Magnetic Monopoles Research Articles

The heat engine of magnetic black holes in AdS space with rational nonlinear electrodynamics

The heat engine of magnetic black holes in Einstein-AdS gravity coupled to rational nonlinear electrodynamics, as the working substance, is studied. The dynamical negative cosmological constant is considered as a thermodynamic pressure. We investigate the efficiency of black hole heat engines in extended space thermodynamics for rectangle closed path in the P−V plane and the maximally efficient Carnot cycles. The exact efficiency formula which is written in terms of the mass of the black hole is obtained. It was demonstrated that the black hole efficiency decreases when the nonlinear electrodynamics coupling increases and the black hole efficiency increases if the magnetic charge increases. The relation between the efficiency, event horizon radiuses (entropy) and pressure is obtained. We study an efficiency of the holographic heat engine of a cycle in the vicinity of a critical point. Thus, the heat engine of our model can produce work.

Black Holes with Electroweak Hair

We construct static and axially symmetric magnetically charged hairy black holes in the gravity-coupled Weinberg-Salam theory. Large black holes merge with the Reissner-Nordström (RN) family, while the small ones are extremal and support a hair in the form of a ring-shaped electroweak condensate carrying superconducting W currents and up to 22% of the total magnetic charge. The extremal solutions are asymptotically RN with a mass below the total charge, M<|Q|, due to the negative Zeeman energy of the condensate interacting with the black hole magnetic field. Therefore, they cannot decay into RN black holes. As their charge increases, they show a phase transition when the horizon symmetry changes from spherical to oblate. At this point they have the mass typical for planetary size black holes of which ≈11% is stored in the hair. Being obtained within a well-tested theory, our solutions are expected to be physically relevant. Published by the American Physical Society 2024

Gravitational lensing around a dual-charged stringy black hole in plasma background

One of the strongest tools to verify the predictions of general relativity (GR) has been the gravitational lensing around various compact objects. Using a dual charged stringy black hole produced from dilaton-Maxwell gravity, we investigate the impact of the plasma parameter on gravitational lensing and black hole shadow in this study. Detailed investigations are performed to mark the impact of the homogeneous and non-homogeneous plasma environment on the electric and magnetic charge parameters of stringy black hole. In order to compare the results, we have also considered the vacuum scenario of the dual charged stringy black hole. Our results show that the effect of homogeneous plasma environment is much stronger in comparison to vacuum for the case of electrically charged stringy black hole. However, in the case of magnetically charged stringy black hole, the deflection angle gets decreased in presence of the homogeneous plasma medium. It has been observed that the radius of the shadow increases in a non-homogeneous plasma environment for electrically charged stringy black hole, whereas it decreases for magnetically charged stringy black hole in presence of the same plasma environment. This study aims to investigate how different plasma environments influence these fascinating astrophysical phenomena.

Magnetic monopole phenomenology at future hadron colliders

Abstract In the grand tapestry of Physics, the magnetic monopole is a holy grail. Therefore, numerous efforts
are underway in search of this hypothetical particle at CMS, ATLAS and MoEDAL experiments of LHC
by employing different production mechanisms. The cornerstone of our comprehension of monopoles lies
in Dirac’s theory which outlines their characteristics and dynamics. Within this theoretical framework, an
effective U (1) gauge field theory, derived from conventional models, delineates the interaction between spin
magnetically-charged fields and ordinary photons under electric-magnetic dualization.
The focus of this paper is the production of magnetic monopoles through Drell-Yan and the Photon-Fusion
mechanisms to generate velocity-dependent scalar, fermionic, and vector monopoles of spin angular mo-
mentum 0, 1
2 , 1 respectively at LHC. A computational study compares the monopole pair-production cross-
sections for both methods at various center-of-mass energies (√s) with different magnetic dipole moments.
The comparison of kinematic distributions of monopoles at Parton and reconstructed level are demonstrated
for both DY and PF mechanisms.
Extracted results showcase how modern machine-learning techniques can be used to study the production
of magnetic monopoles at the Future proton-proton Particle Colliders at 100 TeV. We demonstrate the ob-
servability of magnetic monopoles against the most relevant Standard Model background using multivariate
methods such as Boosted Decision Trees (BDT), Likelihood, and Multilayer Perceptron (MLP). This study
compares the performance of these classifiers with traditional cut-based and counting approaches, proving
the superiority of our methods

Selective Control of Electric Charge of Weyl Fermions in Pyrochlore Iridates.

Weyl fermions can exhibit exotic phenomena due to their magnetic charge in momentum space, while Weyl nodes are usually located away from Fermi energy, which forms electron or hole pockets as the electric charges. Previous studies have mostly focused on the magnetic charge, however, the electric charges are rarely explored. Here, the intriguing Hall responses arising from the interplay between magnetic and electric charges of Weyl fermions in pyrochlore iridates are reported. Explicitly, unexpected linear scaling is observed between the anomalous Hall conductivity and Hall carrier density in strained Nd2Ir2O7 thin films, and its slope shows a sign change approaching the Néel temperature of Nd. Theoretical calculations unveil that the cluster magnetic multipoles induce local energy inversion of Weyl nodes, which alters the electric charge of Weyl fermions and accounts for the observed nontrivial Hall responses. Moreover, the correlation between the magnetic and electric charges is further probed by voltage-controlled hydrogenation, which leads to the suppression of the anomalous Hall effect through electron filling. This work not only reveals the essential role of the both magnetic and electric charges of Weyl fermions, but also demonstrates the hydrogenation as an effective tuning knob in exploring correlated topological properties.

Traversable wormholes with electric and magnetic charges in general relativity theory

Traversable wormholes with electric and magnetic charges in general relativity theory

Study of first-order quantum corrections of thermodynamics to a Dyonic black hole solution surrounded by a perfect fluid

In this work, we review the metric for a dyonic global monopole with a perfect fluid. To calculate the standard temperature of a Dyonic black hole surrounded by a perfect fluid, we analyze the graphical interpretation of the Hawking temperature concerning the horizon under the effects of the black hole's surrounding field and electric-magnetic charges. For this purpose, we follow the semi-classical method, the Wentzel-Kramers-Brillouin (WKB) approximation, and the Lagrangian equation in the presence of quantum gravity as seen in the generalized uncertainty principle (GUP). We calculate the improved temperature of a Dyonic black hole using a bosonic tunneling strategy based on the Hamilton-Jacobi technique. We observe that the physical state of the Dyonic black hole is surrounded by a perfect fluid under the effects of the black hole solution and the gravity parameter. Further, we examine the improved entropy to study the influences of quantum gravity and black hole geometry on entropy. We explore the graphical behavior of entropy based on the black hole's horizon structure and analyze the influence of perfect fluid parameters, electric charge, magnetic charge, and quantum gravity on entropy. Finally, we investigate the unstable and stable conditions of a black hole via graphical results.

On the stability of electrovacuum space-times in scalar–tensor gravity

We study the behavior of static, spherically symmetric solutions to the field equations of scalar–tensor theories (STT) of gravity belonging to the Bergmann–Wagoner–Nordtvedt class, in the presence of an electric and/or magnetic charge. This class of theories includes the Brans–Dicke, Barker and Schwinger STT as well as nonminimally coupled scalar fields with an arbitrary parameter ξ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\xi $$\\end{document}. The study is restricted to canonical (nonphantom) versions of the theories and scalar fields without a self-interaction potential. Only radial (monopole) perturbations are considered as the most likely ones to cause an instability. The static background solutions contain naked singularities, but we formulate the boundary conditions in such a way that would preserve their meaning if a singularity is smoothed, for example, due to quantum gravity effects. These boundary conditions look more physical than those used by other authors. Since the solutions of all STT under study are related by conformal transformations, the stability problem for all of them reduces to the same wave equation, but the boundary conditions for perturbations (and sometimes the boundaries themselves) are different in different STT, which affects the stability results. The stability or instability conclusions are obtained for different branches of solutions in the theories under consideration and are presented in a table form.

Harmonic oscillator in topologically charged deformed gravity space–time and Wu–Yang magnetic monopole

We investigate the quantum dynamics of a harmonic oscillator (HO) system within the framework of topologically charged modified Eddington-inspired Born–Infeld (EiBI) gravity space–time. Additionally, we incorporate the Wu–Yang magnetic monopole (WYMM) into the quantum system and analyze the influences of modified gravity, the topological charge, and WYMM on this HO quantum mechanical system. Using analytical methods, we derive the energy eigenvalues and the corresponding eigenfunctions of the HO. Moreover, we consider a scenario where the modified EiBI-gravity parameter is absent and introduce an inverse square potential, including the WYMM, into the HO system. Our findings show significant deviations in the behavior of the HO system compared to the traditional quantum mechanical HO model, including alterations in the bound-state spectra and eigenfunctions. These results provide valuable insights into the interplay between quantum mechanical problems and alternative gravitational theories.

Effect of Nonlinear Magnetic Forces on Transverse Galloping Dynamics of Square Cylinders

Under the influence of cross-fluid flow, a cylinder of a square cross-section may gallop. Galloping is a self-excited vibration mode that can be utilized for low-power harvesting applications. The harvested power depends on several factors, including upstream flow velocity and system dynamics. This study explores the potential of magnetically-induced nonlinear stiffness to improve the power output of galloping-based energy harvesters. In this experimental study, the vibration response of a square rod with a mass ratio of 10 is investigated at a Reynolds number of 200. The vibration behavior of two identical coaxial square rods with magnetic monopoles at opposite ends is analyzed. Results reveal that the magnets’ configuration and strength significantly affect vibration amplitude and the critical flow velocity necessary for the onset of galloping.

Theory of Classical Electrodynamics with Topologically Quantized Singularities as Electric Charges

AbstractA theory of classical electrodynamics, where the only admissible electric charges are topological singularities in the electromagnetic field, is formulated. Charge quantization is accounted by the Chern theorem, such that Dirac magnetic monopoles are not needed. The theory allows positive and negative charges of equal magnitude, where the sign of the charge corresponds to the chirality of the topological singularity. Given the trajectory of the singularity, one can calculate electric and magnetic fields identical to those produced by Maxwell's equations for a moving point charge, apart from a multiplicative constant factor related to electron charge and vacuum permittivity. The theory is based on the relativistic Weyl equation in frequency‐wavevector space, with eigenstates comprising the position, velocity, and acceleration of the singularity, and eigenvalues defining the retarded position of the charge. From the eigenstates, one calculates the Berry connection and the Berry curvatures, and identifies the curvatures as electric and magnetic fields.

Monopoles and fermions in the Standard Model

We consider all magnetic monopoles that could have settled in the Standard Model after descending from a generic microscopic theory. These monopoles have Standard Model quantum numbers, are stable, and we also require that their magnetic fluxes are consistent with the electroweak symmetry breaking. Scattering processes involving quarks, leptons and protons on these monopoles are studied using partial waves decomposition. These processes in the lowest partial wave are known to be unsuppressed by the monopole mass and are relevant for monopole catalysis of proton decay. We provide estimates for scattering cross-sections and investigate and confirm the applicability of the twisted sector approach to scattering processes on these Standard Model monopoles. We find that the SM monopole catalysis processes are universal and model-independent.

Exploring possible magnetic monopoles-induced magneto-electricity in spin ices

The possibilities of combining several degrees of freedom inside a unique material have recently been highlighted in their dynamics and proposed as information carriers in quantum devices where their cross-manipulation by external parameters such as electric and magnetic fields could enhance their functionalities. An emblematic example is that of electromagnons, spin-waves dressed with electric dipoles, that are fingerprints of multiferroics. Point-like objects have also been identified, which may take the form of excited quasiparticles. This is the case for magnetic monopoles, the exotic excitations of spin ices, that have been recently proposed to carry an electric dipole, although experimental evidences remain elusive. Presently, we investigate the electrical signature of a classical spin ice and a related compound that supports quantum fluctuations. Our in-depth study clearly attributes magneto-electricity to the correlated spin ice phase distinguishing it from extrinsic and single-ion effects. Our calculations show that the proposed model conferring magneto-electricity to monopoles is not sufficient, calling for higher-order contributions.

Coherence resonance in a memristive map neuron and adaptive energy regulation

Involvement of memristive term and additive physical variables including magnetic flux and charge can enhance the physical description of the biophysical neurons. Neural circuits coupled with memristors can be built and tamed to mimic the intrinsic biophysical characteristics and dynamical properties of biological neurons, and these memristive oscillator models are effective in predicting the mode transition in neural activities and self-organization in collective electric behaviors of neural networks. Any proposal of memristive map neurons requires reliable physical description. For example, the energy definition and self-adaptive working mechanism are crucial to verify the reliability of memristive maps. A capacitive variable is useful to describe the membrane potential, while the complexity of ion channels requires careful evaluation and description by using inductive variables relative to the electromagnetic field. In this work, a charge-controlled memristor is connected to an inductor in series for building a hybrid ion channel, and then a capacitor and a nonlinear resistor are combined to couple the ion channel. As a result, a simple memristive neural circuit is designed to discern the inner effect of electric field and magnetic field synchronously. The energy function is defined and verified with theoretical proof. Furthermore, a linear transformation is applied to convert this memristive neuron into a memristive map with an exact energy description, in which its dynamics and mode transition will be controlled by an adaptive law when its energy is beyond the threshold. Additive noise is imposed to induce coherence resonance, which can be detected by using the statistical analysis and average value for Hamilton energy function during changes in noise intensity. This scheme provides guidance for energy definition in memristive maps and the intrinsic energy regulation mechanism in neural activities is explained from physical and dynamical aspects.

Quantum embedding method with transformer neural network quantum states for strongly correlated materials

The neural-network quantum states (NNQS) method is rapidly emerging as a powerful tool in quantum mechanisms. While significant advancements have been achieved in simulating simple molecules using NNQS, the ab initio simulation of complex solid-state materials remains challenging. Here in this work, we have adopted the periodic density matrix embedding theory to extend the NNQS method to deal with complex solid-state systems. Our approach notably reduces the computational problem size while maintaining high accuracy. We have validated the accuracy and efficiency of our method against traditional methodologies and experimental data in extended systems, and have investigated the magnetic ordering and charge density wave state in transition metal compounds. The findings from our research indicate that the integration of quantum embedding with intuitive chemical fragmentation can significantly enhance the NNQS simulation of realistic materials.

Quantum vortices, M2-branes and black holes

We study the partition functions of BPS vortices and magnetic monopole operators, in gauge theories describing N M2-branes. In particular, we explore two closely related methods to study the Cardy limit of the index on S2 × ℝ. The first method uses the factorization of this index to vortex partition functions, while the second one uses a continuum approximation for the monopole charge sums. Monopole condensation confines most of the N2 degrees of freedom except N32\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {N}^{\\frac{3}{2}} $$\\end{document} of them, even in the high temperature deconfined phase. The resulting large N free energy statistically accounts for the Bekenstein-Hawking entropy of large BPS black holes in AdS4 × S7. Our Cardy free energy also suggests a finite N version of the N32\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {N}^{\\frac{3}{2}} $$\\end{document} degrees of freedom.

Thermodynamics of a newly constructed black hole coupled with nonlinear electrodynamics and cloud of strings

This paper finds an exact singular black hole solution in the presence of nonlinear electrodynamics as the source of matter field surrounded by a cloud of strings in 4DAdS spacetime. Here, the presence of the cloud of string, the usual Bardeen solution, becomes singular. The obtained black hole solution interpolates with the AdS Letelier black hole in the absence of both the deviation parameter and magnetic charge and interpolates with the AdS Bardeen black hole in the absence of the deviation parameter and a cloud of strings parameter. We analyse the horizon structure and thermodynamics properties, including the stability of the resulting black hole, numerically and graphically. Thermodynamical quantities associated with the black hole get modified due to the nonlinear electrodynamics and cloud of strings. Moreover, we study the effect of a cloud of strings parameter, magnetic charge and deviation parameter on critical points and phase transition of the obtained black hole where the cosmological constant is treated as the thermodynamics pressure. The critical radius increases with increasing deviation parameter values and magnetic charge values. In contrast, the critical pressure and temperature decrease with increasing deviation parameters and magnetic charge values.

Gauge-invariant magnetic charges in linearised gravity

Abstract Linearised gravity has magnetic charges carried by (linearised) Kaluza–Klein monopoles. A gauge-invariant expression is found for these charges that is similar to Penrose’s gauge-invariant expression for the ADM charges. A systematic search is made for other gauge-invariant charges.

Cartan monopoles

The effective Hamiltonians for chiral supersymmetric gauge theories at small spatial volume are generalizations of the Hamiltonians describing the motion of a scalar or a spinor particle in a field of Dirac monopoles (we are dealing in fact with a certain lattice of monopoles supplemented with a periodic singular potential). The gauge fields in such Hamiltonians belong to the Cartan subalgebras of the corresponding gauge algebras. Such a construction exists for all groups admitting complex representations, i.e., for SU(N≥3), Spin(4n+2) with n≥1 and E6. We give explicit expressions for these Hamiltonians for SU(3), SU(4)≃Spin(6) and for SU(5). The simplified version of such a Hamiltonian, deprived of fermion terms, of the extra scalar potential and when only one node of the lattice is taken into consideration, describe a 3r-dimensional motion (r being the rank of the group) in the field what we call a “Cartan monopole.” As is the case for the ordinary monopole, the Lagrangian of this system enjoys gauge symmetry, rotational symmetry, and the parameter, generalizing the notion of magnetic charge for Cartan monopoles, is quantized. Published by the American Physical Society 2024

On the cosmological abundance of magnetic monopoles

We demonstrate that Debye shielding cannot be employed to constrain the cosmological abundance of magnetic monopoles, contrary to what is stated in the previous literature. Current model-independent bounds on the monopole abundance are then revisited for unit Dirac magnetic charge. We find that the Andromeda Parker bound can be employed to set an upper limit on the monopole flux at the level of FM ≲ 5.3 × 10−19cm−2s−1sr−1 for a monopole mass 1013 GeV/c2 ≲ m ≲ 1016 GeV/c2, which is more stringent than the MACRO direct search limit by two orders of magnitude. This translates into stringent constraints on the monopole density parameter ΩM at the level of 10−7˘10−4 depending on the mass. For larger monopole masses the scenarios in which magnetic monopoles account for all or the majority of dark matter are disfavored.