We derive for the first time the form of the spiral null geodesics around the photon sphere of the Reissner–Nordstrom black hole in the de Sitter expanding universe. Moreover, we obtain the principal parameter we need for deriving, according to our method [I. I. Cotăescu, Eur. Phys. J. C81, 32 (2021)], the black hole shadow and the related redshift as measured by a remote observer situated in the asymptotic

In this paper, the cosmological perturbations of dynamical dark energy and dark matter, which interact non-gravitationally are studied. This dark energy–dark matter non-gravitational interaction is linearly dependent on the energy densities of dark components. However, in the interacting quintessence dark energy models with such type of interaction, the non-adiabatic instabilities of cosmological perturbations

We consider an extension of the Standard Model with three right-handed (RH) neutrinos and a Dirac pair of extra sterile neutrinos, odd under a discrete Z2 symmetry, in order to have left–right symmetry in the neutrino content and obtain tiny neutrino masses from the latter ones only. Our working hypothesis is that the heavy RH neutrinos do not influence phenomenology at low energies. We use the usual

The eigenvalues and eigenfunctions of Dirac–Pauli equation have been obtained for a neutron with anomalous magnetic moment (AMM) in the presence of a strong magnetic field with cylindrical symmetry. In our calculations, the Nikiforov and Uvarov (NU) method has been used. Using the eigenfunctions and construction of the ladder operators, we show that these generators satisfy su(2) Lie algebra and computed

In this paper, we study temperature fluctuations in the initial stages of the relativistic heavy ion collision using a multiphase transport model. We consider the plasma in the initial stages after collision before it has a chance to equilibrate. We have considered Au+Au collision with a center-of-mass energy of 200 GeV. We use the nonextensive Tsallis statistics to find the entropic index in the partonic

In this paper, we consider three-dimensional massive gravity’s rainbow and obtain black hole solutions in three different cases of Born–Infeld, logarithmic, and exponential theories of nonlinear electrodynamics. We discuss the horizon structure and geometrical properties. Then, we study thermodynamics of these models by considering the first-order quantum correction effects, which appear as a logarithmic

With the end of Daya Bay experimental operations in December 2020, I review the history, discoveries, measurements and impact of the Daya Bay reactor neutrino experiment in China.

This work is continuation of a stochastic quantization program reported earlier. In this paper, we propose a consistent scheme of doing computations directly in four dimensions using conventional quantum field theory methods.

The spectral energy distribution (SED) sequence for type Ia supernovae (SN Ia) is modeled by an artificial neural network. The SN Ia luminosity is characterized as a function of phase, wavelength, a color parameter and a decline rate parameter. After training and testing the neural network, the SED sequence could give both the spectrum with wavelength range from 3000 Åto 8000 Åand the light curve with

In this work, we analyze the motion properties of the test particle, that has a variable mass within the frame of Hénon–Heiles system. We derive the equations of motion of the test particle which varies its mass according to Jean’s law. We also determine the quasi-Jacobi integral which shows the effective variation due to variable mass parameters. Further, we studied the locations of stationary points

A stellar model with an electrically charged anisotropic fluid as a source of matter is presented. The radial pressure is described by a Chaplygin state equation, Pr(ρ)=μc2ρ−ν/(c2ρ), while the anisotropy Δ≡Pt−Pr=r2f(r) is annulled in the center of the star (f(r) is regular and f(0)≠0), the electric field, is also annulled in the center. The density pressures and the tangential speed of sound are regular

Thorium is the primary candidate fuel in Thorium-based Molten Salt Reactor (TMSR) and Accelerator Driven System (ADS). However, to utilize Thorium in the reactor and accelerator systems, nuclear data in the literature are not sufficient for neutron-induced fission reaction process. Therefore, we estimated neutron fission cross-section σ (mb), independent Y(A) and primary fission fragment yield YI(A)

In this paper, we introduce an SU(1, 1) algebraic approach to study the (2 + 1)-Dirac oscillator in the presence of the Aharonov–Casher effect coupled to an external electromagnetic field in the Minkowski spacetime and the cosmic string spacetime. This approach is based on a quantum mechanics factorization method that allows us to obtain the su(1, 1) algebra generators, the energy spectrum and the

In this paper, we propose a scheme where Alice shares an arbitrary m-particle unknown state with her agents, Bob and Charlie. Alice starts by distributing 2m Einstein–Podolsky–Rosen pairs with her agents and performs m joint three-particle Greenberger–Horne–Zeilinger state measurements on her particles. Bob, who acts as the controller, performs a product measurement σx1⊗σx2⊗⋯⊗σxm on his m qubit states

The no-masking theories show that it is impossible to mask the set of all qubit states into the quantum correlation of bipartite qubit system or tripartite qubit system. In this paper, we give a new proof of the no-masking situation of the tripartite qubit system. Recent work has shown that there exists a universal masker which can mask an arbitrary set of qubit states in four-qubit systems perfectly

Measurements for the expansion rate of the universe disagree. Indeed, local measurements suggest a higher value of the Hubble constant than those performed through the cosmic microwave background. This fact led to a very interesting debate within the scientific community. The paper is not devoted to give solutions to the problem of “Hubble tension”. The aim of this paper is, on the contrary, to deduce

We discuss equilibration process in expanding Universes as compared to the thermalization process in Minkowski spacetime. The final goal is to answer the following question: Is the equilibrium reached before the rapid expansion stops and quantum effects have a negligible effect on the background geometry or stress–energy fluxes in a highly curved early Universe have strong effects on the expansion

The Fradkin–Schwinger functional methods to represent a Green function in an external gravitational field are used to study the eikonal and the next-to-eikonal limit, including the nonlinear gravitational interactions, of the scattering amplitudes of an ultra-relativistic scalar particle on a static super-massive scalar target in the nearly forward limit. The functional approach confirms the exponentiation

Magnetars are comparatively young neutron stars with ultra-strong surface magnetic field in the range 1014–1016G. The old neutron stars have surface magnetic field somewhat less ∼108G which clearly indicates the decay of field with time. One possible way of magnetic field decay is by ambipolar diffusion. We describe the general procedure to solve for the ambipolar velocity inside the star core without

This paper is devoted for the formulation of new anisotropic solutions for non-static spherically symmetric self-gravitating systems through gravitational decoupling technique. Initially, we add a gravitational source in the perfect matter distribution for inducing the effects of anisotropy in the considered model. We then decouple the field equations through minimal geometric deformation approach

This paper explores the influence of special type of higher order generalized uncertainty principle on the thermodynamics of five-dimensional black hole in Einstein–Gauss–Bonnet gravity coupled to nonlinear electrodynamics. We examine the corrected thermodynamical properties of the black hole with some interesting limiting cases k→0 and α→0 and compared our results with usual thermodynamical relations

The proton radius puzzle has motivated several new experiments that aim to extract the proton charge radius and resolve the puzzle. Recently, PRad, a new electron–proton scattering experiment at Jefferson Lab, reported a proton charge radius of 0.831±0.007statistical±0.012systematic. The value was obtained by using a rational function model for the proton electric form factor. We perform a model-independent

In this work, we would like to apply the asymptotic iteration method (AIM) to a newly proposed Morse-like deformed potential introduced recently by Assi, Alhaidari and Bahlouli.23 This interesting potential can support bound states and/or resonances. However, in this work, we are only interested in bound states. We considered several choices of the potential parameters and obtained the associated spectrum

The discrete phase space continuous time representation of relativistic quantum mechanics involving a characteristic length l is investigated. Fundamental physical constants such as ℏ, c, and l are retained for most sections of the paper. The energy eigenvalue problem for the Planck oscillator is solved exactly in this framework. Discrete concircular orbits of constant energy are shown to be circles

In this work, we explore a generalization of the Dirac and Klein–Gordon (KG) oscillators, provided with a deformed linear momentum inspired in nonextensive statistics, that gives place to the Morse potential in relativistic contexts by first principles. In the (1 + 1)-dimensional case, the relativistic oscillators are mapped into the quantum Morse potential. Using the Pekeris approximation, in the

In this paper, we give a brief review of recent theoretical studies of double prompt J/ψ production at the FNAL Tevatron and the CERN LHC, to which both single- and double-parton-scattering processes contribute. In single parton scattering, we mainly present the results computed within the framework of non-relativistic quantum chromodynamics factorization combined with one of the two approaches to

We construct a non-renormalizable B−L model based on Σ(18) symmetry, whereby, neutrino mass ordering and the tiny neutrino masses are explained at tree level via type I seesaw mechanism. The model can reproduce the recent observed neutrino oscillation data in which neutrino oscillation parameters including three mixing angles 𝜃12,23,13, Dirac CP phase plus neutrino squared-mass splittings Δm21,32

We compute the string susceptibility γstr for the regularized Nambu–Goto string in d dimensions and obtain γstr=1/2 in 2

One of the most important mathematical tools necessary for Quantum Field Theory calculations is the field propagator. Applications are always done in terms of plane waves and although this has furnished many magnificent results, one may still be allowed to wonder what is the form of the most general propagator that can be written. In this paper, by exploiting what is called polar form, we find the

Based on the Pomeranchuk theorem, one constructs the δ(s) parameter to measure the difference between experimental data for the particle–particle and particle–antiparticle total cross-section at same energy. The experimental data for the proton–proton and proton–antiproton total cross-section were used to show that, at the same energy, this parameter tends to zero as the collision energy grows. Furthermore

In this paper, we investigate the relationship between quadratic gravity and a restricted Weyl symmetry where a gauge parameter Ω(x) of Weyl transformation satisfies a constraint □Ω=0 in a curved spacetime. First, we briefly review a model with a restricted gauge symmetry on the basis of QED, where a U(1) gauge parameter 𝜃(x) obeys a similar constraint □𝜃=0 in a flat Minkowski spacetime, and explain

In the first part of this note, we observe that a non-Riemannian piece in the affine connection (a “dark connection”) leads to an algebraically determined, conserved, symmetric 2-tensor in the Einstein field equations that is a natural dark matter candidate. The only other effect it has, is through its coupling to standard model fermions via covariant derivatives. If the local dark matter density is

Thomas–Fermi model is considered here to make it cogent to capture the Planck-scale effect with the use of a generalization of uncertainty relation. Here generalization contains both linear and quadratic terms of momentum. We first reformulate the Thomas–Fermi model for the non-relativistic case. We have shown that it can also be reformulated for taking into account the relativistic effect. We study

Experimental evidences of a first-order phase transition from a superfluid to a non-interacting Fermi gas system are studied for 97,98Mo isotopes. The experimental observations are compared with the semi-empirical macroscopic model and superfluid formalism. We have shown that the entropy excess ratio introduced in our previous publications within the superfluid model can describe the first-order phase

We review a testable, the axion quark nugget (AQN) model outside of the standard WIMP paradigm. The model was originally invented to explain the observed similarity between the dark and the visible components, ΩDM≈Ωvisible, in a natural way as both types of matter are formed during the same QCD transition and proportional to the same dimensional fundamental parameter of the system, ΛQCD. In this framework

Dark energy and dark matter are two of the biggest mysteries of modern cosmology, and our understanding of their fundamental nature is incomplete. Many parametrizations of couplings between the two in the continuity equation have been studied in the literature, and observational data from the growth of perturbations can constrain these parametrizations. Assuming standard general relativity with a simple

We propose a simple classical electrodynamics model in which a Lorentz pseudoscalar field and a Dirac field are present in the general Lagrangian of the system. The model is constructed by allowing explicit violation of chiral symmetry. This approach is intended to predict possible electromagnetic decays of the neutral pion in effective terms.

The analysis of the new TOTEM data at 13 TeV in a wide momentum transfer region reveals the unusual phenomenon — the presence in the elastic scattering amplitude of a term with a very large slope that is responsible for the behavior of hadron scattering at a very small momentum transfer. This term can be connected with hadron interactions at large distances.

In this paper, we discuss fundamental aspects related to the helicity and dynamics of the spin-1/2 fermions encompassed within the very well-known Lounesto’s classification. More specifically, we investigate how the bi-spinorial structures behave under discrete symmetries, as well as analyze some consequences on the spinors dynamics. In addition, we find an interesting relation between the spinor helicity

The teleparallel gravitational energy–momentum tensor density of the Friedmann–Lemaître–Robertson–Walker spacetime is calculated and analyzed: it is decomposed into density, isotropic pressure, non-isotropic pressures, and the heat-flux 4-vector; the antisymmetric part is decomposed into “electric” and “magnetic” components. It is found that the gravitational field obeys a radiation-like equation of

A systematic study of shapes in Ni (Z=28) isotopes has been made in the Relativistic–Hartree–Bogoliubov (RHB) formalism with two types of density-dependent NN interactions which are based on the range of meson-exchange. The constraint calculations assuming the axial and triaxial-symmetry predict the shape isomerism in the case of 56,64,66,68,70,80Ni isotopes. Significant jumps at N=28,40,50 in the

A deformation of the Landau problem based on a modification of Fock algebra is considered. Systems with the Hamiltonians f(Ĥ) where Ĥ is the Landau Hamiltonian in the lowest level are discussed. The case f(Ĥ)=α1Ĥ+α2Ĥ2 is studied and it is shown that in this particular example, parameters of the problem can be fixed by using the quadratic Zeeman effect data and the Breit–Rabi formula.

This paper deals with Maxwell equations with Dunkl derivatives. Dunkl-deformed gauge transform is investigated. Dunkl-electrostatics in spherical coordinates is also studied. The multi-pole expansion of potential is obtained for even and odd potential for parity in z-direction. The conducting sphere in a uniform electric field in Dunkl-electrostatics is also discussed.

We investigate an alternative quantization of R-NS string theory. In the alternative quantization, we define the distinct vacuum for the left-moving mode and the right-moving mode by exchanging the role of creation operators and annihilation operators in the left-moving sector. The resulting string theory has only a finite number of propagating degrees of freedom. We show that an appropriate choice

Using the most recent experimental data on parameters of the standard electroweak theory, as well as renormalization group equations with a boundary matching condition, we derive a refined and more accurate value for the mass of the doubly-charged bilepton (Y±±) occurring in the spontaneous breaking of the gauge group SU(3)L×U(1)X to the standard electroweak gauge group SU(2)L×U(1)Y. Our result is

We discuss the macroscopic quantum tunneling from the black hole to the white hole of the same mass. Previous calculations in [G. E. Volovik, Universe 6, 133 (2020)] demonstrated that the probability of the tunneling is p∝exp(−2SBH), where SBH is the entropy of the Schwarzschild black hole. This in particular suggests that the entropy of the white hole is with minus sign the entropy of the black hole

The vacuum catastrophe results from the disagreement between the theoretical value of the energy density of the vacuum in quantum field theory and the estimated one observed in cosmology. In a similar attempt in which the ultraviolet catastrophe was solved, we search for the value of the cosmological constant by brute-force through computation. We explore combinations of the fundamental constants in

In this paper, we find the cosmological solutions of the massive conformal gravity field equations in the presence of matter fields. In particular, we show that the solution of negative curvature is in good agreement with the late universe.

In this paper, we derived an exact solution of the spherically symmetric Hayward black hole surrounded by perfect fluid dark matter (PFDM). By applying the Newman–Janis algorithm, we generalized it to the corresponding rotating black hole. Then, we studied the shadows of rotating Hayward black hole in PFDM. The apparent shape of the shadow depends upon the black hole spin a, the magnetic charge Q and

We consider electrogeodesics on which the energy E<0 in the Reissner–Nordström metric. It is shown that outside the horizon there is exactly one turning point inside the ergoregion for such particles. This entails that such a particle passes through an infinite chain of black–white hole regions or terminates in the singularity. These properties are relevant for two scenarios of high energy collisions

This study aims to investigate an Nflationary phase diagram with a multifield polynomial potential. The gradual vanishing of the inflationary phase during slow roll phase of the Nflation model has been demonstrated for a large number of fields in the case when there are voluminous N phase transitions occurring in it. A phase diagram for Nflation model illustrates its phase transitions for a multifield

We identify a strong similarity among several distinct originally second-class systems, including both mechanical and field theory models, which can be naturally described in a gauge-invariant way. The canonical structure of such related systems is encoded into a gauge-invariant generalization of the quantum rigid rotor. We perform the BRST symmetry analysis and the BFV functional quantization for

A short introduction to N = 1 supergravity in four dimensions in the superspace approach is given emphasizing on all steps to obtain the final Lagrangian. In particular, starting from geometrical principles and the introduction of superfields in curved superspace, the action coupling matter and gauge fields to supergravity is derived. This paper is based on the book [M. Rausch de Traubenberg and M

We show that in the quadratic curvature theory of gravity, or simply Rμν2 gravity, the tree-level unitarity bound (tree unitarity) is violated in the UV region but an analog for S-matrix unitarity (SS†=1) is satisfied. This theory is renormalizable, and hence the failure of tree unitarity is a counter example of Llewellyn Smith’s conjecture on the relation between them. We have recently proposed a

Entropy is a key concept widely used in physics and other fields. At the same time, the meaning of entropy with different names and the relationship among them are confusing. In this paper, we discuss the relationship among the Clausius entropy, Boltzmann entropy and information entropy and further show that the three kinds of entropy are equivalent to each other to some extent. Moreover, we point

In this paper, we find analytical solutions for the scalar and gauge fields in the cosmological multiply warped braneworld scenario. Having done that, we find the precise mass spectra for Bosonic fields. We compare those spectra to the ones previously found in the literature for the static case.

In this paper, we attempt to further study the heat engine efficiency for the regular black hole (BH) with an anti-de Sitter (AdS) background where the working material is the Hayward–AdS (HAdS) BH. In the extended phase space, we investigate the heat engine efficiency of the HAdS BH by defining the cosmological constant as the thermodynamic pressure P and deriving the mechanical work from the PdV

We present wormhole as a solution of Euclidean field equations as well as the solution of Wheeler–DeWitt equation in (4 + 1)-dimensional Kaluza–Klein cosmology minimally coupled with scalar field. A simple analytic solution of the Euclidean field equations enlightens classical forbidden domain in the wormhole configuration under analytic continuation in the Euclidean space by τ=it. Numerical solutions

In this paper, we study the effect of the constant magnetic field on energy levels of the Dirac particles such as electron, proton and heavy ions. We calculate the energy eigenvalues of the Dirac equation in the presence of the magnetic field and two-dimensional harmonic oscillator potential with spin symmetry by using the supersymmetric quantum mechanics and asymptotic iteration methods.

Rotational transformations describe relativistic effects in rotating frames. There are four major kinematic rotational transformations: the Langevin metric; Post transformation; Franklin transformation; and the rotational form of the absolute Lorentz transformation. The four transformations exhibit different combinations of relativistic effects and simultaneity frameworks, and generate different predictions