[en] We use three different data sets, specifically $H\left(z\right)$ measurements from cosmic chronometers, the HII-galaxy Hubble diagram, and reconstructed quasar-core angular-size measurements, to perform a joint analysis of three flat cosmological models: the $R_{\mathrm{h}}=ct$ Universe, $\Lambda$CDM, and $w$CDM. For $R_{\mathrm{h}}=ct$, the 1$\sigma$ best-fit value of the Hubble constant $H_0$ is $62.336\pm 1.464$ ${\mathrm{km\; s}}^{-1}{\mathrm{Mpc}}^{-1}$, which matches previous measurements ($\sim 63$ ${\mathrm{km\; s}}^{-1}{\mathrm{Mpc}}^{-1}$) based on best fits to individual data sets. For $\Lambda$CDM, our inferred value of the Hubble constant, $H_0=67.013\pm 2.578$ ${\mathrm{km\; s}}^{-1}{\mathrm{Mpc}}^{-1}$, is more consistent with the Planck optimization than the locally measured value using Cepheid variables, and the matter density ${\Omega }_{\mathrm{m}}=0.347\pm 0.049$ similarly coincides with its Planck value to within 1$\sigma$. For $w$CDM, the optimized parameters are $H_0=64.718\pm 3.088$ ${\mathrm{km\; s}}^{-1}{\mathrm{Mpc}}^{-1}$, ${\Omega }_{\mathrm{m}}=0.247\pm 0.108$ and $w=-0.693\pm 0.276$, also consistent with Planck. A direct comparison of these three models using the Bayesian Information Criterion shows that the $R_{\mathrm{h}}=ct$ universe is favored by the joint analysis with a likelihood of $\sim 97\text{\%}$ versus $\lesssim 3\text{\%}$ for the other two cosmologies.

[en] The lack of power anomaly is an intriguing feature at the largest angular scales of the CMB anisotropy temperature pattern, whose statistical significance is not strong enough to claim any new physics beyond the standard cosmological model. We revisit the former statement by also considering polarisation data. We propose a new one-dimensional estimator which takes jointly into account the information contained in the TT, TE and EE CMB spectra. By employing this estimator on Planck 2015 low-$\ell$ data, we find that a random $\Lambda$CDM realisation is statistically accepted at the level of 3.68%. Even though Planck polarisation contributes a mere 4% to the total information budget, its use pushes the lower-tail-probability down from the 7.22% obtained with only temperature data. Forecasts of future CMB polarised measurements, as e.g. the LiteBIRD satellite, can increase the polarisation contribution up to 6 times with respect to Planck at low-$\ell$. We argue that the large-scale E-mode polarisation may play an important role in analysing CMB temperature anomalies with future mission.

[en] We explore a collapsing cosmology driven by a scalar field which is minimally coupled to gravity in a spatially flat and spherically symmetric, isotropic and homogeneous space–time, with a variable timescale that avoid the final singularity. The equation of state that describes the collapse is $\omega =1$. We calculate the back-reaction of the space–time during the collapse and the energy density fluctuations related to this back-reaction has a spectral index $n_s=0$, favoring short-wavelengths modes to be detected. The interesting is that the amplitude of these fluctuations increase with time when the collapse is sufficiently strong.

[en] We re-analyse current single-field inflationary models related to primordial black holes formation. We do so by taking into account recent developments on the estimations of their abundances and the influence of non-gaussianities. We show that, for all of them, the gaussian approximation, which is typically used to estimate the primordial black holes abundances, fails. However, in the case in which the inflaton potential has an inflection point, the contribution of non-gaussianities is only perturbative. Finally, we infer that only models featuring an inflection point in the inflationary potential, might predict, with a very good approximation, the desired abundances by the sole use of the gaussian statistics.

[en] The manifesto of the current article is to investigate the compact anisotropic matter profiles in the context of one of the modified gravitational theories, known as $f(\mathcal{R},\mathcal{T})$ gravity, where $\mathcal{R}$ is a Ricci Scalar and $\mathcal{T}$ is the trace of the energy–momentum tensor. To achieve the desired goal, we capitalized on the spherical symmetric space–time and utilized the embedding class-1 solution via Karmarkar’s condition in modeling the matter profiles. To calculate the unidentified constraints, Schwarzschild exterior solution along with experimental statistics of three different stars LMC X-4, Cen X-3, and EXO 1785-248 are taken under consideration. For the evaluation of the dynamical equations, a unique model $f(\mathcal{R},\mathcal{T})=\mathcal{R}+\beta {\mathcal{R}}^2+\lambda \mathcal{T}$ has been considered, with $\beta$ and $\lambda$ being the real constants. Different physical aspects have been exploited with the help of modified dynamical equations. Conclusively, all the stars under observations are realistic, stable, and are free from all singularities.

[en] We investigate the solutions of black holes in $f\left(T\right)$ gravity with nonlinear power-law Maxwell field, where $T$ is the torsion scalar in teleparallelism. In particular, we introduce the Lagrangian with diverse dimensions in which the quadratic polynomial form of $f\left(T\right)$ couples with the nonlinear power-law Maxwell field. We explore the leverage of the nonlinear electrodynamics on the space–time behavior. It is found that these new black hole solutions tend towards those in general relativity without any limit. Furthermore, it is demonstrated that the singularity of the curvature invariant and the torsion scalar is softer than the quadratic form of the charged field equations in $f\left(T\right)$ gravity and much milder than that in the classical general relativity because of the nonlinearity of the Maxwell field. In addition, from the analyses of physical and thermodynamic quantities of the mass, charge and the Hawking temperature of black holes, it is shown that the power-law parameter affects the asymptotic behavior of the radial coordinate of the charged terms, and that a higher-order nonlinear power-law Maxwell field imparts the black holes with the local stability.

[en] The concordance of the $\Lambda$CDM cosmological model in light of current observations has been the subject of an intense debate in recent months. The 2018 Planck Cosmic Microwave Background (CMB) temperature anisotropy power spectrum measurements appear at face value to favour a spatially closed Universe with curvature parameter ${\Omega }_K<0$. This preference disappears if Baryon Acoustic Oscillation (BAO) measurements are combined with Planck data to break the geometrical degeneracy, although the reliability of this combination has been questioned due to the strong tension present between the two datasets when assuming a curved Universe. Here, we approach this issue from yet another point of view, using measurements of the full-shape (FS) galaxy power spectrum, $P\left(k\right)$, from the Baryon Oscillation Spectroscopic Survey DR12 CMASS sample. By combining Planck data with FS measurements, we break the geometrical degeneracy and find ${\Omega }_K=0.0023\pm 0.0028$. This constrains the Universe to be spatially flat to sub-percent precision, in excellent agreement with results obtained using BAO measurements. However, as with BAO, the overall increase in the best-fit ${\chi }^2$ suggests a similar level of tension between Planck and $P\left(k\right)$ under the assumption of a curved Universe. While the debate on spatial curvature and the concordance between cosmological datasets remains open, our results provide new perspectives on the issue, highlighting the crucial role of FS measurements in the era of precision cosmology.

[en] In this work, we study the potential of the Cherenkov Telescope Array (CTA) for the detection of Galactic dark matter (DM) subhalos. We focus on low-mass subhalos that do not host any baryonic content and therefore lack any multiwavelength counterpart. If the DM is made of weakly interacting massive particles (WIMPs), these dark subhalos may thus appear in the gamma-ray sky as unidentified sources. A detailed characterization of the instrumental response of CTA to dark subhalos is performed, for which we use the ctools analysis software and simulate CTA observations under different array configurations and pointing strategies, such as the scheduled extragalactic survey. This, together with information on the subhalo population as inferred from N-body cosmological simulations, allows us to predict the CTA detectability of dark subhalos, i.e., the expected number of subhalos in each of the considered observational scenarios. In the absence of detection, for each observation strategy we set competitive limits to the annihilation cross section as a function of the DM particle mass, that are at the level of $〈\sigma v〉\sim 4\times 10^{-24}$ ($7\times 10^{-25}$) ${\mathrm{cm}}^3{s}^{-1}$ for the $b\bar{b}$ (${\tau }^{+}{\tau }^{-}$) annihilation channel in the best case scenario. Interestingly, we find the latter to be reached with no dedicated observations, as we obtain the best limits by just accumulating exposure time from all scheduled CTA programs and pointings over the first 10 years of operation. This way CTA will offer the most constraining limits from subhalo searches in the intermediate range between $\sim 1-3\mathrm{TeV}$, complementing previous results with Fermi-LAT and HAWC at lower and higher energies, respectively.

[en] The multi-messenger observation of GW170817 enabled the first historic measurement of the Hubble constant via a standard siren, so-called in analogy to standard candles that enabled the measurement of the luminosity distance versus redshift relationship at small redshift. In the next decades, third-generation observatories are expected to detect hundreds to thousand of gravitational wave events from compact binary coalescences with potentially a joint electromagnetic counterpart. In the present work, we show how future standard siren detections can be used within the framework of Bayesian model selection to discriminate between cosmological models differing by the parameterization of the late-time acceleration. In particular, we found quantitative conditions for the standard $\Lambda$CDM model to be favored with respect to other models with varying dark energy content, by reducing the uncertainty in the gravitational determination of the luminosity distance with respect to current expectations.

[en] The observation of strongly lensed Type Ia supernovae enables both the luminosity and angular diameter distance to a source to be measured simultaneously using a single observation. This feature can be used to measure the distance duality parameter $\eta \left(z\right)$ without relying on multiple datasets and cosmological assumptions to reconstruct the relation between angular and luminosity distances. In this paper, we show how this can be achieved by future observations of strongly lensed Type Ia systems. Using simulated datasets, we reconstruct the function $\eta \left(z\right)$ using both parametric and non-parametric approaches, focusing on Genetic Algorithms and Gaussian processes for the latter. In the parametric approach, we find that in the realistic scenario of $N_{\mathrm{lens}}=20$ observed systems, the parameter ${ϵ}_0$ used to describe the trend of $\eta \left(z\right)$ can be constrained with the precision achieved by current SNIa and BAO surveys, while in the futuristic case ($N_{\mathrm{lens}}=1000$) these observations could be competitive with the forecast precision of upcoming LSS and SN surveys. Using the machine learning approaches of Genetic Algorithms and Gaussian processes, we find that both reconstruction methods are generally well able to correctly recover the underlying fiducial model in the mock data, even in the realistic case of $N_{\mathrm{lens}}=20$. Both approaches learn effectively from the features of the mock data points, yielding $1\sigma$ constraints that are in excellent agreement with the parameterised results.