ABSTRACT
A dark-energy, which behaves as the cosmological constant until a sudden phantom transition at very low redshift (z < 0.1), seems to solve the >4σ disagreement between the local and ...high-redshift determinations of the Hubble constant, while maintaining the phenomenological success of the Λ cold dark matter model with respect to the other observables. Here, we show that such a hockey-stick dark energy cannot solve the H0 crisis. The basic reason is that the supernova absolute magnitude MB that is used to derive the local H0 constraint is not compatible with the MB that is necessary to fit supernova, baryon acoustic oscillation, and cosmic microwave background data, and this disagreement is not solved by a sudden phantom transition at very low redshift. We make use of this example to show why it is preferable to adopt in the statistical analyses the prior on MB as an alternative to the prior on H0. The three reasons are: (i) one avoids potential double counting of low-redshift supernovae, (ii) one avoids assuming the validity of cosmography, in particular, fixing the deceleration parameter to the standard model value q0 = −0.55, (iii) one includes in the analysis the fact that MB is constrained by local calibration, an information which would otherwise be neglected in the analysis, biasing both model selection and parameter constraints. We provide the priors on MB relative to the recent Pantheon and DES-SN3YR supernova catalogs. We also provide a Gaussian joint prior on H0 and q0 that generalizes the prior on H0 by Supernova H0 for the Equation of State.
ABSTRACT
The cosmic distance ladder is the succession of techniques by which it is possible to determine distances to astronomical objects. Here, we present a new method to build the cosmic distance ...ladder, going from local astrophysical measurements to the CMB. Instead of relying on high-redshift cosmography in order to model the luminosity–distance relation and calibrate supernovae with BAO, we exploit directly the distance–duality relation dL = (1 + z)2dA – valid if photon number is conserved and gravity is described by a metric theory. The advantage is that the results will not depend on the parametrization of the luminosity–distance relation at z > 0.15: no model is adopted in order to calibrate BAO with supernovae. This method yields local measurements of the Hubble constant and deceleration parameter. Furthermore, it can directly assess the impact of BAO observations on the strong 4–5σ tension between local and global H0. Using the latest supernova, BAO and CMB observations, we found a consistently low value of q0 and strong inconsistency between angular-only BAO constraints and anisotropic BAO measurements, which are, or not, in agreement with CMB depending on the kind of analysis (see Table 4). We conclude that, in order to understand the reasons behind the H0 crisis, a first step should be clarifying the tension between angular and perpendicular anisotropic BAO as this will help understanding if new physics is required at the pre-recombination epoch or/and during the dark energy era.
Brazil ranks second worldwide in total number of COVID-19 cases and deaths. Understanding the possible socioeconomic and ethnic health inequities is particularly important given the diverse ...population and fragile political and economic situation. We aimed to characterise the COVID-19 pandemic in Brazil and assess variations in mortality according to region, ethnicity, comorbidities, and symptoms.
We conducted a cross-sectional observational study of COVID-19 hospital mortality using data from the SIVEP-Gripe (Sistema de Informação de Vigilância Epidemiológica da Gripe) dataset to characterise the COVID-19 pandemic in Brazil. In the study, we included hospitalised patients who had a positive RT-PCR test for severe acute respiratory syndrome coronavirus 2 and who had ethnicity information in the dataset. Ethnicity of participants was classified according to the five categories used by the Brazilian Institute of Geography and Statistics: Branco (White), Preto (Black), Amarelo (East Asian), Indígeno (Indigenous), or Pardo (mixed ethnicity). We assessed regional variations in patients with COVID-19 admitted to hospital by state and by two socioeconomically grouped regions (north and central-south). We used mixed-effects Cox regression survival analysis to estimate the effects of ethnicity and comorbidity at an individual level in the context of regional variation.
Of 99 557 patients in the SIVEP-Gripe dataset, we included 11 321 patients in our study. 9278 (82·0%) of these patients were from the central-south region, and 2043 (18·0%) were from the north region. Compared with White Brazilians, Pardo and Black Brazilians with COVID-19 who were admitted to hospital had significantly higher risk of mortality (hazard ratio HR 1·45, 95% CI 1·33–1·58 for Pardo Brazilians; 1·32, 1·15–1·52 for Black Brazilians). Pardo ethnicity was the second most important risk factor (after age) for death. Comorbidities were more common in Brazilians admitted to hospital in the north region than in the central-south, with similar proportions between the various ethnic groups. States in the north had higher HRs compared with those of the central-south, except for Rio de Janeiro, which had a much higher HR than that of the other central-south states.
We found evidence of two distinct but associated effects: increased mortality in the north region (regional effect) and in the Pardo and Black populations (ethnicity effect). We speculate that the regional effect is driven by increasing comorbidity burden in regions with lower levels of socioeconomic development. The ethnicity effect might be related to differences in susceptibility to COVID-19 and access to health care (including intensive care) across ethnicities. Our analysis supports an urgent effort on the part of Brazilian authorities to consider how the national response to COVID-19 can better protect Pardo and Black Brazilians, as well as the population of poorer states, from their higher risk of dying of COVID-19.
None.
The determination of the Hubble constant H_{0} from the cosmic microwave background by the Planck Collaboration (N. Aghanim et al., arXiv:1807.06209) is in tension at 4.2σ with respect to the local ...determination of H_{0} by the SH0ES collaboration M. J. Reid et al., Astrophys. J. Lett. 886, L27 (2019)2041-821310.3847/2041-8213/ab552d. Here we improve upon the local determination, which fixes the deceleration parameter to the standard ΛCDM model value of q_{0}=−0.55, that is, uses information from observations beyond the local universe. First, we derive the effective calibration prior on the absolute magnitude M_{B} of type Ia supernovae, which can be used in cosmological analyses in order to avoid the double counting of low-redshift supernovae. We find M_{B}=−19.2334±0.0404 mag. Then we use the above M_{B} prior in order to obtain a determination of the local H_{0} which uses only local observations and assumes only the cosmological principle, that is, large-scale homogeneity and isotropy. This is achieved by adopting an uninformative flat prior for q_{0} in the cosmographic expansion of the luminosity distance. We use the latest Pantheon sample and find H_{0}=75.35±1.68kms^{−1}Mpc^{−1}, which features a 2.2% uncertainty, close to the 1.9% error obtained by the SH0ES Collaboration. Our determination is at the higher tension of 4.5σ with the latest results from the Planck Collaboration that assume the ΛCDM model. Furthermore, we also constrain the deceleration parameter to q_{0}=−1.08±0.29, which disagrees with the Planck Collaboration at the 1.9σ level. These estimations only use supernovae in the redshift range 0.023≤z≤0.15.
We test both the Friedmann-Lemaître-Robertson-Walker geometry and ΛCDM cosmology in a model-independent way by reconstructing the Hubble function H(z), the comoving distance D(z), and the growth of ...structure fσ8(z) using the most recent data available. We use the linear model formalism in order to optimally reconstruct the above cosmological functions, together with their derivatives and integrals. We then evaluate four of the null tests available in the literature that probe both background and perturbation assumptions. For all the four tests, we find agreement, within the errors, with the standard cosmological model.
There is an approximately 9% discrepancy, corresponding to 2.4 σ, between two independent constraints on the expansion rate of the Universe: one indirectly arising from the cosmic microwave ...background and baryon acoustic oscillations and one more directly obtained from local measurements of the relation between redshifts and distances to sources. We argue that by taking into account the local gravitational potential at the position of the observer this tension--strengthened by the recent Planck results--is partially relieved and the concordance of the Standard Model of cosmology increased. We estimate that measurements of the local Hubble constant are subject to a cosmic variance of about 2.4% (limiting the local sample to redshifts z > 0.010) or 1.3% (limiting it to z > 0.023), a more significant correction than that taken into account already. Nonetheless, we show that one would need a very rare fluctuation to fully explain the offset in the Hubble rates. If this tension is further strengthened, a cosmology beyond the Standard Model may prove necessary.
ABSTRACT
We pursue a program to confront observations with inhomogeneous extensions of the FLRW metric. The main idea is to test the Copernican principle (CP) rather than assuming it a priori. We ...consider the ΛCDM model endowed with a spherical ΛLTB inhomogeneity around us, that is, we assume isotropy and test the hypothesis of homogeneity. We confront the ΛLTB model with the latest available data from cosmic microwave background, BAO, type Ia supernovae, local H0, cosmic chronometers, Compton y-distortion, and kinetic Sunyaev–Zeldovich effect. We find that these data can constrain tightly this extra inhomogeneity, almost to the cosmic variance level: on scales ≳ 100 Mpc structures can have a small non-Copernican effective contrast of just δL ∼ 0.01. Furthermore, the constraints on the standard ΛCDM parameters are not weakened after marginalizing over the parameters that model the local structure, to which we assign ignorance priors. In other words, dropping the CP assumption does not imply worse constraints on the cosmological parameters. This positive result confirms that the present and future data can be meaningfully analyzed within the framework of inhomogeneous cosmology.
ABSTRACT
Luminous matter produces very energetic events, such as active galactic nuclei and supernova explosions, that significantly affect the internal regions of galaxy clusters. Although the ...current uncertainty in the effect of baryonic physics on cluster statistics is subdominant as compared to other systematics, the picture is likely to change soon as the amount of high-quality data is growing fast, urging the community to keep theoretical systematic uncertainties below the ever-growing statistical precision. In this paper, we study the effect of baryons on galaxy clusters, and their impact on the cosmological applications of clusters, using the magneticum suite of cosmological hydrodynamical simulations. We show that the impact of baryons on the halo mass function can be recast in terms on a variation of the mass of the haloes simulated with pure N-body, when baryonic effects are included. The halo mass function and halo bias are only indirectly affected. Finally, we demonstrate that neglecting baryonic effects on haloes mass function and bias would significantly alter the inference of cosmological parameters from high-sensitivity next-generations surveys of galaxy clusters.
Background:A number of estimates of the infection fatality ratio (IFR) of SARS-CoV-2 in different countries have been published. In Brazil, the fragile political situation, together with ...socioeconomic and ethnic diversity, could result in substantially different IFR estimates.
Methods:We infer the IFR in Brazil in 2020 by combining three datasets. We compute the prevalence via the population-based seroprevalence survey, EPICOVID19-BR. For the fatalities we obtain the absolute number using the public Painel Coronavírus dataset and the age-relative number using the public SIVEP-Gripe dataset. The time delay between the development of antibodies and subsequent fatality is estimated via the SIVEP-Gripe dataset. We obtain the IFR for each survey stage and 27 federal states. We include the effect of fading IgG antibody levels by marginalizing over the test detectability time window.
Results:We infer a country-wide average IFR (maximum posterior and 95% CI) of 1.03% (0.88–1.22%) and age-specific IFRs of 0.032% (0.023–0.041%) < 30 years, 0.22% (0.18–0.27%) 30–49 years, 1.2% (1.0–1.5%) 50–69 years, and 3.0% (2.4–3.9%) ≥ 70 years. We find that the fatality ratio in the country increased significantly at the end of June 2020, likely due to the increased strain on the health system.
Conclusions: Our IFR estimate is based on data and does not rely on extrapolating models. This estimate sets a baseline value with which future medications and treatment protocols may be confronted.
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