Type Ia Supernovae Data Research Articles

Constraints on dark energy from TDCOSMO & SLACS lenses

ABSTRACT Problems with the cosmological constant model of dark energy motivate the investigation of alternative scenarios. I make the first measurement of the dark energy equation of state using the hierarchical strong lensing time delay likelihood provided by TDCOSMO. I find that the combination of seven TDCOSMO lenses and 33 SLACS lenses is only able to provide a weak constraint on the dark energy equation of state, w < −1.75 at 68 per cent confidence, which nevertheless implies the presence of a phantom dark energy component. When the strong lensing time delay data is combined with a collection of cosmic microwave background, baryon acoustic oscillation and Type Ia supernova data, I find that the equation of state is w = −1.025 ± 0.029.

Viscous effect in the late time evolution of phantom universe

We investigate the cosmological implications of a phantom dark energy model with bulk viscosity. We explore this model as a possible way to resolve the big rip singularity problem that plagues the phantom models. We use the latest type Ia supernova and Hubble parameter data to constrain the model parameters and find that the data favor a significant bulk viscosity over a non-constant potential term for the phantom field. We perform a dynamical analysis of the model and show that the only stable and physical attractor corresponds to a phantom-dominated era with a total equation of state that can be greater than -1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-1$$\\end{document} due to the viscosity. We also study the general effect of viscosity on the phantom field and the late time evolution of the universe. We apply the statefinder diagnostic to the model and find that it approaches a nearby fixed point asymptotically, indicating that the universe can escape the big rip singularity with the presence of bulk viscosity. We conclude that bulk viscosity can play an important role in affecting the late-time behavior as well as alleviating the singularity problem of the phantom universe.

Cosmological Tensions and the Transitional Planck Mass Model

In this follow-up analysis, we update previous constraints on the transitional Planck mass (TPM) modified gravity model using the latest version of EFTCAMB and provide new constraints using South Pole Telescope (SPT) and Planck anisotropy data along with Planck cosmic microwave background lensing, baryon acoustic oscillations, and Type Ia supernovae data and a Hubble constant, H 0, prior from local measurements. We find that large shifts in the Planck mass lead to large suppression of power on small scales that is disfavored by both the SPT and Planck data. Using only the SPT temperature-polarization–polarization-polarization (TE-EE) data, this suppression of power can be compensated for by an upward shift of the scalar index to n s = 1.003 ± 0.016, resulting in km m−1 Mpc−1 and a ∼7% shift in the Planck mass. Including the Planck temperature-temperature (TT) ℓ ≤ 650 and Planck TE-EE data restricts the shift to be <5% at 2σ with H 0 = 70.65 ± 0.66 km m−1 Mpc−1. Excluding the H 0 prior, the SPT and Planck data constrain the shift in the Planck mass to be <3% at 2σ with a best-fit value of 0.04%, consistent with the Λ cold dark matter limit. In this case km s−1 Mpc−1, which is partially elevated by the dynamics of the scalar field in the late Universe. This differs from early dark energy models that prefer higher values of H 0 when the high-ℓ Planck TT data are excluded. We additionally constrain TPM using redshift space distortion data from BOSS DR12 and cosmic shear, galaxy–galaxy lensing, and galaxy clustering data from DES Y1, finding both disfavor transitions close to recombination, but earlier Planck mass transitions are allowed.

Probing accelerating cosmos via reconstructed Hubble parameter and its influence on f(T) gravity models

This article introduces a new way of studying the accelerating cosmos without relying on specific models. It proposes a new parametric form of the Hubble parameter (HP) and uses a Markov Chain Monte Carlo (MCMC) approach to determine the model parameters. The analysis incorporates a comprehensive dataset consisting of 34 cosmic chronometers (CC) data points, 40 non-correlated baryonic acoustic oscillations (BAO) points, and 1701 updated Pantheon+ supernovae type Ia (SNeIa) data points. The study investigates various aspects of the model's behavior, such as the transition from deceleration to acceleration, and the evolution of jerk and snap parameters. Constraints are applied to the model parameters as well as the Hubble constant (H0). Additionally, the parameter values obtained are used to study f(T) gravity models and compare them with observational data. This research provides valuable insights into the nature of the accelerating Universe and highlights the importance of using a parametrized approach in cosmological studies.

Investigating the accelerated expansion of the Universe through updated constraints on viable f(R) models within the metric formalism

ABSTRACT Modified theories of gravity encompass a class of f(R) models that seek to elucidate the observed late-time accelerated expansion of the universe. In this study, we examine a set of viable f(R) models (Hu–Sawicki: two cases, Satrobinsky, Tsujikawa, exponential and arcTanh models) in metric formalism, using recent cosmological data sets: type Ia supernovae data, cosmic chronometer observations, baryonic acoustic oscillations data, data from H ii starburst galaxies, local measurements of the Hubble parameter (H0), and cosmic microwave background radiation data. We re-parametrize the f(R) models using a distortion/deviation parameter (b) which is a measure of their deviation from the lambda-cold dark matter (ΛCDM) model. Taking into account the ‘Hubble tension,’ we perform the study both with and without a Gaussian prior for H0 from local measurements, following the standard statistical procedures for constraining parameters and comparing models. Our findings are as follows: (i) in many cases the f(R) models are strongly favoured over the standard ΛCDM model, (ii) the deviation parameter (b) significantly deviates from zero in several cases, (iii) the inclusion of local H0 not only increases the fitted value of H0 (as expected) but also affects the gap between predictions of f(R) models and the ΛCDM model, and (iv) the relevant quantities characterizing the (accelerated) expansion of the universe such as transition redshift and the equations-of-state parameters, obtained in our models, are consistent with those obtained in a model-independent way by others. Our investigation and results present a compelling case for pursuing further research on f(R) models with future observations to come.

Bianchi type-III THDE quintessence model with hybrid scale factor

The current research investigates the behavior of the Tsallis holographic dark energy (THDE) model with quintessence in a homogeneous and anisotropic Bianchi type-III space–time. We construct the model by using two conditions: ( i) expansion scalar ( θ) is proportionate to shear scalar ( σ) in the model and ( ii) hybrid scale factor a = t βe γt, where β &gt; 0 and γ &gt; 0 are constants. Our study is based on Type Ia supernovae data in combination with CMB and BAO observations (Giostri et al., JCAP 3, 27); the present values of Hubble constant and deceleration parameter are H0 = 73.8 and q0 = −0.54, respectively. Compiling our theoretical models with these data, we obtain [Formula: see text] for [Formula: see text], respectively. We completed an entirely novel form of cosmic model where the expansion occurs during the present accelerated phase for the constraints. We have discussed the conformity among the scalar field model of quintessence and THDE model. To understand the Universe, we have also established the relations for distance modulus, luminosity distance, and angular-diameter distance. Some geometric and physical aspects of the THDE model are also highlighted.

Revisiting constraints on the photon rest mass with cosmological fast radio bursts

Fast radio bursts (FRBs) have been suggested as an excellent celestial laboratory for testing the zero-mass hypothesis of the photon. In this work, we use the dispersion measure (DM)–redshift measurements of 23 localized FRBs to revisit the photon rest mass mγ . As an improvement over previous studies, here we take into account the more realistic probability distributions of DMs contributed by the FRB host galaxy and intergalactic medium (IGM) from the IllustrisTNG simulation. To better account for the systematic uncertainty induced by the choices of priors of cosmological parameters, we also combine the FRB data with the cosmic microwave background data, the baryon acoustic oscillation data, and type Ia supernova data to constrain the cosmological parameters and mγ simultaneously. We derive a new upper limit of mγ ≤ 3.8 × 10-51 kg, or equivalently mγ ≤ 2.1 × 10-15 eV/c2 (mγ ≤ 7.2 × 10-51 kg, or equivalently mγ ≤ 4.0 × 10-15 eV/c2) at 1σ (2σ) confidence level. Meanwhile, our analysis can also lead to a reasonable estimation for the IGM baryon fraction f IGM = 0.873+0.061 -0.050. With the number increment of localized FRBs, the constraints on both mγ and f IGM will be further improved. A caveat of constraining mγ within the context of the standard ΛCDM cosmological model is also discussed.

A new approach to flatness, horizon and late-time accelerating expansion problems on the basis of Mach’s principle

Based on the idea that the components of a cosmological metric may be determined by the total gravitational potential of the universe, the scalar field $\phi=1/G$ in the Jordan-Brans-Dicke (JBD) theory is introduced as evolving with the inverse square of the scale factor. Since the gravitational potential is related to the field $\phi$ resulting from Mach's principle and depends on time due to the expansion of space, the temporal evolution of the field should be in accord with the evolution of time and space intervals in the metric tensor. For the same reason, the time dependence of the field makes these comoving intervals relative for different points on the time axis. Thus, it is shown that introduction of the cosmic gravitational potential as a time dependent scalar field proportional to $1/a^2$ may resolve the flatness, the horizon and the late-time accelerating expansion problems of the standard model of cosmology. The luminosity distance vs redshift data of Type Ia supernovae is in agreement with this approach.

Hubble parameter reconstruction: A tool to explore the acceleration of the universe with observational constraints

This article introduces a novel parametric form of the Hubble parameter for exploring the accelerating cosmos in a model-independent manner. The model parameters are constrained using a Markov Chain Monte Carlo (MCMC) approach with a combined dataset spanning 31 cosmic chronometers (CC) data points, 26 non-correlated baryonic acoustic oscillations (BAO) points, and 1701 updated Pantheon+ supernovae type Ia (SNeIa) data points. We investigate the model’s kinematic behavior, including the transition from the deceleration phase to the acceleration phase, the jerk evolution, and the energy conditions. The results of the equation of state parameter suggest that our model behaves like the quintessence model and supports the current accelerating Universe. Additionally, we impose constraints on both the model parameters and the Hubble constant H0, and find that the values obtained for H0 align with other works obtained through reconstruction methods and observational data. Overall, this study provides valuable insights into the accelerating cosmos and highlights the importance of a model-independent approach in cosmological studies.

Cosmological constraints on dark energy in [formula omitted] gravity: A parametrized perspective

In this paper, we focus on the parametrization of the effective equation of state (EoS) parameter within the framework of f(Q) symmetric teleparallel gravity. Here, the gravitational action is represented by an arbitrary function of the non-metricity scalar Q. By utilizing a specific parametrization of the effective EoS parameter and a power-law model of f(Q) theory, namely f(Q)=βQm+1 (where β and m are arbitrary constants), we derive the cosmological solution of the Hubble parameter H(z). To constrain model parameters, we employ recent observational data, including the Observational Hubble parameter Data (OHD), Baryon Acoustic Oscillations data (BAO), and Type Ia supernovae data (SNe Ia). The current constrained value of the deceleration parameter is found to be q0=−0.50−0.01+0.01, indicating that the current Universe is accelerating. Furthermore, we examine the evolution of the density, EoS, and Om(z) diagnostic parameters to deduce the accelerating nature of the Universe. Finally, we perform a stability analysis with linear perturbations to confirm the model’s stability.

Measurement of the matter-radiation equality scale using the extended baryon oscillation spectroscopic survey quasar sample

ABSTRACT The position of the peak of the matter power spectrum, the so-called turnover scale, is set by the horizon size at the epoch of matter-radiation equality. It can easily be predicted in terms of the physics of the universe in the relativistic era, and so can be used as a standard ruler, independent of other features present in the matter power spectrum, such as baryon acoustic oscillations (BAOs). We use the distribution of quasars measured by the extended Baryon Oscillation Spectroscopic Survey (eBOSS) to determine the turnover scale in a model-independent fashion statistically. We avoid modelling the BAO by down-weighting affected scales in the covariance matrix using the mode deprojection technique. We measure the wavenumber of the peak to be $k_\mathrm{TO} = \left(17.6^{+1.9}_{-1.8} \right) \times 10^{-3}h/\mathrm{Mpc}$, corresponding to a dilation scale of $D_\mathrm{V}(z_\mathrm{eff} = 1.48) = \left(31.1^{+4.1}_{-3.4}\right)r_\mathrm{H}$. This is not competitive with current BAO distance measures in terms of determining the expansion history but does provide a useful cross-check. We combine this measurement with low-redshift distance measurements from type-Ia supernova data from Pantheon and BAO data from eBOSS to make a sound-horizon free estimate of the Hubble–Lemaître parameter and find it to be $H_0=64.8^{+8.4}_{-7.8} \ \mathrm{km/s/Mpc}$ with Pantheon, and $H_0=63.3^{+8.2}_{-6.9} \ \mathrm{km/s/Mpc}$ with eBOSS BAO. We make predictions for the measurement of the turnover scale by the Dark Energy Spectroscopic Instrument (DESI) survey, the Maunakea Spectroscopic Explorer (MSE), and MegaMapper, which will make more precise and accurate distance determinations.

Low-redshift estimates of the absolute scale of baryon acoustic oscillations

Measurements of the characteristic length scale r_s of the baryon acoustic oscillations (BAO) provide a robust determination of the distance-redshift relation. Currently, the best (sub-per cent) estimate of r_s at the drag epoch is provided by Cosmic Microwave Background (CMB) observations assuming the validity of the standard Lambda CDM model at z sim 1000. Therefore, inferring r_s from low-z observations in a model-independent way and comparing its value with CMB estimates provides a consistency test of the standard cosmology and its assumptions at high-z. In this paper, we address this question and estimate the absolute BAO scale combining angular BAO measurements and type Ia Supernovae data. Our analysis uses two different methods to connect these data sets and finds a good agreement between the low-z estimates of r_{s} with the CMB sound horizon at drag epoch, regardless of the value of the Hubble constant H_0 considered. These results highlight the robustness of the standard cosmology at the same time that they also reinforce the need for more precise cosmological observations at low-z.

Covariant formulation of refracted gravity

We propose a covariant formulation of refracted gravity (RG), which is a classical theory of gravity based on the introduction of gravitational permittivity – a monotonic function of the local mass density – in the standard Poisson equation. Gravitational permittivity mimics dark matter phenomenology. The covariant formulation of RG (CRG) that we propose belongs to the class of scalar-tensor theories, where the scalar fieldφhas a self-interaction potential 𝒱(φ) = − Ξφ, with Ξ being a normalization constant. We show that the scalar field is twice the gravitational permittivity in the weak-field limit. Far from a spherical source of densityρs(r), the transition between the Newtonian and the RG regime appears below the acceleration scaleaΞ = (2Ξ − 8πGρ/φ)1/2, withρ = ρs + ρbgandρbgbeing an isotropic and homogeneous background. In the limit 2Ξ ≫ 8πGρ/φ, we obtainaΞ ∼ 10−10m s−2. This acceleration is comparable to the accelerationa0originally introduced in MOdified Newtonian Dynamics (MOND). From CRG, we also derived the modified Friedmann equations for an expanding, homogeneous, and isotropic universe. We find that the same scalar fieldφthat mimics dark matter also drives the accelerated expansion of the Universe. From the stress-energy tensor ofφ, we derived the equation of state of a redshift-dependent effective dark energywDE = pDE/ρDE. Current observational constraints onwDEand distance modulus data of type Ia supernovae suggest that Ξ has a comparable value to the cosmological constant Λ in the standard model. Since Ξ also plays the same role of Λ, CRG suggests a natural explanation of the known relationa0 ∼ Λ1/2. CRG thus appears to describe both the dynamics of cosmic structure and the expanding Universe with a single scalar field, and it falls within the family of models that unify the two dark sectors, highlighting a possible deep connection between phenomena currently attributed to dark matter and dark energy separately.

Kernel Selection for Gaussian Process in Cosmology: With Approximate Bayesian Computation Rejection and Nested Sampling

The Gaussian process (GP) has gained much attention in cosmology due to its ability to reconstruct cosmological data in a model-independent manner. In this study, we compare two methods for GP kernel selection: approximate Bayesian computation (ABC) rejection and nested sampling. We analyze three types of data: cosmic chronometer data, type Ia supernovae data, and gamma-ray burst data, using five kernel functions. To evaluate the differences between kernel functions, we assess the strength of evidence using Bayes factors. Our results show that, for ABC rejection, the Matérn kernel with ν = 5/2 (M52 kernel) outperformes the commonly used radial basis function (RBF) kernel in approximating all three data sets. Bayes factors indicate that the M52 kernel typically supports the observed data better than the RBF kernel but with no clear advantage over other alternatives. However, nested sampling gives different results, with the M52 kernel losing its advantage. Nevertheless, Bayes factors indicate no significant dependence of the data on each kernel.

H0=69.8±1.3 km s−1 Mpc−1 , Ωm0=0.288±0.017 , and other constraints from lower-redshift, non-CMB, expansion-rate data

We use updated Type Ia Pantheon+ supernova, baryon acoustic oscillation, and Hubble parameter (now also accounting for correlations) data, as well as new reverberation-measured C IV quasar data, and quasar angular size, H II starburst galaxy, reverberation-measured Mg II quasar, and Amati-correlated gamma-ray burst data to constrain cosmological parameters. We show that these data sets result in mutually consistent constraints and jointly use them to constrain cosmological parameters in six different spatially-flat and non-flat cosmological models. Our analysis provides summary model-independent determinations of two key cosmological parameters: the Hubble constant, $H_0=69.8\pm1.3$ $\rm{km \ s^{-1} \ Mpc^{-1}}$, and the current non-relativistic matter density parameter, $\Omega_{m0}=0.288\pm0.017$. Our summary error bars are 2.4 and 2.3 times those obtained using the flat $\Lambda$CDM model and Planck TT,TE,EE+lowE+lensing cosmic microwave background (CMB) anisotropy data. Our $H_0$ value is very consistent with that from the local expansion rate based on the Tip of the Red Giant Branch data, is 2$\sigma$ lower than that from the local expansion rate based on Type Ia supernova and Cepheid data, and is 2$\sigma$ higher than that in the flat $\Lambda$CDM model based on Planck TT,TE,EE+lowE+lensing CMB data. Our data compilation shows at most mild evidence for non-flat spatial hypersurfaces, but more significant evidence for dark energy dynamics, 2$\sigma$ or larger in the spatially-flat dynamical dark energy models we study.

Thermal friction as a solution to the Hubble and large-scale structure tensions

Thermal friction offers a promising solution to the Hubble and the large-scale structure (LSS) tensions. This additional friction acts on a scalar field in the early universe and extracts its energy density into dark radiation, the cumulative effect being similar to that of an early dark energy (EDE) scenario. The dark radiation automatically redshifts at the minimal necessary rate to improve the Hubble tension. On the other hand, the addition of extra radiation to the Universe can mitigate the LSS tension. We explore this model in light of cosmic microwave background (CMB), baryon acoustic oscillation, and type Ia supernova data, including the SH0ES ${H}_{0}$ measurement and the Dark Energy Survey Y1 data release in our analysis. Our results indicate a preference for the regime where the scalar field converts to dark radiation at very high redshifts ($z\ensuremath{\gtrsim}{10}^{5}$), asymptoting effectively to an extra self-interacting radiation species rather than an EDE-like injection. In this limit, thermal friction can ease both the Hubble and the LSS tensions, but not resolve them. We find the source of this preference to be the incompatibility of the CMB data with the linear density perturbations of the dark radiation when injected at redshifts close to matter-radiation equality.

Testing ΛCDM cosmology in a binned universe: Anomalies in the deceleration parameter

We study the reconstructed deceleration parameter splitting the data in different redshift bins, fitting both a cosmographic luminosity distance and also assuming a flat $\Lambda$CDM model, using the Pantheon+ sample of type Ia supernova data (SNIA). We observe tensions $\sim 2\sigma-3\sigma$ for different redshift and distance indicators if the full sample is used. However, those tensions disappear when the SNIA at $z<0.008$ are removed. If the data is splitted in 2 hemispheres according to our movement w.r.t CMB, a strange $3.8 \sigma$ tension appears in one of the samples between particular redshift bins. Finally, considering posterior distribution as Gaussian, general linear model prefers a positive slope for $q_0$ across redshift bins opposed to a zero slope expected in a $\Lambda$CDM universe. We discuss possible explanations for our results and the influence of lowest redshift SNIA data in cosmological analysis.

Exact Solutions and Cosmological Constraints in Fractional Cosmology

This paper investigates exact solutions of cosmological interest in fractional cosmology. Given μ, the order of Caputo’s fractional derivative, and w, the matter equation of state, we present specific exact power-law solutions. We discuss the exact general solution of the Riccati Equation, where the solution for the scale factor is a combination of power laws. Using cosmological data, we estimate the free parameters. An analysis of type Ia supernovae (SNe Ia) data and the observational Hubble parameter data (OHD), also known as cosmic chronometers, and a joint analysis with data from SNe Ia + OHD leads to best-fit values for the free parameters calculated at 1σ, 2σ and 3σ confidence levels (CLs). On the other hand, these best-fit values are used to calculate the age of the Universe, the current deceleration parameter (both at 3σ CL) and the current matter density parameter at 1σ CL. Finding a Universe roughly twice as old as the one of ΛCDM is a distinction of fractional cosmology. Focusing our analysis on these results, we can conclude that the region in which μ&gt;2 is not ruled out by observations. This parameter region is relevant because fractional cosmology gives a power-law solution without matter, which is accelerated for μ&gt;2. We present a fractional origin model that leads to an accelerated state without appealing to Λ or dark energy.

Fitting Type Ia Supernova Data to a Cosmological Model Based on Einstein–Newcomb–De Sitter Space

Einstein–Newcomb–de Sitter (ENdS) space is de Sitter’s modification of spherical space used by Einstein in his first cosmological model paper published in 1917. The modification by de Sitter incorporated the topological identification of antipodal points in space previously proposed by Newcomb in 1877. De Sitter showed that space topologically modified in this way (called elliptical or projective space) satisfies Einstein’s field equations. De Sitter also found that in a space with constant positive curvature, spectral lines of remote galaxies would be red-shifted (called the de Sitter effect). However, de Sitter’s formulae relating distances to red shifts do not satisfy observational data. The likely reason for this mismatch is that de Sitter mainly focused on space curvature and ignored the identification of antipodal points. Herein, we demonstrate that it is this particular feature that allows an almost perfect fit of the ENdS-based cosmological model to observational data. We use 1701 sources from the type Ia supernovae data sample called Pantheon+, which was previously used to fit the ΛCDM model. ΛCDM and ENdS diverge in their predictions for red shifts exceeding z∼2.3. Since there are no available type Ia supernovae (SNe) data for higher red shifts, both models can be validated by using an additional sample of 193 gamma-ray bursts (GRBs) spanning red shifts up to z∼8. This validation shows that the minimum χ2 for the SNe+GRBs sample is about 2.7% smaller for the ENdS space model than for the ΛCDM model.

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.