Hubble Tension Research Articles

Non-oscillating early dark energy and quintessence from [formula omitted]-attractors

Early dark energy (EDE) is one of the most promising possibilities in order to resolve the Hubble tension: the discrepancy between the locally measured and cosmologically inferred values of the Hubble constant. In this paper we propose a toy model of unified EDE and late dark energy (DE), driven by a scalar field in the context of α-attractors. The field provides an injection of a subdominant dark energy component near matter-radiation equality, and redshifts away shortly after via free-fall, later refreezing to become late-time DE at the present day. Using reasonable estimates of the current constraints on EDE from the literature, we find that the parameter space is narrow but viable, making our model readily falsifiable. Since our model is non-oscillatory, the density of the field decays faster than the usual oscillatory EDE, thereby possibly achieving better agreement with observations.

On the statistical assumption on the distance moduli of Supernovae Ia and its impact on the determination of cosmological parameters

Type Ia Supernovae (SNe Ia) are considered the most reliable standard candles and they have played an invaluable role in cosmology since the discovery of the Universe's accelerated expansion. During the last decades, the SNe Ia samples have been improved in number, redshift coverage, calibration methodology, and systematics treatment. These efforts led to the most recent “Pantheon” (2018) and “Pantheon +” (2022) releases, which enable to constrain cosmological parameters more precisely than previous samples. In this era of precision cosmology, the community strives to find new ways to reduce uncertainties on cosmological parameters. To this end, we start our investigation even from the likelihood assumption of Gaussianity, implicitly used in this domain. Indeed, the usual practice involves constraining parameters through a Gaussian distance moduli likelihood. This method relies on the implicit assumption that the difference between the distance moduli measured and the ones expected from the cosmological model is Gaussianly distributed. In this work, we test this hypothesis for both the Pantheon and Pantheon + releases. We find that in both cases this requirement is not fulfilled and the actual underlying distributions are a logistic and a Student's t distribution for the Pantheon and Pantheon + data, respectively. When we apply these new likelihoods fitting a flat ΛCDM model, we significantly reduce the uncertainties on the matter density ΩM and the Hubble constant H0 of ∼40%. As a result, the Hubble tension is increased at >5σ level. This boosts the SNe Ia power in constraining cosmological parameters, thus representing a huge step forward to shed light on the current debated tensions in cosmology.

Interacting dark energy: clarifying the cosmological implications and viability conditions

In this study, cosmological models are considered, where dark matter and dark energy are coupled and may exchange energy through non-gravitational interactions with one other. These interacting dark energy (IDE) models have previously been introduced to address problems with the standard ΛCDM model of cosmology (which include the coincidence problem, Hubble tension and S_8 discrepancy). However, conditions ensuring positive energy densities have often been overlooked. Assuming two different linear dark energy couplings, Q = δ H ρ_de and Q = δ H ρ_dm, we find that negative energy densities are inevitable if energy flows from dark matter to dark energy (iDMDE regime) and that consequently, we should only seriously consider models where energy flows from dark energy to dark matter (iDEDM regime). To additionally ensure that these models are free from early time instabilities, we need to require that dark energy is in the `phantom' (ω<-1) regime. This has the consequence that model Q=δ H ρ_dm will end with a future big rip singularity, while Q = δ H ρ_de may avoid this fate with the right choice of cosmological parameters.

Hubble Tension Explanation from This Cosmological Model AΛΩ (Slow Bang Model, SB)

Hubble Tension Explanation from This Cosmological Model AΛΩ (Slow Bang Model, SB)

An effective description of Laniakea: impact on cosmology and the local determination of the Hubble constant

We propose an effective model to describe the bias induced on cosmological observables by Laniakea, the gravitational supercluster hosting the Milky Way, which was defined using peculiar velocity data from Cosmicflows-4 (CF4). The structure is well described by an ellipsoidal shape exhibiting triaxial expansion, reasonably approximated by a constant expansion rate along the principal axes. Our best fits suggest that the ellipsoid, after subtracting the background expansion, contracts along the two smaller axes and expands along the longest one, predicting an average expansion of ∼ -1.1 km/s/Mpc. The different expansion rates within the region, relative to the mean cosmological expansion, induce line-of-sight-dependent corrections in the computation of luminosity distances. We apply these corrections to two low-redshift datasets: the Pantheon+ catalog of type Ia Supernovae (SN Ia), and 63 measurements of Surface Brightness Fluctuations (SBF) of early-type massive galaxies from the MASSIVE survey. We find corrections on the distances of order ∼ 2-3%, resulting in a shift in the inferred best-fit values of the Hubble constant H 0 of order ΔH 0 SN Ia ≈ 0.5 km/s/Mpc and ΔH 0 SBF ≈ 1.1 km/s/Mpc, seemingly worsening the Hubble tension.

CMBR constrained Milky-Way mass resolving the Hubble tension

CMBR constrained Milky-Way mass resolving the Hubble tension

Big Bang Nucleosynthesis Constraints and Indications for Beyond Standard Model Neutrino Physics

We use Big Bang Nucleosynthesis (BBN) to probe Beyond Standard Model physics in the neutrino sector. Recently, the abundances of primordially produced light elements D and He-4 were determined from observations with better accuracy. The good agreement between the theoretically predicted abundances of primordially produced light elements and those derived from observations allows us to update the BBN constraints on Beyond Standard Model (BSM) physics. We provide numerical analysis of several BSM models of BBN and obtain precise cosmological constraints and indications for new neutrino physics. Namely, we derive more stringent BBN constraints on electron neutrino–sterile neutrino oscillations corresponding to 1% uncertainty of the observational determination of the primordial He-4. The cosmological constraints are obtained both for the zero and non-zero cases of the initial population of the sterile neutrino state. Then, in a degenerate BBN model with neutrino νe↔νs oscillations, we analyze the change in the cosmological constraints in case lepton asymmetry L is big enough to suppress oscillations. We obtain constraints on the lepton asymmetry L. We discuss a possible solution to the dark radiation problem in degenerate BBN models with νe↔νs oscillations in case L is large enough to suppress neutrino oscillations during the BBN epoch. Interestingly, the required value of L for solving the DR problem is close to the value of L indicated by the EMPRESS experiment, and also it is close to the value of lepton asymmetry that is necessary to relax Hubble tension.

Reconstructing the Hubble Parameter with Future Gravitational-wave Missions Using Machine Learning

We study the prospects of Gaussian processes (GPs), a machine-learning (ML) algorithm, as a tool to reconstruct the Hubble parameter H(z) with two upcoming gravitational-wave (GW) missions, namely, the evolved Laser Interferometer Space Antenna (eLISA) and the Einstein Telescope (ET). Assuming various background cosmological models, the Hubble parameter has been reconstructed in a nonparametric manner with the help of a GP using realistically generated catalogs for each mission. The effects of early-time and late-time priors on the reconstruction of H(z), and hence on the Hubble constant (H 0), have also been focused on separately. Our analysis reveals that a GP is quite robust in reconstructing the expansion history of the Universe within the observational window of the specific missions under consideration. We further confirm that both eLISA and ET would be able to provide constraints on H(z) and H 0, which would be competitive to those inferred from current data sets. In particular, we observe that an eLISA run of a ∼10 yr duration with ∼80 detected bright siren events would be able to constrain H 0 as precisely as a ∼3 yr ET run assuming ∼1000 bright siren event detections. Further improvement in precision is expected for longer eLISA mission durations such as a ∼15 yr time frame having ∼120 events. Lastly, we discuss the possible role of these future GW missions in addressing the Hubble tension, for each model, on a case-by-case basis.

Hubble tension and fifth forces

Fifth forces are ubiquitous in modified theories of gravity. In this paper, we analyze their effect on the Cepheid-calibrated cosmic distance ladder, specifically with respect to the inferred value of the Hubble constant (H0). We consider a variety of effective models where the strength, or amount of screening, of the fifth force is estimated using proxy fields related to the large-scale structure of the Universe. To quantify the level of tension between the local distance ladder and the value for H0, we calculate the probability of obtaining a test result at least as extreme as the observed one, assuming that the model is correct (the p-value). For all models considered, the level of agreement is ≳20%, relieving the tension compared to the concordance model, exhibiting an agreement of only 1%. The alleviated discrepancy comes partially at the cost of an increased tension between distance estimates from Cepheids and the tip of the red-giant branch (TRGB). Demanding also that the consistency between Cepheid and TRGB distance estimates is not impaired, some fifth force models can still accommodate the data with a probability ≳20%. This provides incentive for more detailed investigations of fundamental theories on which the effective models are based and their effect on the Hubble tension. Published by the American Physical Society 2023

Emergent Unparticles Dark Energy can restore cosmological concordance

Addressing the discrepancy between the late and early time measurements of the Hubble parameter, H 0, and the so-called S 8 parameter has been a challenge in precision cosmology. Several models are present to address these tensions, but very few of them can do so simultaneously. In the past, we have suggested Banks-Zaks/Unparticles as an emergent Dark Energy model, and claimed that it can ameliorate the Hubble tension. In this work, we test this claim, and perform a likelihood analysis of the model and its parameters given current data, and compare it to ΛCDM. The model offers a possible resolution of Hubble tension and softens the Large Scale Structure (LSS) tension without employing a scalar field or modifying the gravitational sector. Our analysis shows a higher value of H 0 ∼ 70 – 73 km/sec/Mpc and a slightly lower value of S 8 for certain combinations of data sets. Consideration of Planck CMB data combined with the Pantheon sample and SH0ES priors lowers the H 0 and S 8 tension to 0.96σ and 0.94σ respectively with best-fit Δχ 2 ≈ -11 restoring cosmological concordance. Significant improvement in the likelihood persists for other combinations of data sets as well. Evidence for the model is given by inferring one of its parameters to be x 0 ≃ -4.46.The improvement in the fit is driven by the inclusion of the SH0ES prior. In its absence most of the improvement is due to larger error bars in the Emergent Unparticles Dark Energy model.

Probing early modification of gravity with Planck, ACT and SPT

We consider a model of early modified gravity (EMG) that was recently proposed as a candidate to resolve the Hubble tension. The model consists of a scalar field σ with a nonminimal coupling (NMC) to the Ricci curvature of the form F(σ) = M pl 2+ξσ 2 and an effective mass induced by a quartic potential V(σ) = λσ 4/4. We present the first analyses of the EMG model in light of the latest ACT DR4 and SPT-3G data in combination with full Planck data, and find a ≳ 2σ preference for a non-zero EMG contribution from a combination of primary CMB data alone, mostly driven by ACT-DR4 data. This is different from popular `Early Dark Energy' models, which are detected only when the high-ℓ information from Planck temperature is removed. We find that the NMC plays a key role in controlling the evolution of density perturbations that is favored by the data over the minimally coupled case. Including measurements of supernovae luminosity distance from Pantheon+, baryonic acoustic oscillations and growth factor from BOSS, and CMB lensing of Planck leaves the preference unaffected. In the EMG model, the tension with SH 0ES is alleviated from ∼ 6σ to ∼ 3σ. Further adding SH 0ES data raises the detection of the EMG model above 5σ.

Little Ado about Everything: ηCDM, a Cosmological Model with Fluctuation-driven Acceleration at Late Times

We propose a model of the Universe (dubbed ηCDM) featuring a controlled stochastic evolution of the cosmological quantities that is meant to render the effects of small deviations from homogeneity/isotropy on scales of 30–50 h −1 Mpc at late cosmic times associated with the emergence of the cosmic web. Specifically, we prescribe that the behavior of the matter/radiation energy densities in different patches of the Universe with such a size can be effectively described by a stochastic version of the mass–energy evolution equation. The latter includes, besides the usual dilution due to cosmic expansion, an appropriate noise term that statistically accounts for local fluctuations due to inhomogeneities, anisotropic stresses, and matter flows induced by complex gravitational processes. The evolution of the different patches as a function of cosmic time is rendered via the diverse realizations of the noise term; meanwhile, at any given cosmic time, sampling the ensemble of patches will create a nontrivial spatial distribution of the various cosmological quantities. Finally, the overall behavior of the Universe will be obtained by averaging over the patch ensemble. We assume a simple and physically reasonable parameterization of the noise term, gauging it against a wealth of cosmological data sets in the local and high-redshift Universe. We find that, with respect to standard ΛCDM, the ensemble-averaged cosmic dynamics in the ηCDM model is substantially altered by the stochasticity in three main respects: (i) an accelerated expansion is enforced at late cosmic times without the need for any additional exotic component (e.g., dark energy), (ii) the spatial curvature can stay small even in a low-density Universe constituted solely by matter and radiation, (iii) matter can acquire an effective negative pressure at late times. The ηCDM model is Hubble tension–free, meaning that the estimates of the Hubble constant from early- and late-time measurements do not show marked disagreement as in ΛCDM. We also provide specific predictions for the variance of the cosmological quantities among the different patches of the Universe at late cosmic times. Finally, the fate of the Universe in the ηCDM model is investigated to show that the cosmic coincidence problem is relieved without invoking the anthropic principle.

Dark Matter Cosmology with Varying Viscosity: A Possible Resolution to the S 8 Tension

We study varying forms of viscous dark matter (DM) and try to address the intriguing tensions of the standard model of cosmology with recent cosmological data, including the Hubble and S 8 tensions. We note that by assuming the DM viscosity depends on the Hubble parameter, DM density, or both, one can improve the statistics. Although the models tend to aggravate the Hubble tension a bit, they tend to reduce the S 8 tension, even in comparison with the constant viscosity case. Since similar-to-viscosity massive neutrinos suppress the power spectrum of matter on small length scales, considering them along with the viscous DM, we find that the neutrino mass range is tightened.

The Unsettled Number: Hubble’s Tension

One of main sources of uncertainty in modern cosmology is the present rate of the universe’s expansion, H0, called the Hubble constant. Once again, different observational techniques bring about different results, causing new “Hubble tension”. In the present work, we review the historical roots of the Hubble constant from the beginning of the twentieth century, when modern cosmology originated, to the present. We develop the arguments that gave rise to the importance of measuring the expansion of the Universe and its discovery, and we describe the different pioneering works attempting to measure it. There has been a long dispute on this matter, even in the present epoch, which is marked by high-tech instrumentation and, therefore, in smaller uncertainties in the relevant parameters. It is, again, currently necessary to conduct a careful and critical revision of the different methods before one invokes new physics to solve the so-called Hubble tension.

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.

The Hubble tension survey: A statistical analysis of the 2012–2022 measurements

ABSTRACT In order to investigate the potential Hubble tension, we compile a catalogue of 216 measurements of the Hubble–Lemaître constant H0 between 2012 and 2022, which includes 109 model-independent measurements and 107 ΛCDM model-based measurements. Statistical analyses of these measurements show that the deviations of the results with respect to the average H0 are far larger than expected from their error bars if they follow a Gaussian distribution. We find that xσ deviation is indeed equivalent in a Gaussian distribution to xeqσ deviation in the frequency of values, where xeq = 0.72x0.88. Hence, a tension of 5σ, estimated between the Cepheid-calibrated type Ia supernovae and cosmic microwave background (CMB) data, is indeed a 3σ tension in equivalent terms of a Gaussian distribution of frequencies. However, this recalibration should be independent of the data whose tension we want to test. If we adopt the previous analysis of data of 1976–2019, the equivalent tension is reduced to 2.25σ. Covariance terms due to correlations of measurements do not significantly change the results. None the less, the separation of the data into two blocks with H0 &amp;lt; 71 and H0 ≥ 71 km s−1 Mpc−1 finds compatibility with a Gaussian distribution for each of them without removing any outlier. These statistical results indicate that the underestimation of error bars for H0 remain prevalent over the past decade, dominated by systematic errors in the methodologies of CMB and local distance ladder analyses.

Cosmic-void observations reconciled with primordial magnetogenesis

It has been suggested that the weak magnetic field hosted by the intergalactic medium in cosmic voids could be a relic from the early Universe. However, accepted models of turbulent magnetohydrodynamic decay predict that the present-day strength of fields originally generated at the electroweak phase transition (EWPT) without parity violation would be too low to explain the observed scattering of γ-rays from TeV blazars. Here, we propose that the decay is mediated by magnetic reconnection and conserves the mean square fluctuation level of magnetic helicity. We find that the relic fields would be stronger by several orders of magnitude under this theory than was indicated by previous treatments, which restores the consistency of the EWPT-relic hypothesis with the observational constraints. Moreover, efficient EWPT magnetogenesis would produce relics at the strength required to resolve the Hubble tension via magnetic effects at recombination and seed galaxy-cluster fields close to their present-day strength.

Canonical Hubble-Tension-Resolving Early Dark Energy Cosmologies Are Inconsistent with the Lyman-α Forest.

Current cosmological data exhibit discordance between indirect and some direct inferences of the present-day expansion rate H_{0}. Early dark energy (EDE), which briefly increases the cosmic expansion rate prior to recombination, is a leading scenario for resolving this "Hubble tension" while preserving a good fit to cosmic microwave background (CMB) data. However, this comes at the cost of changes in parameters that affect structure formation in the late-time universe, including the spectral index of scalar perturbations n_{s}. Here, we present the first constraints on axionlike EDE using data from the Lyman-α forest, i.e., absorption lines imprinted in background quasar spectra by neutral hydrogen gas along the line of sight. We consider two independent measurements of the one-dimensional Lyα forest flux power spectrum from the Sloan Digital Sky Survey (SDSS eBOSS) and from the MIKE/HIRES and X-Shooter spectrographs. We combine these with a baseline dataset comprised of Planck CMB data and baryon acoustic oscillation (BAO) measurements. Combining the eBOSS Lyα data with the CMB and BAO dataset reduces the 95% confidence level (C.L.) upper bound on the maximum fractional contribution of EDE to the cosmic energy budget f_{EDE} from 0.07 to 0.03 and constrains H_{0}=67.9_{-0.4}^{+0.4} km/s/Mpc (68% C.L.), with maximum aposteriori value H_{0}=67.9 km/s/Mpc. Similar results are obtained for the MIKE/HIRES and X-Shooter Lyα data. Our Lyα-based EDE constraints yield H_{0} values that are in >4σ tension with the SH0ES distance-ladder measurement and are driven by the preference of the Lyα forest data for n_{s} values lower than those required by EDE cosmologies that fit Planck CMB data. Taken at face value, the Lyα forest severely constrains canonical EDE models that could resolve the Hubble tension.

Impact of big bang nucleosynthesis on the H 0 tension

We investigate the impact of big bang nucleosynthesis (BBN) on the Hubble tension, focusing on how the treatment of the reaction rate and observational data affect the evaluation of the tension. We show that the significance of the tension is increased to 4.41σ from 3.61σ and to 5.22σ from 4.58σ in axionlike early dark energy model with n = 2 and n = ∞, respectively, depending on the treatment of the reaction rate and observational data. This indicates that how we include the BBN data in the analysis can give a significant impact on the Hubble tension, and we need to carefully consider the assumptions of the analysis to evaluate the significance of the tension when the BBN data is used.

Cosmic chronometers with photometry: a new path to H(z)

We present a proof-of-principle determination of the Hubble parameter H(z) from photometric data, obtaining a determination at an effective redshift of z = 0.75 (0.65 < z < 0.85) of H(0.75) = 105.0±7.9(stat)±7.3(sys) km s-1 Mpc-1, with 7.5% statistical and 7% systematic (10% with statistical and systematics combined in quadrature) accuracy. This is obtained in a cosmology model-independent fashion, but assuming a linear age-redshift relation in the relevant redshift range, as such, it can be used to constrain arbitrary cosmologies as long as H(z) can be considered slowly varying over redshift. In particular, we have applied a neural network, trained on a well-studied spectroscopic sample of 140 objects, to the COSMOS2015 survey to construct a set of 19 thousand near-passively evolving galaxies and build an age-redshift relation. The Hubble parameter is given by the derivative of the red envelope of the age-redshift relation. This is the first time the Hubble parameter is determined from photometry at ≲ 10% accuracy. Accurate H(z) determinations could help shed light on the Hubble tension; this study shows that photometry, with a reduction of only a factor of two in the uncertainty, could provide a new perspective on the tension.