We explore cosmological implications of a genuinely Weyl invariant (WI) gravitational interaction. The latter reduces to general relativity in a particular conformal frame for which the gravitational coupling and active gravitational masses are fixed. Specifically, we consider a cosmological model in this framework that is {\it dynamically} identical to the standard model (SM) of cosmology. However, {\it kinematics} of test particles traveling in the new background metric is modified thanks to a new (cosmological) fundamental mass scale, $γ$, of the model. Since the lapse-function of the new metric is radially-dependent any incoming photon experiences (gravitational) red/blueshift in the {\it comoving} frame, unlike in the SM. Distance scales are modified as well due to the scale $γ$. The claimed $4.4σ$ tension level between the locally measured Hubble constant, $H_{0}$, with SH0ES and the corresponding value inferred from the cosmic microwave background (CMB) could then be significantly alleviated by an earlier-than-thought recombination. Assuming vanishing spatial curvature, either one of the Planck 2018 (P18) or dark energy survey (DES) yr1 data sets subject to the SH0ES prior imply that $γ^{-1}$ is $O(100)$ times larger than the Hubble scale, $H_{0}^{-1}$. Considering P18+SH0ES or P18+DES+SH0ES data set combinations, the odds against vanishing $γ$ are over 1000:1 and 2000:1, respectively, and the model is strongly favored over the SM with a deviance information criterion (DIC) gain $\gtrsim 10$ and $\gtrsim 12$, respectively. The tension is reduced in this model to $\sim 1.5$ and $1.3 σ$, respectively. We conclude that the $H_{0}$ tension may simply result from a yet unrecognized fundamental symmetry of the gravitational interaction -- Weyl invariance. (abridged)
We are at an interesting juncture in cosmology. With new methods and technology, the accuracy in measurement of the Hubble constant has vastly improved, but a recent tension has arisen that is either signaling new physics or as-yet unrecognized uncertainties.
As observations of the Hubble parameter from both early and late sources have improved, the tension between these has increased to be well above the 5$σ$ threshold. Given this, the need for an explanation of such a tension has grown. In this paper, we explore a set of 7 assumptions, and show that, in order to alleviate the Hubble tension, a model needs to break at least one of these 7, providing a quick and easy to apply check for new model proposals. We also use this framework to make a rough categorisation of current proposed models, and show the existence of at least one under-explored aven…
The Hubble tension that the standard $Λ$CDM model is suffering from can be resolved with pre-recombination early dark energy. We present the first constraint on the tensor-to-scalar ratio $r$ in corresponding Hubble-tension-free cosmologies using the most recent BICEP/Keck cosmic microwave background (CMB) B-mode polarization data. We find, combining BICEP/Keck with Planck18 CMB and baryon acoustic oscillation data, that the models with larger Hubble constant $H_0$ will have tighter upper bound on $r$, and resolution $H_0\sim73$ km/s/Mpc of the Hubble tension tightens the upper bound to $r<0.0…
Although both early and late-time modifications of the $Λ$CDM model have been proposed to address the Hubble tension, compelling arguments suggest that for a solution to be successful it needs to modify the expansion history of the universe prior to recombination. This greatly increases the importance of precise CMB observations, and in this letter we make the argument for CMB spectral distortions, highlighting their potential role in constraining models that introduce significant shifts in the standard $Λ$CDM parameters, such as the scalar spectral index, in attempt to solve the Hubble tensio…
Small-scale inhomogeneities in the baryon density around recombination have been proposed as a solution to the tension between local and global determinations of the Hubble constant. These baryon clumping models make distinct predictions for the cosmic microwave background anisotropy power spectra on small angular scales. We use recent data from the Atacama Cosmology Telescope to test these predictions. No evidence for baryon clumping is found, assuming a range of parameterizations for time-independent baryon density probability distribution functions. The inferred Hubble constant remains in s…
Local measurements of the Hubble parameter obtained from the distance ladder at low redshift are in tension with global values inferred from cosmological standard rulers. A key role in the tension is played by the assumptions on the cosmological history, in particular on the origin of dark energy. Here we consider a scenario where dark energy originates from the amplification of quantum fluctuations of a light field in inflation. We show that spatial correlations inherited from inflationary quantum fluctuations can reduce the Hubble tension down to one standard deviation, thus relieving the pr…
Future precision measurements of CMB polarizations can shed new light on the problem so called Hubble tension. The Hubble tension comes from the difference of the evolutions of the Hubble parameter which are determined with two different distance ladders. The standard distance ladder with the observation of Cepheid variables and type Ia supernovae gives larger values of the Hubble constant, and the inverse distance ladder with the observation of the baryon acoustic oscillations both in the CMB and in the clustering of galaxies gives smaller values of the Hubble constant. These different evolut…
In this article, we elaborate further on the $Λ$CDM "tension", suggested recently by the authors \cite{Lusso:2019akb,Risaliti:2018reu}. We combine Supernovae type Ia (SNIa) with quasars (QSO) and Gamma Ray Bursts (GRB) data in order to reconstruct a model independent Hubble diagram to as high redshifts as possible. Specifically, in the case of either SNIa or SNIa/QSO data, we find that current values of the cosmokinetic parameters extracted from the Gaussian process are consistent with those of $Λ$CDM. Including GRBs, in the analysis, we find a tension, which however is not as significant as t…
Hubble tension in k-essence: Evidence for robust tension alleviation
Botswana International University of Science and Technology（博茨瓦纳国际科学与技术大学）；University of Cape Town（开普敦大学）；North-West University（西北大学）；Omdurman Islamic University（恩图曼伊斯兰大学）
Using sedimentary and eclipse-based measurements of the lunar recession velocity, we derive a new local-Universe measurement of the Hubble constant ($H_0$) from the recession rate of Earth's Moon. Taking into account the effects of tides, we find a value of $H_{0}$ = 63.01 $\pm$ 1.79 km s$^{-1}$ Mpc$^{-1}$, which is in approximate agreement with the Planck space mission's measurement using the cosmic microwave background (CMB) and base $Λ$CDM. Our new measurement represents the first ever model-independent, single-step measurement of the Universe's current expansion rate. This is also the firs…
The Hubble tension seems to be a crisis with $\sim5σ$ discrepancy between the most recent local distance ladder measurement from type Ia supernovae calibrated by Cepheids and the global fitting constraint from the cosmic microwave background data. To narrow down the possible late-time solutions to the Hubble tension, we have used in a recent study [Phys. Rev. D 105, L021301 (2022)] an improved inverse distance ladder method calibrated by the absolute measurements of the Hubble expansion rate at high redshifts from the cosmic chronometer data, and found no appealing evidence for new physics at …
A current problem within the ΛCDM framework is the tension between late and early time measurements of the Hubble parameter today, H0. We entertain the possibility that dark energy modeled as multiple interacting axion-like-particle species can alleviate the current Hubble tension. We then test these parameters against the milder tension between the CMB and large scale structure (LSS) observations of σ8 to ensure that these models do not exacerbate the tension. We find that there exist parameter spaces for models of two and three axion-like-particles which can potentially alleviate the Hubble …
Early dark energy (EDE) offers a particularly interesting theoretical approach to the Hubble tension, albeit one that introduces its own set of challenges, including a new `why then' problem related to the EDE injection time at matter-radiation equality, and a mild worsening of the large-scale structure (LSS) tension. Both these challenges center on the properties of dark matter, which becomes the dominant component of the Universe at EDE injection and is also responsible for seeding LSS. Motivated by this, we present the potential of couplings between EDE and dark matter to address these chal…
Recently Risaliti \& Lusso [Nature Astron. 3 (2019) 3 272] reported new measurements of the expansion rate of the Universe by constructing the Hubble diagram of 1598 quasars in the redshift range $0.5<z<5.5$. It is claimed a $4σ$ tension with the standard concordance $Λ$CDM concerning both the fractionary matter density $Ω_{m0}$ and the dark energy equation of state parameter $w_{de}$ standard values. In this work we promote an independent analysis of the same data set using a model-independent estimator for cosmic acceleration. Our results corroborate that the source of such tension can be re…
The $Λ$ Cold Dark Matter model ($Λ$CDM) represents the current standard model in cosmology. Within this, there is a tension between the value of the Hubble constant, $H_0$, inferred from local distance indicators and the angular scale of fluctuations in the Cosmic Microwave Background (CMB). We investigate whether the tension is significant enough to warrant new physics in the form of modifying or adding energy components to the standard cosmological model. We find that late time dark energy explanations are slightly disfavoured whereas a pre-CMB decoupling extra dark energy component has a ma…
In this manuscript we reassess the potential of interacting dark matter-dark energy models in solving the Hubble constant tension. These models have been proposed but also questioned as possible solutions to the $H_0$ problem. Here we examine several interacting scenarios against cosmological observations, focusing on the important role played by the calibration of Supernovae data. In order to reassess the ability of interacting dark matter-dark energy scenarios in easing the Hubble constant tension, we systematically confront their theoretical predictions using a prior on the Supernovae Ia ab…
The Hubble tension, if not caused by any systematics, could be relieved or even resolved from modifying either the early-time or late-time Universe. The early-time modifications are usually in tension with either galaxy clustering or galaxy lensing constraints. The late-time modifications are also in conflict with the constraint from the inverse distance ladder, which, however, is weakened by the dependence on a sound-horizon prior and some particular approximation for the late-time expansion history. To achieve a more general no-go argument for the late-time scenarios, we propose to use a glo…
We propose a dark energy model based on the physics of critical phenomena which is consistent with both the Planck's CMB and the Riess et al.'s local Hubble measurements. In this model the dark energy density behaves like the magnetization of the Ising model. This means the dark energy is an emergent phenomenon and we named it critically emergent dark energy model, CEDE. In CEDE, dark energy emerges at a transition redshift, $z_c$, corresponding to the critical temperature in critical phenomena. Combining the Planck CMB data and local measurement of the Hubble constant from Riess et al. (2019)…
The Hubble constant ($H_0$) tension is one of the major open problems in modern cosmology. This tension is the discrepancy, ranging from 4 to 6 $σ$, between the $H_0$ value estimated locally with the combination of Supernovae Ia (SNe Ia) + Cepheids and the cosmological $H_0$ obtained through the study of the Cosmic Microwave Background (CMB) radiation. The approaches adopted in Dainotti et al. 2021 (ApJ) and Dainotti et al. 2022 (Galaxies) are introduced. Through a binning division of the Pantheon sample of SNe Ia (Scolnic et al. 2018), the value of $H_0$ has been estimated in each of the reds…
The combination of Baryonic Acoustic Oscillation (BAO) data together with light element abundance measurements from Big Bang Nucleosynthesis (BBN) has been shown to constrain the cosmological expansion history to an unprecedented degree. Using the newest LUNA data and DR16 data from SDSS, the BAO+BBN probe puts tight constraints on the Hubble parameter ($H_0 = 67.6 \pm 1.0 \mathrm{km/s/Mpc}$), resulting in a $3.7σ$ tension with the local distance ladder determination from SH0ES in a $Λ$CDM model. In the updated BAO data the high- and low-redshift subsets are mutually in excellent agreement, an…
We explore a model introduced by Cyr-Racine, Ge, and Knox (arXiv:2107.13000(2)) that resolves the Hubble tension by invoking a ``mirror world" dark sector with energy density a fixed fraction of the ``ordinary" sector of Lambda-CDM. Although it reconciles cosmic microwave background and large-scale structure observations with local measurements of the Hubble constant, the model requires a value of the primordial Helium mass fraction that is discrepant with observations and with the predictions of Big Bang Nucleosynthesis (BBN). We consider a variant of the model with standard Helium mass fract…
The Hubble constant ($H_0$) estimated from the local Cepheid-supernova (SN) distance ladder is in 3-$σ$ tension with the value extrapolated from cosmic microwave background (CMB) data assuming the standard cosmological model. Whether this tension represents new physics or systematic effects is the subject of intense debate. Here, we investigate how new, independent $H_0$ estimates can arbitrate this tension, assessing whether the measurements are consistent with being derived from the same model using the posterior predictive distribution (PPD). We show that, with existing data, the inverse di…
We investigate the Hubble tension in the non-flat Super-$Λ{\rm CDM}$ model. The non-flat Super-$Λ{\rm CDM}$ model extends the Super-$Λ{\rm CDM}$ model by including the spatial curvature as a free parameter. The Super-$Λ{\rm CDM}$ model extends the standard $Λ{\rm CDM}$ model of cosmology through additional parameters accounting for the possible effect of a trispectrum in the primordial fluctuations. In the cosmic microwave background data, this effect can be parameterized using parameters that change the observed angular power spectrum from the theoretical power spectrum due to a trispectrum t…
Ningbo University（宁波大学）；Institute of Theoretical Physics, Chinese Academy of Sciences (CAS)（中国科学院理论物理研究所）；Asia Pacific Center for Theoretical Physics (APCTP)（亚太理论物理中心）
Hubble tension and the search for preferred direction are two crucial unresolved issues in modern cosmology. Different measurements of the Hubble constant provide significantly different values, and this is known as the Hubble tension. The cosmological principle assumes that the universe is homogeneous and isotropic; however, deviations from the isotropy have often been observed. We apply the Bayesian tools and the Extreme Value theory dependent statistic to address the above issues. These techniques have been applied to the Panstarrs1 type Ia supernovae data. Our analysis for Hubble constant …
It is shown, from the two independent approaches of McCrea-Milne and of Zeldovich, that one can fully recover the set equations corresponding to the relativistic equations of the expanding universe of Friedmann-Lemaitre-Robertson-Walker geometry. Although similar, the Newtonian and relativistic set of equations have a principal difference in the content and hence define two flows, local and global ones, thus naturally exposing the Hubble tension at the presence of the cosmological constant Λ. From this, we obtain absolute constraints on the lower and upper values for the local Hubble parameter…
Self-interaction among the neutrinos in the early Universe has been proposed as a solution to the Hubble tension, a discrepancy between the measured values of the Hubble constant from CMB and low-redshift data. However, flavor-universal neutrino self-interaction is highly constrained by Big Bang Nucleosynthesis and other laboratory experiments such as, tau and K-meson decay, double-neutrino beta decay etc. We study the cosmology when only one or two neutrino states are self-interacting. Such flavor-specific interactions are less constrained by the laboratory experiments. Lastly, we address the…
We extend our previous analysis of a model for "dark energy" based on a Weyl scaling invariant dark energy action. We reexpress all prior results in terms of proper time, using the fluctuation amplitude $Φ$ without approximation, and derive a compact formula for the squared effective Hubble parameter. This formula involves effective dark energy and matter densities that differ from their expressions in the standard $ΛCDM$ cosmology. We also give new analytic results for the function $ Φ$ and discuss their implications.
