Explore the vast range of titles available.

The COVID-19 pandemic continues to have a devastating impact on Brazil. Brazil’s social, health and economic crises are aggravated by strong societal inequities and persisting political disarray. This complex scenario motivates careful study of the clinical, socioeconomic, demographic and structural factors contributing to increased risk of mortality from SARS-CoV-2 in Brazil specifically. We consider the Brazilian SIVEP-Gripe catalog, a very rich respiratory infection dataset which allows us to estimate the importance of several non-laboratorial and socio-geographic factors on COVID-19 mortality. We analyze the catalog using machine learning algorithms to account for likely complex interdependence between metrics. The XGBoost algorithm achieved excellent performance, producing an AUC-ROC of 0.813 (95% CI 0.810–0.817), and outperforming logistic regression. Using our model we found that, in Brazil, socioeconomic, geographical and structural factors are more important than individual comorbidities. Particularly important factors were: The state of residence and its development index; the distance to the hospital (especially for rural and less developed areas); the level of education; hospital funding model and strain. Ethnicity is also confirmed to be more important than comorbidities but less than the aforementioned factors. In conclusion, socioeconomic and structural factors are as important as biological factors in determining the outcome of COVID-19. This has important consequences for policy making, especially on vaccination/non-pharmacological preventative measures, hospital management and healthcare network organization.

Dark matter is currently one of the main mysteries of the Universe. There is much strong indirect evidence that supports its existence, but there is yet no sign of a direct detection 1 – 3 . Moreover, at the scale of galaxies, there is tension between the theoretically expected dark matter distribution and its indirectly observed distribution 4 – 7 . Therefore, phenomena associated with dark matter have a chance of serving as a window towards new physics. The radial acceleration relation 8 , 9 confirms that a non-trivial acceleration scale a 0 can be found from the internal dynamics of several galaxies. The existence of such a scale is not obvious as far as the standard cosmological model is concerned 10 , 11 , and it has been interpreted as a possible sign of modified gravity 12 , 13 . Here, we consider 193 high-quality disk galaxies and, using Bayesian inference, show that the probability of existence of a fundamental acceleration is essentially 0: the null hypothesis is rejected at more than 10 σ . We conclude that a 0 is of emergent nature. In particular, the modified Newtonian dynamics theory 14 – 17 —a well-known alternative to dark matter based on the existence of a fundamental acceleration scale—or any other theory that behaves like it at galactic scales, is ruled out as a fundamental theory for galaxies at more than 10 σ . By studying the properties of almost 200 disk galaxies, it is shown that modified Newtonian dynamics (MOND), or MOND-like alternative theories of gravity based on the existence of a fundamental acceleration scale, are ruled out as fundamental theories for galaxies at more than 10σ.

Despite the observational success of the standard model of cosmology, present-day observations do not tightly constrain the nature of dark matter and dark energy and modifications to the theory of general relativity. Here, we will discuss some of the ongoing and upcoming surveys that will revolutionize our understanding of the dark sector.

During the process of structure formation in the universe matter is converted into radiation through a variety of processes such as light from stars, infrared radiation from cosmic dust, and gravitational waves from binary black holes/neutron stars and supernova explosions. The production of this astrophysical radiation background (ARB) could affect the expansion rate of the universe and the growth of perturbations. Here, we aim at understanding to which level one can constraint the ARB using future cosmological observations. We model the energy transfer from matter to radiation through an effective interaction between matter and astrophysical radiation. Using future supernova data from large synoptic survey telescope and growth-rate data from Euclid we find that the ARB density parameter is constrained, at the 95% confidence level, to be Ω ar 0 < 0.008 . Estimates of the energy density produced by well-known astrophysical processes give roughly Ω ar 0 ∼ 10 - 5 . Therefore, we conclude that cosmological observations will only be able to constrain exotic or not-well understood sources of radiation.

We review some of our recent results about the Radial Acceleration Relation (RAR) and its interpretation as either a fundamental or an emergent law. The former interpretation is in agreement with a class of modified gravity theories that dismiss the need for dark matter in galaxies (MOND in particular). Our most recent analysis, which includes refinements on the priors and the Bayesian test for compatibility between the posteriors, confirms that the hypothesis of a fundamental RAR is rejected at more than 5σ from the very same data that was used to infer the RAR.

Polarization of opinion is an important feature of public debate on political, social and cultural topics. The availability of large internet databases of users’ ratings has permitted quantitative analysis of polarization trends—for instance, previous studies have included analyses of controversial topics on Wikipedia, as well as the relationship between online reviews and a product’s perceived quality. Here, we study the dynamics of polarization in the movie ratings collected by the Internet Movie database (IMDb) website in relation to films produced over the period 1915–2015. We define two statistical indexes, dubbed hard and soft controversiality, which quantify polarized and uniform rating distributions, respectively. We find that controversy decreases with popularity and that hard controversy is relatively rare. Our findings also suggest that more recent movies are more controversial than older ones and we detect a trend of “convergence to the mainstream” with a time scale of roughly 40–50 years. This phenomenon appears qualitatively different from trends observed in both online reviews of commercial products and in political debate, and we speculate that it may be connected with the absence of long-lived “echo chambers” in the cultural domain. This hypothesis can and should be tested by extending our analysis to other forms of cultural expression and/or to databases with different demographic user bases.

This study aims to elucidate the tension in the Hubble constant (\\(H_0\\)), a key metric in cosmology representing the universe's expansion rate. Conflicting results from independent measurements such as the Planck satellite mission and the SH0ES collaboration have sparked interest in exploring alternative cosmological models. We extend the analysis by SH0ES to an arbitrary cosmographic model, obtaining a competitive local \\(H_0\\) determination which only assumes the standard flat \\(\\Lambda\\)CDM model (\\(73.14 \\pm 1.10\\) km/s/Mpc), and another which only assumes the FLRW metric (\\(74.56 \\pm 1.61\\) km/s/Mpc). The study also stresses the importance of the supernova magnitude calibration (\\(M_B\\)) in cosmological inference and highlights the tension in \\(M_B\\) when supernovae are calibrated either by CMB and BAO observations or the first two rungs of the cosmic distance ladder. This discrepancy, independent of the physics involved, suggests that models solely changing the Hubble flow and maintaining a sound horizon distance consistent with CMB, fail to explain the discrepancy between early- and late-time measurements of \\(H_0\\).

Covariance matrices are important tools for obtaining reliable parameter constraints. Advancements in cosmological surveys lead to larger data vectors and, consequently, increasingly complex covariance matrices, whose number of elements grows as the square of the size of the data vector. The most straightforward way of comparing these matrices, in terms of their ability to produce parameter constraints, involves a full cosmological analysis, which can be very computationally expensive. Using the concept and construction of compression schemes, which have become increasingly popular, we propose a fast and reliable way of comparing covariance matrices. The basic idea is to focus only on the portion of the covariance matrix that is relevant for the parameter constraints and quantify, via a fast Monte Carlo simulation, the difference of a second candidate matrix from the baseline one. To test this method, we apply it to two covariance matrices that were used to analyse the cosmic shear measurements for the Dark Energy Survey Year 1. We found that the uncertainties on the parameters change by 2.6%, a figure in agreement with the full cosmological analysis. While our approximate method cannot replace a full analysis, it may be useful during the development and validation of codes that estimate covariance matrices. Our method takes roughly 100 times less CPUh than a full cosmological analysis.