Results for "Motohiko Ezawa"

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Pseudospin 3/2 Fermions, Type-II Weyl Semimetals and Critical Weyl Semimetals in Tricolor Cubic LatticeSep 11 2016Multi-band touchings such as 3-band, 6-band and 8-band touchings together with the emergence of high pseudospin fermions were predicted recently at high-symmetry points in three-dimensional space. In this paper, we propose a simple cubic model whose unit ... More
High-topological-number magnetic skyrmions and topologically protected dissipative structureMay 04 2015Jan 05 2016The magnetic skyrmion with the topological number of unity ($Q=1$) is a well-known nanometric swirling spin structure in the nonlinear $\sigma$ model with the Dzyaloshinskii-Moriya interaction. Here, we show that magnetic skyrmion with the topological ... More
Electric circuits for non-Hermitian Chern insulatorsApr 08 2019We analyze the non-Hermitian Haldane model where the spin-orbit interaction is made non-Hermitian. The Dirac mass becomes complex. We propose to realize it by an $LC$ circuit with operational amplifiers. A topological phase transition is found to occur ... More
Spin Filter, Spin Amplifier and Other Spintronic Applications in Graphene NanodisksAug 13 2008Graphene nanodisk is a graphene derivative with a closed edge. The trigonal zigzag nanodisk with size $N$ has $N$-fold degenerated zero-energy states. A nanodisk can be interpletted as a quantum dot with an internal degree of freedom. The grand state ... More
Electric-circuit realization of Hermitian and non-Hermitian Majorana edge statesFeb 11 2019We study non-Hermitian generalizations of the Kitaev and $p_x+ip_y$ topological superconductor models only by requiring the particle-hole symmetry. The condition of the emergence of the Majorana edge states in non-Hermitian systems is that the states ... More
Electric circuit simulations of $n$th-Chern insulators in $2n$-dimensional space and their non-Hermitian generalizations for arbitral $n$May 26 2019We show that topological phases of the Dirac system in arbitral even dimensional space are simulated by $LC$ electric circuits with operational amplifiers. The lattice Hamiltonian for the hypercubic lattice in $2n$ dimensional space is characterized by ... More
Electric-circuit simulation of the Schrödinger equation and non-Hermitian quantum walksAug 06 2019Recent progress has witnessed that various topological physics can be simulated by electric circuits under alternating current. However, it is still a nontrivial problem if we may simulate the dynamics subject to the Schr\"{o}dinger equation based on ... More
Non-Abelian braiding of Majorana-like edge states and scalable topological quantum computations in electric circuitsJul 16 2019Majorana fermions subject to the non-Abelian braid group are believed to be the basic ingredients of future topological quantum computations. In this work, we propose to simulate Majorana fermions of the Kitaev model in electric circuits. We generate ... More
Giant magnetoresistance and perfect spin filter in silicene, germanene, and staneneDec 06 2013May 12 2014Silicene, germanene and stanene are two-dimensional topological insulators exhibiting helical edge states. We investigate global and local manipulations at the edges by exposing them to (i) a charge-density-wave order, (ii) a superconductor, (iii) an ... More
A reversible conversion between a skyrmion and a domain-wall pair in junction geometryApr 13 2014A skyrmion is a topological texture in the continuum field theory. Recent experimental observation of skyrmions in chiral magnet evokes a flourish of its extensive study. Skyrmion is expected to be a key component of the next generation spintronics device ... More
Control and manipulation of a magnetic skyrmionium in nanostructuresApr 20 2016Sep 03 2016A magnetic skyrmionium is a nontopological soliton, which has a doughnut-like out-of-plane spin texture in thin films, and can be phenomenologically viewed as a coalition of two topological magnetic skyrmions with opposite topological numbers. Due to ... More
Current Modulator based on Topological Insulator with Sliding Magnetic SuperlatticeFeb 04 2010We study theoretically the surface of a topological insulator with a sliding magnetic superlattice coated above. By analyzing time-dependent Dirac equations, the dynamics of the zero mode is investigated. When the superlattice's sliding velocity is smaller ... More
All-magnetic control of skyrmions in nanowires by a spin waveApr 01 2015Aug 27 2015Magnetic skyrmions are topologically protected nanoscale objects, which are promising building blocks for novel magnetic and spintronic devices. Here, we investigate the dynamics of a skyrmion driven by a spin wave in a magnetic nanowire. It is found ... More
Interference of Topologically Protected Edge States in Silicene NanoribbonsJan 27 2013Silicene is a two-dimensional quantum spin-Hall insulator. We study the edge channels of silicene nanoribbons from the viewpoint of the topological protection and the interference between the two edges. It is found that the behaviors of the helical edge ... More
Arsenene: Two-dimensional buckled and puckered honeycomb arsenic systemsOct 20 2014Recently phosphorene, monolayer honeycomb structure of black phosphorus, was experimentally manufactured and attracts rapidly growing interests. Here we investigate stability and electronic properties of honeycomb structure of arsenic system based on ... More
Skyrmion dynamics in a frustrated ferromagnetic film and current-induced helicity locking-unlocking transitionMar 22 2017Nov 23 2017The helicity-orbital coupling is an intriguing feature of magnetic skyrmions in frustrated magnets. Here, we explore the skyrmion dynamics in a frustrated magnet based on the $J_{1}$-$J_{2}$-$J_{3}$ classical Heisenberg model explicitly by including the ... More
Current-Driven Dynamics of Frustrated Skyrmions in a Synthetic Antiferromagnetic BilayerDec 03 2018Mar 27 2019We report the current-driven dynamics of frustrated skyrmions in an antiferromagnetically exchange coupled bilayer system, where the bilayer skyrmion consists of two monolayer skyrmions with opposite skyrmion numbers $Q$. We show that the in-plane current-driven ... More
Manipulation of magnetic skyrmions in a locally modified synthetic antiferromagnetic racetrackJul 18 2018Mar 07 2019In skyrmion-based racetrack memories, the information encoded by skyrmions may be destroyed due to the skyrmion Hall effect, which can be surmounted by using synthetic antiferromagnetic racetracks. Hence, the manipulation of skyrmions in synthetic antiferromagnetic ... More
Spin torque nano-oscillators based on antiferromagnetic skyrmionsNov 07 2018Skyrmion-based spin torque nano-oscillators are potential next-generation microwave signal generators. However, ferromagnetic skyrmion-based spin torque nano-oscillators cannot reach high oscillation frequencies. In this work, we propose to use the circular ... More
Dynamics of the antiferromagnetic skyrmion induced by a magnetic anisotropy gradientAug 27 2018Oct 09 2018The dynamics of antiferromagnets is a current hot topic in condensed matter physics and spintronics. However, the dynamics of insulating antiferromagnets cannot be excited by an electric current, which is a method usually used to manipulate ferromagnetic ... More
Topological Phase Transition without Gap ClosingJul 28 2013Feb 12 2014Topological phase transition is accompanied with a change of topological numbers. It has been believed that the gap closing and the breakdown of the adiabaticity at the transition point is necessary in general. However, the gap closing is not always needed ... More
Aluminene as Highly Hole Doped GrapheneFeb 20 2015Monolayer structures made up of purely one kind of atoms are fascinating. Many kinds of honeycomb systems including carbon, silicon, germanium, tin, phosphorus and arsenic have been shown to be stable. However, so far the structures are restricted to ... More
Magnetic skyrmion logic gates: conversion, duplication and merging of skyrmionsOct 12 2014Mar 25 2015Magnetic skyrmions, which are topological particle-like excitations in ferromagnets, have attracted a lot of attention recently. Skyrmionics is an attempt to use magnetic skyrmions as information carriers in next generation spintronic devices. Proposals ... More
Magnetic bilayer-skyrmions without skyrmion Hall effectApr 09 2015Arising from emergent electromagnetic field of magnetic skyrmions due to their nontrivial topology, the skyrmion Hall effect might be a roadblock for practical applications since any longitudinal motions of skyrmions in nanotrack is accompanied by a transverse ... More
Quantized Anomalous Hall Effects in Skyrmion CrystalApr 23 2015May 01 2015We theoretically study the quantized anomalous Hall effect (QAHE) in skyrmion crystal (SkX) without external magnetic field. The emergent magnetic field in SkX could be gigantic as much as $\sim4000$T when its lattice constant is $\sim1$nm. The band structure ... More
Edge States in Silicene NanodisksAug 01 2013Silicene is a honeycomb-structure silicon atoms, which shares many intriguing properties with graphene. Silicene is expected to be a quantum spin-Hall insulator due to its spin-orbit interactions. We investigate the electronic properties of silicene nanodisks, ... More
Thermally stable magnetic skyrmions in multilayer synthetic antiferromagnetic racetracksJan 15 2016Jul 22 2016A magnetic skyrmion is a topological magnetization structure with a nanometric size and a well-defined swirling spin distribution, which is anticipated to be an essential building block for novel skyrmion-based device applications. We study the motion ... More
Antiferromagnetic Skyrmion: Stability, Creation and ManipulationApr 06 2015Apr 04 2016Magnetic skyrmions are particle-like topological excitations in ferromagnets, which have the topological number $Q=\pm 1$, and hence show the skyrmion Hall effect (SkHE) due to the Magnus force effect originating from the topology. Here, we propose the ... More
Manipulation of two spin qubits in a double quantum dot using an electric fieldMay 17 2010Nov 05 2010We propose purely electric manipulation of spin qubits by means of the spin-orbit interaction (SOI) {\it without magnetic field or magnets} in a double-quantum dot. All the unitary transformations can be constructed by the time-dependent Dzyaloshinsky-Moriya ... More
Purely electrical detection of a skyrmion in constricted geometryDec 25 2015How to detect the skyrmion position is a crucial problem in future skyrmionics since it corresponds to the reading process of information. We propose a method to detect the skyrmion position purely electrically by measuring the Hall conductance in a constricted ... More
Electric field-induced creation and directional motion of domain walls and skyrmion bubblesAug 07 2017Dec 12 2018Magnetization dynamics driven by an electric field could provide long-term benefits to information technologies because of its ultralow power consumption. Meanwhile, the Dzyaloshinskii-Moriya interaction in interfacially asymmetric multilayers consisting ... More
Domain wall of a ferromagnet on a three-dimensional topological insulatorDec 26 2014Sep 02 2015Topological insulators (TIs) show rich phenomena and functions which can never be realized in ordinary insulators. Most of them come from the peculiar surface or edge states. Especially, the quantized anomalous Hall effect (QAHE) without an external magnetic ... More
Majorana Fermions and Multiple Topological Phase Transition in Kitaev Ladder Topological SuperconductorsJan 21 2014May 23 2014Motivated by the InSb nanowire superconductor system, we investigate a system where one-dimensional topological superconductors are placed in parallel. It would be simulated well by a ladder of the Kitaev chains. The system undergoes multiple topological ... More
Direct Band Gaps in Group IV-VI Monolayer Materials: Binary Counterparts of PhosphoreneDec 23 2015Mar 07 2016We perform systematic investigation on the geometric, energetic and electronic properties of group IV-VI binary monolayers (XY), which are the counterparts of phosphorene, by employing density functional theory based electronic structure calculations. ... More
PC Cluster Machine Equipped with Low-Latency Communication SoftwareJul 30 2004Dec 08 2004A high performance Beowulf (PC cluster) machine installed with Linux operating system and MPI (Message Passing Interface) for interprocessor communications has been constructed using Gigabit Ethernet and the communication software GAMMA (Genoa Active ... More
Electrophoresis of a rod macroion under polyelectrolyte salt: Is mobility reversed for DNA?Nov 01 2003Jan 30 2004By molecular dynamics simulation, we study the charge inversion phenomenon of a rod macroion in the presence of polyelectrolyte counterions. We simulate electrophoresis of the macroion under an applied electric field. When both counterions and coions ... More
Combinatorial solutions to the Hamiltonian constraint in (2+1)-dimensional Ashtekar gravityJun 22 1995Jun 23 1995Dirac's quantization of the (2+1)-dimensional analog of Ashtekar's approach to quantum gravity is investigated. After providing a diffeomorphism-invariant regularization of the Hamiltonian constraint, we find a set of solutions to this Hamiltonian constraint ... More
Fermion Fractionalization to Majorana Fermions in Dimerized Kitaev SuperconductorMay 06 2014Jul 10 2014We study theoretically a one-dimensional dimerized Kitaev superconductor model which belongs to BDI class with time-reversal, particle-hole, and chiral symmetries. There are two sources of the particle-hole symmetry, i.e., the sublattice symmetry and ... More
The Effects of Asymmetric Salt and a Cylindrical Macroion on Charge Inversion: Electrophoresis by Molecular Dynamics SimulationsMar 25 2003Sep 16 2003The charge inversion phenomenon is studied by molecular dynamics simulations, focusing on size and valence asymmetric salts, and a threshold of surface charge density for charge inversion. The charge inversion criteria by the electrophoretic mobility ... More
Pregalactic LiBeB Production by Supernova Cosmic RaysMar 24 2008I calculate the evolution of Be and B abundances produced by cosmic rays generated by massive stars in the pregalactic phase of the universe. The inputs for calculation, i.e. the star formation rate and the nuclear abundances of cosmic rays, which I assume ... More
Charge transport in pn and npn junctions of siliceneMar 23 2013Sep 11 2013We investigate charge transport of pn and npn junctions made from silicene, Si analogue of graphene. The conductance shows the distinct gate-voltage dependences peculiar to the topological and non-topological phases, where the topological phase transition ... More
Deterministic creation and deletion of a single magnetic skyrmion observed by direct time-resolved X-ray microscopyJun 21 2017Apr 06 2018Spintronic devices based on magnetic skyrmions are a promising candidate for next-generation memory applications due to their nanometre-size, topologically-protected stability and efficient current-driven dynamics. Since the recent discovery of room-temperature ... More
Nonperturbative solutions for canonical quantum gravity: an overviewJan 31 1996Feb 29 1996In this paper we will make a survey of solutions to the Wheeler-Dewitt equation which have been found up to now in Ashtekar's formulation for canonical quantum gravity. Roughly speaking they are classified into two categories, namely, Wilson-loop solutions ... More
Transition Amplitude in 2+1 dimensional Chern-Simons Gravity on a TorusMay 29 1993Nov 16 1993The discussions on the modular invariance in section 5 are refined.
Addendum to "Classical and Quantum Evolutions of the de Sitter and the anti-de Sitter Universes in 2+1 dimensions"Mar 26 1994Apr 11 1994The previous discussion \cite{ezawa} on reducing the phase space of the first order Einstein gravity in 2+1 dimensions is reconsidered. We construct a \lq\lq correct" physical phase space in the case of positive cosmological constant, taking into account ... More
Classical and Quantum Evolutions of the de Sitter and the anti-de Sitter Universes in 2+1 dimensionsNov 18 1993Nov 19 1993Two canonical formulations of the Einstein gravity in 2+1 dimensions, namely, the ADM formalism and the Chern-Simons gravity, are investigated in the case of nonvanishing cosmological constant. General arguments for reducing phase spaces of the two formalisms ... More
Chern-Simons Quantization of (2+1)-Anti-De Sitter Gravity on a TorusSep 14 1994Chern-Simons formulation of 2+1 dimensional Einstein gravity with a negative cosmological constant is investigated when the spacetime has the topology $ R\times T^{2}$. The physical phase space is shown to be a direct product of two sub-phase spaces each ... More
A semiclassical interpretation of the topological solutions for canonical quantum gravityDec 08 1995Ashtekar's formulation for canonical quantum gravity is known to possess the topological solutions which have their supports only on the moduli space $\CN$ of flat $SL(2,C)$ connections. We show that each point on the moduli space $\CN$ corresponds to ... More
Reduced Phase Space of the first order Einstein Gravity on ${\bf R}\times T^{2}$Dec 17 1993Dec 23 1993Chern-Simons formulation of the 2+1 dimensional Einstein gravity with negative cosmological constant is investigated when the spacetime has the topology ${\bf R}\times T^{2}$. The physical phase space is shown to be a direct product of two sub-phase spaces ... More
DNA in nanopore-counterion condensation and coion depletionDec 13 2004Molecular dynamics simulations are used to study the equilibrium distribution of monovalent ions in a nanopore connecting two water reservoirs separated by a membrane, both for the empty pore and that with a single stranded DNA molecule inside. In the ... More
Destruction of 7Be in big bang nucleosynthesis via long-lived sub-strongly interacting massive particles as a solution to the Li problemDec 02 2010Feb 10 2011We identify reactions which destroy 7Be and 7Li during big bang nucleosynthesis (BBN) in the scenario of BBN catalyzed by a long-lived sub-strongly interacting massive particle (sub-SIMP or X particle). The destruction associated with non radiative X ... More
Curvaton Scenario in the Presence of Two Dilatons Coupled to the Scalar CurvatureJan 06 2006Feb 27 2006The possibility of the realization of a curvaton scenario is studied in a theory in which two dilatons are introduced along with coupling to the scalar curvature. It is shown that when the two dilatons have an approximate O(2) symmetric coupling, a scalar ... More
Initial Li Abundances in the Protogalaxy and Globular Clusters Based upon the Chemical Separation and Hierarchical Structure FormationMar 19 2019The chemical separation of Li+ ions induced by a magnetic field during the hierarchical structure formation can reduce initial Li abundances in cosmic structures. It is shown that cosmological reionization of neutral Li atoms quickly completes as soon ... More
Giant Charge Inversion of a Macroion Due to Multivalent Counterions and Monovalent Coions: Molecular Dynamics StudyFeb 12 2001Feb 21 2001We report molecular dynamics simulation of the (overall neutral) system consisting of an immobile macroion surrounded by the electrolyte of multivalent counterions and monovalent coions. As expected theoretically, counterions adsorb on the macroion surface ... More
Microwave Heating of Water, Ice and Saline Solution: Molecular Dynamics StudyJul 28 2006Sep 24 2006In order to study the heating process of water by the microwaves of 2.5-20GHz frequencies, we have performed molecular dynamics simulations by adopting a non-polarized water model that have fixed point charges on rigid-body molecules. All runs are started ... More
Roles of $^7$Be$(n,p)^7$Li resonances in big bang nucleosynthesis with time-dependent quark mass and Li reduction by a heavy quark massJan 13 2019Big bang nucleosynthesis (BBN) has been used as a probe of beyond-standard physics in the early Universe, which includes a time-dependent quark mass m_q. We investigate effects of a quark mass variation delta m_q on the cross sections of the 7Be(n, p)7Li ... More
Chemical separation of primordial Li$^+$ during structure formation caused by nanogauss magnetic fieldApr 14 2014Oct 08 2014During the structure formation, charged and neutral chemical species may have separated from each other at the gravitational contraction in primordial magnetic field (PMF). A gradient in the PMF in a direction perpendicular to the field direction leads ... More
Third quantization of $f(R)$-type gravityMar 07 2012Mar 14 2012We examine the third quantization of $f(R)$-type gravity, based on its effective Lagrangian in the case of a flat Friedmann-Lemaitre-Robertson-Walker metric. Starting from the effective Lagrangian, we execute a suitable change of variable and the second ... More
Value of Evidence on Influence DiagramsFeb 27 2013In this paper, we introduce evidence propagation operations on influence diagrams and a concept of value of evidence, which measures the value of experimentation. Evidence propagation operations are critical for the computation of the value of evidence, ... More
Osp(1|2) Chern-Simons gauge theory as 2D N=1 Induced SupergravityDec 03 1996Dec 13 1996We demonstrate the close relationship between Chern-Simons gauge theory with gauge group Osp(1|2) and N=1 induced supergravity in two dimensions. More precisely, the inner product of the physical states in the former yields the partition function of the ... More
Initial Li Abundances in the Protogalaxy and Globular Clusters Based upon the Chemical Separation and Hierarchical Structure FormationMar 19 2019Apr 17 2019The chemical separation of Li+ ions induced by a magnetic field during the hierarchical structure formation can reduce initial Li abundances in cosmic structures. It is shown that cosmological reionization of neutral Li atoms quickly completes as soon ... More
Tunable skewed edges in puckered structuresDec 07 2015Jun 15 2016We propose a new type of edges, arising due to the anisotropy inherent in the puckered structure of a honeycomb system such as in phosphorene. Skewed-zigzag and skewed-armchair nanoribbons are semiconducting and metallic, respectively, in contrast to ... More
The study of the microwave heating of bulk metals without microwave susceptorsAug 01 2011This paper discusses the physical aspects of the microwave heating of bulk metals in multimode cavity. The concept of power balance and thermodynamics are utilized to explain the preheating step required for successful microwave heating.
Production of 9Be through alpha-fusion reaction of metal-poor cosmic ray and stellar flareAug 21 2012Mar 20 2013Spectroscopic observations of metal-poor stars have indicated possible 6Li abundances that are much larger than the primordial abundance predicted in the standard big bang nucleosynthesis model. Possible mechanisms of 6Li production in metal-poor stars ... More
Updated constraint on a primordial magnetic field during big bang nucleosynthesis and a formulation of field effectsApr 27 2012Jul 10 2012A new upper limit on the amplitude of primordial magnetic field (PMF) is derived by a comparison between a calculation of elemental abundances in big bang nucleosynthesis (BBN) model and the latest observational constraints on the abundances. Updated ... More
Resonant annihilation of long-lived massive colored particles through hadronic collisionsDec 05 2011Dec 23 2011Hypothetical long-lived massive colored particles (MCPs or Ys) would be confined in colorless exotic strongly interacting massive particles (SIMPs) at color confinement temperature of T_C /sim 200 MeV. Two long-lived MCPs form a bound state (Y /bar{Y}) ... More
Current-driven dynamics of frustrated skyrmions in a synthetic antiferromagnetic bilayerDec 03 2018Magnetic skyrmions can be stabilized and manipulated in frustrated magnets, and are useful for building nonvolatile magnetic memories and logic devices. Here we study the current-driven dynamics of frustrated skyrmions in an antiferromagnetically exchange ... More
Dynamics of a magnetic skyrmionium driven by spin wavesFeb 12 2018Mar 23 2018The magnetic skyrmionium is a skyrmion-like structure but carries a zero net skyrmion number, which can be used as a building block for non-volatile information processing devices. Here, we study the dynamics of a magnetic skyrmionium driven by propagating ... More
Manipulation of magnetic skyrmions in a locally modified synthetic antiferromagnetic racetrackJul 18 2018In skyrmion-based racetrack-type memory devices, the information encoded by magnetic skyrmions may be destroyed due to the skyrmion Hall effect, which can be surmounted by using synthetic antiferromagnetic racetracks. Hence, the manipulation of skyrmions ... More
Nonlinear spin current generation in noncentrosymmetric spin-orbit coupled systemsJun 27 2017Spin current plays a central role in spintronics. In particular, finding more efficient ways to generate spin current has been an important issue and studied actively. For example, representative methods of spin current generation include spin polarized ... More
Observation of magnetic skyrmion crystals in a van der Waals ferromagnet Fe3GeTe2Jul 02 2019Since the discovery of long-range magnetic orders in the two-dimensional (2D) van der Waals (vdW) crystals, significant interest on such 2D magnets has emerged, inspired by their appealing physical properties and integration with other 2D family for unique ... More
On the canonical formalism of $f(R)$-type gravity using Lie derivativesDec 15 2014Jun 25 2015We present a canonical formalism of the $f(R)$-type gravity using the Lie derivatives instead of the time derivatives by refining the formalism of our group. The previous formalism is a direct generalization of the Ostrogradski's formalism. However the ... More
Third quantization of $f(R)$-type gravity II - General $f(R)$ case -Oct 10 2012Oct 26 2012In the previous paper we examined the third quantization of the $f(R)$-type gravity and studied the Heisenberg uncertainty relation of the universe in the example of $f(R)=R^2$. In this work the Heisenberg uncertainty relation of the universe is investigated ... More
Spin-Pseudospin Coherence and CP$^{3}$ Skyrmions in Bilayer Quantum Hall FerromagnetsDec 11 1998Apr 23 1999We analyze bilayer quantum Hall ferromagnets, whose underlying symmetry group is SU(4). Spin-pseudospin coherence develops spontaneously when the total electron density is low enough. Quasiparticles are CP^3 skyrmions. One skyrmion induces charge modulations ... More
Improved Composite-Boson Theory of Monolayer and Bilayer Quantum Hall FerromagnetsOct 01 1998An improved composite-boson theory of quantum Hall ferromagnets is formulated both for the monolayer and bilayer systems. In this scheme the field operator describes solely the physical degrees of freedom representing the deviation from the ground state. ... More
Quantum Coherence and W_infty*SU(2) Algebra in Bilayer Quantum Hall SystemsMay 13 1997We analyze the bilayer quantum Hall (QH) system by mapping it to the monolayer QH system with spin degrees of freedom. By this mapping the tunneling interaction term is identified with the Zeeman term. We clarify the mechanism of a spontaneous development ... More
Improved Composite-Boson Theory of Quantum Hall Ferromagnets and Skyrmions without Sigma ModelsMar 12 1998Jun 11 1998We propose an improved composite-boson theory of quantum Hall ferromagnets, where the field operator describes solely the physical degrees of freedom representing the deviation from the ground state. In this scheme skyrmions appear merely as generic excitations ... More
Nondeterministic fuzzy automataDec 10 2010Fuzzy automata have long been accepted as a generalization of nondeterministic finite automata. A closer examination, however, shows that the fundamental property---nondeterminism---in nondeterministic finite automata has not been well embodied in the ... More
The equivalence theorem in the generalized gravity of f(R)-type and canonical quantization IIApr 11 2012We first review the equivalence theorem of the f(R)-type gravity to Einstein gravity with a scalar field by deriving it in a self-contained and pedagogical way. Then we describe the problem of to what extent the equivalence holds. Main problems are (i) ... More
Refined form of the paper "Canonical formalism of the f(R)-type gravity in terms of Lie derivatives"Apr 12 2013Sep 16 2013We refine the presentation of the previous paper of our group, Y.Ezawa et al., Class. Quantum Grav. {\bf 23} (2006), 3205 [arXiv:gr-qc/0507060]. In that paper, we proposed a canonical formalism of f(R)-type generalized gravity by using the Lie derivatives ... More
Field Theory of Quantum Hall Effects, Composite Bosons, Vortices and SkyrmionsMar 13 1998A field theory of quantum Hall effects is constructed based on the \CB picture. It is tightly related with the microscopic wave-function theory. The characteristic feature is that the field operator describes solely the physical degrees of freedom representing ... More
Effects of power law primordial magnetic field on big bang nucleosynthesisDec 12 2012Big bang nucleosynthesis (BBN) is affected by the energy density of a primordial magnetic field (PMF). For an easy derivation of constraints on models for PMF generations, we assume a PMF with a power law (PL) distribution in wave number defined with ... More
Cyclotron resonance of correlated electrons in semiconductor heterostructuresNov 06 2003The cyclotron resonance absorption of two-dimensional electrons in semiconductor heterostructures in high magnetic fields is investigated. It is assumed that the ionized impurity potential is a dominant scattering mechanism, and the theory explicitly ... More
Microscopic Theory of Skyrmions in Quantum Hall FerromagnetsSep 10 2005We present a microscopic theory of skyrmions in the monolayer quantum Hall ferromagnet. It is a peculiar feature of the system that the number density and the spin density are entangled intrinsically as dictated by the W$%_{\infty}$ algebra. The skyrmion ... More
Topological Solitons in Noncommutative Plane and Quantum Hall SkyrmionsSep 10 2005We analyze topological solitons in the noncommutative plane by taking a concrete instance of the quantum Hall system with the SU(N) symmetry, where a soliton is identified with a skyrmion. It is shown that a topological soliton induces an excitation of ... More
Skyrmions and Quantum Hall Ferromagnets in Improved Composite-Boson TheoryJan 22 1999An improved composite-boson theory of quantum Hall ferromagnets is proposed. It is tightly related with the microscopic wave-function theory. The characteristic feature is that the field operator describes solely the physical degrees of freedom representing ... More
Thermal and Tunneling Pair Creation of Quasiparticles in Quantum Hall SystemsJul 19 1999We make a semiclassical analysis of thermal pair creations of quasiparticles at various filling factors in quantum Hall systems. It is argued that the gap energy is reduced considerably by the Coulomb potential made by impurities. It is also shown that ... More
Current-Induced Dynamics and Chaos of an Antiferromagnetic BimeronMay 22 2019Magnetic bimeron is a topologically non-trivial spin texture carrying an integer topological charge, which can be regarded as the counterpart of skyrmion in easy-plane magnets. The controllable creation and manipulation of bimerons are crucial for practical ... More
Electrophoresis of a charge inverted macroion complex: Molecular dynamics studyJun 27 2001Apr 12 2002We have performed molecular dynamics simulations to study the effect of an external electric field on a macroion in the solution of multivalent Z:1 salt. To obtain plausible hydrodynamics of the medium, we explicitly make the simulation of many neutral ... More
Fraud/Uncollectible Debt Detection Using a Bayesian Network Based Learning System: A Rare Binary Outcome with Mixed Data StructuresFeb 20 2013The fraud/uncollectible debt problem in the telecommunications industry presents two technical challenges: the detection and the treatment of the account given the detection. In this paper, we focus on the first problem of detection using Bayesian network ... More
SU(4) Skyrmions and Activation Energy Anomaly in Bilayer Quantum Hall SystemsNov 18 2003Jun 11 2004The bilayer QH system has four energy levels in the lowest Landau level, corresponding to the layer and spin degrees of freedom. We investigate the system in the regime where all four levels are nearly degenerate and equally active. The underlying group ... More
Interlayer Exchange Interactions, SU(4) Soft Waves and Skyrmions in Bilayer Quantum Hall FerromagnetsApr 24 2001Aug 06 2001The Coulomb exchange interaction is the driving force for quantum coherence in quantum Hall systems. We construct a microscopic Landau-site Hamiltonian for the exchange interaction in bilayer quantum Hall ferromagnets, which is characterized by the SU(4) ... More
Grassmannian Fields and Doubly Enhanced Skyrmions in Bilayer Quantum Hall system at $ν=2$Oct 03 2001Nov 12 2002At the filling factor $\nu=2$ the bilayer quantum Hall system has three phases, the ferromagnetic phase (spin phase), the spin singlet phase (ppin phase) and the canted antiferromagnetic phase. We analyze soft waves and quasiparticle excitations in the ... More
Selective Heating Mechanism of Magnetic Metal Oxides by Alternating Magnetic Field in Microwave Sintering ProcessJun 18 2008Feb 13 2009The mechanism of rapid and selective heating of magnetic metal oxides under the magnetic field of microwaves which continues beyond the Curie temperature $ T_{c} $ is identified by using the Heisenberg model. Monte Carlo calculations based on the energy ... More
Microwave heating and collapse of methane hydrate by molecular dynamics simulationsSep 03 2019Microwave heating of methane hydrate is investigated with electrostatic molecular dynamics simulations. The structure I of methane hydrate is constructed. When the methane hydrate with a density of 0.91 $\rm{g/cm}^3$ and temperature of 273 K is exposed ... More
Microwave heating and collapse of methane hydrate by molecular dynamics simulationsSep 03 2019Sep 05 2019Microwave heating of methane hydrate is investigated with electrostatic molecular dynamics simulations. The structure I of methane hydrate is constructed. When the methane hydrate with a density of 0.91 $\rm{g/cm}^3$ and temperature of 273 K is exposed ... More
Operator Ordering Ambiguity and Third QuantizationJun 30 2019In this paper, we will constrain the operator ordering ambiguity of Wheeler-DeWitt equation by analyzing the quantum fluctuations in the universe. This will be done using a third quantized formalism. It is expected that the early stages of the universe ... More
A decade of skyrmionics: Writing, deleting, reading and processing magnetic skyrmions toward spintronic applicationsJun 11 2019Jun 12 2019The field of skyrmionics has been actively investigated across a wide range of topics during the last decade. In this topical review, we review and discuss key results and findings in skyrmionics since the first experimental observation of magnetic skyrmions ... More
$^6$Li Production by the Radiative Decay of Long-Lived ParticlesMay 10 2006May 31 2006Recent spectroscopic observations of metal poor stars have indicated that both $^7$Li and $^6$Li have abundance plateaus with respect to the metallicity. Abundances of $^7$Li are about a factor three lower than the primordial abundance predicted by standard ... More
Production of the p-Process Nuclei in the Carbon-Deflagration Model for Type Ia SupernovaeDec 31 2009Nov 17 2010We calculate nucleosynthesis of proton-rich isotopes in the carbon-deflagration model for Type Ia supernovae (SNe Ia). The seed abundances are obtained by calculating the s-process nucleosynthesis that is expected to occur in the repeating helium shell ... More