Strong Uniform Magnetic Field Research Articles

Entanglement between chiral and deconfinement transitions under strong uniform magnetic background field

Effects of a uniform (electro-) magnetic background field are investigated in the two-flavor nonlocal Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model. Temperature-dependences of the chiral order-parameter and the Polyakov-loop are investigated under the magnetic field. In the nonlocal PNJL model with four-dimensional momentum dependent distribution function, pseudo-critical temperatures of the chiral and deconfinement transitions are coincident each other even if the magnetic field is strong. It means that we can check the reliability of the distribution function under the strong magnetic field by comparing with lattice QCD data, particularly from the viewpoint of the entanglement between the chiral and deconfinement transitions.

Oscillations of weakly viscous conducting liquid drops in a strong magnetic field

We analyse small-amplitude oscillations of a weakly viscous electrically conducting liquid drop in a strong uniform DC magnetic field. An asymptotic solution is obtained showing that the magnetic field does not affect the shape eigenmodes, which remain the spherical harmonics as in the non-magnetic case. A strong magnetic field, however, constrains the liquid flow associated with the oscillations and, thus, reduces the oscillation frequencies by increasing effective inertia of the liquid. In such a field, liquid oscillates in a two-dimensional (2D) way as solid columns aligned with the field. Two types of oscillations are possible: longitudinal and transversal to the field. Such oscillations are weakly damped by a strong magnetic field – the stronger the field, the weaker the damping, except for the axisymmetric transversal and inherently 2D modes. The former are overdamped because of being incompatible with the incompressibility constraint, whereas the latter are not affected at all because of being naturally invariant along the field. Since the magnetic damping for all other modes decreases inversely with the square of the field strength, viscous damping may become important in a sufficiently strong magnetic field. The viscous damping is found analytically by a simple energy dissipation approach which is shown for the longitudinal modes to be equivalent to a much more complicated eigenvalue perturbation technique. This study provides a theoretical basis for the development of new measurement methods of surface tension, viscosity and the electrical conductivity of liquid metals using the oscillating drop technique in a strong superimposed DC magnetic field.

An Effective Mass Theorem for the Bidimensional Electron Gas in a Strong Magnetic Field

We study the limiting behavior of a singularly perturbed Schrödinger-Poisson system describing a 3-dimensional electron gas strongly confined in the vicinity of a plane (x, y) and subject to a strong uniform magnetic field in the plane of the gas. The coupled effects of the confinement and of the magnetic field induce fast oscillations in time that need to be averaged out. We obtain at the limit a system of 2-dimensional Schrödinger equations in the plane (x, y), coupled through an effective selfconsistent electrical potential. In the direction perpendicular to the magnetic field, the electron mass is modified by the field, as the result of an averaging of the cyclotron motion. The main tools of the analysis are the adaptation of the second order long-time averaging theory of ODEs to our PDEs context, and the use of a Sobolev scale adapted to the confinement operator.

Effect of electron–phonon interaction on the energy spectrum of a quantum antidot in the presence of a uniform strong magnetic field

Abstract We have studied the effect of electron–phonon interaction for small electron–phonon coupling on the electronic energy spectrum of an electron confined by a parabolic potential and a repulsive antidot potential in the presence of a uniform strong magnetic field and an Aharonov–Bohm flux field by using a variational procedure. We have shown that the presence of the antidot potential removes degeneracy of the Landau levels and electron–phonon interaction has nonnegligible effects on these levels.

High Q calcium titanate cylindrical dielectric resonators for magnetic resonance microimaging

At high magnetic fields radiation losses, wavelength effects, self-resonance, and the high resistance of typical components all contribute to increased losses in conventional RF coil designs. High permittivity ceramic dielectric resonators create strong uniform magnetic fields in a compact structure at high frequencies and can potentially solve some of the challenges of high field coil design. In this study an NMR probe was constructed for operation at 600 MHz (14.1 T) using an inductively fed CaTiO 3 (relative permittivity of 156) cylindrical hollow bore dielectric resonator. The design has an unmatched Q value greater than 2000, and the electric field is largely confined to the dielectric itself, with near zero values in the hollow bore which accommodates the sample. Experimental and simulation mapping of the RF field show good agreement, with the ceramic resonator giving a pulse width approximately 25% less than a loop gap resonator of similar inner dimensions. High resolution images, with voxel dimensions less than 50 μm 3, have been acquired from fixed zebrafish samples, showing excellent delineation of several fine structures.

Numerical modelling of rotating tangential layers (jets) in shells under strong uniform magnetic field

AbstractA numerical study of tangential layers in steady‐state magnetohydrodynamic rotating flows is presented using CFD to solve the inductionless governing equations. The analysis considers two basic flow configurations. In the first, a fluid is enclosed in a cylinder with electrically perfect conducting walls and the flow is driven by a small rotating, conducting disk. In the second, a flow is considered in a spherical shell with an inner rotating sphere. The fluid in both cases is subjected to an external axial uniform magnetic field. The results show that these flows exhibit two different types of flow cores separated from each other by a tangential layer parallel to the axis of rotation. The inner core follows a solid‐body rotation while the outer is quasistagnant. A counter‐rotating jet is developed in the tangential layer between the cores. The characteristics of the tangential layer and the properties of the meridional motion are determined for a wide range of Hartmann numbers. Distributions of angular velocity of circumferential flow and electric potential are obtained and the results are compared with those of analytic methods. Copyright © 2009 John Wiley & Sons, Ltd.

High-resolution calorimetric study of the nematic to smectic-Atransition in aligned liquid crystal–aerosil gels

High-resolution ac calorimetry has been used to study the nematic to smectic- A (N-SmA) phase transition in the liquid crystal octylcyanobiphenyl (8CB) confined in aligned colloidal aerosil gels. A stable and robust nematic alignment was achieved by repeated thermal cycling of the samples in the presence of a strong uniform magnetic field. In some ways (such as transition temperature and integrated enthalpy), the dependence of the specific heat peak associated with the N-SmA transition on the aerosil density for aligned gels is consistent with that observed in unaligned (random) gel samples. However, a power-law analysis reveals that the behavior of the critical exponent alpha is quite different. For random gels, alpha varies gradually with aerosil density, whereas we find that alpha for aligned gels shifts abruptly to an XY -like value for the lowest aerosil density studied and remains essentially constant as the sil density increases. This aerosil density independence of alpha is consistent with the critical behavior of the smectic correlation lengths obtained from an x-ray scattering study of 8CB in aligned aerosil gels. The combined calorimetric and x-ray results indicate that the role of quenched randomness in aligned gels of 8CB+sils differs significantly from that in random gels.

Low-profile transducer

One embodiment of a low-profile transducer includes a at least one fin perpendicularly mounted on a planar diaphragm, with a voice coil mounted onto the fin. The voice coil may reside in a strong uniform magnetic field. The locations at which the diaphragm is connected to a frame may be coplanar with a center of mass of the diaphragm. The three-dimensional structure of diaphragm and fins may be formed using origami techniques.

Frame Dragging Effect on Properties of Rotating Neutron Stars with Strong Magnetic Field

The general relativistic frame dragging effect on the properties, such as the moments of inertia and the radii of gyration of fast rotating neutron stars with a uniform strong magnetic field, is calculated accurate to the first order in the uniform angular velocity. The results show that compared with the corresponding non-rotating static spherical symmetric neutron star with a weaker magnetic field, a fast rotating neutron star (millisecond pulsar) with a stronger magnetic field has a relative smaller moment of inertia and radius of gyration.

Efficient positronium laser excitation for antihydrogen production in a magnetic field

Antihydrogen production by charge exchange reaction between positronium (Ps) atoms and antiprotons requires an efficient excitation of Ps atoms up to high-$n$ levels (Rydberg levels). In this study it is assumed that a Ps cloud is produced within a relatively strong uniform magnetic field $(1\phantom{\rule{0.3em}{0ex}}\mathrm{T})$ and with a relatively high temperature $(100\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. Consequently, the structure of energy levels are deeply modified by Zeeman and motional Stark effects. A two-step laser light excitation, the first one from ground to $n=3$ and the second from this level to a Rydberg level, is proposed and the physics of the problem is discussed. We derive a simple formula giving the absorption probability with substantially incoherent laser pulses. A 30% population deposition in high-$n$ states can be reached with feasible lasers suitably tailored in power and spectral bandwidth.

The Gravitational Waves from Test Particles around Black Holes Immersed in a Strong Magnetic Field

In this paper, we calculate the gravitational waveform from free test particles around Schwarzschild black holes immersed in a uniform strong magnetic field. By comparing with the cases of the Schwarzschild black holes, we find that for stable circle orbits, magnetic field can amplify amplitude and frequency of gravitational waves (here after GWs). For other general orbits, the uniform magnetic field also can amplify amplitude of GWs, enhance energy radiation of GWs and make it to shift to higher frequency. Another obvious influence of magnetic field B is that it can change the form of h× component of GWs.

Polarization of spin-1 particles in a uniform magnetic field

The exact solution of the Corben–Schwinger equations is obtained for spin-1 particles without an anomalous magnetic moment in a uniform magnetic field. The exact Hamiltonian in the Foldy–Wouthuysen representation is derived. The conservation of projections of the polarization operator onto four directions is proved. The approximate conservation of projections of this operator onto the horizontal axes of the cylindrical coordinate system is established. For spin-1 particles with the anomalous magnetic moment, the Hamiltonian in the Foldy–Wouthuysen representation is deduced within first order terms in the Planck constant. Dynamics of spin-1 particles with the anomalous magnetic moment and their spins in the strong uniform magnetic field are calculated.

Backward Compton scattering and QED with noncommutative plane in the strong uniform magnetic field**Supported by National Natural Science Foundation of China (90403021), PhD Program Funds of the Education Ministry of China, Pujiang Talent Project of the Shanghai Science and Technology Committee (06PJ14114), and Hundred Talents Project of Shanghai Institute of Applied Physics

In the strong uniform magnetic field, the noncommutative plane (NCP) caused by the lowest Landau level (LLL) effect, and QED with NCP (QED-NCP) are studied. Being similar to the condensed matter theory of quantum Hall effect, an effective filling factor f(B) is introduced to characterize the possibility that the electrons stay on the LLL. The analytic and numerical results of the differential cross section for the process of backward Compton scattering in accelerator with unpolarized or polarized initial photons are calculated. The existing data of BL38B2 in Spring-8 have been analyzed roughly and compared with the numerical predictions primitively. We propose a precise measurement of the differential cross sections of backward Compton scattering in a strong perpendicular magnetic field, which may reveal the effects of NCP.

The effect of combined viscous dissipation and Joule heating on unsteady mixed convection MHD flow on a rotating cone in a rotating fluid with variable properties in the presence of Hall and ion-slip currents

This paper is concerned with the effect of combined viscous dissipation and Joule heating on unsteady mixed convention magnetohydrodynamics (MHD) flow on a rotating cone in an electrically conducting rotating fluid in the presence of Hall and ion-slip currents. The fluid properties (density, (ρ), viscosity, (μ) and thermal conductivity, (κ)) are taken to be dependent on temperature and a strong uniform magnetic field is applied in the z-direction. It has been shown that a self-similar solution is possible when the free stream angular velocity and the angular velocity of the cone vary inversely as a linear functions of time. The unsteady Navier–Stokes equations along with the energy equation are reduced to a system of ordinary differential equations by using similarity transformations and the resulting equation system is solved numerically by using a shooting method. Results for the details of the velocity as well as temperature are shown graphically and the numerical values of the skin friction and the rate of heat transfer are entered in tables.

Optimum wall conductance ratio in magnetoconvective flow in a long vertical rectangular duct

The entropy generation minimization method is applied to the optimization of a buoyancy-driven laminar magnetohydrodynamic flow in a long vertical rectangular duct with thin conducting or insulating walls. The flow takes place under a strong uniform magnetic field applied transversally to one pair of walls and is driven by a known constant temperature gradient aligned with the field. Numerical solutions for the velocity and electric current density in both fluid and walls are calculated using a spectral collocation method. It is shown that an optimum value of the wall conductance ratio (i.e. the ratio of the electrical conductance of the wall to that of the fluid) that minimizes the global entropy generation rate can be found. The analysis of the irreversibilities caused by heat conduction, viscosity and Joule dissipation allows to explain the existence of the optimum value.

Small-scale anisotropy in magnetohydrodynamic turbulence under a strong uniform magnetic field

Small-scale statistics in magnetohydrodynamic turbulence under an externally applied strong stationary uniform magnetic field is studied theoretically and numerically. A simple expression for the velocity correlation spectrum is derived by applying the idea of the perturbation method by Ishihara et al. [Phys. Rev. Lett. 88 154501 (2002)]. It gives not only the scale dependence but also the angular dependence of the anisotropic velocity correlation spectrum at small scales. It is in good agreement with direct numerical simulation with 5123 grid points.

MHD waves within noncommutative Maxwell theory

In the presence of a strong uniform magnetic field, we study the influence of space noncommutativity on the electromagnetic waves propagating through a quasi-static homogeneous plasma. In this treatment, we have adopted a physical model which considers plasma as quasi-neutral single fluid. By using noncommutative Maxwell theory, the ideal magnetohydrodynamics (MHD) equations are established, in which new equilibrium conditions are extracted. As an empirical study, some attractive features of MHD waves behavior are investigated. Furthermore, it is shown that the presence of space noncommutativity enhances slightly the phase velocity of the incompressive shear Alfvén waves. In a compressible plasma, the noncommutativity plays the role of an additional compression on the medium, in which its relevant effect on the fast mode occurs for highly oblique branches, while the low effect appears when the propagations are nearly parallel or anti-parallel. In addition, it turned out that the influence of space deformation on the slow modes is ∼103 times smaller than that on the fast modes. The space noncommutativity effect on the slow waves is negligible in low plasma β value, and could appear when β is higher than 0.1, thus the extreme modification occurs for oblique slow waves propagating with angles between 30° and 60°. Finally, we comment on the possible effect of such waves on CMB spectrum in photon–baryon plasma.

Structure of Rotating Neutron Stars in Uniform Strong MagneticField

Properties and deformations ofthe rotating neutron stars in uniform strong magnetic field arecalculated. The magnetic field will soften the equation of stateof the neutron star matters and make an obvious effect on thestructure of the rotating neutron star. If the magnetic field issuperstrong (B = 1017 T), the mass, radius, andthe deformation will become smaller effectively.

Properties of Neutron Stars Rotating at Kepler Frequency withUniform Strong Magnetic Field

A uniform strong magnetic field is considered in calculating theproperties of neutron star rotating at the Kepler frequency. Theresults show that the effect of the magnetic field on the properties ofneutron star is evident, and the properties of the neutron starsrotating at the Kepler frequency can be used as a criterion to theequations of states of the neutron star matters.

Non-Relativistic H2+-Molecule in a Strong Magnetic Field

We show that under the influence of a strong uniform magnetic field the energy of the H2+-ion at the 0-th order Born-Oppenheimer approximation goes over into that of the corresponding united atom limit, He+.