and mild evidence against the redshift-evolutionary relation constructed by considering a redshift-dependent correction to the luminosities of quasars. This suggests that the redshift-evolutionary L X–L UV relation of quasars constructed from copula is favored by the observations.

Evidence of dynamical dark energy in a non-flat universe: current and future observations

We investigate the dark energy phenomenology in an extended parameter space where we allow the curvature density of our universe as a free-to-vary parameter. The inclusion of the curvature density parameter is motivated from the recently released observational evidences indicating the closed universe model at many standard deviations. Here we assume that the dark energy equation-of-state follows the PADE approximation, a generalized parametrization that may recover a variety of existing dark energy models. Considering three distinct PADE parametrizations, labeled as PADE-I, SPADE-I and PADE-II, we first constrain the cosmological scenarios driven by them using the joint analyses of a series of recently available cosmological probes, namely, Pantheon sample of Supernovae Type Ia, baryon acoustic oscillations, big bang nucleosynthesis, Hubble parameter measurements from cosmic chronometers, cosmic microwave background distance priors from Planck 2018 and then we include the future Gravitational Waves standard sirens (GWSS) data from the Einstein telescope with the combined analyses of these current cosmological probes. We find that the current cosmological probes indicate a very strong evidence of a dynamical dark energy at more than 99% C.L. in both PADE-I, and PADE-II, but no significant evidence for the non-flat universe is found in any of these parametrizations. Interestingly, when the future GWSS data from the Einstein telescope are included with the standard cosmological probes an evidence of a non-flat universe is found in all three parametrizations together with a very strong preference of a dynamical dark energy at more than 99% C.L. in both PADE-I, and PADE-II. Although from the information criteria analysis, namely, AIC, BIC, DIC, the non-flat Λ-Cold Dark Matter model remains the best choice, however, in the light of DIC, PADE parametrizations are still appealing.

Revisiting the Epoch of Cosmic Acceleration

We revisit the epoch of cosmic speed-up characterized by the redshift of transition from a decelerated to an accelerated phase. This redshift is termed the transition redshift (z t ). We use the spatially flat and non-flat variants of the most common ΛCDM and XCDM models to put constraints on the transition redshift along with the other model parameters. The data for this analysis come from the recent and updated Pantheon+ supernova (SN) data set and the Hubble parameter measurements obtained from Cosmic Chronometers. We consider both data sets with their respective covariance matrices incorporating all statistical and systematic uncertainties. We observe that using the combined data sets of H(z) and SNe, the best fit value of transition redshift lies in the range 0.61 < z t < 0.79 for all four dark energy models. Incidentally, we observe a positive curvature for the non-flat models, correlations between several model parameters and a strong degeneracy between the curvature and the equation of state parameter.

Constraints on the transition redshift using Hubble phase space portrait

One of the most significant discoveries in modern cosmology is that the universe is currently in a phase of accelerated expansion after a switch from a decelerated expansion. The redshift corresponding to this epoch is commonly referred to as the transition redshift [Formula: see text]. In this work, we put constraints on the transition redshift with both model-independent and model-dependent approaches. We consider the recently compiled database of 32 Hubble parameter measurements and the Pantheon sample of Type Ia Supernovae (SNe). In order to include the possible systematic effects in this analysis, we use the full covariance matrix of systematic uncertainties for the Hubble parameter measurements. We plot a Hubble Phase Space Portrait (HPSP) between [Formula: see text] and [Formula: see text] in a model-independent way. From this HPSP diagram, we estimate the transition redshift as well as the current value of the equation of state parameter [Formula: see text] in a model-independent way. By considering H(z) measurements, we find the best fit value of [Formula: see text] and [Formula: see text]. We obtain the best fit value of [Formula: see text] and [Formula: see text] using the Pantheon database. Further, we also use a model-dependent approach to determine [Formula: see text]. Here, we consider a nonflat [Formula: see text]CDM model as a background cosmological model. We reconstruct the cosmic triangle plot among [Formula: see text], [Formula: see text] and [Formula: see text] where the constraints of each parameter are determined by the location in this triangle plot. By using [Formula: see text] and [Formula: see text] values, we find the best value of the transition redshift [Formula: see text], which is in good agreement with the Planck 2018 results at [Formula: see text] confidence level. We also simulate the observed Hubble parameter measurements in the redshift range [Formula: see text] and perform the same analysis to estimate the transition redshift.

Cosmological-model-independent Determination of Hubble Constant from Fast Radio Bursts and Hubble Parameter Measurements

We establish a cosmological-model-independent method to determine the Hubble constant H 0 from the localized fast radio bursts (FRBs) and the Hubble parameter measurements from cosmic chronometers and obtain a first such determination H 0 = 71 ± 3 km s−1 Mpc−1, with an uncertainty of 4%, from the eighteen localized FRBs and nineteen Hubble parameter measurements in the redshift range 0 < z ≤ 0.66. This value, which is independent of the cosmological model, is consistent with the results from the nearby Type Ia supernovae (SNe Ia) data calibrated by Cepheids and the Planck cosmic microwave background radiation observations at the 1σ and 2σ confidence level, respectively. Simulations show that the uncertainty of H 0 can be decreased to the level of that from the nearby SNe Ia when mock data from 500 localized FRBs with 50 Hubble parameter measurements in the redshift range of 0 < z ≤ 1 are used. Since localized FRBs are expected to be detected in large quantities, our method will be able to give a reliable and more precise determination of H 0 in the very near future, which will help us to figure out the possible origin of the Hubble constant disagreement.

Viscous cosmology in holographic dark energy with Granda–Oliveros cut-off

We study the effect of bulk viscosity on holographic dark energy (HDE) with Granda–Oliveros infra-red cut-off. We focus on a generalized form of the bulk viscous coefficient which successfully describes the present-day evolution of the Universe. We observe that the model with bulk viscosity provides an elegant description of the early and late-time evolution of the Universe. We constrain the model through the combined observational data of the Strong Lensing System (SLS), measurements of Hubble parameter, Type Ia supernova data of Pantheon sample and local H 0 measured by SH0ES. Using best-fit values obtained from two different combinations of data, we estimate the present value of Hubble’s constant and , the deceleration parameter and , and the equation of state and , respectively. The HDE model with bulk viscosity exhibits the phase transition from decelerated epoch to accelerated epoch. A comparison of the model with the standard ΛCDM model is discussed with the statefinder and cosmographic parameters.

Cosmological impact of microwave background temperature measurements

The cosmic microwave background temperature is a cornerstone astrophysical observable. Its present value is tightly constrained, but its redshift dependence, which can now be determined until redshift z∼6.34, is also an important probe of fundamental cosmology. We show that its constraining power is now comparable to that of other background cosmology probes, including Type Ia supernovae and Hubble parameter measurements. We illustrate this with three models, each based on a different conceptual paradigm, which aim to explain the recent acceleration of the universe. We find that for parametric extension of ΛCDM the combination of temperature and cosmological data significantly improves constraints on the model parameters, while for alternative models without a ΛCDM limit this data combination rules them out.

Fermionic wave functions and Grassmann fields as possible sources of dark energy

We study a cosmological model with a fermionic field which can be interpreted as a source of dark energy in the universe. Two different approaches were considered, the first one with a massless fermionic field represented by a standard wave-function and the second one where a massive field is a Grassmann variable. The first case naturally reduces to a XCDM model with a constant equation of state parameter, while the last case reproduces a w(z)CDM model for a massive field, and in the massless limit, the intrinsic Grassmannian property of the field leads always to a vacuum equation of state parameter, irrespective the specific form of the potential. Both cases leads to a dark energy contribution of the fermionic sector. The models are totally compatible with recent cosmological data from Supernovae, BAO and Hubble parameter measurements. A brief study of linear evolution of density perturbations shows that some of the small scale problems related to standard model can be at least alleviated.

Data-driven predictive modeling of Hubble parameter

We redesign the generalized pressure dark energy (GPDE) model, which is covering three common types of pressure parameterizations, with the help of a caloric framework to construct a theoretical ground for the machine learning (ML) analysis of cosmic Hubble parameter. The theoretical setup was optimized to find out appropriate values of its arbitrary parameters with the help of genetic neural network (GNN) algorithm and the most recent observational measurements of Hubble parameter. Since there is a shortcoming that the GNN process does not provide a direct method to calculate errors on the optimized values of free model parameters, we therefore take the Fisher Information Matrix (FIM) algorithm into account to deal with this issue. We see that the best-fitting value of Hubble constant and dimensionless dark energy density are in very good agreement with the most recent observations. Also, we discussed the optimized model from a cosmological perspective by making use of the evolutionary behavior of some cosmological parameters to present additional cosmological aspects of our theoretical proposal. It is concluded that our model implies physically meaningful results. In summary, the constructed model can explain the current accelerated expansion phase of the cosmos via Hubble parameter successfully.

Screening mechanism and late-time cosmology: Role of a Chameleon–Brans–Dicke scalar field

ABSTRACT We discuss a way in which the geometric scalar field in a Brans–Dicke (BD) theory can evade local astronomical tests and act as a driver of the late-time cosmic acceleration. This requires a self-interaction of the BD scalar as well as an interaction with ordinary matter. The scalar field in this construct acquires a density-dependent effective mass much like a Chameleon field. We discuss the viability of this setup in the context of Equivalence Principle, Fifth Force, and Solar System tests. The cosmological consistency is adjudged in comparison with observational data from recalibrated light curves of type Ia supernova (JLA), the Hubble parameter measurements (OHD) and the Baryon Acoustic Oscillation (BAO). We deduct that the astrophysical constraints indeed favour the existence of a mild scalar-matter interaction in the Jordan Frame.

Do reverberation-measured Hβ quasars provide a useful test of cosmology?

ABSTRACT We use 118 Hβ quasar (QSO) observations in the redshift range 0.0023 ≤ z ≤ 0.89 to simultaneously constrain cosmological model parameters and QSO 2-parameter radius-luminosity (R–L) relation parameters in six different cosmological models. We find that the R–L relation parameters for these QSOs are independent of the assumed cosmology so these QSOs seem to be standardizable through the R–L relation (although there is a complication that might render this untrue). Cosmological constraints obtained using these QSOs are weak, more favour currently decelerated cosmological expansion, and typically are in ∼2σ tension with those obtained from a joint analysis of baryon acoustic oscillation and Hubble parameter measurements. Extending the R–L relation to a 3-parameter one to try to correct for the accretion rate effect does not result in a reduction of the cosmological constraints discrepancy nor does it result in the hoped-for significant reduction of the intrinsic scatter of the R–L relation.

Dark matter from torsion in Friedmann cosmology

A cosmological model in an Einstein–Cartan framework endowed with torsion is studied. For a torsion function assumed to be proportional to Hubble expansion function, namely phi =-alpha H, the contribution of torsion function as a dark matter component is studied in two different approaches. In the first one, the total matter energy density is altered by torsion coupling alpha , giving rise to an effective dark matter and cosmological constant terms that reproduce quite well the flat cosmic concordance model. In the second approach, starting with just standard baryonic matter plus a cosmological constant term, it is obtained that the coupling of torsion with baryons and cosmological constant term naturally gives rise to a dark matter contribution, together a modified cosmological term. In this model the dark matter sector can be interpreted as an effective coupling of the torsion function with the ordinary baryonic matter and cosmological constant. Finally, it is shown that both models are totally compatible with recent cosmological data from Supernovae and Hubble parameter measurements.

Observational constraints and predictions of the interacting dark sector with field-fluid mapping

We consider an interacting field theory model that describes the interaction between dark energy-dark matter interaction. Only for a specific interaction term, this interacting field theory description has an equivalent interacting fluid description. For inverse power law potentials and linear interaction function, we show that the interacting dark sector model with field-fluid mapping is consistent with four cosmological data sets — Hubble parameter measurements (Hz), Baryonic Acoustic Oscillation data (BAO), Supernova Type Ia data (SN), and High redshift HII galaxy measurements (HIIG). More specifically, these data sets prefer a negative value of interaction strength in the dark sector and lead to consistent best-fit values of Hubble constant and other cosmological parameters. Having established that this interacting field theory model is consistent with cosmological observations, we obtain quantifying tools to distinguish between the interacting and non-interacting dark sector scenarios. We focus on the variation of the scalar metric perturbed quantities as a function of redshift related to structure formation, weak gravitational lensing, and the integrated Sachs-Wolfe effect. We show that the difference in the evolution becomes significant for z < 20, for all length scales, and the difference peaks at smaller redshift values z < 5. We then discuss the implications of our results for the upcoming missions.

Barrow holographic dark energy in a nonflat universe

We construct Barrow holographic dark energy in the case of nonflat universe. In particular, considering closed and open spatial geometry we extract the differential equations that determine the evolution of the dark-energy density parameter, and we provide the analytical expression for the corresponding dark energy equation-of-state parameter. We show that the scenario can describe the thermal history of the universe, with the sequence of matter and dark energy epochs. Comparing to the flat case, where the phantom regime is obtained for relative large Barrow exponents, the incorporation of positive curvature leads the universe into the phantom regime for significantly smaller values. Additionally, in the case of negative curvature we find a reversed behavior, namely for increased Barrow exponent we acquire algebraically higher dark-energy equation-of-state parameters. Furthermore, we confront the scenario with Hubble parameter measurements and supernova type Ia data. Hence, the incorporation of slightly non-flat spatial geometry to Barrow holographic dark energy improves the phenomenology while keeping the new Barrow exponent to smaller values.

CMB lensing in a modified ΛCDM model in light of the H0 tension

The observed discrepancy of the Hubble parameter measurements in the local universe with the cosmic microwave background (CMB) data may indicate a new physics. It is vital to test the alternative models that reconcile the Hubble tension with other cosmological observations in this direction. The CMB lensing is a crucial observation that relates the early universe perturbations to the matter's late-time distribution. In this work, we study the prediction of the \"u$\Lambda$CDM as a solution for $H_0$ tension for CMB lensing and the low- and high-$\ell$'s temperature (TT) power spectrum internal inconsistency. We show that this model relaxes the low- and high-$\ell$'s TT mild inconsistency and the CMB lensing tensions simultaneously. Accordingly, \"u$\Lambda$CDM having the same number of free parameters as $\Lambda$CDM with lensing amplitude $A_L$ added, has a better fit with $\Delta \chi^2=-3.3$.

The minimally extended Varying Speed of Light (meVSL)

Even though there have been various models of the time-varying speed of light (VSL), they remain out of the mainstream because of their possible violation of physics laws built into fundamental physics. In order to be the VSL as a viable theory, it should inherit the success of special relativity including Maxwell equations and thermodynamics at least. For this purpose, we adopt the assumption that the speed of light, c̃, i.e., c̃[a], varies for the scale factor, a. The background FLRW universe can be defined by the constant cosmic time hypersurface using physical quantities such as temperature, density, c̃, etc. It is because they evolve in cosmic time and the homogeneity of the Universe demands that they must equal at the equal cosmic time. The variation of c̃ accompanies the joint variations of all related physical constants in order to satisfy the Lorentz invariance, thermodynamics, Bianchi identity, etc. We dub this VSL model as a “minimally extended VSL (meVSL)”. We derive cosmological observables of meVSL and obtain the constraints on the variation of c̃ by using current cosmological observations. Interestingly, both the cosmological redshift z and all geometrical distances except the luminosity distance of meVSL are the same as those of general relativity. However, the Hubble parameter of meVSL is rescaled as H(z) = (1+z)-b/4 H(GR)(z), where H(GR)(z) denotes the Hubble parameter obtained from general relativity. Thus, it might be used as an alternative solution for the tension of the Hubble parameter measurements. In this manuscript, we provide the main effects of the meVSL model on various cosmological observations including BBN, CMB, SZE, BAO, SNe, GWs, H, SL, and Δα. Compared to previous VSL models, meVSL might provide alternative solutions for various late time problems of the standard ΛCDM model. This is the main motivation for proposing the meVSL model.

Using Pantheon and DES supernova, baryon acoustic oscillation, and Hubble parameter data to constrain the Hubble constant, dark energy dynamics, and spatial curvature

ABSTRACT We use Pantheon Type Ia supernova (SN Ia) apparent magnitude, DES-3 yr binned SN Ia apparent magnitude, Hubble parameter, and baryon acoustic oscillation measurements to constrain six spatially flat and non-flat cosmological models. These sets of data provide mutually consistent cosmological constraints in the six cosmological models we study. A joint analysis of these data sets provides model-independent estimates of the Hubble constant, $H_0=68.8\pm 1.8\ \rm {km \, s^{-1} \ Mpc^{-1}}$, and the non-relativistic matter density parameter, $\Omega _{\rm m_0}=0.294\pm 0.020$. Although the joint constraints prefer mild dark energy dynamics and a little spatial curvature, they do not rule out dark energy being a cosmological constant and flat spatial hypersurfaces. We also add quasar angular size and H ii starburst galaxy measurements to the combined data set and find more restrictive constraints.

Hubble parameter estimation via dark sirens with the LISA-Taiji network.

The Hubble parameter is one of the central parameters in modern cosmology, and describes the present expansion rate of the universe. The values of the parameter inferred from late-time observations are systematically higher than those inferred from early-time measurements by about n}{}10%. To reach a robust conclusion, independent probes with accuracy at percent levels are crucial. Gravitational waves from compact binary coalescence events can be formulated into the standard siren approach to provide an independent Hubble parameter measurement. The future space-borne gravitational wave observatory network, such as the LISA-Taiji network, will be able to measure the gravitational wave signals in the millihertz bands with unprecedented accuracy. By including several statistical and instrumental noises, we show that, within a five-year operation time, the LISA-Taiji network is able to constrain the Hubble parameter within n}{}1% accuracy, and possibly beats the scatters down to n}{}0.5% or even better.

Cosmological Constraints on the Coupling Model from Observational Hubble Parameter and Baryon Acoustic Oscillation Measurements

In the paper, we consider two models in which dark energy is coupled with either dust matter or dark matter, and discuss the conditions that allow more time for structure formation to take place at high redshifts. These models are expected to have a larger age of the universe than that of ΛCDM [universe consists of cold dark matter (CDM) and dark energy (a cosmological constant, Λ)], so it can explain the formation of high redshift gravitationally bound systems which the ΛCDM model cannot interpret. We use the observational Hubble parameter data (OHD) and Hubble parameter obtained from cosmic chronometers method (H(z)) in combination with baryon acoustic oscillation (BAO) data to constrain these models. With the best-fitting parameters, we discuss how the age, the deceleration parameter, and the energy density parameters evolve in the new universes, and compare them with that of ΛCDM.

Kinematical models of latetime cosmology and the statefinder diagnostic

The present work deals with kinematical models of latetime cosmology. It is based on purely phenomenological assumption about the deceleration parameter. The models are confronted to observational data sets of type Ia supernovae distance modulus measurements and measurements of Hubble parameter at different redshift. Constraints on the cosmological parameters are obtained by Markov Chanin Monte Charlo (MCMC) analysis using the observation data sets. The values of present Hubble parameter, deceleration parameter and the redshift of transition from decelerated to accelerated phase of expansion are estimated for the present kinematical models. Further the properties of dark energy for the present models are explored with general relativistic assumptions. The dark energy diagnostics, namely the Om diagnostic and the statefinder are adopted for a comparison of the present models. A phase space constructed of two different statefinder parameters breaks the degeneracy of the models. It is observed that the kinematical models attain the corresponding {\Lambda}CDM value on the phase space in the course of evolution. The evolution of matter density contrast at linear level has also been studied for the present kinematical models.