The recent determination of the local value of the Hubble constant by Riess et al., 2016 (hereafter R16) is now 3.3 sigma higher than the value derived from the most recent CMB anisotropy data ...provided by the Planck satellite in a ΛCDM model. Here we perform a combined analysis of the Planck and R16 results in an extended parameter space, varying simultaneously 12 cosmological parameters instead of the usual 6. We find that a phantom-like dark energy component, with effective equation of state w=−1.29−0.12+0.15 at 68% c.l. can solve the current tension between the Planck dataset and the R16 prior in an extended ΛCDM scenario. On the other hand, the neutrino effective number is fully compatible with standard expectations. This result is confirmed when including cosmic shear data from the CFHTLenS survey and CMB lensing constraints from Planck. However, when BAO measurements are included we find that some of the tension with R16 remains, as also is the case when we include the supernova type Ia luminosity distances from the JLA catalog.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We explore whether nonstandard dark sector physics might be required to solve the existing cosmological tensions. The properties we consider in combination are (a) an interaction between the dark ...matter and dark energy components and (b) a dark energy equation of state w different from that of the canonical cosmological constant w = −1. In principle, these two parameters are independent. In practice, to avoid early-time, superhorizon instabilities, their allowed parameter spaces are correlated. Moreover, a clear degeneracy exists between these two parameters in the case of cosmic microwave background (CMB) data. We analyze three classes of extended interacting dark energy models in light of the 2019 Planck CMB results and Cepheid-calibrated local distance ladder H0 measurements of Riess et al. (R19), as well as recent baryon acoustic oscillation (BAO) and type Ia supernovae (SNeIa) distance data. We find that in quintessence coupled dark energy models, where w > − 1, the evidence for a nonzero coupling between the two dark sectors can surpass the 5σ significance. Moreover, for both Planck + BAO or Planck + SNeIa, we find a preference for w > − 1 at about three standard deviations. Quintessence models are, therefore, in excellent agreement with current data when an interaction is considered. On the other hand, in phantom coupled dark energy models, there is no such preference for a nonzero dark sector coupling. All the models we consider significantly raise the value of the Hubble constant, easing the H0 tension. In the interacting scenario, the disagreement between Planck + BAO and R19 is considerably reduced from 4.3σ in the case of the Λ cold dark matter (Λ CDM) model to about 2.5σ . The addition of low-redshift BAO and SNeIa measurements leaves, therefore, some residual tension with R19 but at a level that could be justified by a statistical fluctuation. Bayesian evidence considerations mildly disfavor both the coupled quintessence and phantom models, while mildly favoring a coupled vacuum scenario, even when late-time datasets are considered. We conclude that nonminimal dark energy cosmologies, such as coupled quintessence, phantom, or vacuum models, are still an interesting route toward softening existing cosmological tensions, even when low-redshift datasets and Bayesian evidence considerations are taken into account.
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Investigating Cosmic Discordance Di Valentino, Eleonora; Melchiorri, Alessandro; Silk, Joseph
Astrophysical journal. Letters,
02/2021, Volume:
908, Issue:
1
Journal Article
Peer reviewed
Open access
Abstract
We show that a combined analysis of cosmic microwave background anisotropy power spectra obtained by the Planck satellite and luminosity distance data simultaneously excludes a flat universe ...and a cosmological constant at 99% confidence level. These results hold separately when combining Planck with three different data sets: the two determinations of the Hubble constant from Riess et al. and Freedman et al., and the Pantheon catalog of high-redshift Type Ia supernovae. We conclude that either the Lambda cold dark matter model needs to be replaced by a different paradigm, or else there are significant but still undetected systematics. Our result calls for new observations and stimulates the investigation of alternative theoretical models and solutions.
We show that a general late-time interaction between cold dark matter and vacuum energy is favored by current cosmological data sets. We characterize the strength of the coupling by a dimensionless ...parameter q(V) that is free to take different values in four redshift bins from the primordial epoch up to today. This interacting scenario is in agreement with measurements of cosmic microwave background temperature anisotropies from the Planck satellite, supernovae Ia from Union 2.1 and redshift space distortions from a number of surveys, as well as with combinations of these different data sets. Our analysis of the 4-bin interaction shows that a nonzero interaction is likely at late times. We then focus on the case q(V)≠0 in a single low-redshift bin, obtaining a nested one parameter extension of the standard ΛCDM model. We study the Bayesian evidence, with respect to ΛCDM, of this late-time interaction model, finding moderate evidence for an interaction starting at z=0.9, dependent upon the prior range chosen for the interaction strength parameter q(V). For this case the null interaction (q(V)=0, i.e., ΛCDM) is excluded at 99% C.L.
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We show that the new precise measurements of Cosmic Microwave Background (CMB) temperature and polarization anisotropies made by the Planck satellite significantly improves previous constraints on ...the cosmic gravitational waves background (CGWB) at frequencies f>10−15 Hz. On scales smaller than the horizon at the time of decoupling, primordial gravitational waves contribute to the total radiation content of the Universe. Considering adiabatic perturbations, CGWB affects temperature and polarization CMB power spectra and matter power spectrum in a manner identical to relativistic particles. Considering the latest Planck results we constrain the CGWB energy density to Ωgwh2<1.7×10−6 at 95% CL. Combining CMB power spectra with lensing, BAO and primordial Deuterium abundance observations, we obtain Ωgwh2<1.2×10−6 at 95% CL, improving previous Planck bounds by a factor 3 and the recent direct upper limit from the LIGO and VIRGO experiments a factor 2. A combined analysis of future satellite missions as COrE and EUCLID could improve current bound by more than an order of magnitude.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The detection of Primordial Gravitational Waves (PGWs) is one of the most important goals of modern cosmology since PGWs can both provide substantial evidence for primordial inflation and shed light ...on its physical nature. Small scale experiments on gravitational waves such as LIGO/VIRGO and, in future, LISA and Einstein Telescope (ET), being sensitive to the stochastic background of gravitational waves, can be used together with the CMB data to constrain the inflationary parameters. In performing these analyses the primordial tensor spectrum is usually parametrized with a power law that includes only the amplitude and a scale independent tilt. In this paper, we investigate the robustness of assuming the tensor tilt as scale independent. We show that due to the huge difference in the scales probed by CMB and GWs data, even a small scale dependence can remarkably affect the shape of the primordial spectrum possibly breaking the power-law assumption. When the non-linear corrections are considered the final constraints can be significantly changed. We also study the scale dependence in two different physical models of inflation providing an example of negligible scale dependence and an example of non-negligible scale dependence.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the current 3 ν paradigm, neutrino flavor oscillations probe three mixing angles (θ12, θ23, θ13), one C P-violating phase δ, and two independent differences between the squared masses ..., that ...can be chosen as ... and ..., where sign (Δm2) = +(−) for normal (inverted) mass ordering. Absolute ν masses can be probed by the effective mass m β in beta decay, by the total mass Σ in cosmology and-if neutrinos are Majorana-by another effective mass m β β in neutrinoless double beta decay. Within an updated global analysis of oscillation and nonoscillation data, we constrain these 3 ν parameters, both separately and in selected pairs, and highlight the concordance or discordance among different constraints. Five oscillation parameters (δm2, |Δm2|, θ12, θ23, θ13) are consistently measured, with an overall accuracy ranging from ~ 1 % for |Δm2| to ~ 6 % for sin 2θ23 (due to its persisting octant ambiguity). We find overall hints for normal ordering (at ~ 2.5σ), as well as for θ23 < π / 4 and for sin δ < 0 (both at 90% C.L.), and discuss some tensions among different datasets. Concerning nonoscillation data, we include the recent KATRIN constraints on m β, and we combine the latest 76Ge , 130Te and 136Xe bounds on mββ, accounting for nuclear matrix element covariances. We also discuss some variants related to cosmic microwave background (CMB) anisotropy and lensing data, which may affect cosmological constraints on Σ and hints on sign (Δm2). The default option, including all Planck results, irrespective of the so-called lensing anomaly, sets upper bounds on Σ at the level of ~ 10−1 eV , and further favors normal ordering up to ~ 3σ. An alternative option, that includes recent ACT results plus other independent results (from WMAP and selected Planck data) globally consistent with standard lensing, is insensitive to the ordering but prefers Σ ~ few × 10−1 eV, with different implications for mβ and mββ searches. In general, the unfinished fabric of the 3ν paradigm appears to be at the junction of diverse searches in particle and nuclear physics, astrophysics and cosmology, whose convergence will be crucial to achieve a convincing completion.
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Abstract
The simplest ΛCDM model provides a good fit to a large span of cosmological data but harbors large areas of phenomenology and ignorance. With the improvement of the number and the accuracy ...of observations, discrepancies among key cosmological parameters of the model have emerged. The most statistically significant tension is the 4
σ
to 6
σ
disagreement between predictions of the Hubble constant,
H
0
, made by the early time probes in concert with the ‘vanilla’ ΛCDM cosmological model, and a number of late time, model-independent determinations of
H
0
from local measurements of distances and redshifts. The high precision and consistency of the data at both ends present strong challenges to the possible solution space and demands a hypothesis with enough rigor to explain multiple observations—whether these invoke new physics, unexpected large-scale structures or multiple, unrelated errors. A thorough review of the problem including a discussion of recent Hubble constant estimates and a summary of the proposed theoretical solutions is presented here. We include more than 1000 references, indicating that the interest in this area has grown considerably just during the last few years. We classify the many proposals to resolve the tension in these categories: early dark energy, late dark energy, dark energy models with 6 degrees of freedom and their extensions, models with extra relativistic degrees of freedom, models with extra interactions, unified cosmologies, modified gravity, inflationary models, modified recombination history, physics of the critical phenomena, and alternative proposals. Some are formally successful, improving the fit to the data in light of their additional degrees of freedom, restoring agreement within 1–2
σ
between
Planck
2018, using the cosmic microwave background power spectra data, baryon acoustic oscillations, Pantheon SN data, and R20, the latest SH0ES Team Riess,
et al
(2021
Astrophys. J.
908
L6) measurement of the Hubble constant (
H
0
= 73.2 ± 1.3 km s
−1
Mpc
−1
at 68% confidence level). However, there are many more unsuccessful models which leave the discrepancy well above the 3
σ
disagreement level. In many cases, reduced tension comes not simply from a change in the value of
H
0
but also due to an increase in its uncertainty due to degeneracy with additional physics, complicating the picture and pointing to the need for additional probes. While no specific proposal makes a strong case for being highly likely or far better than all others, solutions involving early or dynamical dark energy, neutrino interactions, interacting cosmologies, primordial magnetic fields, and modified gravity provide the best options until a better alternative comes along.
ABSTRACT
Axions, if realized in nature, can be copiously produced in the early universe via thermal processes, contributing to the mass-energy density of thermal hot relics. In light of the most ...recent cosmological observations, we analyse two different thermal processes within a realistic mixed hot dark matter scenario which includes also massive neutrinos. Considering the axion–gluon thermalization channel, we derive our most constraining bounds on the hot relic masses ma < 7.46 eV and ∑mν < 0.114 eV both at 95 per cent CL; while studying the axion–pion scattering, without assuming any specific model for the axion–pion interactions, and remaining in the range of validity of the chiral perturbation theory, our most constraining bounds are improved to ma < 0.91 eV and ∑mν < 0.105 eV, both at 95 per cent CL. Interestingly, in both cases, the total neutrino mass lies very close to the inverted neutrino mass ordering prediction. If future terrestrial double beta decay and/or long-baseline neutrino experiments find that the nature mass ordering is the inverted one, this could rule out a wide region in the currently allowed thermal axion window. Our results therefore, strongly support multi messenger searches of axions and neutrino properties, together with joint analyses of their expected sensitivities.
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