Intrinsic Magnetic Dipole Moment Research Articles

Nuclear DFT electromagnetic moments in heavy deformed open-shell odd nuclei

Within the nuclear DFT approach, we determined the magnetic dipole and electric quadrupole moments for paired nuclear states corresponding to the proton (neutron) quasiparticles blocked in the π11/2− (ν13/2+) intruder configurations. We performed calculations for all deformed open-shell odd nuclei with 63≤Z≤82 and 82≤N≤126. Time-reversal symmetry was broken in the intrinsic reference frame and self-consistent shape and spin core polarizations were established. We determined spectroscopic moments of angular-momentum-projected wave functions and compared them with available experimental data. We obtained good agreement with data without using effective g-factors or effective charges in the dipole or quadrupole operators, respectively. We also showed that the intrinsic magnetic dipole moments, or those obtained for conserved intrinsic time-reversal symmetry, do not represent viable approximations of the spectroscopic ones.

Smith–Purcell radiation of a vortex electron

A wide variety of emission processes by electron wave packets with an orbital angular momentum ℓℏ, called the vortex electrons, can be influenced by a nonparaxial contribution due to their intrinsic electric quadrupole moment. We study Smith–Purcell radiation from a conducting grating generated by a vortex electron, described as a generalized Laguerre–Gaussian packet, which has an intrinsic magnetic dipole moment and an electric quadrupole moment. By using a multipole expansion of the electromagnetic field of such an electron, we employ a generalized surface-current method, applicable for a wide range of parameters. The radiated energy contains contributions from the charge, from the magnetic moment, and from the electric quadrupole moment, as well as from their interference. The quadrupole contribution grows as the packet spreads while propagating, and it is enhanced for large ℓ. In contrast to the linear growth of the radiation intensity from the charge with a number of strips N, the quadrupole contribution reveals an N 3 dependence, which puts a limit on the maximal grating length for which the radiation losses stay small. We study spectral-angular distributions of the Smith–Purcell radiation both analytically and numerically and demonstrate that the electron’s vorticity can give rise to detectable effects for non-relativistic and moderately relativistic electrons. On a practical side, preparing the incoming electron’s state in a form of a non-Gaussian packet with a quadrupole moment—such as the vortex electron, an Airy beam, a Schrödinger cat state, and so on—one can achieve quantum enhancement of the radiation power compared to the classical linear regime. Such an enhancement would be a hallmark of a previously unexplored quantum regime of radiation, in which non-Gaussianity of the packet influences the radiation properties much stronger than the quantum recoil.

Steady states of non-axial dipolar rods driven by rotating fields.

We investigate a two-dimensional system of magnetic colloids with anisotropic geometry (rods) subjected to an oscillating external magnetic field. The structural and dynamical properties of the steady states are analyzed, by means of Langevin dynamics simulations, as a function of the misalignment of the intrinsic magnetic dipole moment of the rods with respect to their axial direction, and also in terms of the strength and rotation frequency of an external magnetic field. The misalignment of the dipole relative to their axial direction is inspired by recent studies, and this is extremely relevant in the microscopic aggregation states of the system. The dynamical response of the magnetic rods to the external magnetic field is strongly affected by such a misalignment. Concerning the synchronization between the magnetic rods and the direction of the external magnetic field, we define three distinct regimes of synchronization. A set of steady states diagrams are presented, showing the magnitude and rotation frequency intervals in which the distinct self-organized structures are observed.

Quantum Hall Effect with Composites of Magnetic Flux Tubes and Charged Particles

Composites formed from charged particles and magnetic flux tubes, proposed by Wilczek, are one model for anyons-particles obeying fractional statistics. Here we propose a scheme for realizing charged flux tubes, in which a charged object with an intrinsic magnetic dipole moment is placed between two semi-infinite blocks of a high-permeability (μ_{r}) material, and the images of the magnetic moment create an effective flux tube. We show that the scheme can lead to a realization of Wilczek's anyons, when a two-dimensional electron system, which exhibits the integer quantum Hall effect, is sandwiched between two blocks of the high-μ_{r} material with a temporally fast response (in the cyclotron and Larmor frequency range). The signature of Wilczek's anyons is a slight shift of the resistivity at the plateau of the IQHE. Thus, the quest for high-μ_{r} materials at high frequencies, which is underway in the field of metamaterials, and the quest for anyons, are here found to be on the same avenue.

Constraining the intrinsic structure of top-quarks

The basic structure of top-quarks as spin-1/2 particles is characterized by the radius Rt and the intrinsic magnetic dipole moment κt, both individually associated with gauge interactions. They are predicted to be zero in pointlike theories as the Standard Model. We derive upper limits of these parameters in the color sector from cross sections measured at Tevatron and LHC in top pair production pp¯/pp→tt¯, and we predict improved limits expected from LHC in the future, especially for analyses exploiting boosted top final states. An additional method for measuring the intrinsic parameters is based on tt¯+jet final states.

Null Geodesic Congruences, Asymptotically-Flat Spacetimes and Their Physical Interpretation.

A priori, there is nothing very special about shear-free or asymptotically shear-free null geodesic congruences. Surprisingly, however, they turn out to possess a large number of fascinating geometric properties and to be closely related, in the context of general relativity, to a variety of physically significant effects. It is the purpose of this paper to try to fully develop these issues.This work starts with a detailed exposition of the theory of shear-free and asymptotically shear-free null geodesic congruences, i.e., congruences with shear that vanishes at future conformal null infinity. A major portion of the exposition lies in the analysis of the space of regular shear-free and asymptotically shear-free null geodesic congruences. This analysis leads to the space of complex analytic curves in an auxiliary four-complex dimensional space, {mathcal H}-space. They in turn play a dominant role in the applications.The applications center around the problem of extracting interior physical properties of an asymptotically-flat spacetime directly from the asymptotic gravitational (and Maxwell) field itself, in analogy with the determination of total charge by an integral over the Maxwell field at infinity or the identification of the interior mass (and its loss) by (Bondi’s) integrals of the Weyl tensor, also at infinity.More specifically, we will see that the asymptotically shear-free congruences lead us to an asymptotic definition of the center-of-mass and its equations of motion. This includes a kinematic meaning, in terms of the center-of-mass motion, for the Bondi three-momentum. In addition, we obtain insights into intrinsic spin and, in general, angular momentum, including an angular-momentum-conservation law with well-defined flux terms. When a Maxwell field is present, the asymptotically shear-free congruences allow us to determine/define at infinity a center-of-charge world line and intrinsic magnetic dipole moment.

MAGNETOSPHERES OF “HOT JUPITERS”: THE IMPORTANCE OF MAGNETODISKS IN SHAPING A MAGNETOSPHERIC OBSTACLE

Weak intrinsic magnetic dipole moments of tidally locked close-in giant exoplanets ( hot Jupiters ) have been shown in previous studies to be unable to provide an efficient magnetospheric protection for their expanding upper atmospheres against the stellar plasma flow, which should lead to significant non-thermal atmosphere mass loss. The present work provides a more complete view of the magnetosphere structure of hot Jupiters, based on a paraboloid magnetospheric model (PMM). Besides the intrinsic planetary magnetic dipole, the PMM considers among the main magnetic field sources also the electric current system of the magnetotail, magnetopause currents, and the ring current of a magnetodisk. Due to the outflow of ionized particles from the hydrodynamically expanding upper atmosphere, hot Jupiters may have extended magnetodisks. The magnetic field produced by magnetodisk ring currents dominates above the contribution of an intrinsic magnetic dipole of a hot Jupiter and finally determines the size and shape of the whole magnetosphere. A slower-than-the-dipole-type decrease of the magnetic field with the distance forms the essential specifics of magnetodisk-dominated magnetospheres of hot Jupiters. This results in their 40%–70% larger scales compared to those traditionally estimated by only the planetary dipole taken into account. Therefore, the formation of magnetodisks has to be included in the studies of the stellar wind plasma interaction with close-in exoplanets, as well as magnetospheric protection for planetary atmospheres against non-thermal escape due to erosion by the stellar plasma flow. Key words: planets and satellites: magnetic fields – planets and satellites: physical evolution – planets and satellites: rings – planet–star interactions

Null Geodesic Congruences, Asymptotically-Flat Spacetimes and Their Physical Interpretation

A priori, there is nothing very special about shear-free or asymptotically shear-free null geodesic congruences. Surprisingly, however, they turn out to possess a large number of fascinating geometric properties and to be closely related, in the context of general relativity, to a variety of physically significant effects. It is the purpose of this paper to try to fully develop these issues.This work starts with a detailed exposition of the theory of shear-free and asymptotically shear-free null geodesic congruences, i.e., congruences with shear that vanishes at future conformal null infinity. A major portion of the exposition lies in the analysis of the space of regular shear-free and asymptotically shear-free null geodesic congruences. This analysis leads to the space of complex analytic curves in an auxiliary four-complex dimensional space, {mathcal H}-space. They in turn play a dominant role in the applications.The applications center around the problem of extracting interior physical properties of an asymptotically-flat spacetime directly from the asymptotic gravitational (and Maxwell) field itself, in analogy with the determination of total charge by an integral over the Maxwell field at infinity or the identification of the interior mass (and its loss) by (Bondi’s) integrals of the Weyl tensor, also at infinity.More specifically, we will see that the asymptotically shear-free congruences lead us to an asymptotic definition of the center-of-mass and its equations of motion. This includes a kinematic meaning, in terms of the center-of-mass motion, for the Bondi three-momentum. In addition, we obtain insights into intrinsic spin and, in general, angular momentum, including an angular-momentum-conservation law with well-defined flux terms. When a Maxwell field is present, the asymptotically shear-free congruences allow us to determine/define at infinity a center-of-charge world line and intrinsic magnetic dipole moment.

Twisting null geodesic congruences and the Einstein–Maxwell equations

In a recent article, we returned to the study of asymptotically flat solutions of the vacuum Einstein equations with a rather unconventional point of view. The essential observation in that work was that from a given asymptotically flat vacuum spacetime with a given Bondi shear, one can find a class of asymptotically shear-free (but, in general, twisting) null geodesic congruences where the class was uniquely given up to the arbitrary choice of a complex analytic ‘worldline’ in a four-dimensional complex space. By imitating certain terms in the Weyl tensor that are found in the algebraically special type II metrics, this complex worldline could be made unique and given—or assigned—the physical meaning as the complex centre of mass. Equations of motion for this case were found. The purpose of the present work is to extend those results to asymptotically flat solutions of the Einstein–Maxwell equations. Once again, in this case, we get a class of asymptotically shear-free null geodesic congruences depending on a complex worldline in the same four-dimensional complex space. However in this case there will be, in general, two distinct but uniquely chosen worldlines, one of which can be assigned as the complex centre of charge while the other could be called the complex centre of mass. Rather than investigating the situation where there are two distinct complex worldlines, we study instead the special degenerate case where the two worldlines coincide, i.e., where there is a single unique worldline. This mimics the case of algebraically special Einstein–Maxwell fields where the degenerate principle null vector of the Weyl tensor coincides with a Maxwell principle null vector. Again we obtain equations of motion for this worldline—but explicitly found here only in an approximation. Though there are ambiguities in assigning physical meaning to different terms it appears as if reliance on the Kerr and charged Kerr metrics and classical electromagnetic radiation theory helps considerably in this identification. In addition, the resulting equations of motion appear to have many of the properties of a particle with intrinsic spin and an intrinsic magnetic dipole moment. At first order there is even the classical radiation-reaction term , now obtained without any use of the Lorentz force law but obtained directly from the asymptotic fields themselves. One even sees the possible suppression of the classical run-away solutions due to the radiation-reaction force.

Electromagnetic dipole radiation fields, shear-free congruences and complex centre of charge world lines

We show that for asymptotically vanishing Maxwell fields in Minkowski space with non-vanishing total charge, one can find a unique geometric structure, a null direction field, at null infinity. From this structure a unique complex analytic world line in complex Minkowski space can be found and then identified as the complex centre of charge. By ‘sitting’—in an imaginary sense—on this world line both the electric and intrinsic magnetic dipole moments vanish. The intrinsic magnetic dipole moment is (in some sense) obtained from the ‘distance’ the complex world line is from the real space (times the charge). This point of view unifies the asymptotic treatment of the dipole moments. For electromagnetic fields with vanishing magnetic dipole moments the world line is real and defines the real (ordinary centre of charge). We illustrate these ideas with the Lienard–Wiechert Maxwell field. In the conclusion we discuss its generalization to general relativity where the complex centre of charge world line has its analogue in a complex centre of mass allowing a definition of the spin and orbital angular momentum—the analogues of the magnetic and electric dipole moments.

Classical electrodynamics of a point particle from action integral

A new approach to the classical electrodynamics of a point particle (with arbitrary finite number of electromagnetic moments) is presented. It is argued that the notion of a non-singular pointlike current, previously introduced by the author, appropriately describes an electromagnetic point particle. This current is then used in the most standard action integral of an electromagnetic field in interaction with matter to yield a non-singular theory. In the simplest cases this theory yields the Lorentz–Dirac equation of motion of a point charge, or its generalization together with the spin equation of motion for a point charge with an intrinsic magnetic dipole moment. No approximations are involved. From the general theory the conservation of the energy-momentum and of the angular momentum follows.

Stationary transverse dipolar magnetostatic distributions for a nonlocal radiation field and energy functional for such model

In previous papers (1), a generalization was expounded of the basic aspects of a QED model suitable for describing magnetic-charge distributions carried by a spinor Gordon current. A modified minimal-coupling interaction and an anomalous contribut ion to the intrinsic magnetic-dipole moment were found, with application to the CA quark model. The purpose of this note is to explain how the integro-differential equations that resolve themselves to the usual Maxwell set

Limits on the possible intrinsic magnetic field of Venus

Magnetic field measurements obtained by the Pioneer Venus orbiter at low altitudes in the solar wind wake region are examined to search for possible surface‐correlated features and any possible intrinsic magnetic moment. The observed field variations in the wake do not resemble our expectations for a solar wind interaction with even a weak intrinsic magnetic field. There is little orbit‐to‐orbit persistence of features in the magnetic records. The magnetic field measurements in the wake have been averaged in 10° × 10° bins to minimize the effects of external field sources. The average fields in these 37 bins appear to be randomly oriented and consistent with zero mean in the region mapped. Using these 37 averaged vector fields, we obtain a maximum intrinsic magnetic dipole moment of 4.3±2.0 × 1021 G cm³, approximately an order of magnitude less than previous estimates. A more conservative estimate of the probable error of the mean is 5.5 × 1021 G cm³. Thus the Pioneer Venus measurements are consistent with zero planetary moment. The present measurements are also far below estimates based on angular momentum, the so‐called ‘magnetic Bode's law’ and far below the dynamo scaling law of Busse.

Interaction of molecules with electromagnetic fields. I. Classical particles and fields

Classical models of electrons and nuclei are developed which behave surprisingly like their quantum mechanical counterparts. The particles are finite in size and have both electrical charge density and current density. Classical spin results from the angular momentum of the particles rotating about their ’’center of mass’’. Internal electromagnetic fields are produced by the motion of the charged particles. These internal fields have dynamical properties of their own and produce the interaction between the particles. In this paper, the internal fields are derived through the second order of retardation or terms in 1/c2. Since higher order terms in the internal fields are not included, no difficulties are encountered with respect to the classical particles radiating. This same result could also be obtained by using equal parts of the retarded and advanced potentials. The Lagrangian, the (canonical, mechanical, and angular) momenta, the energy, and the Hamiltonian are derived in a gauge invariant manner for a ’’molecular system’’ of particles in the presence of an arbitrary (time and space varying) external electromagnetic field. The classical Hamiltonian corresponds term-by-term with the comparable quantum mechanical Breit–Pauli Hamiltonian. The correspondence includes the spin–orbit interaction terms, the Darwin terms (usually attributed to zitterbewegung), and the nuclear quadrupole terms (usually omitted from molecular Hamiltonians). A detailed comparison of classical and quantum mechanical dynamical properties will be given in a subsequent paper. Delta functions occur in both the classical and the quantum mechanical Hamiltonians to approximate the effect of overlapping when particles come close together. Otherwise, overlapping is generally not considered in either the classical or quantum treatments. In deriving the kinetic energy of a particle rotating about its center of mass, there was discovered a new relation which the rate of change of intrinsic spin (in the laboratory reference frame) must satisfy in order that the Lagrangian should completely describe the motion of the particle. This led to the discovery of a condition of compatibility between the dynamical properties of classical and quantum mechanical systems. This condition then led to a novel derivation of the relationship between the explicit expressions for the multipole moments of a particle in its laboratory reference frame (the observed moments) and the multipole moments in the particle’s rest frame (the intrinsic moments). It is assumed that an electron has only an intrinsic magnetic dipole moment whereas a nucleus has both an intrinsic magnetic dipole moment and an intrinsic electric quadrupole moment. The condition of compatibility also led to the derivation of canonical equations of change and generalized Poisson brackets, in both of which the spins are included as basic dynamical variables. The generalized Poisson brackets of the positions, the canonical momenta, and the spins exhibit the same forms as the commutation relations of their quantum mechanical counterparts. The (time and space varying) functions of the fields are expanded in Taylor series which have many of the features of Cartesian tensorial representations. If these functions were expanded in terms of spherical harmonics, the formulation would have been much more complicated.

The magnetic moment of Venus: Venera‐4 measurements reinterpreted

Re‐examination of the Venera‐4 magnetic field measurements at Venus encounter suggests that Venus may have an intrinsic magnetic dipole moment of about 6.5×1022 Gauss‐cm³ which corresponds to a surface field of 30 gammas (1γ=10−9 Tesla).

Observed absence of energetic electrons and protons near Venus

Abstract : The report discusses the following points: (a) The environment of Venus is almost, if not completely, devoid of energetic particles associated with the planet, as is the environment of Mars and that of the moon. (b) On the basis of physical similitude with observational and theoretical knowledge of the earth's magnetosphere, we conclude that the intrinsic magnetic dipole moment of Venus is certainly less than 0.01 and probably less than 0.001 of that of the earth. Corresponding upper limits on the equatorial surface magnetic field of Venus are about 350 and 35 x 10 to the -5th power gauss, respectively. (c) The magneto-fluid dynamical interaction of the solar wind with the conducting ionosphere and/or the body of Venus is too weak to generate an observable intensity of electrons having energies exceeding 45 keV.

Venus: An Upper Limit on Intrinsic Magnetic Dipole Moment Based on Absence of a Radiation Belt

On the basis of the absence of energetic electrons (E(e) 45 kiloelectron volts) and protons (E(p) 320 kiloelectron volts) associated with Venus to within a radial distance of 10,150 kilometers from the center of the planet and using a physical similitude argument and the observational and theoretical knowledge of the magnetosphere of Earth, we conclude that the intrinsic magnetic dipole moment of Venus is almost certainly less than 0.01 and probably less than 0.001 of that of Earth. Corresponding upper limits on the magnetic field at the equatorial surface of Venus are about 350 and 35 x 10(-5) gauss, respectively.