Magnetic Monopoles Research Articles

Observational appearance of Kaluza–Klein black holes

The optical properties of rotating black holes in Kaluza–Klein theory described by the total mass, spin, and electric and magnetic charges are investigated in detail. Using a developed general relativistic ray-tracing code to calculate the motion of photons, shadows of Kaluza–Klein black holes are generated. The properties of the shadow and the light deflection angle around these black holes are also studied in order to put constraints on the parameters of Kaluza–Klein black holes using M87* shadow observations. The possibility of imposing constraints on Kaluza–Klein black holes using shadow observations is investigated. Moreover, we find that small charges (electric and magnetic) of the black hole can meet these constraints. We conclude that with the current precision of the M87* black hole shadow image observation by the EHT collaboration, the shadow observations of Kaluza–Klein black holes are indistinguishable from that of the Kerr black hole. Much better observational accuracy than the current capabilities of the EHT collaboration are required in order to place verified constraints on the parameters of modified theories of gravity in the strong field regime.

Applicability of the 0–1 test for chaos in magnetized Kerr–Newman spacetimes

The dynamics of electrically neutral or charged particles around a magnetized Kerr–Newman black hole immersed in an external electromagnetic field can be described by a dimensionless Hamiltonian system. This Hamiltonian is given an appropriate time transformation, which allows for construction of explicit symplectic integrators. Selecting one of the integrators with good accuracy, long-term stabilized Hamiltonian error behavior and less computational cost, we employ the 0–1 binary test correlation method to distinguish between regular and chaotic dynamics of electrically neutral or charged particles. The correlation method is almost the same as the techniques of Poincaré map and fast Lyapunov indicators in identifying the regular and chaotic two cases. It can well describe the dependence of the transition from regularity to chaos on varying one or two dynamical parameters. From a statistical viewpoint, chaos occurs easily under some circumstances with an increase of the external magnetic field strength and the particle electric charge and energy or a decrease of the black hole spin and the particle angular momentum. A small change of the black hole electric charge does not very sensitively affect the dynamics of neutral particles. With the black hole electric charge increasing, positively charged particles do not easily yield chaotic motions, but negatively charged particles do. On the other hand, the effect of a small change of the black hole magnetic charge on the dynamical transition from order to chaos has no universal rule.

Static magnetic signature of a ghost-ship propulsor system as a composite ferromagnetic medium

In this paper, it is shown that the static magnetic signature of a propulsor belonging to a ghost ship, whose hull is made of fiberglass, can be calculated by regarding it as a composite ferromagnetic medium. The calculation of the magnetic signature in the static regime is carried out using finite-element method simulations and according to a simple analytical model based on the concepts of volume averaged magnetization arising from a source magnetic field, volume averaged permeability, surface magnetic charges, and the demagnetization tensor applied to a composite magnetic medium. Using targeted simulations, it is demonstrated that the magnetostatic field of demagnetizing nature forming inside the propulsor almost cancels the contribution of the volume averaged magnetization. From the interplay between the numerical simulations and the analytical model, the elements of the demagnetization tensor in the region filled by the propulsor are locally calculated, and their role in determining the localization effects of the magnetic signature is discussed. By replacing the original ferromagnetic materials with weakly ferromagnetic ones, it is shown that, in the underwater region outside the propulsor, the magnetic signature drop is 64%. This analysis suggests an experimental way to use a simple passive method to minimize the magnetic signature of a propulsor as an alternative to more complex and time-consuming methods, such as the deperming and degaussing methods, widely employed to reduce the magnetic signature of ships and underwater objects in military applications.

Strong gravitational lensing of rotating regular black holes in non-minimally coupled Einstein-Yang-Mills theory* *Support of the National Natural Science Foundation of China (11865018); the Natural Science Foundation of Henan Province, China (232300421351); the Talent Introduction Fund at Henan University of Technology, China(2018BS042, 2020BS035)

The strong gravitational lensing of a regular and rotating magnetic black hole in non-minimally coupled Einstein-Yang-Mills theory is studied. We find that, with the increase of any characteristic parameters of this black hole, such as the rotating parameter a, magnetic charge q and EYM parameter λ, the angular image position and relative magnification decrease while deflection angle and image separation s increase. The results will degenerate to that of the Kerr case, RN case with magnetic charge and Schwarzschild case when we take some specific values for the black hole parameters. The results also show that, due to the small influence of magnetic charge and EYM parameters, it is difficult for current astronomical instruments to tell this black hole apart from a General Relativity one.

Interactions of electrical and magnetic charges and dark topological defects

Interactions of electrical and magnetic charges and dark topological defects

Persistent dynamic magnetic state in artificial honeycomb spin ice

Topological magnetic charges, arising due to the non-vanishing magnetic flux on spin ice vertices, serve as the origin of magnetic monopoles that traverse the underlying lattice effortlessly. Unlike spin ice materials of atomic origin, the dynamic state in artificial honeycomb spin ice is conventionally described in terms of finite size domain wall kinetics that require magnetic field or current application. Contrary to this common understanding, here we show that a thermally tunable artificial permalloy honeycomb lattice exhibits a perpetual dynamic state due to self-propelled magnetic charge defect relaxation in the absence of any external tuning agent. Quantitative investigation of magnetic charge defect dynamics using neutron spin echo spectroscopy reveals sub-ns relaxation times that are comparable to the relaxation of monopoles in bulk spin ices. Most importantly, the kinetic process remains unabated at low temperature where thermal fluctuation is negligible. This suggests that dynamic phenomena in honeycomb spin ice are mediated by quasi-particle type entities, also confirmed by dynamic Monte-Carlo simulations that replicate the kinetic behavior. Our research unveils a macroscopic magnetic particle that shares many known traits of quantum particles, namely magnetic monopole and magnon.

Phenomenologies in Hypersphere Soliton and Stringy Photon Models

We consider the Dirac quantization in the first-class formalism to investigate the hypersphere soliton model (HSM) defined on the S3 hypersphere. To do this, we construct the first-class Hamiltonian possessing the Weyl ordering correction. In the HSM, we evaluate the baryon physical quantities such as the baryon masses, magnetic moments, axial coupling constant and charge radii, most predicted values of which are in good agreement with the corresponding experimental data. Moreover, shuffling the baryon and transition magnetic moments, we find the model independent sum rules. In the HSM we also evaluate the baryon intrinsic frequencies such as ωN=0.87×1023s−1 and ωΔ=1.74×1023s−1 of the nucleon and delta baryon, respectively, to yield the identity ωΔ=2ωN. Next, making use of the Nambu-Goto string action and its extended rotating bosonic string theory, we formulate the stringy photon model to obtain the energy of the string configuration, which consists of the rotational and vibrational energies of the open string. Exploiting this total string energy, we evaluate the photon intrinsic frequency ωγ=9.00×1023s−1, which is comparable to the corresponding baryon intrinsic frequencies. We also predict the photon size ⟨r2⟩1/2(photon)=0.17fm, which is approximately 21% of the proton magnetic charge radius.

Exploring the phase diagram of 3D artificial spin-ice

Artificial spin-ices consist of lithographic arrays of single-domain magnetic nanowires organised into frustrated lattices. These geometries are usually two-dimensional, allowing a direct exploration of physics associated with frustration, topology and emergence. Recently, three-dimensional geometries have been realised, in which transport of emergent monopoles can be directly visualised upon the surface. Here we carry out an exploration of the three-dimensional artificial spin-ice phase diagram, whereby dipoles are placed within a diamond-bond lattice geometry. We find a rich phase diagram, consisting of a double-charged monopole crystal, a single-charged monopole crystal and conventional spin-ice with pinch points associated with a Coulomb phase. In experimental demagnetised systems, broken symmetry forces formation of ferromagnetic stripes upon the surface, forbidding the lower energy double-charged monopole crystal. Instead, we observe crystallites of single magnetic charge, superimposed upon an ice background. The crystallites are found to form due to the distribution of magnetic charge around the 3D vertex, which locally favours monopole formation.

Magnetic monopole's role in hydrogen bubbles formation in rapidly solidified Al–Cu–Zn alloys

Hydrogen hydrides are formed when hydrogen is trapped in the aluminum solid solution of rapidly cooled Al–Cu–Zn alloys. The formation of these hydrides is of great interest because they have unique properties that make them useful in a variety of applications. One potential application is in the field of energy storage, where hydrogen hydrides could be used as a way to store hydrogen for use in fuel cells. Another potential application is in the field of catalysis, where these materials could be used to promote chemical reactions. Highlighting of magnetic monopoles in Al-30 wt%Cu-2wt.%Zn and stable skyrmions, at room temperature, in non-magnetic Al-50 wt%Cu-2wt.%Zn is also groundbreaking development in the field of materials science, as it suggests that there may be new ways to manipulate and control the properties of these materials. We observed a remarkable consequence of these phenomena: the transmutation of aluminum into silicon. This is a significant finding, as we believe we are the first to approach this process in this way. This could lead to breakthroughs in materials science and engineering, with potential applications in fields such as electronics, photonics, and nanotechnology.

Квазиклассическое квантовое обобщение уравнений Лондонов и гипотеза монополей

The paper considers the London equation semi-classical generalization leading to a connection between the Cooper pairs magnetic flux quantization and the electric charge discreteness. Using the Bohr --- Sommerfeld quantization rule, a derivation of the magnetic flux quantization was made on the basis of the fluxoid uniqueness. The resulting quantization was applied to the magnetic monopoles hypothesis proposed by Dirac, which remains relevant due to the asymmetry present in the modern physics in describing electrical and magnetic properties of matter. On a fairly simple model of the possible experiment, an option of registering a monopole by a jump in the magnetic induction flux and the associated alteration in the circuit current were studied. The paper analyzed the problems of the monopole different measurement units and the results similar to those obtained on the basis of the Schwinger series of works, where he proceeded from considering introduction of a hypothetical particle with the electric and magnetic charges, i.e., the dyon. Possible explanation of the Abrikosov vortex is presented, it is based on vortex representation in the form of a magnetized thin thread through the magnetic tubes, at the ends of which monopoles of different charges (dipole) are positioned. Unlike most the works devoted to this problem, calculations were performed in the SI system. The monopole quantization conditions were derived

Can electromagnetic charge inhabit in Rastall gravity?

One of the eminent generalizations of theory of general relativity is the Rastall gravity which was constructed based on the assumption of the non-conserved energy–momentum tensor of the matter field. Despite in the literature several solutions of black holes in the Rastall gravity coupled to the electromagnetic field have been presented, in the current paper we argue that the Rastall gravity with non-conserved energy–momentum tensor (with λ≠0 and R≠0) cannot couple to the electrodynamics, i.e., the electromagnetically charged black hole solution cannot be obtained in this case. This statement is adequate for both linear and nonlinear electrodynamics with the electric, magnetic, or dyonic charges coupled to the Rastall gravity.

Design and performance evaluation of novel magnetic tristable wave energy converter

To realize efficient broadband wave-energy conversion, this study proposes a point-absorber wave energy converter with a novel magnetic tristable mechanism (NMT-PAWEC). The tristable mechanism consists of coaxial inner and outer magnetic rings. The outer magnetic ring features two types of sector magnets with opposite poles. The motion control equations of the NMT-PAWEC are established using the Cummins equation and the equivalent magnetic charge method. The preferred parameter region of the novel tristable mechanism was investigated, and the energy-conversion performance of the NMT-PAWEC under regular waves was analyzed. The results show that the NMT-PAWEC with shallower potential wells can easily achieve inter-well oscillation under low-amplitude waves, with higher energy harvesting efficiency, and a wider frequency and work-damping band. Through a nonlinear bifurcation dynamics analysis, the causes of fluctuations and sudden changes in the output power under low-amplitude waves were revealed. Furthermore, the capture width ratio and annual average power of the South China Sea were considered. The influence of optimized PTO parameters on the energy-conversion performance of the NMT-PAWEC in regular and irregular waves was further discussed. In general, the efficient broadband power output capabilities demonstrate the excellent applicability of NMT-PAWEC.

Quantum-mechanical study of the optimal phosphorus atoms arrangement on silicene

Manufacturing precise quantum computers with small errors in quantum operations, long coherence times, and low power consumption is the most important challenge in modern nanoelectronics. To understand the operating modes of such calculators in detail, both the optimal arrangement of the qubit system within the structure and changes in its magnetic properties must be comprehensively investigated. In this paper, the behaviour of one and two phosphorus atoms on the surface of silicene is studied using quantum mechanical non-collinear calculations, which consider spin–orbit coupling. The magnetization and ion charge on phosphorus atoms for substitution and different adsorption positions are determined. The optimal positions, binding energies, and activation barriers for the diffusion of adsorbed phosphorus in the presence and absence of a primary adsorbed or substituting phosphorus atom are also established. Overall, the results of this work have important implications for researchers and technologists in the manufacture of Si:P based quantum computers.

Gradual Charge Order Melting in Bi0.5Ca0.5MnO3 Induced by Ultrahigh Magnetic Fields

We have investigated the magnetization process of Bi0.5Ca0.5MnO3 under ultrahigh magnetic fields. The metamagnetic transition due to the magnetic field-induced charge order melting has been observed. The metamagnetic transition becomes broad and smeared in the field ascending process at low temperatures. However, in the field descending process, a clear metamagnetic transition is observed even at low temperatures. Gradual charge order melting by magnetic field, and its reformation are expected to occur in ascending and descending magnetic fields, respectively. Quenched spatial inhomogeneity of the charge distribution and/or quantum criticality can account for the observed asymmetric broadening of the field induced charge order melting.

T1,1 truncation on the spindle

We study the compactification of the \U0001d4a9 = 2 AdS5 consistent truncation of the conifold, in presence of a Betti vector multiplet, on the spindle. We derive the BPS equations and solve them at the poles, computing the central charge for both the twist and the anti-twist class, turning on the magnetic charge associated to the baryonic symmetry. Then, in the anti-twist class, where there are choices of the quantized flux that give origin to a positive central charge, we numerically solve the BPS equations interpolating between the poles of the spindle. We conclude by comparing our results with the one obtained from the analysis of the dual field theory, finding an exact agreement.

Research on the Forward Solving Method of Defect Leakage Signal Based on the Non-Uniform Magnetic Charge Model.

Pipeline magnetic flux leakage inspection is widely used in the evaluation of material defect detection due to its advantages of having no coupling agent and easy implementation. The quantification of defect size is an important part of magnetic flux leakage testing. Defects of different geometrical dimensions produce signal waveforms with different characteristics after excitation. The key to achieving defect quantification is an accurate description of the relationship between the magnetic leakage signal and the size. In this paper, a calculation model for solving the defect leakage field based on the non-uniform magnetic charge distribution of magnetic dipoles is developed. Based on the traditional uniformly distributed magnetic charge model, the magnetic charge density distribution model is improved. Considering the variation of magnetic charge density with different depth positions, the triaxial signal characteristics of the defect are obtained by vector synthesis calculation. Simultaneous design of excitation pulling experiment. The leakage field distribution of rectangular defects with different geometries is analyzed. The experimental results show that the change in defect size will have an impact on the area of the defect leakage field distribution, and the larger the length and wider the width of the defect, the more sensitive the impact on the leakage field distribution. The solution model is consistent with the experimentally obtained leakage signal distribution law, and the model is a practical guide by which to improve the quality of defect evaluation.

The neutrino emissivity and the cooling energy resources by magnetic monopole in white dwarfs

Some typical low mass and high mass white dwarfs (WDs) are selected and the neutrino emissivity and the cooling energy resources problems are discussed. We present three models (I, II, III) to investigate the number of magnetic monopole (MM) captured, the luminosity, and the neutrino emissivity based on the MM catalytic nuclear decay. Model (I) mainly considers the effect of compression factor on thermonuclear cross section and ignores the effect of mass radius relationship on luminosity and neutrino emissivity. Model (II) only considers the effect of mass radius relationship at zero temperature on the number of MMs captured, the luminosities and the neutrino emissivity. Model (III) discusses the equation of state of the plasma and considers the effect of the number of MMs captured on the mass radius relationship, then investigates the number of MMs captured, the luminosities and the neutrino emissivity. Firstly, we find that the maximum of the number of captured MMs and the luminosities of these WDs can be 1.313×1029, and 2.083×1036ergss−1, respectively. Secondly, the luminosities due to MM catalytic nuclear decay for models (I, III) are agreed well with the observations, but the luminosities for model (II) are higher than the observations. Finally, the maximum of the neutrino emission rates of these WDs can be 1.626×1038s−1. The neutrino emission may not influence the structure and the evolution of the WDs. However, the monopole-catalyzed nucleon decay process may be regarded as a mechanism for keeping WDs hot.

The Asymptotic Structure of the Centred Hyperbolic 2-Monopole Moduli Space

We construct an asymptotic metric on the moduli space of two centred hyperbolic monopoles by working in the point particle approximation, that is treating well-separated monopoles as point particles with an electric, magnetic and scalar charge and re-interpreting the dynamics of the 2-particle system as geodesic motion with respect to some metric. The corresponding analysis in the Euclidean case famously yields the negative mass Taub-NUT metric, which asymptotically approximates the L<sup>2</sup> metric on the moduli space of two Euclidean monopoles, the Atiyah-Hitchin metric. An important difference with the Euclidean case is that, due to the absence of Galilean symmetry, in the hyperbolic case it is not possible to factor out the centre of mass motion. Nevertheless we show that we can consistently restrict to a 3-dimensional configuration space by considering antipodal configurations. In complete parallel with the Euclidean case, the metric that we obtain is then the hyperbolic analogue of negative mass Taub-NUT. We also show how the metric obtained is related to the asymptotic form of a hyperbolic analogue of the Atiyah-Hitchin metric constructed by Hitchin.

An Effective Optimization Method and Implementation of Permanent Magnet Electrodynamic Wheel for Maglev Car

The levitation-propulsion integration ability of radial permanent magnet electrodynamic wheel (PM EDW) renders its competitive edge over other magnetic levitation systems. A low-cost and effective second induction method is proposed to target the synchronous improvement of the saturation speed, levitation and propulsion forces. Its effectiveness is determined from the small-scale EDW to the full-scale EDW via theoretical model, simulation analysis and experiments test. First, according to magnetic charge theory, an updated EDW is proposed and developed. Simulated and tested results of the small-scale EDW demonstrate that the levitation force, propulsion force and saturation speed are increased by 14%, 7% and 30%. This improvement benefits the increased induction current and the mitigated skin effect. Afterwards, further analysis of the full-scale EDW with rings of various conductivity and thickness is conducted. The levitation force, propulsion force and saturation speed are enhanced by more than 50%, 10% and 200% synchronously. Based on analysis of power loss under the same levitation and propulsion forces, the updated EDW is more efficient than the original EDW. Ultimately, a proof-of-principle prototype with the updated EDW and 4-m long guideway are developed. The multi-loop PID control strategy along with dynamic mode implementation methodology are introduced. The scaled prototype is levitated over guideway at 12 mm and the levitation-propulsion ability is implemented with the maximum acceleration of 1.25 m/s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . This proof-of-principle prototype with updated EDW and control strategy paves the way to engineering applications of Maglev car.

Gravitational blocks: Symplectic covariance unveiled

By working in a symplectically covariant real formulation of special Kähler geometry, we propose and give strong evidence for a canonical BPS partition function for AdS×w2M2 near–horizon geometries with arbitrary rotation and generic magnetic and electric charges. Here, M2 is either a two–sphere or a spindle. We also show that how the attractor equations and the Bekenstein–Hawking entropy can be obtained from an extremization principle.