International Journal of Theoretical Physics最新文献

In this paper, the gravity with a deviation is considered. Modification of the Lane-Emden equation and Jeans’ instability condition is performed based on the gravity with a deviation. Some exact and numerical solutions are given for the modified Lane-Emden equation.

A microscopic study of the large or dielectric polaron behaviour has been carried out for the first time for MgFe₂O₄. We have considered a new methodology to study in depth the Overlap Large Polaron Tunneling (OLPT) conduction mechanism in a large temperature range. This methodology consists in extracting theory from experimental data. Unexpected and even spectacular results are determined. However, to the best of our knowledge, it is for the first time, that we prove the existence of the magnetic polaron in MgFe₂O₄ in the ferromagnetic phase as an alternative to the dielectric one. The function added to the trapping potential shows a competitive behavior between the magnetic effect and the crystal lattice acoustic vibration. Our theoretical model can be generalized for ferrite materials exhibiting the (OLPT) conduction mechanism. Indeed, this model allows checking the existence or not of the magnetic polaron, to determine its radius, the magnetic correlation length variation with frequency, the formation temperature of the magnetic polaron (T_M) and other features sometimes inaccessible even experimentally.

Graphical Abstract

The biggest challenge of this article is how to maximize the rest time of intermittent controllers. This paper mainly uses intermittent quantized controller (IQC) to examine asymptotic synchronization between fractional-order neural networks (FONNs). Firstly, by utilizing the advantages of intermittent properties, a novel lemma with asymptotic stability inequalities is proposed. Secondly, combining intermittent properties with quantization technique, two different categories of aperiodically intermittent quantized controllers (AIQCs) are designed to ensure asymptotic convergence of FONNs. Due to the certain correlation between control interval, rest interval, and convergence rate parameters, thus, optimization algorithm becomes particularly important in maximizing rest time as much as possible. Thirdly, by constructing Lyapunov functions, several useful conditions are established for the asymptotic synchronization of FONNs. Finally, the rationality of the proposed theoretical analysis is confirmed by two numerical examples.

We characterize in a novel manner the physical properties of the low temperature Fermi gas in the degenerate domain as a function of temperature and chemical potential. For the first time we obtain low temperature T results in the domain where several fermions are found within a de Broglie spatial cell. In this regime, the usual high degeneracy Sommerfeld expansion fails. The other known semi-classical Boltzmann domain applies when fewer than one particle is found in the de Broglie cell. We also improve on the understanding of the Sommerfeld expansion in the regime where the chemical potential is close to the mass and also in the high temperature regime. In these calculcations we use a novel characterization of the Fermi distribution allowing the separation of the finite and zero temperature phenomena. The relative errors of the three approximate methods (Boltzmann limit, Sommerfeld expansion, and the new domain of several particles in the de Broglie cell) are quantified.

In this paper, based on a remote state preparation (RSP) scheme for arbitrary single quantum bit state and a controlled quantum teleportation protocol, we discuss the decoherence suppression (DS) of weak measurement (WM) and environmentally assisted measurement (EAM). We analyze the application of the decoherence suppression strategy of WM and EAM in improving the efficiency and quality of quantum communication from the perspective of amplitude or phase damped channels. For these two types of noise, the average fidelity and the probability of success of the scheme are calculated as a function of the weak measurement before, after and the channel attenuation parameters. Provided that the decay rate of the amplitude or phase damping is completely known, one can always achieve unit fidelity even for heavy damping cases, which is the biggest advantage of proposed scheme. Influences of several paramters, including strengths of weak measurements and the decay rate of the decoherence channel, on the RSP based on decoherence suppression is discussed. The results indicate that protected CQT of an arbitrary unknown single-qubit state can be achieved with a certain probability and 100% fidelity.

Classical multidimensional scaling is an important dimensionality reduction method that is characterized by preserving the Euclidean distance between samples in high dimensional space in low dimensional space. However the high time complexity limits its application in massive samples and high-dimensional data scenarios. As a promising solution, a quantum algorithm for classical multidimensional scaling is proposed in this work, achieving polynomial speedup in terms of sample size compared to classical algorithms. Our algorithm is built on two quantum subroutines, one involving inner product and matrix multiplication, and the other utilizing quantum singular value estimation.

Variable-coefficient equations can be used to describe certain phenomena when the inhomogeneous media and nonuniform boundaries are taken into consideration. It is meaningful to solve the exact solution of variable-coefficient equations. In this paper, a (2+1)-dimensional variable-coefficient Boussinesq equation is investigated. The integrability is firstly examined by the Painlevé analysis method. Secondly, the Bäcklund transformations, one- and two-soliton solutions of the (2+1)-dimensional variable-coefficient Boussinesq equation are studied by virtue of the Hirota bilinear method. Propagation characteristics and interaction behaviors of the solitons are discussed: (i) soliton shapes and interaction behaviors are affected by the variable coefficients, and (ii) the two-soliton interaction is elastic, and the shape and velocity does not change after the collision, and only the shift changes.

We have conducted an investigation on the quasinormal spectrum of electromagnetic perturbation surrounding the Bardeen black hole which is enveloped by perfect fluid dark matter. With the metric at hand, the influence of the dark matter parameter (alpha ) and the magnetic charge g on the horizon radii of black hole are studied. It turns out that for fixed g, both the Cauchy horizon and event horizon radius increase with the decrease of (alpha ). But, with the increase of g, the Cauchy horizon radius increases while the event horizon radius decreases. Applying the sixth-order WKB approximation method, we have assessed the complex frequencies of the quasinormal modes. Our findings reveal that the oscillation frequency and decay rate of the electromagnetic perturbation are intensified with the augmentation of the dark matter parameter (alpha ) and the spherical harmonic index l respectively. Furthermore, as the magnetic charge g increases, the real component of the quasinormal modes frequencies undergoes escalation, while the imaginary component experiences a decrease. Notably, the variation in (alpha ) and g demonstrates that the imaginary components exhibit an almost linear correlation with the real components. These phenomena serve to distinguish the Bardeen black hole surrounded solely by perfect fluid dark matter.

In this paper, we establish some of the deformed calculus for R-Minkowski space-time. We start by defining the deformed derivative in R-Minkowski spacetime, the deformed exponential and trigonometric functions, deformed Fourier transform and its inverse transformation, and then we apply all that to the study of the one-dimensional box problem in a position representation. Thereafter, we study the one-dimensional Dirac harmonic oscillator, and as a consequence we obtain the energy spectrum of the latter in R-Minkowski space-time.

We construct a unified framework of geometrodynamics based on the Finsler geometry to reveal the relationship between spacetime and dynamics. The Lagrangian of electron in electromagnetic field as the Finsler function gives the Finslerian metric, which modifies spacetime metric in the Finsler-Randers space. The geodesic equation gives the effective mass, forces, and effective (or geometric) fields. Using the Chern connection, we construct the generalized Einstein-Maxwell equations. In the local natural basis, we give generalized Maxwell equations and wave equations. We find that the geometric field couples with electromagnetic field and gives effective charges and currents. We analyze several typical cases, such as flat spacetime, vacuum and Berwald structure. We find that the electromagnetic field coupled with the spacetime torsion emerges in the Berwald space. These results provide some hints to understand some puzzles, such as axion and dark energy. These formulations stimulate some clues to explore deeper geometric structures behind physical phenomena.