Fractionalization of angular momentum at finite temperature around a magnetic vortex

Ambiguities in the definition of angular momentum of a quantum-mechanical particle in the presence of a magnetic vortex are reviewed. We show that the long-standing problem of the adequate definition is resolved in the framework of the second-quantized theory at nonzero temperature. Planar relativistic Fermi gas in the background of a point-like magnetic vortex with arbitrary flux is considered, and we find thermal averages, quadratic fluctuations, and correlations of all observables, including angular momentum, in this system. The kinetic definition of angular momentum is picked out unambiguously by the requirement of plausible behaviour for the angular momentum fluctuation and its correlation with fermion number.     

Total angular momentum and atomic magnetic moments

A new calculation of the magnetic moment of an atom is suggested on the basis of the hypothesis that the total angular momentum of one electron is the same in a complex atom situated in a solid as in a hydrogen-like atom described in Dirac's theory. The latter is first revisited and the quantum states thus defined are compared with those of Schrödinger's theory. Then, the experimental basis of the notion of spin is recalled and compared to the subshell division of the p, d and f shells in Dirac's theory.Using this division in subshells a calculation of the magnetic moment is applied to the heavy rare earth metals, iron, cobalt, nickel and the chromium compounds and compared with experimental data. This leads us to a discussion of the Pauli exclusion principle and to the choice of a convenient electronic configuration of each magnetic element. Finally these configurations are compared to the theoretical magnetic moments.     

Dissipation of spin angular momentum in magnetic switching

Applying one ultrashort magnetic field pulse, we observe up to 10 precessional switches of the magnetization direction in single crystalline Fe films of 10 and 15 atomic layers. We find that the rate at which angular momentum is dissipated in uniform large angle spin precession increases with time and film thickness, surpassing the intrinsic ferromagnetic resonance spin lattice relaxation of Fe by nearly an order of magnitude.     

Quenching of magnetic transitions as an angular momentum effect

We investigate how the mechanisms of nuclear excitations and mesonic currents traditionally invoked to explain the quenching of low multipole magnetic transitions apply to higher spin operators. We find that there is a significant quenching of the low multipolarity spin-isospin operators by Δ-hole polarization, but that this effect decreases for higher multipoles. Conversely, the nucleon-hole polarization which has a negligible effect on low multipoles plays a predominant role in explaining the quenching of higher multipoles. Meson exchange currents provide a significant enhancement of the orbital operators but have only a slight effect on the spin components.     

Acoustic beams with angular momentum

A family of exact solutions of the Helmholtz equation is used to represent transversely bounded helicoidal sound beams. Simple results are obtained for the energy content per unit length, the momentum content per unit length, and the angular momentum content per unit length. The analysis is restricted to lossless media; scattering and viscous damping are neglected. The energy, momentum, and angular momentum are calculated to second order in the velocity potential. The angular momentum content is always equal to m/omega times the energy content, where m (an integer) is the topological charge and omega is the angular frequency.     

Curvature-stabilized skyrmions with angular momentum

Letters in Mathematical Physics - We examine skyrmionic field configurations on a spherical ferromagnet with large normal anisotropy. Exploiting variational concepts of angular momentum, we find a...     

Colour-generated angular momentum with merons

We find a new instance of interaction-dependent angular momentum: a system comprising a nonsingular meron-meron (or meron-antimeron) pair together with a weak colour-nonsinglet source in an exactly colour-symmetric classical minkowskian chromodynamics. Various implications are pointed out.     

On a RPA method with angular momentum projection

In view of projecting the angular momentum eigenstates out of the intrinsic RPA states, we first study linear relations between deformed and spherical phonons. By use of these relations, the deformed RPA Hamiltonian can be expressed in terms of the spherical phonons in the form of a displaced harmonic oscillator. The angular momentum projection can be applied to an intrinsic RPA state determined by the reduced Hamiltonian, and the correspondence with the macroscopic deformed phonon model of Lipaset al. can be done at this stage. Two important parameters, the constant term in the linear relations and the strength of the spherical phonon Hamiltonian, are evaluated and compared with the best-fit values obtained by Lipaset al.     

Extraordinary photons with unusual angular momentum

A series of novel state-vector functions (SVFs), which is the general solution of the Schrödinger equation for a photon, are constructed. Each set of these functions consists of a triplet of eigen-SVFs: The triplet can be broken down into a pair of nonzero l-order functions and a single zero-order function. The photons, described with a triplet of eigen-SVFs, possess all the quantum characteristics of a photon: In addition to common attributes like energy E = ? _ω , and momentum p _z = ? _κ , they also exhibit different angular momenta (AM) L _z+ = l?, L _z? = l?, and L _z0 = 0, where l?1. In other words, in addition to usual eigenvalues L _z±= ±?, there are unusual nonzero l-order eigenvalues L _z± = ±l? and a zero-order eigenvalue L _z0 = 0 for AM of a photon. By a series of SVFs, the pattern from nonzero l-order and zero-order Laguerre-Gaussian modes of a laser beam is explained well from a quantum mechanical point of view.     

Coulomb Green's function with a fixed orbital angular momentum

A real integral representation is found for the Coulomb Green's function in the momentum representation for a negative energy E and for a fixed orbital angular momentuml. The first energy pole (n = 1) is separated and subtracted forl = 0.Translated from Izvestiya VUZ. Fizika, No. 3, pp. 46–49, March, 1970.     

Critical collapse of a complex scalar field with angular momentum

We report a new critical solution found at the threshold of axisymmetric gravitational collapse of a complex scalar field with angular momentum. To carry angular momentum the scalar field cannot be axisymmetric; however, its azimuthal dependence is defined so that the resulting stress-energy tensor and spacetime metric are axisymmetric. The critical solution found is nonspherical, discretely self-similar with an echoing exponent Delta=0.42(+/-4%), and exhibits a scaling exponent gamma=0.11(+/-10%) in near-critical collapse. Our simulations suggest that the solution is universal (within the imposed symmetry class), modulo a family-dependent constant, complex phase.     

Spin angular momentum of a field interacting with a plane interface

The quantization of the spin angular momentum S of a field interacting with a plane boundary is investigated. When a good set of modes is chosen, the component of S along the momentum P is formally the same as that for a free field. In the case of the presence of an evanescent wave the good modes are the same ones that appear in the filtering of the polarisation states by total reflection. But terms due to the discontinuity appear in the expressions. Although they are clearly related to the interaction field-interface, their interpretation is not obvious.     

Diluted magnetic semiconductor at finite temperature

We studied the diluted magnetic semiconductor by the self-consistent Green's function approach, which treats the spin-wave kinematics appropriately at finite temperatures. Our approach leads to a simple formula for the critical temperature in a wide range of parameter space. In addition, the magnetization curve versus temperature in some regimes is concave, which is dramatically different from the usual convex shape. Finally, we discuss the possibility of generalizing the current theory to include the realistic band structure, electronic correlations and disorders in a systematic way.     

Unitary transformations with spin angular momentum operators

Useful formulae for replacing an exponentiated spin scalar product by a finite sum of powers of this product, are presented in the context of Coulomb interactions between magnetic ions and conduction electrons in metals.     

Is energy increasing with angular momentum?

We submit to the community of physicists and mathematical physicists the following problem: prove that the ground-state energy of a system ofN particles without spin, without statistics, and interacting by central forces increases with angular momentum. For two particles, this is obvious. For more than two we give a number of arguments which support our conjecture.     

具有轨道角动量光束入射下的单球粒子散射研究

根据广义Mie理论,研究了具有轨道角动量拉盖尔-高斯光束（LGB）的空间传输特性以及单粒子散射特性.在单体球粒子对高斯光束散射研究的基础上,分析了在自由空间不同传输距离LGB光束的光强分布情况,在不考虑散射和波束相移关系的情况下,将LGB作为入射高斯光束,通过对波束入射时的散射衰减截面求解得到波束因子,利用矢量球谐函数对入射高斯波束进行展开,从而研究了单球粒子在在轴条件下对具轨道角动量高斯波束入射的散射问题.通过数值计算,讨论了散射强度及角分布在不同波束宽度情况下对其散射特性的影响,并与平面波的情况做了对比.结果表明,当波束束腰半径较小时,束腰半径对衰减率的影响较大,而当束腰半径远大于粒子半径时,接近于平面波的情况. 关键词： 广义Mie理论 轨道角动量 Laguerre-Gauss光束 单球粒子     

Fraunhofer diffraction of light with orbital angular momentum by a slit

We study the Fraunhofer diffraction problem while taking into account the orbital angular momentum of light. In this case, the phase singularity of the light beam is incident on the slit in two different cases: in one, it is incident slightly above the slit, and in the other it is centered on the slit. We observed that the symmetry and the fringe formation in the interference pattern strongly depend on the amount of orbital angular momentum and the slit position in relation to the beam.     

角动量问题浅析

大学物理教学中,一些基本概念的讲授不仅对于物理概念本身的深化十分重要,而且对于现代物理学思想的把握和对后续课程的学习也具有十分重要的作用.通过讨论角动量及其在宇称变换下的性质,我们介绍了轴矢量的概念,并在量子力学层次对宇称变换进行了分析,将量子力学层次的态函数和场算符进行了分类,同时说明了在基本粒子物理研究当中对复合粒子进行分类时一个重要的量子数——宇称.     

Some properties of an electromagnetic field with a large angular momentum

An electromagnetic field with a spatial structure such that it has a large angular momentum while its intensity is moderate, typical for linear optics, is shown to exist. Features of the electrodynamics of such a field are discussed. The problem is not purely theoretical, since its formulation preceded any definite experimental facts. Institute of Atmospheric Optics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 93–103, October, 1996.