Magnetic Monopoles Research Articles

Design and experimental study of a two-stage nonlinear vibration isolators with quasi-zero stiffness

Quasi-zero-stiffness (QZS) vibration isolators are practical solutions for isolation in the low-frequency range. However, single-layer QZS isolators have a low roll-off rate of transmissibility in the frequency band of isolation, especially at high frequencies. The purpose of this study is to design a novel two-stage QZS isolator, called TSQZS isolator. In each stage, the quasi-zero stiffness is achieved by combining magnetic rings and linear springs in parallel. The TSQZS isolator can support a wide range of payloads by adjusting the initial compression of the positive-stiffness element (coil spring). Firstly, an analytical model of magnetic spring is given by employing the theory of equivalent magnetic charge, and the parameters are designed using the finite element simulation. Then, the dynamic behaviors of the TSQZS isolation system are revealed by using the harmonic balance method, and the isolation performance is assessed by displacement transmissibility. Finally, an experimental prototype is fabricated and the experimental testing setup is established to verify the isolation performance of the TSQZS system under base excitation. The results demonstrate that the devised TSQZS isolator not only enables vibration isolation at low frequencies, but also gains a high roll-off rate of transmissibility in the frequency band of vibration isolation.

Shadow thermodynamics of the Hayward-AdS black hole* *Supported by the National Natural Science Foundation of China (12047564), the Fundamental Research Funds for the Central Universities (2021CDJZYJH-003) and the Postdoctoral Science Foundation of Chongqing (cstc2021jcyj-bsh0124)

In this paper, the phase structure of the Hayward-anti-de Sitter (AdS) black hole (BH) is studied using shadow formalism. It has been found that the shadow radius is a monotonic function of the horizon radius and can therefore play an equivalent role to the horizon radius in characterizing the thermodynamics of the Hayward-AdS BH. The thermodynamic phase transition (PT) of the Hayward-AdS BH is investigated with the shadow radius. It is shown that as the magnetic charge increases, the shadow radius becomes larger, while the coexistence temperature becomes lower. The thermal profile of the Hayward-AdS BH is established by combining the temperature diagram and the shadow cast diagram, which shows that for a fixed magnetic charge, the temperature of the Hayward-AdS BH increases with the pressure whereas the region of the thermal profile decreases with the pressure. In particular, the temperature of the Hayward-AdS BH follows an N-type change trend when it is smaller than the critical temperature. It implies that the BH shadow may be used to investigate the thermodynamics of the Hayward-AdS BH.

Dyon production from near-extremal Kerr–Newman–(anti-)de Sitter black holes

Using the enhanced symmetry in the near-horizon region of the near-extremal dyonic Kerr–Newman (KN) black hole in the (A)dS space, we find the exact solutions for dyonic charged scalar field in terms of the hypergeometric function and explicitly compute the Schwinger effect for the emission of electric and/or magnetic charges. The emission formula confirms a universal factorization of the Schwinger formula in the AdS_2 and another Schwinger formula in the two-dimensional Rindler space determined by the effective temperature and the Hawking temperature with the chemical potentials of electric and/or magnetic charges and the angular momentum. The emission of the same species of charges from the KN black hole is enhanced in the AdS boundary while it is suppressed in the dS boundary. In addition, the dragging of particles in the KN black hole diminishes the emission of charges in both AdS and dS spaces. The AdS geometry of near-horizon gives the Breitenloher–Freedman (BF) bound, within which the stability of dyonic KN black holes is guaranteed against both the emission of charges and Hawking radiation.

Solutions to axion electromagnetodynamics and new search strategies of sub-μeV axion

The Witten effect implies the electromagnetic interactions between axions and magnetic monopoles, and the quantum electromagnetodynamics (QEMD) properly describes interactions of electric charges, magnetic charges and photons. Based on the QEMD, a generic low-energy axion-photon effective field theory was built by introducing two four-potentials (Aμ and Bμ) to describe a photon. More anomalous axion-photon interactions and couplings (gaAA, gaBB and gaAB) arise in contrary to the ordinary axion coupling {g}_{agamma gamma}{a F}^{mu nu}{overset{sim }{F}}_{mu nu} . As a consequence, the conventional axion Maxwell equations are further modified. We properly solve the new axion-modified Maxwell equations and obtain the axion-induced electromagnetic fields given a static electric or magnetic field. It turns out that the dominant couplings gaAB and gaBB can be probed in the presence of external magnetic field and electric field, respectively. The induced oscillating magnetic fields are always suppressed compared with the electric fields for the axions with large Compton wavelengths. This is contrary to the situation in conventional experiments searching for the oscillating magnetic fields induced by sub-μeV axions. Thus, we propose new strategies to measure the new couplings for sub-μeV axion in haloscope experiments.

Anomalous magnetoresistance by breaking ice rule in Bi2Ir2O7/Dy2Ti2O7 heterostructure

While geometrically frustrated quantum magnets host rich exotic spin states with potentials for revolutionary quantum technologies, most of them are necessarily good insulators which are difficult to be integrated with modern electrical circuit. The grand challenge is to electrically detect the emergent fluctuations and excitations by introducing charge carriers that interact with the localized spins without destroying their collective spin states. Here, we show that, by designing a Bi2Ir2O7/Dy2Ti2O7 heterostructure, the breaking of the spin-ice rule in insulating Dy2Ti2O7 leads to a charge response in the conducting Bi2Ir2O7 measured as anomalous magnetoresistance during the field-induced Kagome ice-to-saturated ice transition. The magnetoresistive anomaly also captures the characteristic angular and temperature dependence of this ice-rule-breaking transition, which has been understood as magnetic monopole condensation. These results demonstrate a novel heteroepitaxial approach for electronically probing the transition between exotic insulating spin states, laying out a blueprint for the metallization of frustrated quantum magnets.

Monopole Josephson effects in a Dirac spin liquid

Dirac Spin liquids (DSLs) are gapless featureless states, yet interesting by virtue of the effective field theory describing them -- (2+1)-dimensional quantum electrodynamics (QED$_3$). Further, a DSL is known to be a "parent state" of various seemingly unrelated ordered states, such as antiferromagnets and valence bond solids in the sense that one can obtain ordered states by condensing magnetic monopoles of the emergent gauge field. Can operators in the effective field theory, such as the emergent electric field, be externally induced and measured? In this work, we exploit the parent state picture to argue that the answer is yes. We propose a range of "monopole Josephson effects" that arise when two ordered states are separated by a region of the parent DSL. In particular, we show that one can induce an AC monopole Josephson effect, which manifests itself as an AC emergent electric field in the spin liquid, accompanied by a measurable spin current. Further, we show that this AC emergent electric field can be measured as a sharp tunable peak in Raman scattering. This work provides a theoretical proof of principle that emergent gauge fields in spin liquids can be externally induced, manipulated, and probed using more conventional states, which offers a generic platform for studying the exotic spin phases.

Internal force distributions in the ’t Hooft-Polyakov monopole and Julia-Zee dyon

The energy-momentum tensor (EMT) of the 't Hooft-Polyakov monopole and the Julia-Zee dyon are studied. This tensor contains important information about the pressure and the shear force distributions which define mechanical properties of systems. Obtaining the violation of the local stability criterion for the magnetic monopole and dyon we decompose the EMTs into the long- and short-range parts. This decomposition depends on the Abelian field strength tensor which cannot be uniquely defined. We suggest to use the modified 't Hooft definition for the tensor. Finally, the long- and short-range parts of the EMTs are computed and new equilibrium equations are obtained. Numerical values for masses, $D$-terms, and various mean square radii for the monopole and the dyon are also computed.

A compact quasi-zero-stiffness device for vibration suppression and energy harvesting

In this study, a novel compact energy harvesting dynamic vibration absorber (EHDVA) with quasi-zero-stiffness (QZS) characteristics is engineered for both vibration suppression and energy harvesting under low frequency. The QZS EHDVA is composed of a negative stiffness magnetic spring (NSMS), a spiral flexure spring (SFS) and coils. Firstly, the analytical expressions of the force and stiffness of the NSMS are derived by using the equivalent magnetic charge method, and the restoring force of the SFS is analyzed with finite element method. The electromechanically coupled equations are then solved using the Harmonic Balance Method (HBM), and the effect of system parameters on both the performances of vibration suppression and energy harvesting is investigated in detail. Finally, the prototype of the QZS EHDVA is fabricated, and an experiment is carried out to verify the theoretical model. According to the testing findings, the QZS EHDVA is able to suppress vibration in the low frequency region between 3.7 Hz and 6.1 Hz. In addition, the maximum output power of 1.51 mW is achieved under a load resistance of 300Ω at a driving frequency of 4.5 Hz.

Dyonic black holes in the theory of two electromagnetic potentials. II

The results obtained in our previous paper are now extended to the case of stationary axially symmetric dyonic black boles within the theory of two electromagnetic potentials. We slightly enlarge the classical Ernst formalism by introducing, with the aid of the $t$- and $\varphi$-components of the dual potential $B_\mu$, the magnetic potential $\Phi_m$ which, similar to the known electric potential $\Phi_e$, also takes constant value on the black hole horizon. We analyze in detail the case of the dyonic Kerr-Newman black hole and show how the Komar mass must be evaluated correctly in this stationary dyonic model. In particular, we rigorously prove the validity of the standard Tomimatsu mass formula and point out that attempts to "improve" it made in recent years are explained by misunderstanding of the auxiliary role that singular potentials play in the description of magnetic charges. Our approach is symmetrical with respect to electric and magnetic charges and, like in the static case considered earlier, Dirac strings of all kind are excluded from the physical picture of the stationary black hole dyonic spacetimes.

Dyonic black holes in the theory of two electromagnetic potentials. I

In the present paper we argue that the dyonic black hole spacetimes must be studied within the theory of two electromagnetic potentials, and we use the dyonic Reissner-Nordstr\"om solution to demonstrate that the field of the monopole magnetic charge is correctly described by the $t$-component of the dual electromagnetic potential. As a result, the Dirac string associated with the $\varphi$-component of the usual electromagnetic 4-potential becomes just a mathematical object, without any physical content, that arises in some calculations when one employs unsymmetrical representations of the electromagnetic field. We use three different, though equivalent, forms of the electromagnetic energy-momentum tensor to calculate the Komar mass of the Reissner-Nordstr\"om black hole, and in one case the Dirac string is linked to the magnetic charge, in another to the electric charge, while the third, symmetrical case, is string-free.

Noninvertible Chiral Symmetry and Exponential Hierarchies

We elucidate the fate of classical symmetries which suffer from Abelian Adler-Bell-Jackiw anomalies. Instead of being completely destroyed, these symmetries survive as noninvertible topological global symmetry defects with world volume anyon degrees of freedom that couple to the bulk through a magnetic 1-form global symmetry as in the fractional Hall effect. These noninvertible chiral symmetries imply selection rules on correlation functions and arise in familiar models of massless quantum electrodynamics and models of axions (as well as their non-Abelian generalizations). When the associated bulk magnetic 1-form symmetry is broken by the propagation of dynamical magnetic monopoles, the selection rules of the noninvertible chiral symmetry defects are violated nonperturbatively. This leads to technically natural exponential hierarchies in axion potentials and fermion masses.Received 3 August 2022Accepted 2 February 2023DOI:https://doi.org/10.1103/PhysRevX.13.011034Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAnomaliesPhysical SystemsAxionsPropertiesChiral symmetryTechniquesMonopolesParticles & Fields

Carrollian motion in magnetized black hole horizons

We revisit the motion of massless particles with anyonic spin in the horizon of Kerr-Newman geometry. As recently shown, such particles can move within the horizon of the black hole due to the coupling of charges associated with a two-parametric central extension of the two-dimensional Carroll group to the magnetic field generated by the black hole---the so-called ``anyonic spin-Hall effect.'' We show that the previously computed magnetic field is not invariant under Carroll diffeomorphisms and find another result which respects these symmetries of the horizon. We also consider a more astrophysically relevant case of a (weakly charged) rotating back hole placed in a uniform magnetic field, which could, for instance, be induced by the surrounding plasma. We show that a qualitatively similar magnetic field assisted anyonic spin-Hall effect takes place, even in the absence of black hole rotation. The theoretical possibility of a motion induced by a magnetic monopole is also studied.

Magnetic Moment Method with the Idea of Magnetic Surface Charge Method

Magnetic Moment Method (MMM) is well known for its ”lightweight” and simplicity of implementation; however, meshing must be carefully treated to obtain accurate results. In this paper, the MMM with the idea of the Magnetic Surface Charge method is proposed that is free from the meshing problem. Accelerator magnets; a C-shaped dipole and a quadrupole magnet, are analyzed, and it is shown that the proposed method outperforms currently available finite-element packages with respect to the CPU time and accuracy of the magnetic field.

Engineering the electronic structure on MXenes via multidimensional component interlayer insertion for enhanced electromagnetic shielding

• CNTs/Ni hybrids were used as an isolation agent to disperse Ti 3 C 2 T x sheets in the interlayers, which form a multiple-dimensional laminated structure. • Introduction of 2D hexagonal magnetic Ni flakes boosts interfacial polarization and magnetic-responding ability, visualized by electron holography. • The 3D freestanding films can achieve precise regulation of components and excellent EMI shielding performance (67.4 dB). MXene-based functional electromagnetic interference (EMI) shielding films are highly desirable for modern integrated electronic and telecommunication systems in aerospace, military, artificial intelligence, and smart and wearable electronics field. In this work, 3D freestanding Ti 3 C 2 T x /CNTs/Ni film assembled by 1D multi-walled carbon nanotubes (MWCNTs)/Ni and 2D Ti 3 C 2 T x MXene sheets was synthesized by a facile vacuum filtration process. By electrostatic incorporation, hexagonal nickel plates embed on the CNTs and then the CNTs/Ni insert into the Ti 3 C 2 T x layers to form magnetized Ti 3 C 2 T x -based functional film with a compact and laminated structure. Due to the outstanding electron migration capacity in the highly conductive Ti 3 C 2 T x sheet and multiple internal reflections from porous and segregated structures, the optimized Ti 3 C 2 T x /CNTs/Ni composite films show excellent EMI shielding effectiveness of 67.4 dB with electrical conductivity of 744 S cm –1 . Surprisingly, a magnetization compensation strategy is built to boost the EMI shielding effectiveness with decreased conductivity. Meanwhile, the visual magnetic coupling phenomenon and charge distribution in the heterogeneous interfaces could be observed in the reconstructed electron holography images. Those encouraging results shed light on novel magnetized MXene-based functional films for high-performance EMI shielding.

Dressed vs. pairwise states, and the geometric phase of monopoles and charges

We construct the Faddeev-Kulish dressed multiparticle states of electrically and magnetically charged particles, incorporating the effects of real and virtual soft photons. We calculate the properties of such dressed states under Lorentz transformations, and find that they can be identified with the pairwise multi-particle states that transform under the pairwise little group. The shifts in the dressing factors under Lorentz transformations are finite and have a simple geometric interpretation. Using the transformation properties of the dressed states we also present a novel, fully quantum field theoretic derivation of the geometric (Berry) phase obtained by an adiabatic rotation of the Dirac string, and also of the Dirac quantization condition. For half integer pairwise helicity, we show that these multiparticle states have flipped spin-statistics, reproducing the surprising fact that fermions can be made out of bosons.

Curved domain-wall fermion and its anomaly inflow

AbstractWe investigate the effect of a U(1) gauge field on lattice fermion systems with a curved domain-wall mass term. In the same way as the conventional flat domain-wall fermion, the chiral edge modes appear localized at the wall, whose Dirac operator contains the induced gravitational potential as well as the U(1) vector potential. In the case of anS1 domain-wall fermion on a two-dimensional flat lattice, we find a competition between the Aharonov–Bohm(AB) effect and a gravitational gap in the Dirac eigenvalue spectrum, which leads to an anomaly inthe time-reversal (T) symmetry. Our numerical result shows a good consistency with the Atiyah–Patodi–Singer index theorem on a disk inside the S1 domain wall, which describes the cancellation of the T anomaly between the bulk and edge. When the U(1) flux is squeezed inside one plaquette, and the AB phase takes a quantized value π mod $2\pi \mathbb {Z}$, the anomaly inflow drastically changes: the strong flux creates another domain wall around the flux to make the two zero modes coexist. This phenomenon is also observed in the S2 domain-wall fermion in the presence of a magnetic monopole. We find that the domain-wall creation around the monopole microscopically explains the Witten effect.

Magnetic monopoles with no strings attached: a portal to the dark side of dual electrodynamics

It has long been known that in the absence of electric charges and currents, Maxwell’s electromagnetism in 4 dimensional vacuum Minkowski space-time is invariant under SO(2) dual transformations that mix its electric and magnetic fields. Extending this symmetry to include the coupling to electrically charged matter, requires a dual coupling to magnetically charged matter as well, leading to Maxwell equations for SO(2) dual electrodynamics. Based on a doubled ensemble of SO(2) dual 4-vector gauge potentials which does away with the need of Dirac string singularities for magnetic monopoles, a local Lagrangian action principle for SO(2) dual electromagnetism is known, which manifestly displays all the required space-time and internal symmetries, and reduces to the experimentally well established Maxwell electrodynamics in the absence of magnetic charges and currents. Applying the same considerations for the matter action of electrically and magnetically charged point particles, a unique SO(2) dual generalised Lorentz force is identified for SO(2) dual electrodynamics, truly different from the usual SO(2) dual invariant choice motivated by simplicity, but yet made arbitrarily and which does not derive from some action principle. This generalised Lorentz force involves a single real and new coupling constant of unknown value, without the requirement of a Dirac–Schwinger–Zwanziger quantisation condition for electric and magnetic charges of dyons. A physical consequence for SO(2) dual electrodynamics of this coupling constant if nonvanishing, is to open a channel, or portal between the otherwise mutually totally “dark” sectors of electric and magnetic charges for electromagnetic interactions.

Axion-fermion coupling and dyon charge as physical signatures of a space-time inner symmetry

In this paper we intend to complement the identification given in Kuerten and Fernandes-Silva (Mod Phys Lett A 33:1850092, 2018) which relates the axion to a metric spinor phase by means of Maxwell’s theory in the Infeld-van der Waerden’s $$\gamma $$ -formalism. Thus, we obtain two alternative identifications: The first focuses on Dirac’s theory so that when obtaining an axion-like phase-fermion coupling, we achieve the first identification, and the last one investigates the phase behavior under Peccei–Quinn rotations in order to show that the phase changes as an axion pseudoparticle. With the formal aspects established, we also study the semiclassical fermion-photon system to demonstrate that the magnetic monopole current defined in Kuerten and Fernandes-Silva (Mod. Phys. Lett. A. 33:1850092) has dyon charge in flat universe and acquires a Witten effect form when there is a demand for chiral symmetry.

Callan-Rubakov effect and higher charge monopoles

In this paper we study the interaction between magnetic monopoles and massless fermions. In the low energy limit, the monopole’s magnetic field polarizes the fermions into purely in-going and out-going modes. Consistency requires that the UV fermion-monopole interaction leads to non-trivial IR boundary conditions that relate the in-going to out-going modes. These non-trivial boundary conditions lead to what is known as the Callan-Rubakov effect. Here we derive the effective boundary condition by explicitly integrating out the UV degrees of freedom for the general class of spherically symmetric SU(N) monopoles coupled to massless fermions of arbitrary representation. We then show that the boundary conditions preserve symmetries without ABJ-type anomalies. As an application we explicitly derive the boundary conditions for the stable, spherically symmetric monopoles associated to the SU(5) Georgi-Glashow model and comment on the relation to baryon number violation.

Design of a Single-Sided, Coreless, Flat-Type Linear Voice Coil Motor

A voice coil motor is a type of permanent magnet linear motor, which is based on the Ampere force theorem. It has the following advantages: a simple structure, a small size, no cogging force, and a fast response time. In this study, a voice coil motor was designed to provide x-directional thrust in the magnetically levitated cable table of a lithography machine. The voice coil motor designed in this study was based on the Halbach permanent magnet array, and adopted a single-sided, coreless, flat-type structure. First, the magnetic field distribution was analyzed based on the magnetic charge method to obtain an expression for the magnetic field and the thrust. The results of this analysis agreed very well with the finite element simulation results. Next, the main parameters of the motor, including the number of turns made by the coil, the size of the wire, and the size of the permanent magnets, were selected and optimized to increase the force density. Finally, two double-layer, serpentine waterway water-cooling plate configurations were designed for this voice coil motor. The validity of this water-cooling structure was verified for two different winding equivalent models. This provided feasibility to further upgrade the windings’ current density.