Yuki Amari

We study $\mathbb{C}{P}^{2}$ skyrmion crystals in the ferromagnetic $\mathrm{SU}(3)$ 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 h

We construct domain-wall skyrmion chains and domain-wall bimerons in chiral magnets with an out-of-plane easy-axis anisotropy and without a Zeeman term coupling to a magnetic field. Domain-wall skyrmions are skyrmions trapped inside a domain wall, and they are present in the ferromagnetic (FM) phase of a chiral magnet with an out-of-plane easy-axis anisotropy. In this paper, we explore the stability of domain-wall skyrmions in the FM phase and in a chiral soliton lattice (CSL) or spiral phase, w

A bstract Chiral magnets with the Dzyaloshinskii-Moriya (DM) interaction have received quite an intensive focus in condensed matter physics because of the presence of a chiral soliton lattice (CSL), an array of magnetic domain walls and anti-domain walls, and magnetic skyrmions, both of which are important ingredients in the current nanotechnology. In this paper, we realize chiral magnets in type-IIA/B string theory by using the Hanany-Witten brane configuration (consisting of D3, D5 and NS5-bra

We discuss the existence of knot solitons (Hopfions) in a Skryme-Faddeev-Niemi-type model on the target space $SU(3)/U(1)^2$, which can be viewed as an effective theory of both the $SU(3)$ Yang-Mills theory and the $SU(3)$ anti-ferromagnetic Heisenberg model. We derive the knot solitons with two different types of ansatz: the first is a trivial embedding configuration of $SU(2)$ into $SU(3)$, and the second is a non-embedding configuration that can be generated through the B\"{a}cklund transform

We construct static and also time-dependent solutions in a nonlinear sigma model with target space being the flag manifold ${F}_{2}=SU(3)/U(1{)}^{2}$ on the four-dimensional Minkowski spacetime by analytically solving the second-order Euler-Lagrange equation. We show that the static solutions saturate an energy lower bound and can be derived from coupled first-order equations though they are saddle-point solutions. We also discuss basic properties of the time-dependent solutions.

The extended Skyrme--Faddeev model possesses vortex solutions in a ($3+1$)-dimensional Minkowski space-time with target space $C{P}^{N}$. They have finite energy per unit of length and contain waves propagating along the vortices with the speed of light. We introduce various types of the potentials which correspond with holomorphic solutions of the integrable sector and also with several numerical solutions outside of this sector. The presented solutions constitute a strong indication that the c

A bstract The ground state of QCD with two flavors (up and down quarks) at finite baryon density in sufficiently strong magnetic field is in a form of either a chiral soliton lattice(CSL), an array of solitons stacked along the magnetic field, or a domain-wall Skyrmion phase in which Skyrmions are spontaneously created on top of the CSL. In the latter, one 2D (baby) Skyrmion in the chiral soliton corresponds to two 3D Skyrmions (baryons) in the bulk. In this paper, we study spin statistics of to

A bstract We study topological lumps supported by the second homotopy group π 2 ( S 2 ) ⋍ ℤ in a gauged O (3) model without any potential term coupled with a (non)dynamical U(1) gauge field. It is known that gauged-lumps are stable with an easy-plane potential term but are unstable to expand if the model has no potential term. In this paper, we find that these gauged lumps without a potential term can be made stable by putting them in a uniform magnetic field, irrespective of whether the gauge f

A bstract The ground state of QCD in sufficiently strong magnetic field at finite baryon density is an inhomogeneous state consisting of an array of solitons, called the chiral soliton lattice (CSL). It is, however, replaced in a region with higher density and/or magnetic field by the so-called domain-wall Skyrmion (DWSk) phase where Skyrmions are created on top of the CSL. This was previously proposed within the Bogomol’nyi-Prasad-Sommerfield (BPS) approximation neglecting a gauge field dynamic

The Skyrme-Faddeev model has planar soliton solutions with the target space ℂPN. An Abelian Chern-Simons term (the Hopf term) in the Lagrangian of the model plays a crucial role for the statistical properties of the solutions. Because П3(ℂP1) = ℤ, the term becomes an integer for N = 1. On the other hand, for N > 1, it becomes perturbative because П3(ℂPN) is trivial. The prefactor Θ of the Hopf term is not quantized, and its value depends on the physical system. We study the spectral flow of norm

We study a magnetic domain wall in the ferromagnetic phase in chiral magnets in two dimensions with an in-plane easy-axis anisotropy and an out-of-plane Zeeman magnetic field, and find a chiral soliton lattice (spiral) phase beside a ferromagnetic phase inside the domain line, where the former represents a domain-wall skyrmion crystal from the bulk point of view. We first determine the phase diagram on the domain wall by numerically constructing domain-wall solutions. We then analytically reprod

A bstract The spectral flow is ubiquitous in the physics of soliton-fermion interacting systems. We study the spectral flows related to a continuous deformation of background soliton solutions, which enable us to develop insight into the emergence of fermionic zero modes and the localization mechanism of fermion densities. We investigate a ℂ P 2 nonlinear sigma model in which there are the (anti-) instantons and also the sphalerons with vanishing topological charge. The standard Yukawa coupling

The $\mathbb{C}{P}^{N}$ extended Skyrme-Faddeev model possesses planar soliton solutions. We consider quantum aspects of the solutions applying collective coordinate quantization in regime of rigid body approximation. In order to discuss statistical properties of the solutions we include an Abelian Chern-Simons term (the Hopf term) in the Lagrangian. Since ${\mathrm{\ensuremath{\Pi}}}_{3}(\mathbb{C}{P}^{1})=\mathbb{Z}$ then for $N=1$ the term becomes an integer. On the other hand for $N>1$ it

We study stationary rotating topological solitons in a (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mn>2</a:mn><a:mo>+</a:mo><a:mn>1</a:mn></a:mrow></a:math>)-dimensional <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi mathvariant="double-struck">C</c:mi><c:msup><c:mi>P</c:mi><c:mn>2</c:mn></c:msup></c:math> nonlinear sigma model with a stabilizing potential term. We find families of <f:math xmlns:f="http://www.w3.org/1998/Math/Mat

A bstract Nuclear matter with a strong magnetic field is prevalent inside neutron stars and heavy-ion collisions. In a sufficiently large magnetic field, the ground state is either a chiral soliton lattice (CSL), an array of solitons of the neutral pion field, or a domain-wall Skyrmion phase in which Skyrmions emerge inside the chiral solitons. In the region of large chemical potential and a magnetic field lower than its critical value for CSL, a Skyrmion crystal is expected to take up the groun