Universe, Volume 11, Issue 12

Building upon a thermodynamic formalism, we show that one-dimensional self-gravitating systems in hydrostatic equilibrium with a uniform density are in maximal entropy states when submitted to adiabatic perturbations, i.e., perturbations that maintai...

The adventure of the journal Universe began about ten years ago, when I received an invitation from Dr [...]

We review some aspects of accretion disks physics, spacetime photon shell and photon orbits, related to retrograde (counter-rotating) motion in Kerr black hole (BH) spacetimes. In this brief review, we examine the counter-rotating components of the K...

We present a comprehensive sensitivity study of future CE$\nu$NS detectors, focusing on a cryogenic cesium iodide detector and a tonne-scale liquid argon one, currently being developed by the COHERENT Collaboration. These setups will enable precision...

Measuring supermassive black hole (SMBH) masses is fundamental to understanding active galactic nuclei (AGN) and their coevolution with host galaxies. Among existing techniques, H₂O megamaser observations with Very Long Baseline Interferometry (VLBI)...

This review examines the role of differential forms, Pfaffian systems, and hypersurfaces in general relativity. These mathematical constructions provide the essential tools for general relativity, in which the curvature of spacetime—described b...

We study basis-independent structures in the Type-I seesaw mechanism for light Majorana neutrinos, assuming the canonical scenario with three heavy right-handed (sterile) neutrinos. Let $m_{\nu }$ denote the $3\times 3$ mass matrix of light neutrinos, obtai...

This review investigates the application of unsupervised machine learning algorithms to astronomical data. Unsupervised machine learning enables researchers to analyze large, high-dimensional, and unlabeled datasets and is sometimes considered more h...

Dark matter constitutes the predominant component of the universe, yet its fundamental nature remains elusive, motivating diverse physical and astrophysical investigations. Recently, gravitational waves have emerged as a new probe for detecting the d...

Axion warm inflation is studied within the framework of Logamediate inflation. Using a novel approach, we constrain the parameter space of the model and find a reasonable region of free parameters compatible with the temperature, polarization, and le...

In this work, we analyze the dynamical evolution of locally rotationally symmetric anisotropic cosmological models of Bianchi type I (flat curvature) and Bianchi type III (open curvature) within a noncommutative phase space framework characterized by...

In this paper, we investigate the stability and feasibility of an anisotropic stellar model under $f(R,T)$ gravity that embraces the Karmarkar condition. In order to develop the $f(R,T)$ gravity model, the functional form of $f(R,T)$ is taken into consider...

We present a numerical implementation of the proposed Source–Detector Resonance (SDR) as a conceptual analog of a Double-Slit Interference Experiment with discrete particles. Two periodic streams of particles are emitted from two point sources...

The Wigner representation for quantum mechanics of particles is generalized to Bose fields. The standard Hilbert space quantization becomes, via the Weyl transform, a quantization method that consists of adding a Gaussian zeropoint field distribution...

The need to choose appropriate and meaningful names for the objects of scientific inquiry, in the spirit of Michael Faraday and, on a different level, of the ancient Chinese doctrine of rectification of names (正名, Zhèngmín...

In this work, we investigate how the choice of initial vector potential and plasma parameters influences the development of accretion columns and jet formation in magnetized accretion flows. Using general relativistic magnetohydrodynamic simulations,...

We examine the use of a novel variant of Physics-Informed Neural Networks to predict cosmological parameters from recent supernovae and baryon acoustic oscillations (BAO) datasets. Our machine learning framework generates uncertainty estimates for ta...

We demonstrate that the geometric action on a coadjoint orbit of the Virasoro group appropriately describes non-dissipative two-dimensional conformal fluids. While this action has already appeared in the context of AdS₃ gravity, the hydrodynamical in...

In this paper, we investigate the thread oscillations in a quiescent prominence observed by New Vacuum Solar Telescope at the H$\alpha$ line center on 17 April 2024. Each individual thread is traced by the local maximum intensity on the time–dis...

The canonical quantization of a field theory for spin-1/2 massive bosons that satisfy the Klein–Gordon equation is presented. The breakdown of the usual spin–statistics connection is due to the redefinition of the dual field, rendering th...

We investigate the long-term magnetic variability of OP And, a magnetically active single K giant, between 1993 and 2025. To track magnetic activity, we analyze the variability of the H$\alpha$ line and two lines of the calcium infrared triplet. The v...

The Galactic X-ray transient EXO 1846-031 was first discovered during an outburst in 1985 by the EXOSAT mission. The source remained in a quiescent state for nearly 34 years after the first outburst. The source started its second outburst on 23 July...

Gamma-ray bursts (GRBs) are widely recognized to exhibit jet-like emission structures, though previous studies often assumed isotropic emission due to observational constraints. This assumption limited our understanding of the intrinsic properties of...

Flavor-changing neutral current (FCNC) processes play a prominent role in the search for physics beyond the Standard Model (SM) due to their sensitivity to new physics at the TeV scale. Meson–antimeson transitions and rare meson decays provide...

An analysis of the solar differential rotation (DR) during solar cycle No. 24 (SC24) (2009–2019), based on the Kanzelhöhe Observatory for Solar and Environmental Research (KSO) data set, is presented. The white-light images were processed...

This work investigates the evaporation of black holes immersed in a de Sitter environment, using the Vaidya-de Sitter spacetime. The role of cosmological observers is highlighted in the development and Hayward thermodynamics for non-stationary geomet...

In this work, we investigate the (pre)-inflationary dynamics of a flat, homogeneous, and isotropic universe governed by the Starobinsky potential within the framework of noncommutative effective loop quantum cosmology. The field equations are solved...

Radio-loud high-redshift quasars (RHRQs) provide crucial insights into the evolution of relativistic jets and their connection to the growth of supermassive black holes. Beyond the extensively studied population at $z\ge 5$, the cosmic morning epoch ($3$...

We investigate the nonrelativistic quantum dynamics of a spinless particle in a screw-type spacetime endowed with two independent twist controls that interpolate between a pure screw dislocation and a homogeneous twist. From the induced spatial metri...

In this paper we study the properties of Kasner cosmological solutions in Lovelock gravity. Recent progress in the investigation of flat cosmological models in Lovelock gravity unveiled the fact that in quadratic (Gauss–Bonnet) and cubic Lovelo...

The canonical quantization of gravity in general relativity is greatly simplified by the artificial decomposition of space time into a 3 + 1 formalism. Such a simplification appears to come at the cost of general covariance. This quantization procedu...

We resume our analysis of Newtonian Fractional-Dimension Gravity (NFDG), an alternative gravitational model that does not require the dark matter (DM) paradigm. We add three more galaxies (NGC 6946, NGC 3198, NGC 2841) to the catalog of those studied...

In loop quantum gravity (LQG), states of the gravitational field are represented by labeled graphs called spin networks. Their dynamics can be described by a Hamiltonian constraint, which acts on the spin network states, modifying both spins and grap...

In this work, we discuss the conditions that allow the establishment of an equivalence between $f(R,T)=R+\lambda h\left(T\right)$ gravity models and General Relativity (GR) coupled to a modified matter sector. We do so by considering a D-dimensional spacetime and...

Conceivable explanations of Belle-II measurements of a (surprising) excess of missing energy decays of the B meson to the K meson not covered by standard model neutrino–antineutrino pairs might be offered by additional contributions of dark mat...

We carry out a careful analysis of the notion of observation of distant events in a curved Universe. This leads us to hypothesise that all measurements of our physical environment are performed with respect to a representation referential that obeys...

In this paper, we continue the study of the thermodynamics of fluid elements in isothermal turbulent self-gravitating systems, presented by molecular clouds. We build the model again on the hypothesis that, locally, the turbulent kinetic energy per f...

This study examines cosmic acceleration in the framework of $f(Q,T)$ gravity and compares it to the standard $\Lambda$CDM model. It considers a generalized nonlinear form of the nonmetricity, expressed as $f(Q,T)=-Q+{\alpha }_0{Q}^2/H_0^2+{\beta }_{0}T+{\eta }_0$,...

The binary Hercules X-1 exhibits a 35-day brightness X-ray cycle, including a Main High state and a Short High state which are separated by two Low states. The cycle is due to blockage of the neutron star by a rotating twisted disk. The best availabl...