arXiv subjects

A. Yu. Loginov

Publications and source records attributed to A. Yu. Loginov.

At least 19 recordsLinked to original sources

arXiv2026

Tensor analyzing power $T_{20}$ in the reaction $\gamma \vec{d}\to pn$ at photon energies 350-680 MeV

We present measurements of the tensor analyzing power $T_{20}$ in the reaction $\gamma {d}\to pn$ at photon energies $E_\gamma = 350$-$680$~MeV. The experiment was performed at the VEPP-3 storage ring using an internal tensor-polarized deuterium gas target and a tagged quasi-real photon beam. The data were obtained for proton emission angles $\Theta_p = 70^\circ$-$102^\circ$. Comparison with modern meson-baryon calculations shows generally satisfactory agreement within the present uncertainties. A theoretical analysis of an extended data set, covering the energy range from threshold to 680~MeV and including both the new data and the previous results from 2007, is presented.

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arXiv2026

Non-self-dual nontopological soliton in a pure Chern-Simons gauge model

A nontopological soliton of the Q-ball type in a Chern-Simons-Higgs gauge model is studied using both analytical and numerical methods. The general non-self-dual case is considered. It is shown that the soliton solution is an extremum of the energy functional at a fixed Noether charge. A differential relation between the energy, Noether charge, and the boundary value of the gauge potential of the soliton is derived. A linear relation between the components of the soliton energy is obtained. The parametric domain of existence of the soliton solution is determined. It is established that the soliton properties depend significantly on the form of the self-interaction potential of the scalar field. In particular, the energy and charge of the soliton can take arbitrarily large values only if the self-interaction potential has two degenerate zero minima.

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arXiv2025

A nontopological soliton with a dipole chromomagnetic field

A non-Abelian gauge model with a complex isovector scalar field and a sixth-order self-interaction potential is considered. It is shown that it has a nontopological soliton solution. The features of this soliton include a monopole-like core surrounded by a Q-ball-like shell, the existence of radially excited states, and a long-range dipole chromomagnetic field. The properties of the soliton are studied using analytical and numerical methods. In particular, the asymptotic dependencies of the energy and the Noether charge on a phase frequency are obtained for two extreme regimes. It is also found that in these two extreme regimes, the chromomagnetic dipole moment of the soliton is proportional to its linear size.

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arXiv2025

Bound states of a fermion-dyon system

The bound states of fermions in the external field of an Abelian dyon are studied here both analytically and numerically. Their existence is due to the dyon's electric charge resulting from a polarization of the fermionic vacuum. The configuration of the dyon's field is not invariant under $P$ or $CP$ transformations. The dependence of the energy levels of the fermion-dyon system on a parameter of $CP$ violation is investigated. The absence of $P$ invariance results in nonzero electric dipole moments of the bound fermionic states. These depend nontrivially on the parameter of $CP$ violation. The bound fermionic states also possess nonzero magnetic dipole moments. Unlike the electric dipole moments, the magnetic dipole moments are practically independent of the parameter of $CP$ violation. In addition, the magnitudes of the electric dipole moments significantly exceed those of the magnetic dipole moments.

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arXiv2024

A modified dyon solution in a non-Abelian gauge model

A modified $SU(2)$ Georgi-Glashow model is considered here, and it is shown that besides the well-known Julia-Zee dyon solution, the model can also have a modified dyon solution. The properties of the modified dyon solution are studied using analytical and numerical methods. A comparative analysis of the modified dyon and the Julia-Zee dyon shows that their properties are significantly different. In particular, except for the BPS case, the energy and electric charge of the modified dyons exceed considerably those of the Julia-Zee dyons. At the same time, the energy and electric charge of the modified dyon are bounded for all admissible parameter values, whereas those of the Julia-Zee dyon can be arbitrarily large in the BPS case.

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arXiv2024

Fermion-soliton scattering in a modified $\mathbb{CP}^{1}$ model

The scattering of fermions in the background field of a topological soliton of the modified $(2 + 1)$-dimensional $\mathbb{CP}^{1}$ model is studied here both analytically and numerically. Unlike the original $\mathbb{CP}^{1}$ model, the Lagrangian of the modified model contains a potential term. Due to this, a dilatation zero mode of the topological soliton disappears, which results in stability of the fermion-soliton system. The symmetry properties of the fermion-soliton system are established, and the asymptotic forms of fermionic radial wave functions are studied. Questions related to the bound states of the fermion-soliton system are then discussed. General formulae describing the scattering of fermions are presented. The amplitudes of the fermion-soliton scattering are obtained in an analytical form within the framework of the Born approximation, and their symmetry properties and asymptotic forms are studied. The energy levels of the fermionic bound states and the partial phase shifts of fermionic scattering are obtained by numerical methods, and the ultrarelativistic limits of the partial phase shifts are found.

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arXiv2023

A nontopological soliton in an $\mathcal{N} = 1$ supersymmetric gauge Abelian model

A version of $\mathcal{N} = 1$ supersymmetric scalar electrodynamics is considered here, and it is shown that an electrically charged nontopological soliton exists in this model. In addition to the long-range electric field, the soliton also possesses a long-range scalar field, which leads to a modification of the intersoliton interaction potential at large distances. The supersymmetry of the model makes it possible to express fermionic zero modes of the soliton in terms of bosonic fields. The properties of the nontopological soliton are investigated using analytical and numerical methods.

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arXiv2023

Fermion scattering on topological solitons in the $\mathbb{CP}^{N-1}$ model

The scattering of Dirac fermions in the background fields of topological solitons of the $(2+1)$-dimensional $\mathbb{CP}^{N-1}$ model is studied using analytical and numerical methods. It is shown that the exact solutions for fermionic wave functions can be expressed in terms of the confluent Heun functions. The question of the existence of bound states for the fermion-soliton system is then investigated. General formulae describing fermion scattering are obtained, and a symmetry property for the partial phase shifts is derived. The amplitudes and cross-sections of the fermion-soliton scattering are obtained in an analytical form within the framework of the Born approximation, and the symmetry properties and asymptotic forms of the Born amplitudes are investigated. The dependences of the first few partial phase shifts on the fermion momentum are obtained by numerical methods, and some of their properties are investigated and discussed.

hep-th↗

arXiv2022

Scattering of fermions on a one-dimensional Q-ball

The scattering of massless fermions on a one-dimensional Q-ball is studied both analytically and numerically in the background field approximation. The wave functions of the fermionic scattering states are found in analytical form. General expressions are derived for the transmission and reflection coefficients and the corresponding $S$-matrix elements. General formulae describing the evaporation of the Noether charge of the one-dimensional Q-ball are given. A numerical study of the transmission and reflection coefficients along with the corresponding S-matrix elements is performed for a range of values of the model parameters. A study of the dependence of the evaporation rate of the Q-ball on the Yukawa coupling constant is carried out for several values of the Noether charge.

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arXiv2022

Scattering of fermionic isodoublets on the sine-Gordon kink

The scattering of Dirac fermions on the sine-Gordon kink is studied both analytically and numerically. To achieve invariance with respect to a discrete symmetry, the sine-Gordon model is treated as a nonlinear $σ$-model with a circular target space that interacts with fermionic isodublets through the Yukawa interaction. It is shown that the diagonal and antidiagonal parts of the fermionic wave function interact independently with the external field of the sine-Gordon kink. The wave functions of the fermionic scattering states are expressed in terms of the Heun functions. General expressions for the transmission and reflection coefficients are derived, and their dependences on the fermion momentum and mass are studied numerically. The existence condition is found for two fermionic zero modes, and their analytical expressions are obtained. It is shown that the zero modes do not lead to fragmentation of the fermionic charge, but can lead to polarization of the fermionic vacuum. The scattering of the diagonal and antidiagonal fermionic states is found to be significantly different; this difference is shown to be due to the different dependences of the energy levels of these bound states on the fermion mass, and is in accordance with Levinson's theorem.

hep-th↗

arXiv2021

A differential relation between the energy and electric charge of a dyon

The differential relation between the energy and electric charge of a dyon is derived. The relation expresses the derivative of the energy with respect to the electric charge in terms of the boundary value for the temporal component of the dyon's electromagnetic potential. The use of the Hamiltonian formalism and transition to the unitary gauge make it possible to show that this derivative is proportional to the phase frequency of the electrically charged massive gauge fields forming the dyon's core. It follows from the differential relation that the energy and electric charge of the non-BPS dyon cannot be arbitrarily large. Finally, the dyon's properties are investigated numerically at different values of the model parameters.

hep-th↗

arXiv2021

Fermion scattering on topological solitons in the nonlinear $O(3)$ $σ$-model

The scattering of Dirac fermions in the background fields of topological solitons of the $(2+1)$-dimensional nonlinear $O(3)$ $σ$-model is studied using both analytical and numerical methods. General formulae describing fermion scattering are obtained and the symmetry properties of the partial scattering amplitudes and elements of the $S$-matrix are determined. Within the framework of the Born approximation, the scattering amplitudes, differential cross-sections, and total cross-sections of fermion-soliton scattering are obtained in analytical forms, and their symmetry properties and asymptotic behavior are investigated. The dependences of the first several partial elements of the $S$-matrix on the momentum of the fermion are obtained using numerical methods, and some properties of these dependences are ascertained and discussed.

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arXiv2020

Radially and azimuthally excited states of a soliton system of vortex and Q-ball

In the present paper, we continue to study the two-dimensional soliton system that is composed of vortex and Q-ball components interacting with each other through an Abelian gauge field. This vortex-Q-ball system is electrically neutral as a whole, nevertheless it possesses a nonzero electric field. Moreover, the vortex-Q-ball system has a quantized magnetic flux and a nonzero angular momentum, and combines properties of topological and nontopological solitons. We investigate radially and azimuthally excited states of the vortex-Q-ball system along with the unexcited vortex-Q-ball system at different values of gauge coupling constants. We also ascertain the behaviour of the vortex-Q-ball system in several extreme regimes, including thin-wall and thick-wall regimes.

hep-th↗

arXiv2020

Radially excited $U\left(1\right)$ gauged $Q$-balls

Radially excited $U(1)$ gauged $Q$-balls are studied using both analytical and numerical methods. Unlike the nongauged case, there exists only a finite number of radially excited gauged $Q$-balls at given values of the model's parameters. Similarly to the unexcited gauged $Q$-ball, the radially excited one cannot possess the Noether charge exceeding some limiting value. This limiting Noether charge decreases with an increase in the radial excitation of the gauged $Q$-ball. For $n$-th radial excitation, there is a maximum allowable value of the gauge coupling constant, and the existence of the $n$-th radially excited gauged $Q$-ball becomes impossible if the gauge coupling constant exceeds this limiting value. Similarly to the limiting Noether charge, the limiting gauge coupling constant decreases with an increase in the radial excitation. At a fixed Noether charge, the energy of the gauged $Q$-ball increases with an increase in the radial excitation, and thus the radially excited gauged $Q$-ball is unstable against transit into a less excited or unexcited one.

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arXiv2019

One-dimensional soliton system of gauged kink and Q-ball

In the present paper, we consider a $\left(1 + 1\right)$-dimensional gauge model consisting of two complex scalar fields interacting with each other through an Abelian gauge field. When the model's gauge coupling constants are set equal to zero, the model possesses non-gauged Q-ball and kink solutions that do not interact with each other. It is shown that at nonzero gauge coupling constants, the model possesses the soliton solution describing the system consisting of interacting Q-ball and kink components. The kink and Q-ball components of the kink-Q-ball system have opposite electric charges, so the total electric charge of the kink-Q-ball system vanishes. Properties of the kink-Q-ball system are researched analytically and numerically. In particular, it was found that the kink-Q-ball system possesses a nonzero electric field and is unstable with respect to small perturbations of fields.

hep-th↗

arXiv2019

A two-dimensional soliton system in the Maxwell-Chern-Simons gauge model

The (2 + 1)-dimensional Maxwell-Chern-Simons gauge model consisting of two complex scalar fields interacting through a common Abelian gauge field is considered. It is shown that the model has a solution that describes a soliton system consisting of vortex and Q-ball constituents. This two-dimensional soliton system possesses a quantized magnetic flux and a quantized electric charge. Moreover, the soliton system has a nonzero angular momentum. Properties of this vortex-Q-ball system are investigated by analytical and numerical methods. It is found that the system combines properties of a vortex and a Q-ball.

hep-th↗

arXiv2019

A two-dimensional soliton system of vortex and Q-ball

The (2 + 1)-dimensional gauge model describing two complex scalar fields that interact through a common Abelian gauge field is considered. It is shown that the model has a soliton solution that describes a system consisting of a vortex and a Q-ball. This two-dimensional system is electrically neutral, nevertheless it possesses a nonzero electric field. Moreover, the soliton system has a quantized magnetic flux and a nonzero angular momentum. Properties of this vortex-Q-ball system are investigated by analytical and numerical methods. It is found that the system combines properties of topological and nontopological solitons.

hep-th↗

arXiv2019

A one-dimensional soliton system of gauged Q-ball and anti-Q-ball

The (1+1)-dimensional gauge model of two complex self-interacting scalar fields that interact with each other through an Abelian gauge field and a quartic scalar interaction is considered. It is shown that the model has nontopological soliton solutions describing soliton systems consisting of two Q-ball components possessing opposite electric charges. The two Q-ball components interact with each other through the Abelian gauge field and the quartic scalar interaction. The interplay between the attractive electromagnetic interaction and the repulsive quartic interaction leads to the existence of symmetric and nonsymmetric soliton systems. Properties of these systems are investigated by analytical and numerical methods. The symmetric soliton system exists in the whole allowable interval of the phase frequency, whereas the nonsymmetric soliton system exists only in some interior subinterval. Despite the fact that these soliton systems are electrically neutral, they nevertheless possess nonzero electric fields in their interiors. It is found that the nonsymmetric soliton system is more preferable from the viewpoint of energy than the symmetric one. Both symmetric and nonsymmetric soliton systems are stable to the decay into massive scalar bosons.

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