arXiv subjects

Yakov Shnir

Publications and source records attributed to Yakov Shnir.

At least 37 records · Page 2Linked to original sources

arXiv2024

Isospinning ${\mathbb C}P^2$ solitons

We study stationary rotating topological solitons in (2+1)-dimensional ${\mathbb C}P^2$ non-linear sigma model with a stabilizing potential term. We find families of $U(1)\times U(1)$ symmetric solutions with topological degrees larger than 2, which have two angular frequencies and are labelled by two (one topological and the other non-topological) winding numbers $k_1>k_2$. We discuss properties of these solitons and investigate the domains of their existence.

hep-th↗

arXiv2024

Large solitons flattened by small quantum corrections

We propose a general form of the UV-completed Friedberg-Lee-Sirlin (FLS) model. As can be seen from the mechanical interpretation, UV-completion allows thin-wall approximation for non-topological solitons. The 1-loop renormalized effective potential for the UV-completed FLS model is constructed under the assumption of mass hierarchy. By special choice of parameters, we studied how the Coleman-Weinberg mechanism induces a new mass scale $ω_{-}$ in the classical FLS model. It can be expounded in terms of a stable condensate. As a consequence, the asymptotic of a non-topological soliton's energy at large charge is changed from $\sim Q^{3/4}$ to the linear law.

hep-ph↗

arXiv2023

Multisolitons in a gauged Skyrme-Maxwell model

We construct new solutions of a $U(1)$ gauged Skyrme-Maxwell model of topological degrees $Q\leq 5$, which represent Skyrmions coupled to magnetic fluxes. It is found that, generically, in the strong coupling limit, coupling to the magnetic field results in transformation of the configuration to the toroidally shaped Skyrmions bounded to the local magnetic flux.

hep-th↗

arXiv2023

Fermion states localized on a self-gravitating non-Abelian monopole

We study fermionic modes localized on the static spherically symmetric self-gravitating non-Abelian monopole in the $SU(2)$ Einstein-Dirac-Yang-Mills-Higgs theory. We consider dependence of the spectral flow on the effective gravitational coupling constant and show that, in the limiting case of transition to the Reissner-Nordström black hole, the fermion modes are fully absorbed into the interior of the black hole.

hep-th↗

arXiv2023

Solitons in the Gauged Skyrme-Maxwell Model

We consider soliton solutions of the U(1) gauged Skyrme model with the pion mass term. The domain of existence of gauged Skyrmions is restricted from above by the value of the pion mass. Concentrating on the solutions of topological degree one, we find that coupling to the electromagnetic field breaks the symmetry of the configurations, the Skyrmions carrying both an electric charge and a magnetic flux, with an induced dipole magnetic moment. The Skyrmions also possess an angular momentum, which is quantized in the units of the electric charge. The mass of the gauged Skyrmions monotonically decreases with increase of the gauge coupling.

hep-th↗

arXiv2023

Collisions of weakly-bound kinks in the Christ-Lee model

We investigate soliton collisions a one-parameter family of scalar field theories in 1+1 dimensions which was first discussed by Christ and Lee. The models have a sextic potential with three local minima, and for suitably small values of the parameter its kinks have an internal structure in the form of two weakly-bound subkinks. We show that for these values of the parameter kink collisions are best understood as an independent sequence of collisions of these subkinks, and that a static mode analysis is not enough to explain resonant structures emerging in this model. We also emphasise the role of radiation and oscillon formation in the collision process.

hep-th↗

arXiv2023

Charged hairy black holes in the gauged Einstein-Friedberg-Lee-Sirlin model

We obtain charged spherically symmetric black holes in the two-component scalar Einstein-Maxwell-Friedberg-Lee-Sirlin model with a symmetry breaking potential. These asymptotically flat black holes carry resonant scalar Q-hair. As expected, these hairy black holes give rise to non-uniqueness. When comparing these solutions with the corresponding charged boson stars and Reissner-Nordström black holes, we find a different pattern in the case of a massive real scalar component and a massless one. We demonstrate that, as the real component becomes massless, the resonant hairy black holes bifurcate from Reissner-Nordström black holes for sufficiently small gravitational coupling.

hep-th↗

arXiv2022

$\mathbb{C}P^2$ Skyrmion Crystals in an SU(3) Magnet with a Generalized Dzyaloshinskii-Moriya Interaction

We study $\mathbb{C}P^2$ Skyrmion crystals in the ferromagnetic SU(3) Heisenberg model with a generalization of the Dzyaloshinskii-Moriya interaction and the Zeeman term. The model possesses two different types of Skyrmion crystals with unit-Skyrmions that can be interpreted as bound states of two half-Skyrmions or four quarter-Skyrmions. Our study on $\mathbb{C}P^2$ Skyrmion crystals opens up the possibility for useful future applications since $\mathbb{C}P^2$ Skyrmions have more degrees of freedom than the usual $\mathbb{C}P^1$ (magnetic) Skyrmions.

cond-mat.str-el↗

arXiv2022

Remarks on sine-Gordon kink--fermion system: localized modes and scattering

We study numerically the kink-fermion interactions in a 1+1 dimensional toy model, which describes sine-Gordon kinks coupled to the massless Dirac fermions with backreaction. We show that the spectrum of fermionic modes strongly depends on the choice of the coupling, in particular, there are no localized modes for a minimal Yukawa coupling. We analyze the scattering of the fermionic packet by the kink. We demonstrate that the outcome of the collision dynamically depends on the phase of the incoming fermion packet, it results in alternating regimes of positive and negative acceleration of the kink.

hep-th↗

arXiv2022

Q-ball stress stability criterion in the $U(1)$ gauged scalar theories

We study the canonical energy-momentum tensor of the spherically symmetric $U(1)$ gauged Q-ball configurations in the two-component Fridberg-Lee-Sirlin-Maxwell model, and in the one-component scalar model with a sixtic potential. We evaluate the distributions of the corresponding shear forces and pressure and study the stability criteria for these solutions. It is shown that the electrostatic repulsion may destabilize the $U(1)$ gauged Q-balls. However, in the limiting case of the Fridberg-Lee-Sirlin-Maxwell model with a long ranged real scalar component, the gauged Q-balls always remain stable.

hep-th↗

arXiv2022

Boson Stars

We review particle-like configurations of complex scalar field, localized by gravity, so-called boson stars. In the simplest case, these solutions posses spherical symmetry, they may arise in the massive Einstein-Klein-Gordon theory with global $U(1)$ symmetry, as gravitationally bounded lumps of scalar condensate. Further, there are spinning axially symmetric boson stars which possess non-zero angular momentum, and a variety of non-trivial multipolar stationary configurations without any continuous symmetries. In this short overview we discuss important dynamic properties of the boson stars, concentrating on recent results on the construction of multicomponent constellations of boson stars.

gr-qc↗

arXiv2021

Fractional Skyrmion molecules in a $\mathbb{C}P^{N-1}$ model

We study fractional Skyrmions in a $\mathbb{C}P^2$ baby Skyrme model with a generalization of the easy-plane potential. By numerical methods, we find stable, metastable, and unstable solutions taking the shapes of molecules. Various solutions possess discrete symmetries, and the origin of those symmetries are traced back to congruencies of the fields in homogeneous coordinates on $\mathbb{C}P^2$.

hep-th↗

arXiv2021

Spinning gauged boson and Dirac stars: a comparative study

Scalar boson stars and Dirac stars are solitonic solutions of the Einstein{Klein-Gordon and Einstein- Dirac classical equations, respectively. Despite the different bosonic vs: fermionic nature of the matter field, these solutions to the classical field equations have been shown to have qualitatively similar features [1]. In particular, for spinning stars the most fundamental configurations can be in both cases toroidal, unlike spinning Proca stars that are spheroidal [2]. In this paper we gauge the scalar and Dirac fields, by minimally coupling them to standard electromagnetism. We explore the impact of the gauge coupling on the resulting solutions. One of the most relevant difference concerns the gyromagnetic ratio, which for the scalar stars takes values around 1, whereas for Dirac stars takes values around 2.

gr-qc↗

arXiv2021

Resonance structures in kink-antikink collisions in a deformed sine-Gordon model

We study kink-antikink collisions in a model which interpolates smoothly between the completely integrable sine-Gordon theory, the $ϕ^4$ model, and a $ϕ^6$-like model with three degenerate vacua. We find a rich variety of behaviours, including integrability breaking, resonance windows with increasingly irregular patterns, and new types of windows near the $ϕ^6$-like regime. False vacua, extra kink modes and kink fragmentation play important roles in the explanations of these phenomena. Our numerical studies are backed up by detailed analytical considerations.

hep-th↗

arXiv2021

Isolated Skyrmions in the $CP^2$ nonlinear $σ$-model with a Dzyaloshinskii-Moriya type interaction

We study two dimensional soliton solutions in the $CP^2$ nonlinear $σ$-model with a Dzyaloshinskii-Moriya type interaction. First, we derive such a model as a continuous limit of the $SU(3)$ tilted ferromagnetic Heisenberg model on a square lattice. Then, introducing an additional potential term to the derived Hamiltonian, we obtain exact soliton solutions for particular sets of parameters of the model. The vacuum of the exact solution can be interpreted as a spin nematic state. For a wider range of coupling constants, we construct numerical solutions, which possess the same type of asymptotic decay as the exact analytical solution, both decaying into a spin nematic state.

hep-th↗

arXiv2021

Chains of interacting solitons

We present an overview of multisoliton chains arising in various non-integrable field theories, and discuss different mechanisms, which may lead to the occurrence of such axially-symmetric classical solutions. We explain the pattern of interactions between different solitons, in particular Q-balls, Skyrmions and monopoles and show how chains of interacting non-BPS solitons may form in a dynamic equilibrium between repulsive and attractive forces.

hep-th↗

arXiv2020

Q-chains in the $U(1)$ gauged Friedberg-Lee-Sirlin model

We construct static axially symmetric multi-Q-ball configurations in the $U(1)$ gauged two-component Fridberg-Lee-Sirlin model a flat spacetime. The solutions represent electromagnetically bounded chains of stationary spinning charged Q-balls placed along the axis of symmetry. We discuss the properties of these configurations and exhibit their domain of existence.

hep-th↗

arXiv2020

Black holes with Skyrmion-anti-Skyrmion hairs

We construct static axially symmetric black holes in multi-Skyrmion configurations coupled to Einstein gravity in four dimensional asymptotically flat space-time. In a simplest case the event horizon is located in-between a Skyrmion-anti-Skyrmion pair, other solutions represent black holes with gravitationally bounded chains of Skyrmions and anti-Skyrmions placed along the axis of symmetry in alternating order. We discuss the properties of these hairy black holes and exhibit their domain of existence.

hep-th↗