International Journal of Modern Physics A

In this review, we discuss recent developments in both the theory and the experimental searches of magnetic monopoles in past, current and future colliders and in the Cosmos. The theoretical models include, apart from the standard Grand Unified Theories, extensions of the Standard Model that admit magnetic monopole solutions with finite energy and masses that can be as light as a few TeV. Specifically, we discuss, among other scenarios, modified Cho–Maison monopoles and magnetic monopoles in (string-inspired, higher derivative) Born–Infeld extensions of the hypercharge sector of the Standard Model. We also outline the conditions for which effective field theories describing the interaction of monopoles with photons are valid and can be used for result interpretation in monopole production at colliders. The experimental part of the review focuses on, past and present, cosmic and collider searches, including the latest bounds on monopole masses and magnetic charges by the ATLAS and MoEDAL experiments at the LHC, as well as prospects for future searches.

In light of the upcoming measurement of the muon anomalous magnetic moment $(g-2)$, we revisit the corrections to $g-2$ in the context of the $SU{(4)}_L\times U{(1)}_X$ gauge symmetry. We investigate three models based on this gauge symmetry and express our results in terms of the energy scale at which the $SU{(4)}_L\times U{(1)}_X$ symmetry is broken. To draw solid conclusions we put our findings into perspective with existing collider bounds. Lastly, we highlight the difference between our results and those rising from $SU{(3)}_L\times U{(1)}_X$ constructions.

The study of particle dynamics in the vicinity of a black hole environed by dark energy and magnetic field has attracted researchers for their importance in astrophysics and cosmology. In this paper, we study the dynamics of neutral and charged particles in the vicinity of de Sitter–Schwarzschild black hole (DS–Sch-BH) surrounded by quintessence. The effect of the DS part is explored by virtue of effective potential, effective force, and escape velocity of the particle (neutral and charged) moving around DS–Sch-BH. Finally, a comparative study is also investigated.

Recently, the concept of weakly supervised learning has gained popularity in the high-energy physics community due to its ability to learn even with a noisy and impure dataset. This method is valuable in the quest to discover the elusive beyond Standard Model (BSM) particle. Nevertheless, the weakly supervised learning method still requires a learning sample that describes the features of the BSM particle truthfully to the classification model. Even with the various theoretical framework such as supersymmetry and the quantum black hole, creating a BSM sample is not a trivial task since the exact feature of the particle is unknown. Due to these difficulties, we propose an alternative classifier type called the one-class classification (OCC). OCC algorithms require only background or noise samples in its training dataset, which is already abundant in the high-energy physics community. The algorithm will flag any sample that does not fit the background feature as an abnormality. In this paper, we introduce two new algorithms called EHRA and C-EHRA, which use machine learning regression and clustering to detect anomalies in samples. We tested the algorithms’ capability to create distinct anomalous patterns in the presence of BSM samples and also compare their classification output metrics to the Isolation Forest (ISF), a well-known anomaly detection algorithm. Five Monte Carlo supersymmetry datasets with the signal to noise ratio equal to 1, 0.1, 0.01, 0.001, and 0.0001 were used to test EHRA, C-EHRA and ISF algorithm. In our study, we found that the EHRA with an artificial neural network regression has the highest ROC-AUC score at 0.7882 for the balanced dataset, while the C-EHRA has the highest precision-sensitivity score for the majority of the imbalanced datasets. These findings highlight the potential use of the EHRA, C-EHRA, and other OCC algorithms in the quest to discover BSM particles.

A cosmological model for the early universe is investigated where a Schutz fluid and a fermionic field coupled to a gauge field are the sources of the gravitational field. The determination of the scale factor in the classical analysis follows from the Hamiltonian formulation together with Dirac’s method for constrained systems. The expectation value of the scale factor in the quantum analysis is determined from the Wheeler–DeWitt equation. The singularity in the classical solution for the scale factor is avoided in the quantum solution where a bouncing from a minimum value of the scale factor is present. It is shown that: (i) the minimum value of the scale factor depends on the ratio of the fermionic coupling constant and the mass of the vectorial field; (ii) the classical and quantum solutions coincide for large values of the conformal time due to a dilution of the quantum effects with the time evolution; (iii) the behavior of the wave function probability density confirms that the maximum probability occurs when the scale factor has its minimum value equal to its expectation value; (iv) the quantum potential in the Bohmian formulation goes to infinity when the scale factor tends to zero avoiding the singularity at this point.

This article has been retracted due to overlapping of its result with an earlier published article [Annals of Physics, Vol. 383 (2017) 497-510].

We show that the claim by Franklin (Int. J. Mod. Phys. A 35, 2050061 (2020)) with respect to the vanishing charge distribution over the perimeter of an electrically neutral moving current loop is erroneous and is based on a misinterpretation of physical meaning of Lorentz transformations. Moreover, we show that the development of nonvanishing electric dipole moment by a moving current loop (which we named as “relativistic polarization”) represents a direct implication of covariant formulation of classical electrodynamics of material media. In this respect, we analyze some subtle effects related to the motion of magnetic dipoles in an electromagnetic field and disclose their physical meaning.

We construct a thin-shell wormhole using the cut and paste technique from regular charged black holes with a nonlinear electrodynamics source (proposed by Balart and Vagenas). Using Darmois–Israel formalism we determine the surface stresses, which are localized at the wormhole throat. We also determine the amount of exotic matter present in the shell. To analyze the stability of the constructed wormhole we consider an equation of state as a linear perturbation. The stability region is shown in the graph by varying the values of the parameter.

We construct two realizations of the $w_{1+\infty }$ algebra in the classical Calogero model based on the $W_{1+\infty }$ constraints for the Hermitian one-matrix model. We also discuss the quantum Calogero model and construct the new operators which yield the closed $W_{1+\infty }$$n$-algebra. The super $W_{1+\infty }$$n$-algebra is derived for the supersymmetric quantum Calogero model.

We solve the one-dimensional time-independent Klein–Gordon equation in the presence of a smooth potential well. The bound state solutions are given in terms of the Whittaker $M_{\kappa ,\mu }(x)$ function, and the antiparticle bound state is discussed in terms of potential parameters.