Modern Physics Letters A

In this paper, by using the Yukawa coupling mechanism, we consider the fermion localization in two types of braneworld models driven by real scalar fields with non-standard dynamics. Because of the existing freedom in the form of the Yukawa coupling, we consider two coupling forms between the background scalar field and spinors where one is arising from the geometry shape of the warp factor and the other is a function of the background scalar field containing a derivative scalar-fermion coupling. With two coupling functions, it is shown that the massless zero mode of fermion fields is localized on both branes with generalized dynamic depending on the values of the coupling constants. However, there is no localized mode when the Yukawa coupling only contains a derivative term of the background scalar field. Furthermore, effects of the parameters of the models on the zero mode and fermion effective potential are addressed.

We consider a homogeneous and isotropic Universe, described by the minisuperspace Lagrangian with the scale factor as a generalized coordinate. We show that the energy of a closed Universe is zero. We apply the uncertainty principle to this Lagrangian and propose that the quantum uncertainty of the scale factor causes the primordial fluctuations of the matter density. We use the dynamics of the early Universe in the Einstein–Cartan theory of gravity with spin and torsion, which eliminates the big-bang singularity and replaces it with a nonsingular bounce. Quantum particle production in highly curved spacetime generates a finite period of cosmic inflation that is consistent with the Planck satellite data. From the inflated primordial fluctuations we determine the magnitude of the temperature fluctuations in the cosmic microwave background, as a function of the numbers of the thermal degrees of freedom of elementary particles and the particle production coefficient which is the only unknown parameter.

In this paper, we present a physically acceptable internal solution with a perfect fluid, which needs the pressure and density as regular, positive and monotonic decreasing functions and with a speed of sound positive and lower than the speed of light. This solution depends on a parameter $y$, and it is physically acceptable if $w\le 0.36068416388$, the compactness has a maximum value for the maximum value of $y$ and it corresponds to $\frac{GM}{c^{2}R}=0.1884895029$, thus the model can be applicable to the description of compact stars. In a complementary way, we present the description of a star with mass equal to the sun mass and radius of $R=7.85$ Km associated to the neutron star Her X-1, obtaining a central density ${\rho }_c=2.44986086610^{17}{\mathrm{\text{Kg/m}}}^3$ which is characteristic of the neutron stars.

The inflationary scenario in spatially homogeneous and anisotropic Bianchi Type I spacetime with exponential potential $V=e^{-\lambda \varphi }$, $\lambda >0$ and average scale factor (R) is considered as $R^3=ABC=e^{\lambda \varphi (t)}$ is discussed. The model isotropizes in special case and asymptotically. The spatial volume increases with time representing inflationary scenario and the expansion continues for long enough, thus solving the horizon problem. The model represents decelerating and accelerating phases of universe in special case. Also, the model is singularity free at t = 0. In special case, i.e. when constants b = 0, k = 0, then the model leads to FLRW model for which we have the average scale factor $R\propto t^{2/3}$, $𝜃\propto 1/t$ and deceleration parameter $(q)=\frac{1}{2}$. This paper gives the answer why anisotropic and homogeneous Bianchi Type I spacetime is considered than FRW model to discuss inflationary scenario.

This paper presents the application of recently developed metaheuristic optimization algorithm, the spotted hyena optimizer, for solving both convex and non-convex economic dispatch problems. The proposed algorithm has been tested on various test systems (i.e. 6, 10, 20, and 40 generators systems) and compared with other well-known approaches to demonstrate its effectiveness and efficiency. The results show that the proposed algorithm is able to solve economic load power dispatch problem and converge toward the optimum with low computational efforts.

We present here a general relativistic mechanism for accelerated cosmic expansion and the Hubble’s parameter. It is shown that spacetime vorticity coupled to the magnetic field density in galaxies causes the galaxies to recede from one another at a rate equal to the Hubble’s constant. We therefore predict an oscillatory universe, with zero curvature, without assuming violation of Newtonian gravity at large distances or invoking dark energy/dark matter hypotheses. The value of the Hubble’s constant, along with the scale of expansion, as well as the high isotropy of CMB radiation are deduced from the model.

The Landau problem for inhomogeneous magnetic fields is examined in a very general context and several interesting analogies with the Nielsen–Olesen vortices are established. Firstly, we show that the Landau problem with non-homogeneous magnetic fields exhibits Meissner effect that is unstable unless two-body interactions are added and vortices emerge. Using the scaling freedom, we can write the Schrödinger equation in terms of the scales ratio $\kappa =E/m\propto 1-T/T_c$ where the last identification is realized simply by using the Ginzburg–Landau theory. We find our equations are valid in the superconducting regime, and it is not possible for the Cooper pairs amplitude to reach to a constant, nonzero value, and therefore the theory is unstable. The supersymmetric quantum mechanics version, by completeness, is also considered.

The description of very high energy proton–proton cross-sections in terms of a “black disc” with an “edge” allows a simple generalization to highest energy proton–nucleus cross-sections. This results in a leading ln²W term and a ln W term whose coefficient depends linearly on the radius of the nucleus (W the c.m. energy). The necessary parameters are determined from the fits to p–p data. Since the coefficient of the ln W term is rather large, it is doubtful that the regime of ln²W dominance can be reached with available energies in accelerators or cosmic rays. However, the ln W term can be relevant for highest energy cosmic rays in the atmosphere, where a large increase for the cross-section on nitrogen is expected. Tests of the theory should be possible by studying the coefficient of ln W at p-nucleus colliders.