Universe, Volume 9, Issue 12

Finding affine parameters for null geodesics is often of considerable physical importance, especially when studying null geodesics or dealing with conservation laws and/or averaged energy conditions. But explicitly finding null affine parameters is a...

A simple approach to the Hamiltonian theory of radiation phenomena is proposed. It is shown that the so-called “Trautman-Bondi-mass”, known to a rather narrow circle of specialists in general relativity, appears naturally in any special r...

The equations of motion of an isospin-carrying particle in a Yang–Mills and gravitational field were first proposed in 1968 by Kerner, who considered geodesics in a Kaluza–Klein-type framework. Two years later, the flat space Kerner equat...

In this overview, we discuss the (Schwartz) distributional stress–energy quadrupole and show it is a source of gravitational waves. We provide an explicit formula for the metric of linearised gravity in the case of a background Minkowski spacet...

Astrophysical plasma ejections (jets) are formed and powered by black holes that accrete material from their companion star in binary systems. Black hole X-ray binary systems constitute potential powerful galactic and extragalactic neutrino and gamma...

The concept of torsion in geometry, although known for a long time, has not gained considerable attention from the physics community until relatively recently, due to its diverse and potentially important applications to a plethora of contexts of phy...

Unimodular gravity (UG) is often deemed comparable to General Relativity (GR) in many respects, despite the theory exhibiting invariance under a more limited set of diffeomorphic transformations. The discussion we propose in this work relies on the c...

Heartbeat star systems have been reported to exhibit two distinct different orbital dynamic evolution processes: apsidal precession (e.g., KIC 4544587) and orbital decay (e.g., KIC 3766353). While experiencing similar dynamic tidal interactions, thes...

The evolution of a de Sitter Universe is the basis for both the accelerated Universe and the late-stationary Universe. So, how do we differentiate between both universes? In this paper, we state that it is not possible to design an experiment using l...

The neutrino sector offers one of the most sensitive probes of new physics beyond the Standard Model of Particle Physics (SM). The mechanism of neutrino mass generation is still unknown. The observed suppression of neutrino masses hints at a large sc...

Stark broadening parameters, line widths and shifts, for 15 N VI multiplets are calculated using semiclassical perturbation theory for temperatures from 50,000 K to 2,000,000 K, and perturber density of 10${}^{16}$ cm${}^{-3}$. As perturbers have been taken...

This article investigates the radial and non-radial geodesic structures of the generalized K-essence Vaidya spacetime. Within the framework of K-essence geometry, it is important to note that the metric does not possess conformal equivalence to the c...

Kaluza–Klein theory attempts a unification of gravity and electromagnetism through the hypothesis that spacetime has five dimensions, of which only four are observed. The original model gives rise to the standard Einstein–Maxwell theory a...

Grassmann variables are used to formally transform a system with constraints into an unconstrained system. As a result, the Schrödinger equation arises instead of the Wheeler–DeWitt one. The Schrödinger equation describes a system&rsq...

The origin of the spins of stellar-mass black holes is still controversial, and angular momentum transport inside massive stars is one of the main sources of uncertainty. Here, we apply hierarchical Bayesian inference to derive constraints on spin mo...

Tidal orbital decay plays a vital role in the evolution of hot Jupiter systems. As of now, this has only been observationally confirmed for the WASP-12 system. There are a few other candidates, including WASP-4 b, but no conclusive result could be ob...

We present photodynamical models of four eclipsing binary systems that show strong evidence of being members of higher-order multiple systems via their strong eclipse timing variations and/or via the presence of extra eclipse events. Three of these s...

Magnetars form a special class of neutron stars possessing superstrong magnetic fields and demonstrating power flares triggered by these fields. Observations of such flares reveal the presence of quasi-periodic oscillations (QPOs) at certain frequenc...

We prove that the simplest gravitational symmetry-reduced models describing cosmology and black hole mechanics are invariant under the Schrödinger group. We consider the flat FRW cosmology filled with a massless scalar field and the Schwarzschil...

When high-energy particles originating from space penetrate the atmosphere, they may interact with atoms and molecules, initiating air showers composed of secondary and tertiary particles propagating towards the ground. They can cause ionization of t...

Elastic media with defects are considered manifold with nontrivial Riemann–Cartan geometry in the geometric theory of defects. We obtain the solution of three-dimensional Euclidean general relativity equations with an arbitrary number of linear...

One of main sources of uncertainty in modern cosmology is the present rate of the universe’s expansion, H₀, called the Hubble constant. Once again, different observational techniques bring about different results, causing new “Hubble tens...

We review combinatorial quantum gravity, an approach that combines Einstein’s idea of dynamical geometry with Wheeler’s “it from bit” hypothesis in a model of dynamical graphs governed by the coarse Ollivier–Ricci curvat...

The EBLM project aims to characterise very-low-mass stars that are companions to solar-type stars in eclipsing binaries. We describe the history and motivation for this project, the methodology we use to obtain the precise mass, radius, and effective...

We numerically study the evolution of the extrinsic energy density in the context of an inflationary regime at the background level in a five-dimensional model using a Bayesian analysis from a dynamic nested sampler (DYNESTY) code. By means of the Na...

In the spacetime of a linearly accelerating Kinnersley black hole, the Lorentz-breaking theory is used to modify the dynamical equations of Dirac particles by selecting gamma matrices and aether-like field vectors in the curved spacetime of this blac...

We deduce a non-linear commutator higher-spin (HS) symmetry algebra which encodes unitary irreducible representations of the AdS group—subject to a Young tableaux $Y(s_1,\dots ,s_k)$ with $k\ge 2$ rows—in a d-dimensional anti-de Sitter space....

The He–McKellar–Wilkens (HMW) effect in noncommutative space has been explored through two distinct methodologies. One approach treats the neutral particle, which harbors a permanent electric dipole moment, as an unstructured entity, whil...

Mrk 783 is a narrow-line Seyfert 1 galaxy that possesses a relatively large two-sided radio emission extending up to 14 kpc from the active nucleus possibly connected with a large-scale ionized gas emission. We obtained a deep [O iii] image that reve...

The investigation of emission line regions within active galaxies (AGNs) has a rich and extensive history, now extending to the use of AGNs and quasars as “standardizable” cosmological indicators, shedding light on the evolution of our un...

We present a new study of Jupiter’s atmosphere dynamics using for the first time the extremely high-resolution capabilities of VLT/ESPRESSO to retrieve wind velocities in Jupiter’s troposphere, with a dedicated ground-based Doppler veloci...

In a series of papers, Maia and Bakke [...]

In this paper, radio frequency interference (RFI) mitigation by robust maximum likelihood estimators (M-estimators) for typical radio astrophysical signals of, e.g., pulsars and fast radio bursts (FRBs), will be investigated. The current status revea...

The exact solution of the Hamiltonian constraint in canonical gravity and the resultant reduction of Einstein’s theory reveal the synergy between gravitation and the intrinsic cosmic clock of our expanding universe. Intrinsic Time Geometrodynam...

In this study, we examine the efficiency of pair creation by means of the centrifugal mechanism. The strong magnetic field and the effects of rotation, which always take place in Kerr-type black holes, guarantee the frozen-in condition, leading to th...