Space Dependent Magnetic Field Research Articles

Soliton molecules and their scattering by a localized P T-symmetric potential in atomic gases.

We propose a physical scheme to study the formation of optical soliton molecules (SMs), consisting of two solitons bound together with a π-phase difference, and the scattering of SMs by a localized parity-time (P T)-symmetric potential. In order to stabilize SMs, we apply an additional space-dependent magnetic field to introduce a harmonic trapping potential for the two solitons and balance the repulse interaction induced by the π-phase difference between them. On the other hand, a localized complex optical potential obeying P T symmetry can be created through an incoherent pumping and spatial modulation of the control laser field. We investigate the scattering of optical SMs by the localized P T-symmetric potential, which exhibits evident asymmetric behavior and can be actively controlled by changing the incident velocity of SMs. Moreover, the P T symmetry of the localized potential, together with the interaction between two solitons of the SM, can also have a significant effect on the SM scattering behavior. The results presented here may be useful for understanding the unique properties of SMs and have potential applications in optical information processing and transmission.

Analytical energy eigenvalues of a Dirac particle in focusing field of a quadrupole magnet

In this study, the motion of a charged spin-1/2 fermion is found out. It is assumed, in the system, that the free fermion is subjected to a linearly space-dependent magnetic field that can be supposed to be a focusing magnetic field of a quadrupole magnet in beam dynamics in the accelerator physics. In such an examination, two-component Dirac equation is solved via perturbation approximation of the asymptotic iteration method (AIM), which has been widely used for the last decades. The results show that the fermion is bounded to the magnetic field for a certain condition of the strength of the field. For such a system, the analytical form of the energy eigenvalues are obtained. Moreover, to see whether this analytical expression works properly, the numerical eigenvalues are compared with the ones obtained by direct use of the AIM. We have an inspiration that the studies on beam dynamics and magnet design in particle accelerator physics may gain from this work.

Joule and Viscous Dissipation Effects on MHD Boundary Layer Flow over a Stretching Sheet with Variable Thickness

This paper is aimed to investigate the influence of Joule and viscous dissipation effects on boundary layer flow over a stretching sheet with variable thickness and surface temperature. The flow is subjected to space dependent magnetic field applied normal to the sheet. Mathematical modeling is done under boundary layer approximations. The governing partial differential equations are transformed into ordinary differential equations via appropriate similarity transformations. The resulting set of nonlinear equations is solved numerically. The impact of various physical parameters on velocity and temperature profiles is analyzed. Also, their effects on skin friction coefficient and Nusselt number are presented and discussed.

Multifunctional aqueous ferrofluid stabilized by cellulose nanofibrils with long term stability

Due to the excellent flowability and shape adaptability, ferrofluids (or magnetic fluids, MF), offer potential in food and pharma, intelligent materials, fluid seals and devices, such as, robots, and remote controllers. Here, we stabilized a ferrofluid after coprecipitation of metal nanoparticles onto cellulose nanofibrils in aqueous suspension, obtaining a colloidal system with a magnetization value of 3.55 emu/mL. The MF was stable at pH > 7 and showed contactless magnetic direct driving or indirect guiding. Several use demonstrations were tested, for instance, as a flexible plug to separate, stir/mix or seal hydrophobic liquids. In addition, the MF exhibited gradients of relative density under the space-dependent magnetic field, which endowed sorting of plastic particles, according to their density. Our findings provide guidance for the design of multifunctional cellulose-stabilized aqueous MFs.

Chiral magnetic response to arbitrary axial imbalance

The response of chiral fermions to time and space dependent axial imbalance & constant magnetic field is analyzed. The axialvector-vector-vector (AVV) three-point function is studied using a real-time approach at finite temperature in the weak external field approximation. The chiral magnetic conductivity is given analytically for noninteracting fermions. It is pointed out that local charge conservation plays an important role when the axial imbalance is inhomogeneous. Proper regularization is needed which makes the constant axial imbalance limit delicate: for static but spatially oscillating chiral charge the current of the chiral magnetic effect (CME) vanishes. In the homogeneous (but possible time-dependent) limit of the axial imbalance the CME current is determined solely by the chiral anomaly. As a phenomenological consequence, the observability of the charge asymmetry caused by the CME turns out to be a matter of interplay between various scales of the system. Possible plasma instabilities resulting from the gradient corrections to the CME current are also pointed out.

Lorentz forces induce inhomogeneity and flux in active systems

We consider the nonequilibrium dynamics of a charged active Brownian particle in the presence of a space dependent magnetic field. It has recently been shown that the Lorentz force induces a particle flux perpendicular to density gradients, thus preventing a diffusive description of the dynamics. Whereas a passive system will eventually relax to an equilibrium state, unaffected by the magnetic field, an active system subject to a spatially varying Lorentz force settles into a nonequilibrium steady state characterized by an inhomogeneous density and divergence-free bulk fluxes. A macroscopic flux of charged active particles is induced by the gradient of the magnetic field only and does not require additional symmetric breaking such as density or potential gradients. This stands in marked contrast to similar phenomena in condensed matter such as the classical Hall effect. In a confined geometry we observe circulating fluxes, which can be reversed by inverting the direction of the magnetic field. Our theoretical approach, based on coarse-graining of the Fokker-Planck equation, yields analytical results for the density, fluxes, and polarization in the steady state, all of which are validated by direct computer simulation. We demonstrate that passive tracer particles can be used to measure the essential effects of the Lorentz force on the active particle bath, and we discuss under which conditions the effects of the flux could be observed experimentally.

Electron acoustic waves in atmospheric magnetized plasma

Propagation of electron acoustic solitary waves is studied in magnetized plasmas consisting of hot and cold electrons and stationary ions in the presence of varying magnetic field. We show that a space dependent magnetic field adds a dissipative term in the wave equation of motion without presenting known dissipation sources. Localized waves propagating in such space dependent magnetic field are governed by the modified KdV-Burgers equation. The numerical results show that, this phenomenon leads to the formation of oscillatory backward moving shock waves in the plasma. Characters of shock profile, according to the plasma parameters are discussed.

An analysis of hydrodynamic ferrofluid lubrication of an inclined rough slider bearing

The present study aims at analysing the effects of surface roughness, porosity and magnetic field on an inclined slider bearing. The slider bearings mainly are designed for supporting transverse load in an engineering system and enjoy a priority due to its physical wedge pressure generating mechanism. The ferrofluid is being used as lubricant which becomes strongly magnetised in the presence of external magnetic field in a plane inclined rough slider bearing with slip velocity. The earlier studies were related to ferrofluid lubrication based on Shliomis model and it was concluded that the adverse effect of surface roughness was reduced due to magnetisation under the influence of proactive slip parameter. In the present study a space dependent magnetic field of the form has been considered rather than sinusoidal type H2 = KL2 sin (πX). The analysis brings out some interesting results due to change in pattern of magnetic field strength. The pattern of variation of magnetic field considered in the present study contributes to an increase in pressure and load capacity by and load by our conventional lubricant i.e. as that of magnetised lubricant. One interesting finding reported here is that, the adverse effect of slip parameter, reported in earlier studies over load carrying capacity turns rather sinusoidal to be favourable which may be due to the pattern of variation of magnetic field considered in the present study.

Note on effect of joule heating and MHD in the presence of convective boundary condition for upper-convected Maxwell fluid through wall jet

Abstract In this communication some inconsistencies associated with the derivation of the governing flow equation and choice of space dependent applied magnetic field are pointed out in a recent study by Zaidi and Mohyud-Din [1]. The detail derivation of the Lorentz force term appearing in the governing flow equation is presented. Furthermore, it is explicitly shown that Maxwell's equations are violated for the considered space dependent magnetic field. Therefore, all subsequent analysis needs corrections.

Fermionic Particle Production by Varying Electric and Magnetic Fields**Supported by the Research Fund of Mersin University in TURKEY with project number: 2016-1-AP4-1425

Creation of fermionic particles by a time-dependent electric field and a space-dependent magnetic field is studied with the Bogoulibov transformation method. Exact analytic solutions of the Dirac equation are obtained in terms of the Whittaker functions and the particle creation number density depending on the electric and magnetic fields is determined.

Topological Hall Effect of Spin-2 Condensate in a Time and Space-Dependent Magnetic Field

We simulate the dynamics of spin-2 87 R b condensate in a time and space-dependent magnetic field with a time-dependent variational approach. The topological Hall effect is observed, which has been realized in the experiment of spin-1 23 N a condensate [Phys. Rev. Lett. 111, 245301 (2013)]. A driving-induced resonance behavior is observed.

Geometric Hall Effect of $$^{23}$$ 23 Na Condensate in a Time- and Space-Dependent Magnetic Field

We simulate numerically the dynamics of \(^{23}\)Na condensate in a time- and space-dependent magnetic field with a variational approach. It is shown to be an efficient method to describe the complex dynamics of the system, which may excite the breather mode, the scissor mode, and the dipole mode simultaneously. Our results agree with the experimental observations of Choi et al. (Phys Rev Lett 111:245301, 2013). We reproduce qualitatively the geometric Hall effect and resonance behavior. We also find that the condensate shows a scissor-mode-like motion, which may play the shearing force to deform the condensate and consequently leads to the dynamical nucleation of quantized vortices.

Effect of space dependent magnetic field on free convection of Fe3O4–water nanofluid

Effect of spatially variable magnetic field on ferrofluid flow and heat transfer is investigated. The enclosure is filled with Fe3O4–water nanofluid. Control volume based finite element method (CVFEM) is applied to solve the governing equations. The combined effects of ferrohydrodynamic and magnetohydrodynamic have been taken into account. The influences of Magnetic number, Hartmann number, Rayleigh number and nanoparticle volume fraction on the flow and heat transfer characteristics have been examined. Results show that enhancement in heat transfer decrease with increase of Rayleigh number while for two other active parameters different behavior is observed. Also it can be concluded that Nusselt number is an increasing function of Magnetic number, Rayleigh number and nanoparticle volume fraction while it is a decreasing function of Hartmann number.

Phase Transitions in Ferromagnetic Ising Models with Spatially Dependent Magnetic Fields

In this paper we study the nearest neighbor Ising model with ferromagnetic interactions in the presence of a space dependent magnetic field that vanishes as $${|x|^{-\alpha}}$$ , $${\alpha > 0}$$ , as $${|x|\to \infty}$$ . We prove that in dimensions $${d\geq 2}$$ for all β large enough, if $${\alpha > 1}$$ there is a phase transition, while if $${\alpha < 1}$$ there is a unique DLR state.

Geometric phases generated by the non-trivial spatial topology of static vector fields linearly coupled to a neutral spin-endowed particle: application to 171Yb atoms trapped in a 2D optical lattice

We have constructed the geometric phases emerging from the non-trivial topology of a space-dependent magnetic field B(r), interacting with the spin magnetic moment of a neutral particle. Our basic tool, adapted from a previous work on Berry’s phases, is the space-dependent unitary transformation , which leads to the identity, , at each point r. In the ‘rotated’ Hamiltonian , is replaced by the non-Abelian covariant derivative where can be written as A1(r)Sx + A2(r)Sy + A3(r)Sz. The Abelian differentials Ak(r)·dr are given in terms of the Euler angles defining the orientation of B(r). The non-Abelian field transforms as a Yang–Mills field; however, its vanishing ‘curvature’ reveals its purely geometric character. We have defined a perturbation scheme based upon the assumption that in the longitudinal field A3(r) dominates the transverse field A1, 2(r) contributions, evaluated to second order. The geometry embedded in both the vector field A3(r) and the geometric magnetic field is described by their associated Aharonov–Bohm phase. As an illustration we study the physics of cold 171Yb atoms dressed by overlaying two circularly polarized stationary waves with orthogonal directions, which form a 2D square optical lattice. The frequency is tuned midway between the two hyperfine levels of the (6s6p)3P1 states to protect the optical B(r) field generated by the lattice from the dressed atom instability. The geometric field B3(r) is computed analytically in terms of the Euler angles. The magnitude of the second-order corrections due to the transverse fields can be reduced to the per cent level by a choice of light intensity that keeps the dressed atom loss rate ⩽5 s−1. A second optical lattice can be designed to confine the atoms inside 2D domains where . We extend our analysis to the case of a triangular lattice.

The Nambu-Jona-Lasinio model in simple configurations of strong and non-homogeneous magnetic fields

We provide a compact approximation for the electron propagator in a strong magnetic field of the form B x = B y =0, B z = B z ( y). The method developed in this work can be used to discuss some non-perturbative aspects of QED. As a simple application we consider the Nambu-Jona-Lasinio model minimally coupled to an external space-dependent magnetic field. As in the uniform case, the associated gap equation admits non-trivial solutions corresponding to a massive phase.

Cyclotron radiation from a rarefied inhomogeneous magnetoplasma

A comprehensive discussion of effects due to cyclotron radiation (volume power loss and supplementary electron heat conduction) in a rarefied plasma in a space-dependent magnetic field is given. Furthermore, the possibility of using cyclotron radiation as a diagnostic tool is investigated.

A Cyclotron-Wave Rectifier for S-Band and X-Band*

AbstractA device for converting microwave power into either DC power or low-frequency AC power has been investigated both theoretically and experimentally. Rotational energy is stored in an electron beam by a Cuccia coupler, then converted to longitudinal energy by interaction with a space-dependent DC magnetic field, and finally recovered as electric energy by a depressed collector.A simple kinematic analysis demonstrates that the Cuccia coupler can convert large amounts of microwave power into electron beam rotation. Limits on the electric field strength and asynchronism between signal frequency and cyclotron frequency are established for both classical and relativistic coupler operation.Efficiency analyses of the process of conversion from orbital energy to DC electric energy, both classical and relativistic indicate that the efficiency exceeds 95 percent for a particular range of operating conditions. As an AC power supply, the device responds to the modulating frequency of the signal. Theory predicts...

Microscopic Approach to Interfacial Structure in Ising-like Ferromagnets

The properties of an Ising-like ferromagnetic model are investigated in the presence of a space-dependent magnetic field which favors phase separation. The treatment is limited to very low temperatures where molecular-field theory seems to be applicable. The magnetization profile in the interface region is calculated, as well as the interface free energy, within an harmonic approximation to magnetization density modes in our model. The instability of the interface in the limit of vanishing external field, which was recently pointed out for fluid systems, is recovered and discussed in detail.