Triadic Closure in Configuration Models with Unbounded Degree Fluctuations

The configuration model generates random graphs with any given degree distribution, and thus serves as a null model for scale-free networks with power-law degrees and unbounded degree fluctuations. For this setting, we study the local clustering c(k), i.e., the probability that two neighbors of a degree-k node are neighbors themselves. We show that c(k) progressively falls off with k and the graph size n and eventually for \(k=\varOmega (\sqrt{n})\) settles on a power law \(c(k)\sim n^{5-2\tau }k^{-2(3-\tau )}\) with \(\tau \in (2,3)\) the power-law exponent of the degree distribution. This fall-off has been observed in the majority of real-world networks and signals the presence of modular or hierarchical structure. Our results agree with recent results for the hidden-variable model and also give the expected number of triangles in the configuration model when counting triangles only once despite the presence of multi-edges. We show that only triangles consisting of triplets with uniquely specified degrees contribute to the triangle counting.     

Incommensurate Magnetic Fluctuations in the Underdoped Copper Oxide Materials

The doping dependence of magnetic fluctuations in the underdoped copper oxide materials are studied within the t-J model. It is shown that away from the half-filling, the magnetic Bragg peaks from the dynamical spin structure factor spectrum S(k,ω) are incommensurate with the lattice. Although the incommensurability δ(x) is almost energy-independent, the dynamical spin susceptibility χ^'(k,ω) at the incommensurate wave vectors is changed dramatically with energies, which is consistent with the experiments.     

Magnetic Susceptibility and Spin Fluctuations in the Nonsuperconducting Phase of PuCoGa5

Physics of the Solid State - Within the Hubbard model with allowance for Hund’s and spin–orbit interactions, the concepts of thermal spin fluctuations in a strongly correlated system of...     

Magnetic Field in a Screw Flow with Fluctuations

We consider the influence of fluctuations in a screw flow of a conducting liquid on the effect of magnetic field self-excitation; the solution of this problem is important for experimental realization of a turbulent dynamo. We propose a theoretical approach based on the solution of averaged equations obtained in the limit of a short correlation time. The applicability of this approach is confirmed by direct numerical simulation of the initial equations. We demonstrate the influence of the correlation of fluctuations on the dynamo effect threshold. It is shown that the solution of the mean-field equations differs from the solution based on direct numerical simulation for a finite correlation time. The advantages and disadvantages of the two approaches are estimates, as well as the importance of the discovered difference in the context of problems of magnetic field self-excitation. The influence of helicity and intermittency on the type of the solution is considered.     

Theory for the Exciton Magnetic Polaron in Diluted Magnetic Semiconductors with Thermodynamic Fluctuations of Magnetization

The photoinduced self-trapped exciton magnetic polaron (ST-EMP) in diluted magnetic semiconductors has been the subject of intensive investigations related to the observed photoluminescence during the last two decades. The stability, however, seems still controversial. In this article we study the stability of ST-EMP theoretically, including thermodynamic fluctuations of magnetization. The calculation suggests that the EMP in CdTe(Mn) (Mn: 10-20%) is not self-trapped except at low temperatures below ¨ 1 K, but the other primary localization mechanisms, for example, alloy potential fluctuations, are necessary to the localization of EMP above ¨ 1 K.     

Perturbations of the Motion of a Charged Particle in a Noisy Magnetic Field

We consider deterministic and stochastic perturbations of the motion of a charged particle in a noisy magnetic field. The noise in the magnetic field leads to the mixing on the energy surfaces and allows to apply averaging principle. We describe long-time energy evolution and its metastable states for a given initial energy and a time scale.     

Calculation of Magnetic Configuration and Resistance for Nanomagnets

Based on a classical Heisenberg lattice model with dipole interaction and the method of spin dynamic simulation,the magnetic configurations (MC),hysteresis loop (HL) and magnetic resistance (MR) of the nanomagnets with different geometries,such as circle,square and rectangle,are studied for different directions of applied field.In the case of perpendicular field to the plane,the magnetization and MR are reversible and have not hysteresis.When the field is applied in the plane,the HL is irreversible and is qualitatively well agreeable with the current experimental results.The MR loop is also irreversible and appears two peaks distributed at two sides around zero field.The peaks of magnetic resistance are relative to the vortex state of similar configuration.Large easy-axis anisotropy will suppress the MC anisotropy,and the large magnetoresistance effect disappears.     

Stable Configuration of Electric Arcs in Transverse Magnetic Fields

Deviations from rotational symmetry of arc columns exposed to transverse magnetic fields cause convection and a momentum transport between the column and its surrounding gas. As a consequence, the arc moves and changes its geometry until it reaches a stable configuration. Based on the momentum transport equation, the arc behavior is discussed under various operating conditions, and stable arc configurations are determined. In particular, the stability-criteria of a balanced arc column in a transverse gas flow and magnetic field is derived. It turns out that the arc becomes unstable with respect to kinks parallel to the applied magnetic field when ? = p?/(B2/8?)?1. (p? = ambient pressure, Bo = applied magnetic field).     

Motion of Coupled Magnetic Vortices in Parallel Nanostripes

Physics of the Solid State - The periodic motion of the interacting vortex domain walls in a pair of nanostripes has been theoretically investigated. As a model, two parallel nanostripes with...     

Suppression of Edge Localized Modes in High-Confinement KSTAR Plasmas by Nonaxisymmetric Magnetic Perturbations

Edge localized modes (ELMs) in high-confinement mode plasmas were completely suppressed in KSTAR by applying n=1 nonaxisymmetric magnetic perturbations. Initially, the ELMs were intensified with a reduction of frequency, but completely suppressed later. The electron density had an initial 10% decrease followed by a gradual increase as ELMs were suppressed. Interesting phenomena such as a saturated evolution of edge T_{e} and broadband changes of magnetic fluctuations were observed, suggesting the change of edge transport by the applied magnetic perturbations.     

Electron Dynamics of Atoms in Parallel Electric and Magnetic Fields

Through an analysis of the nearest neighbor level fields, we investigate the evolution of the electron spacing statistics for atoms in parallel electric and magnetic dynamics as electric field strength increases. In the ＇inter-l mixing＇ predominant region, the electron shows complex dynamics while in the ＇inter-n mixing＇ predominant region, its dynamics behaves in a relatively stable way and the characteristic quantity ξ shows a slight oscillation. Comparing the dynamics for hydrogen and barium, we find that the core effect makes the main contribution to the chaotic behavior in non-hydrogen atoms.     

Characteristics of Level Anticrossing in Parallel Electric and Magnetic Fields

Using the matrix diagonalization method, we have studied two kinds of level anticrosing of Rydberg cesium atom in parallel electric and magnetic fields. Our numerical results reveal that in the vicinity position of level crossing between different parity states in a magnetic field, the energy levels and other behaviors of the states are quite sensitive to the electric field. We tabulate some features which may be as a guide in experimental verification.     

Optimization of Magnetic Confinement for Quasi-Snowflake Divertor Configuration

JETP Letters - To realize the commercialized operation, it is preferable that tokamak devices achieve the operating scenarios with steady-state, long-pulse, H-mode and high magnetic confinement...     

Interface Polaron Within Parallel Electric and Magnetic Fields

A combinative method of variational wavefunction and harmonic oscillator operator algebra is used to treat the interface polaron in a semi-infinite polar crystal within parallel electric and magnetic fields perpendicular to the interface. Both the bulk longitudinal optical phonon and the interface optical phonon together with the anisotropic mass of the electron are included. The energy level correction up to the second-order perturbation, cyclotron-resonance frequency and cyclotron mass are expressed as functions of the electric and magnetic fields and a parameter characterizing the mean distance of the polaron from the interface. This theory is used to calculate numerically the single heterostructure AlAs/GaAs, when the electron is at the X high-symmetry point of the conduction band of AlAs. The results show that the magnetic field greatly enhances the polaronic correction of the electron energy levels while the electric field only increases the correction of their surface optical phonon part but obviously decreases that of their bulk optical mode part and thus the total energy correction decreases as the electric field increases. The change of red shift due to the electron-phonon interaction with electric and magnetic fields is also obf ained.     

Optimizing the Configuration of the Magnetic Deflection System of an Electron Spectrometer

The results of examination of the magnetic field produced in an electron spectrometer with permanent magnets are presented. The potential to optimize the configuration of the deflection system of this spectrometer using low-coercivity screens is demonstrated. These screens balance out the edge effects at the analyzer input and make the field in the gap more uniform.     

On the Averaged Forces in Bounded Plasma in Parallel Electric and Magnetic Fields

Averaged forces of Miller's type, acting on the particles of a bounded plasma in parallel external a. c. electric and d. c. magnetic fields, are found on the basis of the equations of the two-component MHD. It is assumed, that standing transverse waves are excited in the plasma by the external source before the a. c. electric field is switched on.     

Structure of Magnetic Plasma Fluctuations in the Uragan-3M Torsatron at Rare Collision Frequencies

Technical Physics - Fluctuations of the poloidal component of the plasma magnetic field in the frequency range of 0.5–50 kHz are studied in the Uragan-3M (U-3M) torsatron. Hydrogen plasma is...     

平行共轴双线圈的空间磁场研究

通过计算机及相关的传感器和数据采集接口辅助,获得了平行共轴双线圈的空间磁场分布,并从数值模拟和实验测量两个角度进行了对比研究,在一定程度上弥补了传统亥姆霍兹线圈磁场测量的不足并有助于对其深入的理解和研究.