Quark Orbital Angular Momentum
Burkardt Matthias
2015-01-01
Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asy...
Partonic orbital angular momentum
Arash, Firooz; Taghavi-Shahri, Fatemeh; Shahveh, Abolfazl
2013-04-01
Ji's decomposition of nucleon spin is used and the orbital angular momentum of quarks and gluon are calculated. We have utilized the so called valon model description of the nucleon in the next to leading order. It is found that the average orbital angular momentum of quarks is positive, but small, whereas that of gluon is negative and large. Individual quark flavor contributions are also calculated. Some regularities on the total angular momentum of the quarks and gluon are observed.
Asymptotic Spectrum of Kerr Black Holes in the Small Angular Momentum Limit
Daghigh, Ramin G; Mulligan, Brian W
2010-01-01
We study analytically the highly damped quasinormal modes of Kerr black holes in the small angular momentum limit. To check the previous analytic calculations in the literature, which use a combination of radial and tortoise coordinates, we reproduce all the results using the radial coordinate only. According to the earlier calculations, the real part of the highly damped quasinormal mode frequency of Kerr black holes approaches zero in the limit where the angular momentum goes to zero. This result is not consistent with the Schwarzschild limit where the real part of the highly damped quasinormal mode frequency is equal to c^3 ln(3)/(8 pi G M). In this paper, our calculations suggest that the highly damped quasinormal modes of Kerr black holes in the zero angular momentum limit make a continuous transition from the Kerr value to the Schwarzschild value. We explore the nature of this transition using a combination of analytical and numerical techniques. Finally, we calculate the highly damped quasinormal modes...
Meheut, H; Lesur, G; Joos, M; Longaretti, P -Y
2015-01-01
Angular momentum transport in accretion discs is often believed to be due to magnetohydrodynamic turbulence mediated by the magnetorotational instability. Despite an abundant literature on the MRI, the parameters governing the saturation amplitude of the turbulence are poorly understood and the existence of an asymptotic behavior in the Ohmic diffusion regime is not clearly established. We investigate the properties of the turbulent state in the small magnetic Prandtl number limit. Since this is extremely computationally expensive, we also study the relevance and range of applicability of the most common subgrid scale models for this problem. Unstratified shearing boxes simulations are performed both in the compressible and incompressible limits, with a resolution up to 800 cells per disc scale height. The latter constitutes the largest resolution ever attained for a simulation of MRI turbulence. In the presence of a mean magnetic field threading the domain, angular momentum transport converges to a finite va...
Quark Orbital Angular Momentum
Directory of Open Access Journals (Sweden)
Burkardt Matthias
2015-01-01
Full Text Available Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.
International Nuclear Information System (INIS)
For many years the Institute of Physics has published books on hot topics based on a collection of reprints from different journals, including some remarks by the editors of each volume. The book on Optical Angular Momentum, edited by L Allen, S M Barnett and M J Padgett, is a recent addition to the series. It reproduces forty four papers originally published in different journals and in a few cases it provides direct access to works not easily accessible to a web navigator. The collection covers nearly a hundred years of progress in physics, starting from an historic 1909 paper by Poynting, and ending with a 2002 paper by Padgett, Barnett and coworkers on the measurement of the orbital angular momentum of a single photon. The field of optical angular momentum has expanded greatly, creating an interdisciplinary attraction for researchers operating in quantum optics, atomic physics, solid state physics, biophysics and quantum information theory. The development of laser optics, especially the control of single mode sources, has made possible the specific design of optical radiation modes with a high degree of control on the light angular momentum. The editors of this book are important figures in the field of angular momentum, having contributed to key progress in the area. L Allen published an historical paper in 1999, he and M J Padgett (together with M Babiker) produced few years ago a long review article which is today still the most complete basic introduction to the angular momentum of light, while S M Barnett has contributed several high quality papers to the progress of this area of physics. The editors' choice provides an excellent overview to all readers, with papers classified into eight different topics, covering the basic principles of the light and spin and orbital angular momentum, the laboratory tools for creating laser beams carrying orbital angular momentum, the optical forces and torques created by laser beams carrying angular momentum on
Orbital angular momentum effects
International Nuclear Information System (INIS)
This paper reports that in the context of the parton model description of baryon structure orbital angular momentum effects have long been considered negligible. However, recent results obtained within the framework of QCD and presented in this talk indicate that a substantial fraction of the baryon spin may be carried as orbital angular momentum of its constituents. These results are of particular relevance in the light of new data on the spin structure of the proton recently published by the EMC collaboration
Rotations and angular momentum
International Nuclear Information System (INIS)
This paper is devoted to the analysis of rotational invariance and the properties of angular momentum in quantum mechanics. In particular, the problem of addition of angular momenta is treated in detail, and tables of Clebsch-Gordan coefficients are included
Orbital Angular Momentum and Generalized Transverse Momentum Distribution
Zhao, Yong; Liu, Keh-Fei; Yang, Yibo
2015-01-01
We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of X. S. Chen et al. are the same as those derived from generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally, and discuss the strat...
Angular momentum projected semiclassics
Hasse, Rainer W.
1987-06-01
By using angular momentum projected plane waves as wave functions, we derive semiclassical expressions for the single-particle propagator, the partition function, the nonlocal density matrix, the single-particle density and the one particle-one hole level density for fixed angular momentum and fixed z-component or summed over the z-components. Other quantities can be deduced from the propagator. In coordinate space ( r, r') the relevant quantities depend on |r-r'| instead of | r- r'| and in Wigner space ( R, P) they become proportional to the angular momentum constraints δ(| R × P|/ h̵-l) and δ( R × P) z/ h̵-m) . As applications we calculate the single-particle and one-particle-one hole level densities for harmonic oscillator and Hill-Wheeler box potentials and the imaginary part of the optical potential and its volume integral with an underlying harmonic oscillator potential and a zero range two-body interaction.
Quark Orbital Angular Momentum
Burkardt, Matthias
2016-06-01
Generalized parton distributions provide information on the distribution of quarks in impact parameter space. For transversely polarized nucleons, these impact parameter distributions are transversely distorted and this deviation from axial symmetry leads on average to a net transverse force from the spectators on the active quark in a DIS experiment. This force when acting along the whole trajectory of the active quark leads to transverse single-spin asymmetries. For a longitudinally polarized nucleon target, the transverse force implies a torque acting on the quark orbital angular momentum (OAM). The resulting change in OAM as the quark leaves the target equals the difference between the Jaffe-Manohar and Ji OAMs.
Quark Orbital Angular Momentum
Burkardt, Matthias
2016-03-01
Generalized parton distributions provide information on the distribution of quarks in impact parameter space. For transversely polarized nucleons, these impact parameter distributions are transversely distorted and this deviation from axial symmetry leads on average to a net transverse force from the spectators on the active quark in a DIS experiment. This force when acting along the whole trajectory of the active quark leads to transverse single-spin asymmetries. For a longitudinally polarized nucleon target, the transverse force implies a torque acting on the quark orbital angular momentum (OAM). The resulting change in OAM as the quark leaves the target equals the difference between the Jaffe-Manohar and Ji OAMs.
Orbital angular momentum in phase space
International Nuclear Information System (INIS)
Research highlights: → We propose a comprehensive Weyl-Wigner formalism for the canonical pair angle-angular momentum. → We present a simple and useful toolkit for the practitioner. → We derive simple evolution equations in terms of a star product in the semiclassical limit. - Abstract: A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.
Orbital angular momentum microlaser
Miao, Pei; Zhang, Zhifeng; Sun, Jingbo; Walasik, Wiktor; Longhi, Stefano; Litchinitser, Natalia M.; Feng, Liang
2016-07-01
Structured light provides an additional degree of freedom for modern optics and practical applications. The effective generation of orbital angular momentum (OAM) lasing, especially at a micro- and nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes.
Orbital angular momentum microlaser.
Miao, Pei; Zhang, Zhifeng; Sun, Jingbo; Walasik, Wiktor; Longhi, Stefano; Litchinitser, Natalia M; Feng, Liang
2016-07-29
Structured light provides an additional degree of freedom for modern optics and practical applications. The effective generation of orbital angular momentum (OAM) lasing, especially at a micro- and nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes. PMID:27471299
Orbital angular momentum and generalized transverse momentum distribution
Zhao, Yong; Liu, Keh-Fei; Yang, Yi-Bo
2016-03-01
We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of Chen et al. are the same as those whose matrix elements correspond to the moments of generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally and discuss the strategies of calculating them in lattice QCD.
Orbital Angular Momentum and Generalized Transverse Momentum Distribution
Zhao, Yong; Yang, Yibo
2015-01-01
We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of X. S. Chen et al. are the same as those derived from generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally, and discuss the strategies of calculating them in lattice QCD.
Matter waves with angular momentum
Bracher, C; Kleber, M; Bracher, Christian; Kramer, Tobias; Kleber, Manfred
2003-01-01
An alternative description of quantum scattering processes rests on inhomogeneous terms amended to the Schr\\"odinger equation. We detail the structure of sources that give rise to multipole scattering waves of definite angular momentum, and introduce pointlike multipole sources as their limiting case. Partial wave theory is recovered for freely propagating particles. We obtain novel results for ballistic scattering in an external uniform force field, where we provide analytical solutions for both the scattering waves and the integrated particle flux. As an illustration of the theory, we predict some properties of vortex-bearing atom laser beams outcoupled from a rotating Bose--Einstein condensate under the influence of gravity.
Achromatic orbital angular momentum generator
Bouchard, Frédéric; Mand, Harjaspreet; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W
2014-01-01
We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of \\textit{two glued hollow axicons}, is used to introduce a nonuniform rotation of polarisation into a linearly polarised input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming be...
MBL Experiment in Angular Momentum
Gluck, Paul
2002-04-01
Among the series of beautiful take-home experiments designed by A.P. French and J.G. King for MIT students, the one on angular momentum studies the loss and conservation of angular momentum using a small dc motor as generator. Here we describe a version of the experiment that increases its accuracy, enables students to perform detailed rotational dynamics calculations, and sharpens the ability to isolate the region where the collision occurs.
Angular momentum in subbarrier fusion
International Nuclear Information System (INIS)
We have measured the ratio of the isomer to ground-state yields of 137Ce produced in the fusion reactions 128Te(12C,3n), 133Cs(7Li,3n), 136Ba(3He,2n), 136Ba(4He,3n), and 137Ba(3He,3n), from energies above the Coulomb barrier to energies typically 20--30% below the barrier by observing the delayed x- and γ-ray emission. We deduce the average angular momentum, , from the measured isomer ratios with a statistical model. In the first three reactions we observe that the values of exhibit the behavior predicted for low energies and the expected variation with the reduced mass of the entrance channel. We analyze these data and the associated cross sections with a barrier penetration model that includes the coupling of inelastic channels. Measurements of average angular momenta and cross sections made on other systems using the γ-multiplicity and fission-fragment angular correlation techniques are then analyzed in a similar way with this model. The discrepancies with theory for the γ-multiplicity data show correlations in cross section and angular momentum that suggest a valid model can be found. The measurements of angular momentum using the fission fragment angular correlation technique, however, do not appear reconcilable with the energy dependence of the cross sections. This systematic overview suggests, in particular, that our current understanding of the relationship of angular momentum and anisotropy in fission fragment angular correlations is incomplete. 26 refs
Neo, Richard; Goodwin, Michael; Zheng, Jessica; Lawrence, Jon; Leon-Saval, Sergio; Bland-Hawthorn, Joss; Molina-Terriza, Gabriel
2016-02-01
In recent years, there have been a series of proposals to exploit the orbital angular momentum (OAM) of light for astronomical applications. The OAM of light potentially represents a new way in which to probe the universe. The study of this property of light entails the development of new instrumentation and problems which must be addressed. One of the key issues is whether we can overcome the loss of the information carried by OAM due to atmospheric turbulence. We experimentally analyze the effect of atmospheric turbulence on the OAM content of a signal over a range of realistic turbulence strengths typical for astronomical observations. With an adaptive optics system we are able to recover up to 89% power in an initial non-zero OAM mode (ℓ = 1) at low turbulence strengths (0.30″ FWHM seeing). However, for poorer seeing conditions (1.1″ FWHM seeing), the amount of power recovered is significantly lower (5%), showing that for the terrestrial detection of astronomical OAM, a careful design of the adaptive optics system is needed. PMID:26906859
Angular momentum limit of Hf isotopes produced in three fusion-evaporation reactions
Domscheit, J; Ernst, J; Fallon, P; Herskind, B; Hübel, H; Korten, W; Lee, I Y; Macchiavelli, A O; Nenoff, N; Siem, S; Ward, D; Wilson, J N
2001-01-01
The compound nucleus sup 1 sup 6 sup 8 Hf was populated in three fusion-evaporation reactions with different beam-target mass asymmetries: sup 5 sup 0 Ti+ sup 1 sup 1 sup 8 Sn, sup 6 sup 4 Ni+ sup 1 sup 0 sup 4 Ru and sup 7 sup 4 Ge+ sup 9 sup 4 Zr. Due to the large negative Q values of these reactions the compound nucleus is formed at low excitation energy. At three or four excitation energies for each reaction gamma-ray spectra of the evaporation residues sup 1 sup 6 sup 6 Hf to sup 1 sup 6 sup 3 Hf, corresponding to the 2n to 5n exit channels, respectively, were recorded with the Ge detectors of the 8 pi-spectrometer array. The gamma-ray multiplicity and total energy were measured using the inner ball of BGO detectors. This data was used to determine the maximum angular momentum transferred to each evaporation channel, the gamma-ray decay entry region and the relative cross sections. No differences are observed between the three reactions. This is explained by the very similar dependence of the excitation ...
Orbital angular momentum is dependent on polarization
Li, Chun-Fang
2009-01-01
It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that originates from the former part is spin, and the angular momentum that originates from the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin and or...
Achromatic orbital angular momentum generator
Bouchard, Frédéric; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W
2014-01-01
We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of \\textit{two glued hollow axicons}, is used to introduce a nonuniform rotation of polarisation into a linearly polarised input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarisation, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of $95\\%$ for these three different wavelengths is observed. %, which confirms its wavelen...
Quark Orbital-Angular-Momentum Distribution in the Nucleon
Hoodbhoy, Pervez; Ji, Xiangdong; Lu, Wei
1998-01-01
We introduce gauge-invariant quark and gluon angular momentum distributions after making a generalization of the angular momentum density operators. From the quark angular momentum distribution, we define the gauge-invariant and leading-twist quark {\\it orbital} angular momentum distribution $L_q(x)$. The latter can be extracted from data on the polarized and unpolarized quark distributions and the off-forward distribution $E(x)$ in the forward limit. We comment upon the evolution equations o...
Quantum theory of angular momentum
International Nuclear Information System (INIS)
This monograph pertains to the angular momentum coupling and recoupling coefficients and their relation to generalized hypergeometric functions; their q-generalization; their polynomial zeros; their relation to orthogonal polynomials; and their numerical computation. The book builds on standard textbook material on Angular Momentum Theory and leads the reader to the recent developments in the selected topics. Fortran programs for the computation of the 3-j, 6-j and 9-j coefficients are included for use by atomic, molecular and nuclear physicists/chemists. (orig.)
Controlling neutron orbital angular momentum.
Clark, Charles W; Barankov, Roman; Huber, Michael G; Arif, Muhammad; Cory, David G; Pushin, Dmitry A
2015-09-24
The quantized orbital angular momentum (OAM) of photons offers an additional degree of freedom and topological protection from noise. Photonic OAM states have therefore been exploited in various applications ranging from studies of quantum entanglement and quantum information science to imaging. The OAM states of electron beams have been shown to be similarly useful, for example in rotating nanoparticles and determining the chirality of crystals. However, although neutrons--as massive, penetrating and neutral particles--are important in materials characterization, quantum information and studies of the foundations of quantum mechanics, OAM control of neutrons has yet to be achieved. Here, we demonstrate OAM control of neutrons using macroscopic spiral phase plates that apply a 'twist' to an input neutron beam. The twisted neutron beams are analysed with neutron interferometry. Our techniques, applied to spatially incoherent beams, demonstrate both the addition of quantum angular momenta along the direction of propagation, effected by multiple spiral phase plates, and the conservation of topological charge with respect to uniform phase fluctuations. Neutron-based studies of quantum information science, the foundations of quantum mechanics, and scattering and imaging of magnetic, superconducting and chiral materials have until now been limited to three degrees of freedom: spin, path and energy. The optimization of OAM control, leading to well defined values of OAM, would provide an additional quantized degree of freedom for such studies. PMID:26399831
Fourier relationship between angular position and optical orbital angular momentum
Yao, E.; Franke-Arnold, S.; Courtial, J.; Barnett, S.; Padgett, M. J.
2006-01-01
We demonstrate the Fourier relationship between angular position and angular momentum for a light mode. In particular we measure the distribution of orbital angular momentum states of light that has passed through an aperture and verify that the orbital angular momentum distribution is given by the complex Fourier-transform of the aperture function. We use spatial light modulators, configured as diffractive optical components, to define the initial orbital angular momentum state of the beam, ...
Inverse cascades of angular momentum
International Nuclear Information System (INIS)
Most theoretical and computational studies of turbulence in Navier-Stokes fluids and/or guiding-centre plasmas have been carried out in the presence of spatially periodic boundary conditions. In view of the frequently reproduced result that two-dimensional and/or MHD decaying turbulence leads to structures comparable in length scae to a box dimension, it is natural to ask if periodic boundary conditions are an adequate representation of any physical situation. Here, we study, computationally, the decay of two-dimensional turbulence in a Navier-Stokes fluid or guiding-centre plasma in the presence of circular no-slip rigid walls. The method is wholly spectral, and relies on a Galerkin approximation by a set of functions that obey two boundary conditions at the wall radius (analogues of the Chandrasekhar-Reid functions). It is possible to explore Reynolds numbers up to the order of 1250, based on an RMS velocity and a box radius. It is found that decaying turbulence is altered significantly by the no-slip boundaries. First, strong boundary layers serve as sources of vorticity and enstrophy and enhance the early-time energy decay rate, for a given Reynolds number, well above the periodic boundary condition values. More importantly, angular momentum turns out to be an even more slowly decaying ideal invariant than energy, and to a considerable extent governs the dynamics of the decay. Angular momentum must be taken into account, for example, in order to achieve quantitative agreement with the prediction of maximum entropy, or 'most probable', states. These are predictions of conditions that are established after several eddy turnover times but before the energy has decayed away. Angular momentum will cascade to lower azimuthal mode numbers, even if absent there initially, and the angular momentum modal spectrum is eventually dominated by the lowest mode available. When no initial angular momentum is present, no behaviour that suggests the likelihood of inverse cascades
Spin Angular Momentum Imparted by Gravitational Waves
Sharif, M.
2007-01-01
Following the demonstration that gravitational waves impart linear momentum, it is argued that if they are polarized they should impart angular momentum to appropriately placed 'test rods' in their path. A general formula for this angular momentum is obtained and used to provide expressions for the angular momentum imparted by plane and cylindrical gravitational waves.
Gupta, Manish K.; Dowling, Jonathan P.
2016-06-01
We analytically derive a decoherence model for orbital angular momentum states of a photon in a multimode optical fiber and show that the rate of decoherence scales approximately exponentially with l2, where l is the azimuthal mode order. We also show numerically that for large values of l the orbital angular momentum photon state completely dephases. However, for lower values of l the decoherence can be minimized by using dynamical decoupling to allow for qudit high-bandwidth quantum communication and similar applications.
Angular momentum in QGP holography
Directory of Open Access Journals (Sweden)
Brett McInnes
2014-10-01
Full Text Available The quark chemical potential is one of the fundamental parameters describing the quark–gluon plasma produced by sufficiently energetic heavy-ion collisions. It is not large at the extremely high temperatures probed by the LHC, but it plays a key role in discussions of the beam energy scan programmes at the RHIC and other facilities. On the other hand, collisions at such energies typically (that is, in peripheral collisions give rise to very high values of the angular momentum density. Here we explain that holographic estimates of the quark chemical potential of a rotating sample of plasma can be very considerably improved by taking the angular momentum into account.
Orbital angular momentum in phase space
Rigas, I.; Sanchez-Soto, L. L.; Klimov, A. B.; Rehacek, J.; Hradil, Z.
2010-01-01
A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.
Angular-momentum-bearing modes in fission
International Nuclear Information System (INIS)
The angular-momentum-bearing degrees of freedom involved in the fission process are identified and their influence on experimental observables is discussed. The excitation of these modes is treated in the ''thermal'' limit, and the resulting distributions of observables are calculated. Experiments demonstrating the role of these modes are presented and discussed. 61 refs., 12 figs
Achromatic orbital angular momentum generator
International Nuclear Information System (INIS)
We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of two glued hollow axicons, is used to introduce a nonuniform rotation of polarization into a linearly polarized input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam's polarization, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of 95% for these three different wavelengths is observed. This device may find applications in imaging from micro- to astronomical systems where a white vortex beam is needed. (paper)
Angular Momentum Decomposition for an Electron
Burkardt, Matthias; BC, Hikmat
2008-01-01
We calculate the orbital angular momentum of the `quark' in the scalar diquark model as well as that of the electron in QED (to order $\\alpha$). We compare the orbital angular momentum obtained from the Jaffe-Manohar decomposition to that obtained from the Ji relation and estimate the importance of the vector potential in the definition of orbital angular momentum.
Angular momentum of non-paraxial light beam: Dependence of orbital angular momentum on polarization
Li, Chun-Fang
2009-01-01
It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that is associated with the former part is spin, and the angular momentum that is associated with the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin ...
Plate tectonics conserves angular momentum
Directory of Open Access Journals (Sweden)
C. Bowin
2009-03-01
Full Text Available A new combined understanding of plate tectonics, Earth internal structure, and the role of impulse in deformation of the Earth's crust is presented. Plate accelerations and decelerations have been revealed by iterative filtering of the quaternion history for the Euler poles that define absolute plate motion history for the past 68 million years, and provide an unprecedented precision for plate angular rotation variations with time at 2-million year intervals. Stage poles represent the angular rotation of a plate's motion between adjacent Euler poles, and from which the maximum velocity vector for a plate can be determined. The consistent maximum velocity variations, in turn, yield consistent estimates of plate accelerations and decelerations. The fact that the Pacific plate was shown to accelerate and decelerate, implied that conservation of plate tectonic angular momentum must be globally conserved, and that is confirmed by the results shown here (total angular momentum ~1.4 E+27 kgm^{2}s^{−1}. Accordingly, if a plate decelerates, other plates must increase their angular momentums to compensate. In addition, the azimuth of the maximum velocity vectors yields clues as to why the "bend" in the Emperor-Hawaiian seamount trend occurred near 46 Myr. This report summarizes processing results for 12 of the 14 major tectonic plates of the Earth (except for the Juan de Fuca and Philippine plates. Plate accelerations support the contention that plate tectonics is a product of torques that most likely are sustained by the sinking of positive density anomalies due to phase changes in subducted gabbroic lithosphere at depth in the upper lower mantle (above 1200 km depth. The tectonic plates are pulled along by the sinking of these positive mass anomalies, rather than moving at near constant velocity on the crests of convection cells driven by rising heat. These results imply that spreading centers are primarily passive reactive
Phonons with orbital angular momentum
Energy Technology Data Exchange (ETDEWEB)
Ayub, M. K. [Theoretical Plasma Physics Division, PINSTECH, P. O. Nilore, Islamabad (Pakistan); National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Ali, S. [National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan); Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)
2011-10-15
Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.
Phonons with orbital angular momentum
International Nuclear Information System (INIS)
Ion accoustic waves or phonon modes are studied with orbital angular momentum (OAM) in an unmagnetized collissionless uniform plasma, whose constituents are the Boltzmann electrons and inertial ions. For this purpose, we have employed the fluid equations to obtain a paraxial equation in terms of ion density perturbations and discussed its Gaussian beam and Laguerre-Gauss (LG) beam solutions. Furthermore, an approximate solution for the electrostatic potential problem is presented, allowing to express the components of the electric field in terms of LG potential perturbations. The energy flux due to phonons is also calculated and the corresponding OAM is derived. Numerically, it is shown that the parameters such as azimuthal angle, radial and angular mode numbers, and beam waist, strongly modify the profiles of the phonon LG potential. The present results should be helpful in understanding the phonon mode excitations produced by Brillouin backscattering of laser beams in a uniform plasma.
The difficulty of measuring orbital angular momentum
Preece, D; Nieminen, T. A.; Asavei, T.; Heckenberg, N. R.; Rubinsztein-Dunlop, H.
2011-01-01
Light can carry angular momentum as well as energy and momentum; the transfer of this angular momentum to an object results in an optical torque. The development of a rotational analogue to the force measurement capability of optical tweezers is hampered by the difficulty of optical measurement of orbital angular momentum. We present an experiment with encouraging results, but emphasise the difficulty of the task.
The difficulty of measuring orbital angular momentum
Directory of Open Access Journals (Sweden)
D. Preece
2011-09-01
Full Text Available Light can carry angular momentum as well as energy and momentum; the transfer of this angular momentum to an object results in an optical torque. The development of a rotational analogue to the force measurement capability of optical tweezers is hampered by the difficulty of optical measurement of orbital angular momentum. We present an experiment with encouraging results, but emphasise the difficulty of the task.
Do waves carrying orbital angular momentum possess azimuthal linear momentum?
Speirits, Fiona C.; Barnett, Stephen M.
2013-01-01
All beams are a superposition of plane waves, which carry linear momentum in the direction of propagation with no net azimuthal component. However, plane waves incident on a hologram can produce a vortex beam carrying orbital angular momentum that seems to require an azimuthal linear momentum, which presents a paradox. We resolve this by showing that the azimuthal momentum is not a true linear momentum but the azimuthal momentum density is a true component of the linear momentum density.
Light with orbital angular momentum interacting with trapped ions
Schmiegelow, Christian Tomás; Schmidt-Kaler, Ferdinand
2011-01-01
We study the interaction of a light beams carrying angular momentum with a single, trapped and well localized ion. We provide a detailed calculation of selection rules and excitation probabilities for quadrupole transitions. The results show the dependencies on the angular momentum and polarization of the laser beam as well as the direction of the quantization magnetic field. In order to observe optimally the specific effects, focusing the angular momentum beam close to the diffraction limit ...
Quark orbital-angular-momentum distribution in the nucleon
Energy Technology Data Exchange (ETDEWEB)
Hoodbhoy, P.; Ji, X.; Lu, W. [Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)
1999-01-01
We introduce gauge-invariant quark and gluon angular momentum distributions after making a generalization of the angular momentum density operators. From the quark angular momentum distribution, we define the gauge-invariant and leading-twist quark {ital orbital} angular momentum distribution L{sub q}(x). The latter can be extracted from data on the polarized and unpolarized quark distributions and the off-forward distribution E(x) in the forward limit. We comment upon the evolution equations obeyed by this as well as other orbital distributions considered in the literature. {copyright} {ital 1998} {ital The American Physical Society}
Quantitative measurement of orbital angular momentum in electron microscopy
Clark, L; Guzzinati, G; Verbeeck, J
2014-01-01
Electron vortex beams have been predicted to enable atomic scale magnetic information measurement, via transfer of orbital angular momentum. Research so far has focussed on developing production techniques and applications of these beams. However, methods to measure the outgoing orbital angular momentum distribution are also a crucial requirement towards this goal. Here, we use a method to obtain the orbital angular momentum decomposition of an electron beam, using a multi-pinhole interferometer. We demonstrate both its ability to accurately measure orbital angular momentum distribution, and its experimental limitations when used in a transmission electron microscope.
Quark orbital-angular-momentum distribution in the nucleon
International Nuclear Information System (INIS)
We introduce gauge-invariant quark and gluon angular momentum distributions after making a generalization of the angular momentum density operators. From the quark angular momentum distribution, we define the gauge-invariant and leading-twist quark orbital angular momentum distribution Lq(x). The latter can be extracted from data on the polarized and unpolarized quark distributions and the off-forward distribution E(x) in the forward limit. We comment upon the evolution equations obeyed by this as well as other orbital distributions considered in the literature. copyright 1998 The American Physical Society
Does high harmonic generation conserve angular momentum?
Fleischer, Avner; Diskin, Tzvi; Sidorenko, Pavel; Cohen, Oren
2013-01-01
High harmonic generation (HHG) is a unique and useful process in which infrared or visible radiation is frequency up converted into the extreme ultraviolet and x ray spectral regions. As a parametric process, high harmonic generation should conserve the radiation energy, momentum and angular momentum. Indeed, conservation of energy and momentum have been demonstrated. Angular momentum of optical beams can be divided into two components: orbital and spin (polarization). Orbital angular momentum is assumed to be conserved and recently observed deviations were attributed to propagation effects. On the other hand, conservation of spin angular momentum has thus far never been studied, neither experimentally nor theoretically. Here, we present the first study on the role of spin angular momentum in extreme nonlinear optics by experimentally generating high harmonics of bi chromatic elliptically polarized pump beams that interact with isotropic media. While observing that the selection rules qualitatively correspond...
Orbital angular momentum and the parton model
Energy Technology Data Exchange (ETDEWEB)
Ratcliffe, P.G.
1987-06-25
The role of orbital angular momentum is discussed within the framework of the parton model. It is shown that a consistent interpretation of the Altarelli-Parisi equations governing the Q/sup 2/-evolution of helicity-weighted parton distributions necessitates the assumption that partons carry a large orbital angular momentum, contrary to popular belief. In developing the arguments presented, the Altarelli-Parisi formalism is extended to include orbital angular momentum dependence.
Photoionization with Orbital Angular Momentum Beams
Picón, A.; Mompart, J.; de Aldana, J. R. Vázquez; Plaja, L.; Calvo, G. F.; Roso, L.
2010-01-01
Intense laser ionization expands Einstein's photoelectric effect rules giving a wealth of phenomena widely studied over the last decades. In all cases, so far, photons were assumed to carry one unit of angular momentum. However it is now clear that photons can possess extra angular momentum, the orbital angular momentum (OAM), related to their spatial profile. We show a complete description of photoionization by OAM photons, including new selection rules involving more than one unit of angula...
Quantum formulation of fractional orbital angular momentum
Götte, Jörg B; Franke-Arnold, Sonja; Zambrini, Roberta; Barnett, Stephen M.
2007-01-01
The quantum theory of rotation angles (S. M. Barnett and D. T. Pegg, Phys. Rev. A, 41, 3427-3425 (1990)) is generalised to non-integer values of the orbital angular momentum. This requires the introduction of an additional parameter, the orientation of a phase discontinuity associated with fractional values of the orbital angular momentum. We apply our formalism to the propagation of light modes with fractional orbital angular momentum in the paraxial and non-paraxial regime.
The Angular Momentum of the Solar System
Cang, Rongquin; Guo, Jianpo; Hu, Juanxiu; He, Chaoquiong
2016-05-01
The angular momentum of the Solar System is a very important physical quantity to the formation and evolution of the Solar System. Previously, the spin angular momentum of the Sun and the orbital angular momentum of the Eight Giant Planets were only taken into consideration, when researchers calculated the angular momentum of the Solar System. Nowadays, it seems narrow and conservative. Using Eggleton's code, we calculate the rotational inertia of the Sun. Furthermore, we obtain that the spin angular momentum of the Sun is 1.8838 x 10^41 kg m^2 s^-1. Besides the spin angular momentum of the Sun and the orbital angular momentum of the Eight Giant Planets, we also account for the orbital angular momentum of the Asteroid Belt, the Kuiper Belt, the Oort Cloud, the Ninth Giant Planet and the Solar Companion. We obtain that the angular momentum of the whole Solar System is 3.3212 x 10^45 kg m^2 s^-1.
Orbital Angular Momentum in the Nucleon
Garvey, Gerald T.
2010-01-01
Analysis of the measured value of the integrated \\bar{d}-\\bar{u} asymmetry (Ifas = 0.147+-0.027) in the nucleon show it to arise from nucleon fluctuations into baryon plus pion. Requiring angular momentum conservation in these fluctuations shows the associated orbital angular momentum is equal to the value of the flavor asymmetry.
Detecting orbital angular momentum in radio signals
Then, H.; Thidé, B.; Mendonça, J T; Carozzi, T.D.; Bergman, J.; Baan, W. A.; Mohammadi, S. (Siawoosh); Eliasson, B.
2008-01-01
Electromagnetic waves with an azimuthal phase shift are known to have a well defined orbital angular momentum. Different methods that allow for the detection of the angular momentum are proposed. For some, we discuss the required experimental setup and explore the range of applicability.
The Orbital Angular Momentum Sum Rule
Aslan, Fatma; Burkardt, Matthias
2015-10-01
As an alternative to the Ji sum rule for the quark angular momentum, a sum rule for the quark orbital angular momentum, based on a twist-3 generalized parton distribution, has been suggested. We study the validity of this sum rule in the context of scalar Yukawa interactions as well as in QED for an electron.
Nonzero orbital angular momentum superfluidity in ultracold Fermi gases
Iskin, M.; de Melo, C. A. R. Sá
2006-01-01
We analyze the evolution of superfluidity for nonzero orbital angular momentum channels from the Bardeen-Cooper-Schrieffer (BCS) to the Bose-Einstein condensation (BEC) limit in three dimensions. First, we analyze the low energy scattering properties of finite range interactions for all possible angular momentum channels. Second, we discuss ground state ($T = 0$) superfluid properties including the order parameter, chemical potential, quasiparticle excitation spectrum, momentum distribution, ...
Quark angular momentum in a spectator model
International Nuclear Information System (INIS)
We investigate the quark angular momentum in a model with the nucleon being a quark and a spectator. Both scalar and axial-vector spectators are included. We perform the calculations in the light-cone formalism where the parton concept is well defined. We calculate the quark helicity and canonical orbital angular momentum. Then we calculate the gravitational form factors which are often related to the kinetic angular momentums, and find that even in a no gauge field model we cannot identify the canonical angular momentums with half the sum of gravitational form factors. In addition, we examine the model relation between the orbital angular momentum and pretzelosity, and find it is violated in the axial-vector case
Quark angular momentum in a spectator model
Directory of Open Access Journals (Sweden)
Tianbo Liu
2015-02-01
Full Text Available We investigate the quark angular momentum in a model with the nucleon being a quark and a spectator. Both scalar and axial-vector spectators are included. We perform the calculations in the light-cone formalism where the parton concept is well defined. We calculate the quark helicity and canonical orbital angular momentum. Then we calculate the gravitational form factors which are often related to the kinetic angular momentums, and find that even in a no gauge field model we cannot identify the canonical angular momentums with half the sum of gravitational form factors. In addition, we examine the model relation between the orbital angular momentum and pretzelosity, and find it is violated in the axial-vector case.
Physical Angular Momentum Separation for QED
Sun, Weimin
2016-01-01
We study the non-uniqueness problem of the gauge-invariant angular momentum separation for the case of QED, which stems from the recent controversy concerning the proper definitions of the orbital angular momentum and spin operator of the individual parts of a gauge field system. For the free quantum electrodynamics without matter, we show that the basic requirement of Euclidean symmetry selects a unique physical angular momentum separation scheme from the multitude of the possible angular momentum separation schemes constructed using the various Gauge Invariant Extentions. Based on these results, we propose a set of natural angular momentum separation schemes for the case of interacting QED by invoking the formalism of asymptotic fields. Some perspectives on such a problem for the case of QCD are briefly discussed.
Generalized Uncertainty Principle and Angular Momentum
Bosso, Pasquale
2016-01-01
Various models of quantum gravity suggest a modification of the Heisenberg's Uncertainty Principle, to the so-called Generalized Uncertainty Principle, between position and momentum. In this work we show how this modification influences the theory of angular momentum in Quantum Mechanics. In particular, we compute Planck scale corrections to angular momentum eigenvalues, the Hydrogen atom spectrum, the Stern-Gerlach experiment and the Clebsch-Gordan coefficients. We also examine effects of the Generalized Uncertainty Principle on multi-particle systems.
Radio beam vorticity and orbital angular momentum
Thidé, Bo; Tamburini, Fabrizio; Mari, Elettra; Romanato, Filippo; Barbieri, Cesare
2011-01-01
It has been known for a century that electromagnetic fields can transport not only energy and linear momentum but also angular momentum. However, it was not until twenty years ago, with the discovery in laser optics of experimental techniques for the generation, detection and manipulation of photons in well-defined, pure orbital angular momentum (OAM) states, that twisted light and its pertinent optical vorticity and phase singularities began to come into widespread use in science and technol...
Pretzelosity TMD and Quark Orbital Angular Momentum
Lorce, Cédric; Pasquini, B.
2015-01-01
We study the connection between the quark orbital angular momentum and the pretzelosity transverse-momentum dependent parton distribution function. We discuss the origin of this relation in quark models, identifying as key ingredient for its validity the assumption of spherical symmetry for the nucleon in its rest frame. Finally we show that the individual quark contributions to the orbital angular momentum obtained from this relation can not be interpreted as the intrinsic contributions, but...
Topological Orbital Angular Momentum Hall Current
Hu, Jiangping
2005-01-01
We show that there is a fundamental difference between spin Hall current and orbital angular momentum Hall current in Rashba- Dresselhaus spin orbit coupling systems. The orbital angular momentum Hall current has a pure topological contribution which is originated from the existence of magnetic flux in momentum space while there is no such topological nature for the spin Hall current. Moreover, we show that the orbital Hall conductance is always larger than the spin Hall conductance in the pr...
Wigner Functions and Quark Orbital Angular Momentum
Mukherjee Asmita; Nair Sreeraj; Ojha Vikash Kumar
2014-01-01
Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs). We report on a recent model calculation of the Wigner distributions for the quark and their relation to the orbital angular momentum.
Wigner Functions and Quark Orbital Angular Momentum
Directory of Open Access Journals (Sweden)
Mukherjee Asmita
2015-01-01
Full Text Available Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs and transverse momentum dependent parton distributions (TMDs. We report on a recent model calculation of the Wigner distributions for the quark and their relation to the orbital angular momentum.
The physics of angular momentum radio
Thidé, B; Then, H; Someda, C G; Ravanelli, R A
2014-01-01
Wireless communications, radio astronomy and other radio science applications are mainly implemented with techniques built on top of the electromagnetic linear momentum (Poynting vector) physical layer. As a supplement and/or alternative to this conventional approach, techniques rooted in the electromagnetic angular momentum physical layer have been advocated, and promising results from proof-of-concept radio communication experiments using angular momentum were recently published. This sparingly exploited physical observable describes the rotational (spinning and orbiting) physical properties of the electromagnetic fields and the rotational dynamics of the pertinent charge and current densities. In order to facilitate the exploitation of angular momentum techniques in real-world implementations, we present a systematic, comprehensive theoretical review of the fundamental physical properties of electromagnetic angular momentum observable. Starting from an overview that puts it into its physical context among ...
Angular momentum conservation for dynamical black holes
Hayward, Sean A.
2006-01-01
Angular momentum can be defined by rearranging the Komar surface integral in terms of a twist form, encoding the twisting around of space-time due to a rotating mass, and an axial vector. If the axial vector is a coordinate vector and has vanishing transverse divergence, it can be uniquely specified under certain generic conditions. Along a trapping horizon, a conservation law expresses the rate of change of angular momentum of a general black hole in terms of angular momentum densities of ma...
Efficient separation of light's orbital angular momentum
Mirhosseini, Mohammad; Shi, Zhimin; Boyd, Robert W
2013-01-01
The orbital angular momentum (OAM) of light is an attractive degree of freedom for fundamentals studies in quantum mechanics. In addition, the discrete unbounded state-space provided by OAM has been used to enhance classical and quantum communications. The ability to unambiguously measure the OAM of single photons is a key part of all such experiments. However, state-of-the-art methods for sorting OAM modes are limited to a separation efficiency of about 80 percent. Here we demonstrate a method which uses a series of complex optical transformations to enable the measurement of light's OAM with a separation efficiency of more than 92 percent. Further, we demonstrate the separation of modes in the angular position basis, which is mutually unbiased with respect to the OAM basis. The high degree of certainty makes our approach particularly attractive for quantum key distribution systems employing spatial encoding.
Mass and Angular Momentum in General Relativity
Jaramillo, J L
2010-01-01
We present an introduction to mass and angular momentum in General Relativity. After briefly reviewing energy-momentum for matter fields, first in the flat Minkowski case (Special Relativity) and then in curved spacetimes with or without symmetries, we focus on the discussion of energy-momentum for the gravitational field. We illustrate the difficulties rooted in the Equivalence Principle for defining a local energy-momentum density for the gravitational field. This leads to the understanding of gravitational energy-momentum and angular momentum as non-local observables that make sense, at best, for extended domains of spacetime. After introducing Komar quantities associated with spacetime symmetries, it is shown how total energy-momentum can be unambiguously defined for isolated systems, providing fundamental tests for the internal consistency of General Relativity as well as setting the conceptual basis for the understanding of energy loss by gravitational radiation. Finally, several attempts to formulate q...
Gravitational waves carrying orbital angular momentum
Bialynicki-Birula, Iwo; Bialynicka-Birula, Zofia
2016-02-01
Spinorial formalism is used to map every electromagnetic wave into the gravitational wave (within the linearized gravity). In this way we can obtain the gravitational counterparts of Bessel, Laguerre-Gauss, and other light beams carrying orbital angular momentum.
Angular Momentum Acquisition in Galaxy Halos
Stewart, Kyle R; Bullock, James S; Maller, Ariyeh H; Diemand, Juerg; Wadsley, James; Moustakas, Leonidas A
2013-01-01
We use high-resolution cosmological hydrodynamic simulations to study the angular momentum acquisition of gaseous halos around Milky Way sized galaxies. We find that cold mode accreted gas enters a galaxy halo with ~70% more specific angular momentum than dark matter averaged over cosmic time (though with a very large dispersion). In fact, we find that all matter has a higher spin parameter when measured at accretion than when averaged over the entire halo lifetime, and is well characterized by \\lambda~0.1, at accretion. Combined with the fact that cold flow gas spends a relatively short time (1-2 dynamical times) in the halo before sinking to the center, this naturally explains why cold flow halo gas has a specific angular momentum much higher than that of the halo and often forms "cold flow disks". We demonstrate that the higher angular momentum of cold flow gas is related to the fact that it tends to be accreted along filaments.
Gravitational waves carrying orbital angular momentum
Bialynicki-Birula, Iwo
2015-01-01
Spinorial formalism is used to map every electromagnetic wave into the gravitational wave (within the linearized gravity). In this way we can obtain the gravitational counterparts of Bessel, Laguerre-Gauss, and other light beams carrying orbital angular momentum.
On the relation between angular momentum and angular velocity
Silva, J. P.; Tavares, J. M.
2007-01-01
Students of mechanics usually have difficulties when they learn about the rotation of a rigid body. These difficulties are rooted in the relation between angular momentum and angular velocity, because these vectors are not parallel, and we need in general to utilize a rotating frame of reference or a time dependent inertia tensor. We discuss a series of problems that introduce both difficulties.
Multipolar expansion of orbital angular momentum modes
Molina-Terriza, Gabriel
2008-01-01
In this letter a general method for expanding paraxial beams into multipolar electromagnetic fields is presented. This method is applied to the expansion of paraxial modes with orbital angular momentum (OAM), showing how the paraxial OAM is related to the general angular momentum of an electromagnetic wave. This method can be extended to quasi-paraxial beams, i.e. highly focused laser beams. Some applications to the control of electronic transitions in atoms are discussed.
Orbital angular momentum of partially coherent beams
Serna Galán, Julio; Movilla Serrano, Jesús María
2001-01-01
The definition of the orbital angular momentum established for coherent beams is extended to partially coherent beams, expressed in terms of two elements of the beam matrix. This extension is justified by use of the Mercer expansion of partially coherent fields. General Gauss-Schell-model fields are considered, and the relation between the twist; parameter and the orbital angular momentum is analyzed. © 2001 Optical Society of America.
Entanglement of Polarization and Orbital Angular Momentum
Bhatti, Daniel; von Zanthier, Joachim; Agarwal, Girish S.
2015-01-01
We investigate two-photon entangled states using two important degrees of freedom of the electromagnetic field, namely orbital angular momentum (OAM) and spin angular momentum. For photons propagating in the same direction we apply the idea of $\\textit{entanglement duality}$ and develop schemes to do $\\textit{entanglement sorting}$ based either on OAM or polarization. In each case the entanglement is tested using appropriate witnesses. We finally present generalizations of these ideas to thre...
Experimental determination of high angular momentum states
International Nuclear Information System (INIS)
The current knowledge of the atomic nucleus structure is summarized. A short abstract of the nuclear properties at high angular momentum and a more detailed description of the experimental methods used in the study of high angular momenta is made. (L.C.)
Angular momentum decomposition of Richardson's pairs
International Nuclear Information System (INIS)
The angular momentum decomposition of pairs obtained using Richardson's exact solution of the pairing Hamiltonian for the deformed 174Yb nucleus are displayed. The probabilities for low angular momenta of the collective pairs are strikingly different from the ones obtained in the BCS ground state
Orbital angular momentum induced beam shifts
Hermosa N.; Merano M.; Aiello A.; Woerdman J.P.
2011-01-01
We present experiments on Orbital Angular Momentum (OAM) induced beam shifts in optical reflection. Specifically, we observe the spatial Goos-H\\"anchen shift in which the beam is displaced parallel to the plane of incidence and the angular Imbert-Fedorov shift which is a transverse angular deviation from the geometric optics prediction. Experimental results agree well with our theoretical predictions. Both beam shifts increase with the OAM of the beam; we have measured these for OAM indices u...
Quark Orbital Angular Momentum from Lattice QCD
N. Mathur; Dong, S. J.; Liu, K. F.; Mankiewicz, L.; Mukhopadhyay, N. C.
1999-01-01
We calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the $Z_2$ noise with an unbiased subtraction. This reduced the error by a factor of 4 with negligible overhead. The total quark contribution to the proton spin is found to be $0.30 \\pm 0.07$. From this and the quark spin content we deduce the quark orbital angular momentum to be $0.17 \\pm 0.06$ wh...
Localizing the Angular Momentum of Linear Gravity
Butcher, Luke M; Hobson, Michael; 10.1103/PhysRevD.86.084012
2012-01-01
In a previous article [Phys. Rev. D 82 104040 (2010)], we derived an energy-momentum tensor for linear gravity that exhibited positive energy density and causal energy flux. Here we extend this framework by localizing the angular momentum of the linearized gravitational field, deriving a gravitational spin tensor which possesses similarly desirable properties. By examining the local exchange of angular momentum (between matter and gravity) we find that gravitational intrinsic spin is localized, separately from orbital angular momentum, in terms of a gravitational spin tensor. This spin tensor is then uniquely determined by requiring that it obey two simple physically motivated algebraic conditions. Firstly, the spin of an arbitrary (harmonic-gauge) gravitational plane wave is required to flow in the direction of propagation of the wave. Secondly, the spin tensor of any transverse-traceless gravitational field is required to be traceless. (The second condition ensures that local field redefinitions suffice to ...
Quark orbital angular momentum from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Mathur, N.; Dong, S. J.; Liu, K. F.; Mankiewicz, L.; Mukhopadhyay, N. C.
2000-12-01
We calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice with the quenched approximation. The disconnected insertion is estimated stochastically which employs the Z{sub 2} noise with an unbiased subtraction. This reduced the error by a factor of 3--4 with negligible overhead. The total quark contribution to the proton spin is found to be 0.30{+-}0.07. From this and the quark spin content we deduce the quark orbital angular momentum to be 0.17{+-}0.06 which is {approx}34% of the proton spin. We further predict that the gluon angular momentum is 0.20{+-}0.07; i.e., {approx}40% of the proton spin is due to the glue.
Quark orbital angular momentum from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Liu, K.F.
2000-01-10
The authors calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the Z{sub 2} noise with an unbiased subtraction. This reduced the error by a factor of 4 with negligible overhead. The total quark contribution to the proton spin is found to be 0.30{+-}0.07. From this and the quark spin content the authors deduce the quark orbital angular momentum to be 0.17{+-}0.06 which is {approximately} 34% of the proton spin. The authors further predict that the gluon angular momentum to be 0.20{+-}0.07, i. e. {approximately} 40% of the proton spin is due to the glue.
Quark orbital angular momentum from lattice QCD
International Nuclear Information System (INIS)
The authors calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the Z2 noise with an unbiased subtraction. This reduced the error by a factor of 4 with negligible overhead. The total quark contribution to the proton spin is found to be 0.30±0.07. From this and the quark spin content the authors deduce the quark orbital angular momentum to be 0.17±0.06 which is ∼ 34% of the proton spin. The authors further predict that the gluon angular momentum to be 0.20±0.07, i. e. approximately 40% of the proton spin is due to the glue
Quark orbital angular momentum from lattice QCD
International Nuclear Information System (INIS)
We calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice with the quenched approximation. The disconnected insertion is estimated stochastically which employs the Z2 noise with an unbiased subtraction. This reduced the error by a factor of 3--4 with negligible overhead. The total quark contribution to the proton spin is found to be 0.30±0.07. From this and the quark spin content we deduce the quark orbital angular momentum to be 0.17±0.06 which is ∼34% of the proton spin. We further predict that the gluon angular momentum is 0.20±0.07; i.e., ∼40% of the proton spin is due to the glue
Radio beam vorticity and orbital angular momentum
Thidé, Bo; Mari, Elettra; Romanato, Filippo; Barbieri, Cesare
2011-01-01
It has been known for a century that electromagnetic fields can transport not only energy and linear momentum but also angular momentum. However, it was not until twenty years ago, with the discovery in laser optics of experimental techniques for the generation, detection and manipulation of photons in well-defined, pure orbital angular momentum (OAM) states, that twisted light and its pertinent optical vorticity and phase singularities began to come into widespread use in science and technology. We have now shown experimentally how OAM and vorticity can be readily imparted onto radio beams. Our results extend those of earlier experiments on angular momentum and vorticity in radio in that we used a single antenna and reflector to directly generate twisted radio beams and verified that their topological properties agree with theoretical predictions. This opens the possibility to work with photon OAM at frequencies low enough to allow the use of antennas and digital signal processing, thus enabling software con...
The role of angular momentum conservation law in statistical mechanics
I.M. Dubrovskii
2008-01-01
Within the limits of Khinchin ideas [A.Y. Khinchin, Mathematical Foundation of Statistical Mechanics. NY, Ed. Dover, 1949] the importance of momentum and angular momentum conservation laws was analyzed for two cases: for uniform magnetic field and when magnetic field is absent. The law of momentum conservation does not change the density of probability distribution in both cases, just as it is assumed in the conventional theory. It is shown that in systems where the kinetic energy depends onl...
An orbital angular momentum spectrometer for electrons
Harvey, Tyler; Grillo, Vincenzo; McMorran, Benjamin
2016-05-01
With the advent of techniques for preparation of free-electron and neutron orbital angular momentum (OAM) states, a basic follow-up question emerges: how do we measure the orbital angular momentum state distribution in matter waves? Control of both the energy and helicity of light has produced a range of spectroscopic applications, including molecular fingerprinting and magnetization mapping. Realization of an analogous dual energy-OAM spectroscopy with matter waves demands control of both initial and final energy and orbital angular momentum states: unlike for photons, final state post-selection is necessary for particles that cannot be annihilated. We propose a magnetic field-based mechanism for quantum non-demolition measurement of electron OAM. We show that OAM-dependent lensing is produced by an operator of form U =exp iLzρ2/ℏb2 where ρ =√{x2 +y2 } is the radial position operator, Lz is the orbital angular momentum operator along z, and b is the OAM dispersion length. We can physically realize this operator as a term in the time evolution of an electron in magnetic round lens. We discuss prospects and practical challenges for implementation of a lensing orbital angular momentum measurement. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under the Early Career Research Program Award # DE-SC0010466.
Effects of Angular Momentum on Halo Profiles
Lentz, Erik W; Rosenberg, Leslie J
2016-01-01
The near universality of DM halo density profiles provided by N-body simulations has proven to be robust against changes in total mass density, power spectrum, and some forms of initial velocity dispersion. In this letter we study the effects of coherently spinning up an isolated DM-only progenitor on halo structure. Halos with spins within several standard deviations of the simulated mean ($\\lambda \\lesssim 0.20$) produce profiles with negligible deviations from the universal form. Only when the spin becomes quite large ($\\lambda \\gtrsim 0.20$) do departures become evident. The angular momentum distribution also exhibits a near universal form, which is also independent of halo spin up to $\\lambda \\lesssim 0.20$. A correlation between these epidemic profiles and the presence of a strong bar in the virialized halo is also observed. These bar structures bear resemblance to the radial orbit instability in the rotationless limit.
Parton Transverse Momentum and Orbital Angular Momentum Distributions
Rajan, Abha; Engelhardt, Michael; Liuti, Simonetta
2016-01-01
The quark orbital angular momentum component of proton spin, $L_q$, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark's transverse position and momentum. It can also be independently defined from the operator product expansion for the off-forward Compton amplitude in terms of a twist-three generalized parton distribution. We provide an explicit link between the two definitions, connecting them through their dependence on partonic intrinsic transverse momentum. Connecting the definitions provides the key for correlating direct experimental determinations of $L_q$, and evaluations through Lattice QCD calculations. The direct observation of quark orbital angular momentum does not require transverse spin polarization, but can occur using longitudinally polarized targets.
Quark Wigner distributions and orbital angular momentum
International Nuclear Information System (INIS)
We study the Wigner functions of the nucleon which provide multidimensional images of the quark distributions in phase space. These functions can be obtained through a Fourier transform in the transverse space of the generalized transverse-momentum dependent parton distributions. They depend on both the transverse position and the three-momentum of the quark relative to the nucleon, and therefore combine in a single picture all the information contained in the generalized parton distributions and the transverse-momentum dependent parton distributions. We focus the discussion on the distributions of unpolarized/longitudinally polarized quark in an unpolarized/longitudinally polarized nucleon. In this way, we can study the role of the orbital angular momentum of the quark in shaping the nucleon and its correlations with the quark and nucleon polarizations. The quark orbital angular momentum is also calculated from its phase-space average weighted with the Wigner distribution of unpolarized quarks in a longitudinally polarized nucleon. The corresponding results obtained within different light-cone quark models are compared with alternative definitions of the quark orbital angular momentum, as given in terms of generalized parton distributions and transverse-momentum dependent parton distributions.
Parton Transverse Momentum and Orbital Angular Momentum Distributions
Rajan, Abha; Courtoy, Aurore; Engelhardt, Michael; Liuti, Simonetta
2016-01-01
The quark orbital angular momentum component of proton spin, $L_q$, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark's transverse position and momentum. It can also be independently defined from the operator product expansion for the off-forward Compton amplitude in terms of a twist-three generalized parton distribution. We provide an explicit link between the two definitions, connecting them through their dependence on parton...
Ghost Imaging Using Orbital Angular Momentum
International Nuclear Information System (INIS)
We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum. In the signal arm, object spatial information is encoded as a phase matrix. For an N-grey-scale object, different phase matrices, varying from 0 to π with increment π/N, are used for different greyscales, and then they are modulated to a signal beam by a spatial light modulator. According to the conservation of the orbital angular momentum in the ghost imaging system, these changes will give different coincidence rates in measurement, and hence the object information can be extracted in the idler arm. By simulations and experiments, the results show that our scheme can improve the resolution of the image effectively. Compared with another encoding method using orbital angular momentum, our scheme has a better performance for both characters and the image object. (fundamental areas of phenomenology(including applications))
Chirality and angular momentum in optical radiation
Coles, Matt M
2012-01-01
This paper develops, in precise quantum electrodynamic terms, photonic attributes of the "optical chirality density", one of several measures long known to be conserved quantities for a vacuum electromagnetic field. The analysis lends insights into some recent interpretations of chiroptical experiments, in which this measure, and an associated chirality flux, have been treated as representing physically distinctive "superchiral" phenomena. In the fully quantized formalism the chirality density is promoted to operator status, whose exploration with reference to an arbitrary polarization basis reveals relationships to optical angular momentum and helicity operators. Analyzing multi-mode beams with complex wave-front structures, notably Laguerre-Gaussian modes, affords a deeper understanding of the interplay between optical chirality and optical angular momentum. By developing theory with due cognizance of the photonic character of light, it emerges that only the spin angular momentum of light is engaged in such...
Partons Transverse Momentum and Orbital Angular Momentum Distributions
Liuti, Simonetta; Rajan, Abha; Courtoy, Aurore; Engelhardt, Michael
2015-10-01
We discuss the two definitions of partonic orbital angular momentum given by Ji and by Jaffe and Manohar, respectively. It is by now established that the two definitions are described by the same generalized transverse momentum distribution, F14, while they differ through their gauge link structure. They can also be both described in terms of a twist three generalized parton distribution, G2 which can be measured in DVCS type experiments. Here, starting from nonlocal, kT unintegrated, off-forward matrix elements, instead of the standard OPE, we show how G2 can be written as the sum of twist two, quark mass, and interaction dependent (twist three) terms, thus emphasizing the role of quark intrinsic transverse momentum and off-shellness. The twist two term in particular is given by the kT2 moment of F14. We therefore uncover a relation/sum rule connecting the two definitions of orbital angular momentum, F14 and G2. We explore both the spin and the intrinsic transverse momentum/transverse space correlations as well as the gauge link structure behind the two decomposition frameworks, which are necessary to extract orbital angular momentum from experiment.
Ghost Imaging Using Orbital Angular Momentum
Institute of Scientific and Technical Information of China (English)
赵生妹; 丁建; 董小亮; 郑宝玉
2011-01-01
We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum. In the signal arm, object spatial information is encoded as a phase matrix. For an N-grey-scale object, different phase matrices, varying from 0 to K with increment n/N, are used for different greyscales, and then they are modulated to a signal beam by a spatial light modulator. According to the conservation of the orbital angular momentum in the ghost imaging system, these changes will give different coincidence rates in measurement, and hence the object information can be extracted in the idler arm. By simulations and experiments, the results show that our scheme can improve the resolution of the image effectively. Compared with another encoding method using orbital angular momentum, our scheme has a better performance for both characters and the image object.%We present a novel encoding scheme in a ghost-imaging system using orbital angular momentum.In the signal arm,object spatial information is encoded as a phase matrix.For an N-grey-scale object,different phase matrices,varying from 0 to π with increment π/N,are used for different greyscales,and then they are modulated to a signal beam by a spatial light modulator.According to the conservation of the orbital angular momentum in the ghost imaging system,these changes will give different coincidence rates in measurement,and hence the object information can be extracted in the idler arm.By simulations and experiments,the results show that our scheme can improve the resolution of the image effectively.Compared with another encoding method using orbital angular momentum,our scheme has a better performance for both characters and the image object.
Time-resolved orbital angular momentum spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Noyan, Mehmet A.; Kikkawa, James M. [Department of Physics and Astronomy, The University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)
2015-07-20
We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes.
Time-resolved orbital angular momentum spectroscopy
International Nuclear Information System (INIS)
We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes
Wilson lines and orbital angular momentum
International Nuclear Information System (INIS)
We present an explicit realization of the Chen et al. approach to the proton spin decomposition in terms of Wilson lines, generalizing the light-front gauge-invariant extensions discussed recently by Hatta. Particular attention is drawn to the residual gauge freedom by further separating the pure-gauge term into contour and residual terms. We show that the kinetic orbital angular momentum operator can be expressed in terms of the Wigner operator only when the momentum variable is integrated over. Finally, we confirm from twist-2 arguments that the advanced, retarded and antisymmetric light-front canonical orbital angular momenta are the same
Wilson lines and orbital angular momentum
Energy Technology Data Exchange (ETDEWEB)
Lorcé, Cédric, E-mail: cedric.lorce@googlemail.com [IPNO, Université Paris-Sud, CNRS/IN2P3, 91406 Orsay (France); LPT, Université Paris-Sud, CNRS, 91406 Orsay (France)
2013-02-12
We present an explicit realization of the Chen et al. approach to the proton spin decomposition in terms of Wilson lines, generalizing the light-front gauge-invariant extensions discussed recently by Hatta. Particular attention is drawn to the residual gauge freedom by further separating the pure-gauge term into contour and residual terms. We show that the kinetic orbital angular momentum operator can be expressed in terms of the Wigner operator only when the momentum variable is integrated over. Finally, we confirm from twist-2 arguments that the advanced, retarded and antisymmetric light-front canonical orbital angular momenta are the same.
Angular momentum and the electromagnetic top
Indian Academy of Sciences (India)
GIANFRANCO SPAVIERI; GEORGE T GILLIES
2016-08-01
The electric charge–magnetic dipole interaction is considered. If $\\Gamma_{\\rm em}$ is the electromagnetic and $\\Gamma_{\\rm mech}$ the mechanical angular momentum, the conservation law for the total angular momentum $\\Gamma_{\\rm tot}$ holds: $\\Gamma_{\\rm tot}$ =$\\Gamma_{\\rm em}$ + $\\Gamma_{\\rm mech}$ = ${\\rm const.}$, but when the dipole moment varies with time, $\\Gamma_{\\rm mech}$ is not conserved. We show that the non-conserved $\\Gamma_{\\rm mech}$ of such a macroscopic isolated system might be experimentally observable. With advanced technology, the strength of the interaction hints to the possibility of novel applications for gyroscopes, such as the electromagnetic top.
Orbital angular momentum in the nucleons
Lorcé, Cédric
2014-01-01
In the last decade, it has been realized that the orbital angular momentum of partons inside the nucleon plays a major role. It contributes significantly to nucleon properties and is at the origin of many asymmetries observed in spin physics. It is therefore of paramount importance to determine this quantity if we want to understand the nucleon internal structure and experimental observables. This triggered numerous discussions and controversies about the proper definition of orbital angular momentum and its extraction from experimental data. We summarize the present situation and discuss recent developments in this field.
On the vector model of angular momentum
Saari, Peeter
2016-09-01
Instead of (or in addition to) the common vector diagram with cones, we propose to visualize the peculiarities of quantum mechanical angular momentum by a completely quantized 3D model. It spotlights the discrete eigenvalues and noncommutativity of components of angular momentum and corresponds to outcomes of measurements—real or computer-simulated. The latter can be easily realized by an interactive worksheet of a suitable program package of algebraic calculations. The proposed complementary method of visualization helps undergraduate students to better understand the counterintuitive properties of this quantum mechanical observable.
Orbital angular momentum in the nucleons
Lorcé, Cédric
2014-01-01
In the last decade, it has been realized that the orbital angular momentum of partons inside the nucleon plays a major role. It contributes significantly to nucleon properties and is at the origin of many asymmetries observed in spin physics. It is therefore of paramount importance to determine this quantity if we want to understand the nucleon internal structure and experimental observables. This triggered numerous discussions and controversies about the proper definition of orbital angular ...
Wilson lines and orbital angular momentum
Lorce, Cédric
2013-01-01
We present an explicit realization of the Chen et al. approach to the proton spin decomposition in terms of Wilson lines, generalizing the light-front gauge-invariant extensions discussed recently by Hatta. Particular attention is drawn to the residual gauge freedom by further separating the pure-gauge term into contour and residual terms. We show that the kinetic orbital angular momentum operator can be expressed in terms of the Wigner operator only when the momentum variable is integrated o...
Wigner distributions and quark orbital angular momentum
Cedric LorceOrsay, IPN and Orsay, LPT; Barbara Pasquini(Pavia U. and INFN, Pavia)
2015-01-01
We discuss the quark phase-space or Wigner distributions of the nucleon which combine in a single picture all the information contained in the generalized parton distributions and the transverse-momentum dependent parton distributions. In particular, we present results for the distribution of unpolarized quarks in a longitudinally polarized nucleon obtained in a light-front constituent quark model. We show how the quark orbital angular momentum can be extracted from the Wigner distributions a...
Non-Colinearity of Angular Velocity and Angular Momentum
Burr, A. F.
1974-01-01
Discusses the principles, construction, and operation of an apparatus which serves to demonstrate the non-colinearity of the angular velocity and momentum vectors as well as the inertial tensors. Applications of the apparatus to teaching of advanced undergraduate mechanics courses are recommended. (CC)
Dual electromagnetism: helicity, spin, momentum and angular momentum
International Nuclear Information System (INIS)
The dual symmetry between electric and magnetic fields is an important intrinsic property of Maxwell equations in free space. This symmetry underlies the conservation of optical helicity and, as we show here, is closely related to the separation of spin and orbital degrees of freedom of light (the helicity flux coincides with the spin angular momentum). However, in the standard field-theory formulation of electromagnetism, the field Lagrangian is not dual symmetric. This leads to problematic dual-asymmetric forms of the canonical energy–momentum, spin and orbital angular-momentum tensors. Moreover, we show that the components of these tensors conflict with the helicity and energy conservation laws. To resolve this discrepancy between the symmetries of the Lagrangian and Maxwell equations, we put forward a dual-symmetric Lagrangian formulation of classical electromagnetism. This dual electromagnetism preserves the form of Maxwell equations, yields meaningful canonical energy–momentum and angular-momentum tensors, and ensures a self-consistent separation of the spin and orbital degrees of freedom. This provides a rigorous derivation of the results suggested in other recent approaches. We make the Noether analysis of the dual symmetry and all the Poincaré symmetries, examine both local and integral conserved quantities and show that only the dual electromagnetism naturally produces a complete self-consistent set of conservation laws. We also discuss the observability of physical quantities distinguishing the standard and dual theories, as well as relations to quantum weak measurements and various optical experiments. (paper)
On the "initial" Angular Momentum of Galaxies
Abel, T; Hernquist, L E; Abel, Tom; Croft, Rupert C.; Hernquist, Lars
2001-01-01
Spherical density profiles and specific angular momentum profiles of Dark Matter halos found in cosmological N-body simulations have been measured extensively. The distribution of the total angular momentum of dark matter halos is also used routinely in semi-analytic modeling of the formation of disk galaxies. However, it is unclear whether the initial (i.e. at the time the halo is assembled) angular momentum distributions of baryons is related to the dark matter at all. Theoretical models for ellipticities in weak lensing studies often rely on an assumed correlation of the angular momentum vectors of dark matter and gas in galaxies. Both of these assumptions are shown to be in reasonable agreement with high resolution cosmological smoothed particle hydrodynamical simulations that follow the dark matter as long as only adiabatic gas physics are included. However, we argue that in more realistic models of galaxy formation one expects pressure forces to play a significant role at turn--around. Consequently the ...
Photon Orbital Angular Momentum in Astrophysics
Harwit, Martin
2003-01-01
Astronomical observations of the orbital angular momentum of photons, a property of electromagnetic radiation that has come to the fore in recent years, have apparently never been attempted. Here, I show that measurements of this property of photons have a number of astrophysical applications.
Critical gravitational collapse with angular momentum
Gundlach, Carsten
2016-01-01
We derive a theoretical model of mass and angular momentum scaling in type-II critical collapse with rotation. We focus on the case where the critical solution has precisely one, spherically symmetric, unstable mode. We demonstrate excellent agreement with numerical results for critical collapse of a rotating radiation fluid, which falls into this case.
Angular momentum transfer in incomplete fusion
Indian Academy of Sciences (India)
B S Tomar; K Surendra Babu; K Sudarshan; R Tripathi; A Goswami
2005-02-01
Isomeric cross-section ratios of evaporation residues formed in 12C+93Nb and 16O + 89Y reactions were measured by recoil catcher technique followed by off-line -ray spectrometry in the beam energy range of 55.7-77.5 MeV for 12C and 68-81 MeV for 16O. The isomeric cross-section ratios were resolved into that for complete and incomplete fusion reactions. The angular momentum of the intermediate nucleus formed in incomplete fusion was deduced from the isomeric cross-section ratio by considering the statistical de-excitation of the incompletely fused composite nucleus. The data show that incomplete fusion is associated with angular momenta slightly smaller than critical angular momentum for complete fusion, indicating the deeper interpenetration of projectile and target nuclei than that in peripheral collisions.
Angular momentum alignment in molecular beam scattering
International Nuclear Information System (INIS)
It is shown how the angular momentum alignment in a molecular beam can be determined using laser-induced fluorescence in combination with precession of the angular momenta in a magnetic field. After a general analysis of the method, some results are presented to illustrate the possibilities of the method. Experimental data are presented on the alignment production for Na2 molecules that made a collision induced angular momentum transition. Magnitude as well as direction of the alignment have been determined for scattering with several scattering partners and for a large number of scattering angles and transitions. The last chapter deals with the total alignment production in a final J-state, i.e. without state selection of the initial rotational state. (orig.)
Smoothed dissipative particle dynamics with angular momentum conservation
Energy Technology Data Exchange (ETDEWEB)
Müller, Kathrin, E-mail: k.mueller@fz-juelich.de; Fedosov, Dmitry A., E-mail: d.fedosov@fz-juelich.de; Gompper, Gerhard, E-mail: g.gompper@fz-juelich.de
2015-01-15
Smoothed dissipative particle dynamics (SDPD) combines two popular mesoscopic techniques, the smoothed particle hydrodynamics and dissipative particle dynamics (DPD) methods, and can be considered as an improved dissipative particle dynamics approach. Despite several advantages of the SDPD method over the conventional DPD model, the original formulation of SDPD by Español and Revenga (2003) [9], lacks angular momentum conservation, leading to unphysical results for problems where the conservation of angular momentum is essential. To overcome this limitation, we extend the SDPD method by introducing a particle spin variable such that local and global angular momentum conservation is restored. The new SDPD formulation (SDPD+a) is directly derived from the Navier–Stokes equation for fluids with spin, while thermal fluctuations are incorporated similarly to the DPD method. We test the new SDPD method and demonstrate that it properly reproduces fluid transport coefficients. Also, SDPD with angular momentum conservation is validated using two problems: (i) the Taylor–Couette flow with two immiscible fluids and (ii) a tank-treading vesicle in shear flow with a viscosity contrast between inner and outer fluids. For both problems, the new SDPD method leads to simulation predictions in agreement with the corresponding analytical theories, while the original SDPD method fails to capture properly physical characteristics of the systems due to violation of angular momentum conservation. In conclusion, the extended SDPD method with angular momentum conservation provides a new approach to tackle fluid problems such as multiphase flows and vesicle/cell suspensions, where the conservation of angular momentum is essential.
Quark orbital angular momentum in the Wandzura-Wilczek approximation
Energy Technology Data Exchange (ETDEWEB)
Haegler, Ph.Ph.; Mukherjee, A.; Schaefer, A
2004-02-26
We show that quark orbital angular momentum is directly related to off-forward correlation functions which include intrinsic transverse momentum corresponding to a derivative with respect to the transverse coordinates. Its possible contribution to scattering processes is therefore of higher twist and vanishes in the forward limit. The relation of OAM to other twist 2 and 3 distributions known in the literature is derived and formalized by an unintegrated sum rule.
Angular momentum transfer in deep inelastic scattering
International Nuclear Information System (INIS)
The measured γ-ray multiplicities as a function of exit channel kinetic energy and mass asymmetry for the reactions Au, Ho, Ag + 620 MeV Kr are compared with a diffusion calculation based exclusively upon particle transfer and which reproduces the Z distributions as well as the angular distributions as function of Z. The model correctly predicts the energy and Z dependence of the γ-ray multiplicities, thus lending support to the one-body model on one hand and to the angular-momentum fractionation along the mass asymmetry coordinate on the other
Wilson lines and orbital angular momentum
Lorcé, Cédric
2012-01-01
We present an explicit realization of the Chen et al. approach to the proton spin decomposition in terms of Wilson lines, generalizing the light-front gauge-invariant extensions discussed recently by Hatta. Particular attention is drawn to the residual gauge freedom by further separating the pure-gauge term into contour and residual terms. Contrarily to a recent claim, we show that the Wigner distributions do not give access to the kinetic orbital angular momentum. Finally, we confirm from twist-2 arguments that the advanced, retarded and antisymmetric light-front canonical orbital angular momenta are the same.
Spin-to-orbital angular momentum conversion in dielectric metasurfaces
Devlin, Robert Charles; Wintz, Daniel; Oscurato, Stefano Luigi; Zhu, Alexander Yutong; Khorasaninejad, Mohammadreza; Oh, Jaewon; Maddalena, Pasqualino; Capasso, Federico
2016-01-01
Spin-to-orbital-angular-momentum conversion has attracted considerable interest as a tool to create exotic light beams, leading to the emergence of novel devices that implement this function. These converters exploit the geometrical phase to create helical beams of handedness determined by the chirality of the incident light. This property is finding important applications in quantum optics thanks to the demonstration of liquid crystal spin-to-orbital angular momentum converters (SOC) known as q-plates. Here we demonstrate high-efficiency SOCs in the visible based on dielectric metasurfaces that generate vortex beams with high and even fractional topological charge and show for the first time the simultaneous generation of collinear helical beams with different and arbitrary orbital angular momentum. We foresee that this versatile method of creating vortex beams, which circumvents the limitations of q-plates, will significant impact microscopy and vector beam shaping.
Local spacetime curvature effects on quantum orbital angular momentum
Energy Technology Data Exchange (ETDEWEB)
Singh, Dinesh; Mobed, Nader, E-mail: dinesh.singh@uregina.ca, E-mail: nader.mobed@uregina.ca [Department of Physics, University of Regina, Regina, Saskatchewan S4S 0A2 (Canada)
2011-05-21
This paper claims that local spacetime curvature can nontrivially contribute to the properties of orbital angular momentum in quantum mechanics. Of key importance is the demonstration that an extended orbital angular momentum operator due to gravitation can identify the existence of orbital states with half-integer projection quantum numbers m along the axis of quantization, while still preserving integer-valued orbital quantum numbers l for a simply connected topology. The consequences of this possibility are explored in depth, noting that the half-integer m states vanish as required when the locally curved spacetime reduces to a flat spacetime, fully recovering all established properties of orbital angular momentum in this limit. In particular, it is shown that a minimum orbital number of l = 2 is necessary for the gravitational interaction to appear within this context, in perfect correspondence with the spin-2 nature of linearized general relativity.
Transfer of orbital angular momentum through sub-wavelength waveguides.
Wang, Yanqin; Ma, Xiaoliang; Pu, Mingbo; Li, Xiong; Huang, Cheng; Pan, Wenbo; Zhao, Bo; Cui, Jianhua; Luo, Xiangang
2015-02-01
Data capacity of optical communication is achieving its limit owing to the non-linear effect of optical fiber. As an effective alternative, light carrying orbital angular momentum can greatly increase the capacity for its unprecedented degree of freedom. We demonstrate the propagation of orbital angular momentum with topological charge of 1 and 2 in plasmonic circular waveguide with sub-wavelength diameter with little propagation loss of 2.73 dB/μm, which has never been observed in optical fibers with sub-wavelength diameter. We also confirm that lights carrying orbital angular momentum can be maintained in sharp bended sub-wavelength waveguide. This plasmonic waveguide may serve as a key component in on-chip systems involving OAM. PMID:25836146
Local spacetime curvature effects on quantum orbital angular momentum
International Nuclear Information System (INIS)
This paper claims that local spacetime curvature can nontrivially contribute to the properties of orbital angular momentum in quantum mechanics. Of key importance is the demonstration that an extended orbital angular momentum operator due to gravitation can identify the existence of orbital states with half-integer projection quantum numbers m along the axis of quantization, while still preserving integer-valued orbital quantum numbers l for a simply connected topology. The consequences of this possibility are explored in depth, noting that the half-integer m states vanish as required when the locally curved spacetime reduces to a flat spacetime, fully recovering all established properties of orbital angular momentum in this limit. In particular, it is shown that a minimum orbital number of l = 2 is necessary for the gravitational interaction to appear within this context, in perfect correspondence with the spin-2 nature of linearized general relativity.
Phenomenological determination of the orbital angular momentum.
Energy Technology Data Exchange (ETDEWEB)
Ramsey, G. P.; High Energy Physics; Loyola Univ.
2009-01-01
Measurements involving the gluon spin, {Delta}G(x, t) and the corresponding asymmetry, A(x,t) = {Delta}G(x,t)/G(x,t) play an important role in quantitative understanding of proton structure. We have modeled the asymmetry perturbatively and calculated model corrections to obtain information about non-perturbative spin-orbit effects. These models are consistent with existing COMPASS and HERMES data on the gluon asymmetry. The J{sub z} = 1/2 sum rule is used to generate values of orbital angular momentum at LO and NLO. For models consistent with data, the orbital angular momentum is small. Our studies specify accuracy that future measurements should achieve to constrain theoretical models for nucleon structure.
The role of angular momentum conservation law in statistical mechanics
Directory of Open Access Journals (Sweden)
I.M. Dubrovskii
2008-12-01
Full Text Available Within the limits of Khinchin ideas [A.Y. Khinchin, Mathematical Foundation of Statistical Mechanics. NY, Ed. Dover, 1949] the importance of momentum and angular momentum conservation laws was analyzed for two cases: for uniform magnetic field and when magnetic field is absent. The law of momentum conservation does not change the density of probability distribution in both cases, just as it is assumed in the conventional theory. It is shown that in systems where the kinetic energy depends only on particle momenta canonically conjugated with Cartesian coordinates being their diagonal quadric form,the angular momentum conservation law changes the density of distribution of the system only in case the full angular momentum of a system is not equal to zero. In the gas of charged particles in a uniform magnetic field the density of distribution also varies if the angular momentum is zero [see Dubrovskii I.M., Condensed Matter Physics, 2206, 9, 23]. Two-dimensional gas of charged particles located within a section of an endless strip filled with gas in magnetic field is considered. Under such conditions the angular momentum is not conserved. Directional particle flows take place close to the strip boundaries, and, as a consequence, the phase trajectory of the considered set of particles does not remain within the limited volume of the phase space. In order to apply a statistical thermodynamics method, it was suggested to consider near-boundary trajectories relative to a reference system that moves uniformly. It was shown that if the diameter of an orbit having average thermal energy is much smaller than a strip width, the corrections to thermodynamic functions are small depending on magnetic field. Only the average velocity of near-boundary particles that form near-boundary electric currents creating the paramagnetic moment turn out to be essential.
Arbitrary orbital angular momentum of photons
Pan, Yue; Gao, Xu-Zhen; Ren, Zhi-Cheng; Wang, Xi-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian
2015-01-01
Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrary OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the a...
Quark Orbital Angular Momentum in the Baryon
Song, Xiaotong
2000-01-01
Analytical and numerical results, for the orbital and spin content carried by different quark flavors in the baryons, are given in the chiral quark model with symmetry breaking. The reduction of the quark spin, due to the spin dilution in the chiral splitting processes, is transferred into the orbital motion of quarks and antiquarks. The orbital angular momentum for each quark flavor in the proton as a function of the partition factor $\\kappa$ and the chiral splitting probability $a$ is shown...
Orbital angular momentum photonic quantum interface
Zhou, Zhi-Yuan; Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Shi, Bao-Sen; Guo, Guang-Can
2014-01-01
Light carrying orbital angular momentum (OAM) has great potential in enhancing the information channel capacity in both classical and quantum optical communications. Long distance optical communication requires the wavelengths of light are situated in the low-loss communication windows, but most quantum memories currently being developed for use in a quantum repeater work at different wavelengths, so a quantum interface to bridge the wavelength gap is necessary. So far, such an interface for ...
Orbital angular momentum-entanglement frequency transducer
Zhou, Zhi-Yuan; Liu, Shi-Long; Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Dong, Ming-xin; Shi, Bao-Sen; Guo, Guang-Can
2016-01-01
Entanglement is a vital resource for realizing many tasks such as teleportation, secure key distribution, metrology and quantum computations. To effectively build entanglement between different quantum systems and share information between them, a frequency transducer to convert between quantum states of different wavelengths while retaining its quantum features is indispensable. Information encoded in the photons orbital angular momentum OAM degrees of freedom is preferred in harnessing the ...
Orbital angular momentum entanglement in turbulence
Ibrahim, Alpha Hamadou; Roux, Filippus S.; McLaren, Melanie; Konrad, Thomas; Forbes, Andrew
2013-01-01
The turbulence induced decay of orbital angular momentum (OAM) entanglement between two photons is investigated numerically and experimentally. To compare our results with previous work, we simulate the turbulent atmosphere with a single phase screen based on the Kolmogorov theory of turbulence. We consider two different scenarios: in the first only one of the two photons propagates through turbulence, and in the second both photons propagate through uncorrelated turbulence. Comparing the ent...
Four-photon orbital angular momentum entanglement
Hiesmayr, B. C.; De Dood, M.J.A.; Löffler, W.
2015-01-01
Quantum entanglement shared between more than two particles is essential to foundational questions in quantum mechanics, and upcoming quantum information technologies. So far, up to 14 two-dimensional qubits have been entangled, and an open question remains if one can also demonstrate entanglement of higher-dimensional discrete properties of more than two particles. A promising route is the use of the photon orbital angular momentum (OAM), which enables implementation of novel quantum informa...
Angular momentum distributions in subbarrier fusion reactions
International Nuclear Information System (INIS)
Interest in subbarrier heavy-ion fusion was stimulated by the realization that subbarrier fusion cross sections were enhanced by many orders of magnitude over what would be expected from quantum mechanical one-dimensional barrier penetration. This review focuses on the angular momentum (spin) distributions in heavy-ion fusion reactions. Experimental probes, theoretical considerations, and a comparison of experimental results with model calculations are given. 86 refs., 10 figs
Angular Momentum in Loop Quantum Gravity
Bojowald, Martin
2000-01-01
An angular momentum operator in loop quantum gravity is defined using spherically symmetric states as a non-rotating reference system. It can be diagonalized simultaneously with the area operator and has the familiar spectrum. The operator indicates how the quantum geometry of non-rotating isolated horizons can be generalized to rotating ones and how the recent computations of black hole entropy can be extended to rotating black holes.
Angular Momentum of Dark Matter Black Holes
Frampton, Paul H.
2016-01-01
The putative black holes which may constitute all the dark matter are described by a Kerr metric with only two parameters, mass M and angular momentum J. There has been little discussion of J since it plays no role in the upcoming attempt at detection by microlensing. Nevertheless J does play a central role in understanding the previous lack of detection, especially of CMB distortion. We explain why bounds previously derived from lack of CMB distortion are too strong for primordial black hole...
A practical formula for the radiated angular momentum
Lousto, Carlos O.; Zlochower, Yosef
2007-01-01
We present a simple formula for the radiated angular momentum based on a spin-weighted spherical harmonic decomposition of the Weyl scalar psi_4 representing outgoing radiation in the Kinnersley tetrad. We test our formula by measuring the radiated angular momentum from three simulations of non-spinning equal-mass black-hole binary with orbital angular momentum aligned along the x, y, and z axes respectively. We find that the radiated angular momentum agrees with the differences in the remnan...
Angular momentum nonconservation and conservation in quasiclassical Positronium
Lush, David C.
2010-01-01
It is shown that due to Thomas precession, angular momentum is not generally a constant of the motion in a quasiclassical model of the Positronium atom consisting of circular-orbiting point charges with intrinsic spin and associated magnetic moment. Despite absence of externally-applied torque, angular momentum is a constant of the motion only if the electron and positron intrinsic angular momentum vector components perpendicular to the orbital angular momentum are antiparallel and of equal m...
Angular momentum of a strongly focussed Gaussian beam
Nieminen, Timo A.; Heckenberg, Norman R.; Rubinsztein-Dunlop, Halina
2004-01-01
A circularly polarized rotationally symmetric paraxial laser beams carries hbar angular momentum per photon as spin. Focussing the beam with a rotationally symmetric lens cannot change this angular momentum flux, yet the focussed beam must have spin less than hbar per photon. The remainder of the original spin is converted to orbital angular momentum, manifesting itself as a longitudinal optical vortex at the focus. This demonstrates that optical orbital angular momentum can be generated by a...
Orbital and field angular momentum in the nucleon
Singleton, D; Dzhunushaliev, V.
1998-01-01
The nucleon spin problem raises experimental and theoretical questions regarding the contribution of the orbital angular momentum of the quarks to the total spin of the nucleon. In this article we examine the commutation relationships of various operators that contribute to the total angular momentum of the nucleon. We find that the sum of the orbital plus gluon field angular momentum should satisfy the angular momentum commutators, at least up to the one-loop level. This requirement on the s...
On angular momentum operator in quantum field theory
Iliev, Bozhidar Z.
2002-01-01
Relations between two definitions of (total) angular momentum operator, as a generator of rotations and in the Lagrangian formalism, are explored in quantum field theory. Generally, these definitions result in different angular momentum operators, which are suitable for different purposes in the theory. From the spin and orbital angular momentum operators (in the Lagrangian formalism) are extracted additive terms which are conserved operators and whose sum is the total angular momentum operator.
A critique of the angular momentum sum rules and a new angular momentum sum rule
Bakker, B L G; Trueman, T L
2004-01-01
We show that the expressions in the literature for the tensorial structure of the hadronic matrix elements of the angular momentum operators J are incorrect. Given this disagreement with the published results, we have taken pains to derive the correct expressions in three different ways, two involving explicit physical wave packets and the third, totally independent, based upon the rotational properties of the state vectors. Surprisingly it turns out that the results are very sensitive to the type of relativistic spin state used to describe the motion of the particle i.e. whether a canonical (i.e. boost) state or a helicity state is utilized. We present results for the matrix elements of the angular momentum operators, valid in an arbitrary Lorentz frame, both for helicity states and canonical states. These results are relevant for the construction of angular momentum sum rules, relating the angular momentum of a nucleon to the spin and orbital angular momentum of its constituents. Moreover, we show that it i...
Energy, momentum and angular momentum conservations in de Sitter gravity
Lu, Jia-An
2016-08-01
In de Sitter (dS) gravity, where gravity is a gauge field introduced to realize the local dS invariance of the matter field, two kinds of conservation laws are derived. The first kind is a differential equation for a dS-covariant current, which unites the canonical energy-momentum (EM) and angular momentum (AM) tensors. The second kind presents a dS-invariant current which is conserved in the sense that its torsion-free divergence vanishes. The dS-invariant current unites the total (matter plus gravity) EM and AM currents. It is well known that the AM current contains an inherent part, called the spin current. Here it is shown that the EM tensor also contains an inherent part, which might be observed by its contribution to the deviation of the dust particle’s world line from a geodesic. All the results are compared to the ordinary Lorentz gravity.
Angular Momentum and Galaxy Formation Revisited
Romanowsky, Aaron J.; Fall, S. Michael
2012-12-01
Motivated by a new wave of kinematical tracers in the outer regions of early-type galaxies (ellipticals and lenticulars), we re-examine the role of angular momentum in galaxies of all types. We present new methods for quantifying the specific angular momentum j, focusing mainly on the more challenging case of early-type galaxies, in order to derive firm empirical relations between stellar j sstarf and mass M sstarf (thus extending earlier work by Fall). We carry out detailed analyses of eight galaxies with kinematical data extending as far out as 10 effective radii, and find that data at two effective radii are generally sufficient to estimate total j sstarf reliably. Our results contravene suggestions that ellipticals could harbor large reservoirs of hidden j sstarf in their outer regions owing to angular momentum transport in major mergers. We then carry out a comprehensive analysis of extended kinematic data from the literature for a sample of ~100 nearby bright galaxies of all types, placing them on a diagram of j sstarf versus M sstarf. The ellipticals and spirals form two parallel j sstarf-M sstarf tracks, with log-slopes of ~0.6, which for the spirals are closely related to the Tully-Fisher relation, but for the ellipticals derives from a remarkable conspiracy between masses, sizes, and rotation velocities. The ellipticals contain less angular momentum on average than spirals of equal mass, with the quantitative disparity depending on the adopted K-band stellar mass-to-light ratios of the galaxies: it is a factor of ~3-4 if mass-to-light ratio variations are neglected for simplicity, and ~7 if they are included. We decompose the spirals into disks and bulges and find that these subcomponents follow j sstarf-M sstarf trends similar to the overall ones for spirals and ellipticals. The lenticulars have an intermediate trend, and we propose that the morphological types of galaxies reflect disk and bulge subcomponents that follow separate, fundamental j sstarf
Angular momentum evolution of galaxies in EAGLE
Lagos, Claudia del P; Stevens, Adam R H; Cortese, Luca; Padilla, Nelson D; Davis, Timothy A; Contreras, Sergio; Croton, Darren
2016-01-01
We use EAGLE to study the specific angular momentum of galaxies, j, at z1.2, and then increase as lstars~a. Galaxy mergers reduce lstars by a factor of 2-3. These tracks are driven by both the evolution of the total jstars but also its radial distribution. Regardless of the aperture used to measure j, two distinct channels leading to low jstars in galaxies at z=0 are identified: (i) galaxy mergers, and (ii) early formation of most of the stars.
Angular Momentum of Dark Matter Black Holes
Frampton, Paul H
2016-01-01
The putative black holes which may constitute all the dark matter are described by a Kerr metric with only two parameters, mass M and angular momentum J. There has been little discussion of J since it plays no role in the upcoming attempt at detection by microlensing. Nevertheless J does play a central role in understanding the previous lack of detection, especially of CMB distortion. We explain why bounds previously derived from lack of CMB distortion are too strong for primordial black holes with J non-vanishing. Almost none of the dark matter black holes can be from stellar collapse, and nearly all are primordial, to avoid excessive CMB distortion.
Orbital angular momentum of mixed vortex beams
Czech Academy of Sciences Publication Activity Database
Bouchal, Z.; Kollárová, V.; Zemánek, Pavel; Čižmár, Tomáš
Bellingham : SPIE, 2007, 660907:1-7. ISBN 978-0-8194-6748-5. ISSN 0277-786X. [Czech-Polish-Slovak Conference Wave and Quantum Aspects of Contemporary Optics /15./. Liberec (CZ), 11.09.2006-15.09.2006] R&D Projects: GA MŠk(CZ) LC06007; GA MPO FT-TA2/059 Institutional research plan: CEZ:AV0Z20650511 Keywords : optical vortices * orbital angular momentum * spatial light modulator Subject RIV: BH - Optics, Masers, Lasers
Spin-orbit coupling and the conservation of angular momentum
Hnizdo, V.
2011-01-01
In nonrelativistic quantum mechanics, the total (i.e. orbital plus spin) angular momentum of a charged particle with spin that moves in a Coulomb plus spin-orbit-coupling potential is conserved. In a classical nonrelativistic treatment of this problem, in which the Lagrange equations determine the orbital motion and the Thomas equation yields the rate of change of the spin, the particle's total angular momentum in which the orbital angular momentum is defined in terms of the kinetic momentum ...
Orbital angular momentum of general astigmatic modes
International Nuclear Information System (INIS)
We present an operator method to obtain complete sets of astigmatic Gaussian solutions of the paraxial wave equation. In case of general astigmatism, the astigmatic intensity and phase distribution of the fundamental mode differ in orientation. As a consequence, the fundamental mode has a nonzero orbital angular momentum, which is not due to phase singularities. Analogous to the operator method for the quantum harmonic oscillator, the corresponding astigmatic higher-order modes are obtained by repeated application of raising operators on the fundamental mode. The nature of the higher-order modes is characterized by a point on a sphere, in analogy with the representation of polarization on the Poincare sphere. The north and south poles represent astigmatic Laguerre-Gaussian modes, similar to circular polarization on the Poincare sphere, while astigmatic Hermite-Gaussian modes are associated with points on the equator, analogous to linear polarization. We discuss the propagation properties of the modes and their orbital angular momentum, which depends on the degree of astigmatism and on the location of the point on the sphere
Efficient separation of the orbital angular momentum eigenstates of light
Mirhosseini, Mohammad; Malik, Mehul; Shi, Zhimin; Boyd, Robert W
2013-01-01
Orbital angular momentum (OAM) of light is an attractive degree of freedom for funda- mentals studies in quantum mechanics. In addition, the discrete unbounded state-space of OAM has been used to enhance classical and quantum communications. Unambiguous mea- surement of OAM is a key part of all such experiments. However, state-of-the-art methods for separating single photons carrying a large number of different OAM values are limited to a theoretical separation efficiency of about 77 percent....
Decoherence of orbital angular momentum entanglement in a turbulent atmosphere
Roux, Filippus S.
2010-01-01
The evolution of an entangled photon state propagating through a turbulent atmosphere is formulated in terms of a set of coupled first order differential equations, by using an infinitesimal propagation approach. The orbital angular momentum (OAM) basis is used to described the density matrix of the state. Although the analysis is done in the paraxial limit for a monochromatic optical field, the formalism is comprehensive in the sense that it does not require any assumptions about the strengt...
Polarization control of single photon quantum orbital angular momentum states
Nagali, E.; Sciarrino, F.; De Martini, F.; Piccirillo, B.; Karimi, E.; Marrucci, L.; Santamato, E.
2009-01-01
The orbital angular momentum of photons, being defined in an infinitely dimensional discrete Hilbert space, offers a promising resource for high-dimensional quantum information protocols in quantum optics. The biggest obstacle to its wider use is presently represented by the limited set of tools available for its control and manipulation. Here, we introduce and test experimentally a series of simple optical schemes for the coherent transfer of quantum information from the polarization to the ...
The SKA as a Doorway to Angular Momentum
Obreschkow, D; Popping, A; Power, C; Quinn, P; Staveley-Smith, L
2015-01-01
Angular momentum is one of the most fundamental physical quantities governing galactic evolution. Differences in the colours, morphologies, star formation rates and gas fractions amongst galaxies of equal stellar/baryon mass M are potentially widely explained by variations in their specific stellar/baryon angular momentum j. The enormous potential of angular momentum science is only just being realised, thanks to the emergence of the first simulations of galaxies with converged spins, paralleled by a dramatic increase in kinematic observations. Such observations are still challenged by the fact that most of the stellar/baryon angular momentum resides at large radii. In fact, the radius that maximally contributes to the angular momentum of an exponential disk (3Re-4Re) is twice as large as the radius that maximally contributes to the disk mass; thus converged measurements of angular momentum require either extremely deep IFS data or, alternatively, kinematic measurements of neutral atomic hydrogen (HI), which ...
Coherent detection of orbital angular momentum in radio
Daldorff, L. K. S.; S. M. Mohammadi; Bergman, J. E. S.; Isham, B.; Al-Nuaimi, M. K. T.; Forozesh, K.; Carozzi, T.D.
2015-01-01
The angular momentum propagated by a beam of radiation has two contributions: spin angular momentum (SAM) and orbital angular momentum (OAM). SAM corresponds to wave polarisation, while OAM-carrying beams are characterized by a phase which is a function of azimuth. We demonstrate experimentally that radio beams propagating OAM can be generated and coherently detected using ordinary electric dipole antennas. The results presented here could pave the way for novel radio OAM applications in tech...
Angular momentum and conservation laws for dynamical black holes
Hayward, Sean A.
2006-01-01
Black holes can be practically located (e.g. in numerical simulations) by trapping horizons, hypersurfaces foliated by marginal surfaces, and one desires physically sound measures of their mass and angular momentum. A generically unique angular momentum can be obtained from the Komar integral by demanding that it satisfy a simple conservation law. With the irreducible (Hawking) mass as the measure of energy, the conservation laws of energy and angular momentum take a similar form, expressing ...
Spin and orbital angular momentum of the tensor gauge field
Chen, Xiang-Song; Zhu, Ben-Chao; Murchadha, Niall Ó
2011-01-01
Following the recent studies of the trickiness in spin and orbital angular momentum of the vector gauge fields, we perform here a parallel analysis for the tensor gauge field, which has certain relation to gravitation. Similarly to the vector case, we find a nice feature that after removing all gauge degrees of freedom the angular momentum of the tensor gauge field vanishes for a stationary system. This angular momentum also shows a one-parameter invariance over the infinitely many ways of co...
Quantitative measurement of orbital angular momentum in electron microscopy
Clark, L.; Béché, A.; Guzzinati, G.; Verbeeck, J.
2014-01-01
Abstract: Electron vortex beams have been predicted to enable atomic scale magnetic information measurement, via transfer of orbital angular momentum. Research so far has focused on developing production techniques and applications of these beams. However, methods to measure the outgoing orbital angular momentum distribution are also a crucial requirement towards this goal. Here, we use a method to obtain the orbital angular momentum decomposition of an electron beam, using a multipinhole int...
Parton Orbital Angular Momentum and Final State Interactions
Burkardt, Matthias
2012-01-01
Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar.We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asym...
Quark Orbital Angular Momentum in the MIT Bag Model
Burkardt, Matthias; Jarrah, Abdullah
2010-01-01
Using the MIT bag model, we study the contribution from the gluon vector potential due to the spectators to the orbital angular momentum of a quark in the bag model. For $\\alpha_s = {\\cal O}(1)$, this spectator contribution to the quark orbital angular momentum in the gauge-covariant Ji decomposition is of the same order as the non gauge-covariant quark orbital angular momentum and its magnitude is larger for $d$ than for $u$ quarks and negative for both.
Acoustic orbital angular momentum transfer to matter by chiral scattering
Wunenburger, Régis; Israel, Juan; Lozano, Vazquez; Brasselet, Etienne
2015-01-01
We report on orbital angular momentum exchange between sound and matter mediated by a non-dissipative chiral scattering process. An experimental demonstration is made possible by irradiating a three-dimensional printed, spiral-shaped chiral object with an incident ultrasonic beam carrying zero orbital angular momentum. Chiral refraction is shown to impart a nonzero orbital angular momentum to the scattered field and to rotate the object. This result constitutes a proof of concept of a novel k...
Quark Orbital Angular Momentum and Final State Interactions
Burkardt, Matthias
2014-01-01
Definitions of orbital angular momentum based on Wigner distributions are used to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. The difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive d...
Orbital Angular Momentum Parton Distributions in Light-Front Dynamics
Cano, F.; Faccioli, P.; Scopetta, S.; Traini, M.(Dipartimento di Fisica, Università degli studi di Trento and INFN — TIFPA, Via Sommarive 14, I-38123, Povo (Trento), Italy)
2000-01-01
We study the quark angular momentum distribution in the nucleon within a light-front covariant quark model. Special emphasis is put into the orbital angular momentum: a quantity which is very sensitive to the relativistic treatment of the spin in a light-front dynamical approach. Discrepancies with the predictions of the low-energy traditional quark models where relativistic spin effects are neglected, are visible also after perturbative evolution to higher momentum scales. Orbital angular mo...
Orbital angular momentum from marginals of quadrature distributions
Sanchez-Soto, L. L.; Klimov, A. B.; de la Hoz, P.; Rigas, I.; J. Rehacek; Hradil, Z.; Leuchs, G.
2013-01-01
We set forth a method to analyze the orbital angular momentum of a light field. Instead of using the canonical formalism for the conjugate pair angle-angular momentum, we model this latter variable by the superposition of two independent harmonic oscillators along two orthogonal axes. By describing each oscillator by a standard Wigner function, we derive, via a consistent change of variables, a comprehensive picture of the orbital angular momentum. We compare with previous approaches and show...
Angular momentum evolution in laser-plasma accelerators
Thaury, Cédric; E. Guillaume; Corde, Sébastien; Lehe, R.; Le Bouteiller, M.; Ta Phuoc, K.; X. Davoine; Rax, Jean-Marcel; Rax, J. M.; Rousse, Antoine; Malka, Victor
2013-01-01
The transverse properties of an electron beam are characterized by two quantities, the emittance which indicates the electron beam extend in the phase space and the angular momentum which allows for non-planar electron trajectories. Whereas the emittance of electron beams produced in laser- plasma accelerator has been measured in several experiments, their angular momentum has been scarcely studied. It was demonstrated that electrons in laser-plasma accelerator carry some angular momentum, bu...
Optical communication beyond orbital angular momentum
Trichili, Abderrahmen; Rosales-Guzmán, Carmelo; Dudley, Angela; Ndagano, Bienvenu; Ben Salem, Amine; Zghal, Mourad; Forbes, Andrew
2016-01-01
Mode division multiplexing (MDM) is mooted as a technology to address future bandwidth issues, and has been successfully demonstrated in free space using spatial modes with orbital angular momentum (OAM). To further increase the data transmission rate, more degrees of freedom are required to form a densely packed mode space. Here we move beyond OAM and demonstrate multiplexing and demultiplexing using both the radial and azimuthal degrees of freedom. We achieve this with a holographic approach that allows over 100 modes to be encoded on a single hologram, across a wide wavelength range, in a wavelength independent manner. Our results offer a new tool that will prove useful in realizing higher bit rates for next generation optical networks. PMID:27283799
Arbitrarily tunable orbital angular momentum of photons.
Pan, Yue; Gao, Xu-Zhen; Ren, Zhi-Cheng; Wang, Xi-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian
2016-01-01
Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrarily tunable OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the azimuthally varying polarized vector field. The arbitrarily tunable OAM we presented has the same characteristics as the well-defined integer OAM: intrinsic OAM, uniform local OAM and intensity ring, and propagation stability. The arbitrarily tunable OAM has unique natures: it is allowed to be flexibly tailored and the radius of the focusing ring can have various choices for a desired OAM, which are of great significance to the benefit of surprising applications of the arbitrary OAM. PMID:27378234
Optical communication beyond orbital angular momentum
Trichili, Abderrahmen; Rosales-Guzmán, Carmelo; Dudley, Angela; Ndagano, Bienvenu; Ben Salem, Amine; Zghal, Mourad; Forbes, Andrew
2016-06-01
Mode division multiplexing (MDM) is mooted as a technology to address future bandwidth issues, and has been successfully demonstrated in free space using spatial modes with orbital angular momentum (OAM). To further increase the data transmission rate, more degrees of freedom are required to form a densely packed mode space. Here we move beyond OAM and demonstrate multiplexing and demultiplexing using both the radial and azimuthal degrees of freedom. We achieve this with a holographic approach that allows over 100 modes to be encoded on a single hologram, across a wide wavelength range, in a wavelength independent manner. Our results offer a new tool that will prove useful in realizing higher bit rates for next generation optical networks.
Arbitrarily tunable orbital angular momentum of photons
Pan, Yue; Gao, Xu-Zhen; Ren, Zhi-Cheng; Wang, Xi-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian
2016-01-01
Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrarily tunable OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the azimuthally varying polarized vector field. The arbitrarily tunable OAM we presented has the same characteristics as the well-defined integer OAM: intrinsic OAM, uniform local OAM and intensity ring, and propagation stability. The arbitrarily tunable OAM has unique natures: it is allowed to be flexibly tailored and the radius of the focusing ring can have various choices for a desired OAM, which are of great significance to the benefit of surprising applications of the arbitrary OAM. PMID:27378234
Colliding particles carrying nonzero orbital angular momentum
International Nuclear Information System (INIS)
Photons carrying nonzero orbital angular momentum (twisted photons) are well-known in optics. Recently, using Compton backscattering to boost optical twisted photons to high energies was suggested. Twisted electrons in the intermediate energy range have also been produced recently. Thus, collisions involving energetic twisted particles seem to be feasible and represent a new tool in high-energy physics. Here we discuss some generic features of scattering processes involving twisted particles in the initial and/or final state. In order to avoid additional complications arising from nontrivial polarization states, we focus here on scalar fields only. We show that processes involving twisted particles allow one to perform a Fourier analysis of the plane-wave cross section with respect to the azimuthal angles of the initial particles. In addition, using twisted states, one can probe the autocorrelation function of the amplitude, which is inaccessible in the plane-wave collisions. Finally, we discuss prospects for experimental study of these effects.
Four-photon orbital angular momentum entanglement
Hiesmayr, B C; Löffler, W
2015-01-01
Quantum entanglement shared between more than two particles is essential to foundational questions in quantum mechanics, and upcoming quantum information technologies. So far, up to 14 two-dimensional qubits have been entangled, and an open question remains if one can also demonstrate entanglement of higher-dimensional discrete properties of more than two particles. A promising route is the use of the photon orbital angular momentum (OAM), which enables implementation of novel quantum information protocols, and the study of fundamentally new quantum states. To date, only two of such multidimensional particles have been entangled albeit with ever increasing dimensionality. Here we use pulsed spontaneous parametric downconversion (SPDC) to produce photon quadruplets that are entangled in their OAM, or transverse-mode degrees of freedom; and witness genuine multipartite Dicke-type entanglement. Apart from addressing foundational questions, this could find applications in quantum metrology, imaging, and secret sh...
Arbitrary orbital angular momentum of photons
Pan, Yue; Ren, Zhi-Cheng; Wang, Xi-Lin; Tu, Chenghou; Li, Yongnan; Wang, Hui-Tian
2015-01-01
Orbital angular momentum (OAM) of photons, as a new fundamental degree of freedom, has excited a great diversity of interest, because of a variety of emerging applications. Arbitrarily tunable OAM has gained much attention, but its creation remains still a tremendous challenge. We demonstrate the realization of well-controlled arbitrary OAM in both theory and experiment. We present the concept of general OAM, which extends the OAM carried by the scalar vortex field to the OAM carried by the azimuthally varying polarized vector field. The arbitrary OAM has the same characteristics as the well-defined integer OAM: intrinsic OAM, uniform local OAM and intensity ring, and propagation stability. The arbitrary OAM has unique natures: it is allowed to be flexibly tailored and the radius of the focusing ring can have various choices for a desired OAM, which are of great significance to the benefit of surprising applications of the arbitrary OAM.
Orbital angular momentum entanglement in turbulence
Ibrahim, Alpha Hamadou; McLaren, Melanie; Konrad, Thomas; Forbes, Andrew
2013-01-01
The turbulence induced decay of orbital angular momentum (OAM) entanglement between two photons is investigated numerically and experimentally. To compare our results with previous work, we simulate the turbulent atmosphere with a single phase screen based on the Kolmogorov theory of turbulence. We consider two different scenarios: in the first only one of the two photons propagates through turbulence, and in the second both photons propagate through uncorrelated turbulence. Comparing the entanglement evolution for different OAM values, we found the entanglement to be more robust in turbulence for higher OAM values. We derive an empirical formula for the distance scale at which entanglement decays in term of the scale parameters and the OAM value.
Orbital angular momentum-entanglement frequency transducer
Zhou, Zhi-Yuan; Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Dong, Ming-Xin; Shi, Bao-Sen; Guo, Guang-Can
2016-01-01
Entanglement is a vital resource for realizing many tasks such as teleportation, secure key distribution, metrology and quantum computations. To effectively build entanglement between different quantum systems and share information between them, a frequency transducer to convert between quantum states of different wavelengths while retaining its quantum features is indispensable. Information encoded in the photons orbital angular momentum OAM degrees of freedom is preferred in harnessing the information carrying capacity of a single photon because of its unlimited dimensions. A quantum transducer, which operates at wavelengths from 1558.3 nm to 525 nm for OAM qubits, OAMpolarization hybrid entangled states, and OAM entangled states, is reported for the first time. Nonclassical properties and entanglements are demonstrated following the conversion process by performing quantum tomography, interference, and Bell inequality measurements. Our results demonstrate the capability to create an entanglement link betwe...
Colliding particles carrying nonzero orbital angular momentum
Ivanov, Igor P.
2011-05-01
Photons carrying nonzero orbital angular momentum (twisted photons) are well-known in optics. Recently, using Compton backscattering to boost optical twisted photons to high energies was suggested. Twisted electrons in the intermediate energy range have also been produced recently. Thus, collisions involving energetic twisted particles seem to be feasible and represent a new tool in high-energy physics. Here we discuss some generic features of scattering processes involving twisted particles in the initial and/or final state. In order to avoid additional complications arising from nontrivial polarization states, we focus here on scalar fields only. We show that processes involving twisted particles allow one to perform a Fourier analysis of the plane-wave cross section with respect to the azimuthal angles of the initial particles. In addition, using twisted states, one can probe the autocorrelation function of the amplitude, which is inaccessible in the plane-wave collisions. Finally, we discuss prospects for experimental study of these effects.
Orbital angular momentum photonic quantum interface
Li, Yan; Ding, Dong-Sheng; Zhang, Wei; Shi, Shuai; Shi, Bao-Sen; Guo, Guang-Can
2014-01-01
High dimensional orbital angular momentum (OAM) light states are very important in enhancing the information carrying capacity in optical communications and quantum key distributions. Light at wavelengths of fiber communication windows or free space communication windows are suitable for long distance quantum communication, but most quantum processing tasks are performed in the visible wavelength ranges. The interface to bridge the wavelength gap of single photon with Gaussian shape has been realized, however, to create such interface for OAM-carrying light is a great challenge. We report the demonstration of such an interface to frequency up-conversion of herald single photon OAM state from 1560nm to 525nm with high efficiency by using nonlinear crystal in an external cavity. We show that different single photon OAM light shapes are observed directly by using single photon counting camera and the single photon entangled property is retained in the conversion process.
Optical communication beyond orbital angular momentum.
Trichili, Abderrahmen; Rosales-Guzmán, Carmelo; Dudley, Angela; Ndagano, Bienvenu; Ben Salem, Amine; Zghal, Mourad; Forbes, Andrew
2016-01-01
Mode division multiplexing (MDM) is mooted as a technology to address future bandwidth issues, and has been successfully demonstrated in free space using spatial modes with orbital angular momentum (OAM). To further increase the data transmission rate, more degrees of freedom are required to form a densely packed mode space. Here we move beyond OAM and demonstrate multiplexing and demultiplexing using both the radial and azimuthal degrees of freedom. We achieve this with a holographic approach that allows over 100 modes to be encoded on a single hologram, across a wide wavelength range, in a wavelength independent manner. Our results offer a new tool that will prove useful in realizing higher bit rates for next generation optical networks. PMID:27283799
On angular momentum transport in convection-dominated accretion flows
Igumenshchev, I V
2002-01-01
Convection-dominated accretion flow (CDAF) is a promising model to explain underluminous accreting black holes in X-ray binaries and galactic nuclei. I discuss effects of angular momentum transport in viscous hydrodynamical and MHD CDAFs. In hydrodynamical CDAFs, convection transports angular momentum inward, and this together with outward convection transport of thermal energy determine the radial structure of the flow. In MHD CDAFs, convection can transport angular momentum either inward or outward, depending on properties of turbulence in rotating magnetized plasma, which are not fully understood yet. Direction of convection angular momentum transport can affect the law of rotation of MHD CDAFs.
Mechanical memory for photons with orbital angular momentum
International Nuclear Information System (INIS)
We propose to use an acoustic surface wave as a memory for a photon carrying orbital angular momentum. We clarify the physical mechanism that enables the transfer of information, derive the angular momentum selection rule that must be obeyed in the process and show how to optimize the optoacoustic coupling. We theoretically demonstrate that high fidelities can be achieved, using realistic parameters, for the transfer of a coherent optical Laguerre–Gaussian state, associated with large angular momentum, to a mechanical shear mode. Our results add a significant possibility to the ongoing efforts towards the implementation of quantum information processing using photonic orbital angular momentum. (fast track communication)
Mechanical memory for photons with orbital angular momentum
Shi, H
2013-01-01
We propose to use an acoustic surface wave as a memory for a photon carrying orbital angular momentum. We clarify the physical mechanism that enables the transfer of information, derive the angular momentum selection rule that must be obeyed in the process, and show how to optimize the optoacoustic coupling. We theoretically demonstrate that high fidelities can be achieved, using realistic parameters, for the transfer of a coherent optical Laguerre-Gaussian state, associated with large angular momentum, to a mechanical shear mode. Our results add a significant possibility to the ongoing efforts towards the implementation of quantum information processing using photonic orbital angular momentum.
Angular momentum transfer and equilibrium in heavy-ion reactions
International Nuclear Information System (INIS)
By concentrating on the microscopic degrees of freedom for two colliding ions, we have derived a probability density for angular momentum transfer assuming that, for equilibrium, this probability is proportional to the density of states taken from a fermi gas model. This density has been used to predict angular momentum transfer, assuming first, initial angular momentum fixed, and then, final energy fixed. The results are quite different. The density (final energy fixed) has been used to predict the results of angular momentum transfer experiments. The excellent agreement supports the validity of an assumption of equilibrium. (author)
Total angular momentum for asymptotically flat spacetimes with non-vanishing stress tensor
International Nuclear Information System (INIS)
The asymptotic limit at spatial infinity of Penrose's definition of angular momentum is considered for asymptotically flat spacetimes containing a non-vanishing stress tensor at iota0. The discussion complements some recent work of Bizon, and sufficient conditions for angular momentum conservation in the presence of spin-1/2 or 1 massless fields are obtained. (author)
On angular momentum transfer in binary systems. [stellar orbital period change
Wilson, R. E.; Stothers, R.
1975-01-01
The maximum limit for the conversion of orbital angular momentum into rotational angular momentum of the mass-gaining component in a close binary system is derived. It is shown that this conversion process does not seriously affect the rate of orbital period change and can be neglected in computing the mass transfer rate. Integration of this limit over the entire accretion process results in a value for the maximum accumulated rotational angular momentum that is 3 to 4 times larger than that implied by the observed underluminosity of stars in such systems as Mu(1) Sco, V Pup, SX Aur, and V356 Sgr. It is suggested that shell stars and emission-line stars in binary systems may be produced when the core angular momentum is transferred into an envelope having a rotational angular momentum close to the maximum limit.-
Angular momentum in molecular quantum mechanical integral evaluation
Dunlap, Brett I.
2005-01-01
Solid-harmonic derivatives of quantum-mechanical integrals over Gaussian transforms of scalar, or radial, atomic basis functions create angular momentum about each center. Generalized Gaunt coefficients limit the amount of cross differentiation for multi-center integrals to ensure that cross differentiation does not affect the total angular momentum. The generalized Gaunt coefficients satisfy a number of other selection rules, which are exploited in a new computer code for computing forces in analytic density-functional theory based on robust and variational fitting of the Kohn-Sham potential. Two-center exponents are defined for four or more solid-harmonic differentiations of matrix elements. Those differentiations can either build up angular momentum about the centers or give forces on molecular potential-energy surfaces, thus generalized Gaunt coefficients of order greater than the number of centers are considered. These 4- j generalized Gaunt coefficients and two-center exponents are used to compute the first derivatives of all integrals involving all the Gaussian exponents on a triplet of centers at once. First all angular factors are contracted with the corresponding part of the linear-combination-of-atomic-orbitals density matrix. This intermediate quantity is then reused for the nuclear attraction integral and the integrals corresponding to each basis function in the analytic fit of the Kohn-Sham potential in the muffin-tin-like, but analytic, Slater-Roothaan method that allows molecules to dissociate into atoms having any desired energy, including the experimental electronic energy. The energy is stationary in all respects and all forces precisely agree with a previous code in tests on small molecules. During geometry optimization of an icosahedral C 720 fullerene computing these angular factors and transforming them via the 4- j generalized Gaunt coefficient takes more than sixty percent of the total computer time. These same angular factors could be used
Analysis of orbital angular momentum of a misaligned optical beam
Energy Technology Data Exchange (ETDEWEB)
Vasnetsov, M V [Optics Group, Department of Physics and Astronomy, University of Glasgow, Glasgow (United Kingdom); Pas' ko, V A [Institute of Physics, National Academy of Sciences of Ukraine, Prospect Nauki 46, Kiev 03028 (Ukraine); Soskin, M S [Institute of Physics, National Academy of Sciences of Ukraine, Prospect Nauki 46, Kiev 03028 (Ukraine)
2005-02-01
We report an analysis of the orbital angular momentum of an optical beam misaligned with respect to a reference axis. Both laterally displaced and angularly deflected Laguerre-Gaussian beams are represented in terms of the superposition of azimuthal harmonics with well-defined orbital angular momentum. Simultaneous parallel displacement and angular tilt cause the coupling between azimuthal harmonics and therefore change the projection of the orbital angular momentum on the reference axis. Rotation of beams around the reference axis was simulated by attributing corresponding rotational frequency shifts to the components.
The pretzelosity TMD and quark orbital angular momentum
Energy Technology Data Exchange (ETDEWEB)
Lorce, C. [IPNO, Universite Paris-Sud, CNRS/IN2P3, 91406 Orsay (France); LPT, Universite Paris-Sud, CNRS, 91406 Orsay (France); Pasquini, B., E-mail: pasquini@pv.infn.it [Dipartimento di Fisica, Universita degli Studi di Pavia, Pavia (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia (Italy)
2012-04-12
We study the connection between the quark orbital angular momentum and the pretzelosity transverse-momentum dependent parton distribution function. We discuss the origin of this relation in quark models, identifying as key ingredient for its validity the assumption of spherical symmetry for the nucleon in its rest frame. Finally we show that the individual quark contributions to the orbital angular momentum obtained from this relation cannot be interpreted as the intrinsic contributions, but include the contribution from the transverse centre of momentum which cancels out only in the total orbital angular momentum.
Identification of Observables for Quark and Gluon Orbital Angular Momentum
Courtoy, Aurore; Hernandez, J Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha
2014-01-01
A new debate has recently arisen on the subject of orbital angular momentum in QCD, in particular on its observability and on its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three generalized parton distributions, and it is therefore more readily observable, while, due to parity constraints, canonical angular momentum, if defined as suggested in the literature in terms of generalized transverse momentum distributions, cannot be observed in scattering processes involving a single hadronic reaction plane.
The pretzelosity TMD and quark orbital angular momentum
International Nuclear Information System (INIS)
We study the connection between the quark orbital angular momentum and the pretzelosity transverse-momentum dependent parton distribution function. We discuss the origin of this relation in quark models, identifying as key ingredient for its validity the assumption of spherical symmetry for the nucleon in its rest frame. Finally we show that the individual quark contributions to the orbital angular momentum obtained from this relation cannot be interpreted as the intrinsic contributions, but include the contribution from the transverse centre of momentum which cancels out only in the total orbital angular momentum.
Orbital angular momentum filter of photon based on spin-orbital angular momentum coupling
Chen, Dong-Xu; Zhang, Pei; Liu, Rui-Feng; Li, Hong-Rong; Gao, Hong; Li, Fu-Li
2015-10-01
Determination of the orbital angular momentum (OAM) of vortex beams has been hotly discussed. We propose a new type of method to determine the orbital angular momentum of photons, filtering. We present an OAM filter scheme which consists of a cavity with a polarization-based Mach-Zehnder interferometer inside. Our scheme can purify the specific OAM with unitary efficiency theoretically without the pre-knowledge of the OAM spectrum of the input light. We also implemented a proof-of-principle experiment to demonstrate the feasibility of our scheme by cascading three interferometers. Our method offers a new way to determine the OAM spectrum of a light and this method can also be exploited to prepare the eigenstate of vortex beams.
Observables for Quarks and Gluons Orbital Angular Momentum Distributions
Liuti, Simonetta; Courtoy, Aurore; Goldstein, Gary R.; Hernandez, J. Osvaldo Gonzalez; Rajan, Abha
2015-02-01
We discuss the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term - Ji decomposition - or a canonical term - Jaffe-Manohar decomposition. Orbital angular momentum has been connected in each decomposition to a different observable, a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and a twist three Generalized Parton Distribution (GPD) for the kinetic term. While the latter appears as an azimuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments.
Orbital angular momentum filter of photon based on spin-orbital angular momentum coupling
Energy Technology Data Exchange (ETDEWEB)
Chen, Dong-Xu; Zhang, Pei, E-mail: zhangpei@mail.ustc.edu.cn; Liu, Rui-Feng; Li, Hong-Rong; Gao, Hong; Li, Fu-Li
2015-10-16
Highlights: • We propose a scheme that can filter the orbital angular momentum of photons. • Our scheme filters the specific mode with destroying the mode. • Our scheme can theoretically filter infinity modes. • The orientation of Dove lens and HWP decides which mode will output. - Abstract: Determination of the orbital angular momentum (OAM) of vortex beams has been hotly discussed. We propose a new type of method to determine the orbital angular momentum of photons, filtering. We present an OAM filter scheme which consists of a cavity with a polarization-based Mach–Zehnder interferometer inside. Our scheme can purify the specific OAM with unitary efficiency theoretically without the pre-knowledge of the OAM spectrum of the input light. We also implemented a proof-of-principle experiment to demonstrate the feasibility of our scheme by cascading three interferometers. Our method offers a new way to determine the OAM spectrum of a light and this method can also be exploited to prepare the eigenstate of vortex beams.
Orbital angular momentum filter of photon based on spin-orbital angular momentum coupling
International Nuclear Information System (INIS)
Highlights: • We propose a scheme that can filter the orbital angular momentum of photons. • Our scheme filters the specific mode with destroying the mode. • Our scheme can theoretically filter infinity modes. • The orientation of Dove lens and HWP decides which mode will output. - Abstract: Determination of the orbital angular momentum (OAM) of vortex beams has been hotly discussed. We propose a new type of method to determine the orbital angular momentum of photons, filtering. We present an OAM filter scheme which consists of a cavity with a polarization-based Mach–Zehnder interferometer inside. Our scheme can purify the specific OAM with unitary efficiency theoretically without the pre-knowledge of the OAM spectrum of the input light. We also implemented a proof-of-principle experiment to demonstrate the feasibility of our scheme by cascading three interferometers. Our method offers a new way to determine the OAM spectrum of a light and this method can also be exploited to prepare the eigenstate of vortex beams
Quark and gluon orbital angular momentum: Where are we?
Lorcé, Cédric
2016-01-01
The orbital angular momentum of quarks and gluons contributes significantly to the proton spin budget and attracted a lot of attention in the recent years, both theoretically and experimentally. We summarize the various definitions of parton orbital angular momentum together with their relations with parton distributions functions. In particular, we highlight current theoretical puzzles and give some prospects.
Anomalous Magnetic Moments and Quark Orbital Angular Momentum
Burkardt, M.; Schnell, G.(University of the Basque Country UPV/EHU, 48080 Bilbao, Spain)
2005-01-01
We derive an inequality for the distribution of quarks with non-zero orbital angular momentum, and thus demonstrate, in a model-independent way, that a non-vanishing anomalous magnetic moment requires both a non-zero size of the target as well as the presence of wave function components with quark orbital angular momentum L_z>0.
Quark and Gluon Orbital Angular Momentum: Where Are We?
Lorcé, Cédric; Liu, Keh-Fei
2016-06-01
The orbital angular momentum of quarks and gluons contributes significantly to the proton spin budget and attracted a lot of attention in the recent years, both theoretically and experimentally. We summarize the various definitions of parton orbital angular momentum together with their relations with parton distributions functions. In particular, we highlight current theoretical puzzles and give some prospects.
Conservation of Orbital Angular Momentum in Stimulated Down-Conversion
Caetano, D. P.; Almeida, M. P.; Ribeiro, P. H. Souto; Huguenin, J. A. O.; Santos, B. Coutinho dos; Khoury, A. Z.
2001-01-01
We report on an experiment demonstrating the conservation of orbital angular momentum in stimulated down-conversion. The orbital angular momentum is not transferred to the individual beams of the spontaneous down-conversion, but it is conserved when twin photons are taken individually. We observe the conservation law for an individual beam of the down-conversion through cavity-free stimulated emission.
Orbital Angular Momentum in Scalar Diquark Model and QED
BC, Hikmat; Burkardt, Matthias
2011-01-01
We compare the orbital angular momentum of the 'quark' in the scalar diquark model as well as that of the electron in QED (to order {\\alpha}) obtained from the Jaffe-Manohar de- composition to that obtained from the Ji relation. We estimate the importance of the vector potential in the definition of orbital angular momentum.
Evolution Equations for Higher Moments of Angular Momentum Distributions
Haegler, P.; Schaefer, A
1998-01-01
Based on a sumrule for the nucleon spin we expand quark and gluon orbital angular momentum operators and derive an evolution matrix for higher moments of the corresponding distributions. In combination with the spin-dependent DGLAP-matrix we find a complete set of spin and orbital angular momentum evolution equations.
Creation of orbital angular momentum states with chiral polaritonic lenses
Dall, Robert; Fraser, Michael D.; Desyatnikov, Anton S.; Li, Guangyao; Brodbeck, Sebastian; Kamp, Martin; Schneider, Christian; Höfling, Sven; Ostrovskaya, Elena A.
2014-01-01
Controlled transfer of orbital angular momentum to exciton-polariton Bose-Einstein condensate spontaneously created under incoherent, off-resonant excitation conditions is a long-standing challenge in the field of microcavity polaritonics. We demonstrate, experimentally and theoretically, a simple and efficient approach to generation of nontrivial orbital angular momentum states by using optically-induced potentials -- chiral polaritonic lenses.
Non-negative Wigner functions for orbital angular momentum states
Rigas, I.; Sanchez-Soto, L. L.; Klimov, A. B.; J. Rehacek; Hradil, Z.
2009-01-01
The Wigner function of a pure continuous-variable quantum state is non-negative if and only if the state is Gaussian. Here we show that for the canonical pair angle and angular momentum, the only pure states with non-negative Wigner functions are the eigenstates of the angular momentum. Some implications of this surprising result are discussed.
Orbital Angular Momentum in Scalar Diquark Model and QED
International Nuclear Information System (INIS)
We compare the orbital angular momentum of the 'quark' in the scalar diquark model as well as that of the electron in QED (to order α) obtained from the Jaffe-Manohar decomposition to that obtained from the Ji relation. We estimate the importance of the vector potential in the definition of orbital angular momentum. (author)
Non-negative Wigner functions for orbital angular momentum states
International Nuclear Information System (INIS)
The Wigner function of a pure continuous-variable quantum state is non-negative if and only if the state is Gaussian. Here we show that for the canonical pair angle and angular momentum, the only pure states with non-negative Wigner functions are the eigenstates of the angular momentum. Some implications of this surprising result are discussed.
Quark and Gluon Orbital Angular Momentum: Where Are We?
Lorcé, Cédric; Liu, Keh-Fei
2016-02-01
The orbital angular momentum of quarks and gluons contributes significantly to the proton spin budget and attracted a lot of attention in the recent years, both theoretically and experimentally. We summarize the various definitions of parton orbital angular momentum together with their relations with parton distributions functions. In particular, we highlight current theoretical puzzles and give some prospects.
Distilling angular momentum nonclassical states in trapped ions
Militello, B.; Messina, A.
2004-09-01
In the spirit of quantum nondemolition measurements, we show that by exploiting suitable vibronic couplings and repeatedly measuring the atomic population of a confined ion, it is possible to distill center-of-mass vibrational states with a well-defined square of angular momentum or, alternatively, angular momentum projection Schrödinger cat states.
Distilling angular momentum nonclassical states in trapped ions
Militello, B
2004-01-01
In the spirit of Quantum Non-Demolition Measurements, we show that exploiting suitable vibronic couplings and repeatedly measuring the atomic population of a confined ion, it is possible to distill center of mass vibrational states with well defined square of angular momentum or, alternatively, angular momentum projection Schr\\"odinger cat states.
Angular Momentum Phase State Representation for Quantum Pendulum
Institute of Scientific and Technical Information of China (English)
FAN Hong-Yi; WANG Ji-Suo
2005-01-01
To consummate the quantum pendulum theory whose Hamiltonian takes bosonic operator formalism and manifestly exhibits its dynamic behaviour in the entangled state representation, we introduce angular momentum state representation and phase state representation. It turns out that the angular momentum state is the partial wave expansion of the entangled state.
Acoustic orbital angular momentum transfer to matter by chiral scattering
Wunenburger, Régis; Israel Vazquez Lozano, Juan; Brasselet, Etienne
2015-10-01
We report on orbital angular momentum exchange between sound and matter mediated by a non-dissipative chiral scattering process. An experimental demonstration is made possible by irradiating a three-dimensional printed, spiral-shaped chiral object with an incident ultrasonic beam carrying zero orbital angular momentum. Chiral refraction is shown to impart a nonzero orbital angular momentum to the scattered field and to rotate the object. This result constitutes a proof of concept of a novel kind of acoustic angular manipulation of matter.
Alignment of wave functions for angular momentum projection
Taniguchi, Yasutaka
2016-01-01
Angular momentum projection is used to obtain eigen states of angular momentum from general wave functions. Multi-configuration mixing calculation with angular momentum projection is an important microscopic method in nuclear physics. For accurate multi-configuration mixing calculation with angular momentum projection, concentrated distribution of $z$ components $K$ of angular momentum in the body-fixed frame ($K$-distribution) is favored. Orientation of wave functions strongly affects $K$-distribution. Minimization of variance of $\\hat{J}_z$ is proposed as an alignment method to obtain wave functions that have concentrated $K$-distribution. Benchmark calculations are performed for $\\alpha$-$^{24}$Mg cluster structure, triaxially superdeformed states in $^{40}$Ar, and Hartree-Fock states of some nuclei. The proposed alignment method is useful and works well for various wave functions to obtain concentrated $K$-distribution.
Angular momentum in quantum mechanics as a group study topic
International Nuclear Information System (INIS)
A largely practical approach to the teaching of angular momentum in quantum mechanics at the undergraduate level is described. In an intensive seven week period towards the end of their final year, undergraduates working in pairs perform experiments in nuclear physics which demonstrate some of the important properties of angular momentum. Three experiments are selected and discussed in this article to illustrate the teaching method. The existence of intrinsic spin and parity is investigated by measuring the polarisation of annihilation radiation; the conservation of angular momentum is demonstrated by a measurement of orbital angular momentum in a nucleon transfer reaction and the coupling of angular momenta is illustrated by the method of angular correlation. (author)
Cyclic transformation of orbital angular momentum modes
Schlederer, Florian; Krenn, Mario; Fickler, Robert; Malik, Mehul; Zeilinger, Anton
2016-04-01
The spatial modes of photons are one realization of a QuDit, a quantum system that is described in a D-dimensional Hilbert space. In order to perform quantum information tasks with QuDits, a general class of D-dimensional unitary transformations is needed. Among these, cyclic transformations are an important special case required in many high-dimensional quantum communication protocols. In this paper, we experimentally demonstrate a cyclic transformation in the high-dimensional space of photonic orbital angular momentum (OAM). Using simple linear optical components, we show a successful four-fold cyclic transformation of OAM modes. Interestingly, our experimental setup was found by a computer algorithm. In addition to the four-cyclic transformation, the algorithm also found extensions to higher-dimensional cycles in a hybrid space of OAM and polarization. Besides being useful for quantum cryptography with QuDits, cyclic transformations are key for the experimental production of high-dimensional maximally entangled Bell-states.
Millimetre Wave with Rotational Orbital Angular Momentum.
Zhang, Chao; Ma, Lu
2016-01-01
Orbital angular momentum (OAM) has been widely studied in fibre and short-range communications. The implementation of millimetre waves with OAM is expected to increase the communication capacity. Most experiments demonstrate the distinction of OAM modes by receiving all of the energy in the surface vertical to the radiation axis in space. However, the reception of OAM is difficult in free space due to the non-zero beam angle and divergence of energy. The reception of OAM in the space domain in a manner similar to that in optical fibres (i.e., receiving all of the energy rings vertical to the radiation axis) is impractical, especially for long-distance transmission. Here, we fabricate a prototype of the antenna and demonstrate that rather than in the space domain, the OAM can be well received in the time domain via a single antenna by rotating the OAM wave at the transmitter, i.e., the radio wave with rotational OAM. The phase and frequency measured in the experiment reveal that for different OAM modes, the received signals act as a commonly used orthogonal frequency division multiplexing (OFDM) signal in the time domain. This phase rotation has promising prospects for use in the practical reception of different OAMs of millimetre waves in long-distance transmission. PMID:27596746
Cyclic transformation of orbital angular momentum modes
Schlederer, Florian; Fickler, Robert; Malik, Mehul; Zeilinger, Anton
2015-01-01
The spatial modes of photons are one realization of a QuDit, a quantum system that is described in a D-dimensional Hilbert space. In order to perform quantum information tasks with QuDits, a general class of D-dimensional unitary transformations is needed. Among these, cyclic transformations are an important special case required in many high-dimensional quantum communication protocols. In this paper, we experimentally demonstrate a cyclic transformation in the high-dimensional space of photonic orbital angular momentum (OAM). Using simple linear optical components, we show a successful four-fold cyclic transformation of OAM modes. Interestingly, our experimental setup was found by a computer algorithm. In addition to the four-cyclic transformation, the algorithm also found extensions to higher-dimensional cycles in a hybrid space of OAM and polarization. Besides being useful for quantum cryptography with QuDits, cyclic transformations are key for the experimental production of high-dimensional maximally enta...
Orbital angular momentum in /sup 3/He-A-italic
Energy Technology Data Exchange (ETDEWEB)
Balatskii-breve, A.V.; Mineev, V.P.
1985-12-01
The intrinsic angular momentum in the A-italic phase of superfluid /sup 3/He is found in terms of the response to the angular velocity of rotation. It is shown that in the weak-coupling approximation at an arbitrary temperature and with allowance for the Fermi-liquid renormalization the intrinsic angular momentum is small in accordance with the smallness of the asymmetry in the distribution of particles and holes.
Quantum orbital angular momentum of elliptically-symmetric light
Plick, William N.; Krenn, Mario; Fickler, Robert; Ramelow, Sven; Zeilinger, Anton
2012-01-01
We present a quantum mechanical analysis of the orbital angular momentum of a class of recently discovered elliptically-symmetric stable light fields --- the so-called Ince-Gauss modes. We study, in a fully quantum formalism, how the orbital angular momentum of these beams varies with their ellipticity and discover several compelling features, including: non-monotonic behavior, stable beams with real continuous (non-integer) orbital angular momenta, and orthogonal modes with the same orbital ...
Identification of Observables for Quark and Gluon Orbital Angular Momentum
Courtoy, Aurore; Goldstein, Gary R.; Hernandez, J. Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha(University of Virginia – Physics Department, 382 McCormick Rd., Charlottesville, VA 22904, USA)
2014-01-01
A new debate has recently arisen on the subject of orbital angular momentum in QCD, in particular on its observability and on its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three generalized parton distributions, and it is therefore more readily observable, while, due to parity constr...
Angular momentum projection with quantum effects
International Nuclear Information System (INIS)
We have improved a simple and rapid method of calculating expectation values of operators in states of good angular momentum projected from a hedgehog baryon state introduced by Birse et al. We have included the contributions of quantum mesons, while in the original method only classical meson fields were included. The method has been applied to models where the mean-field approximation does not include loop terms. Hence, for reasons of consistency, contributions of quantum loops to the matrix elements have been dropped. The symmetry of the hedgehog state under grand reversal (the combined operation of time reversal and eiπI2, where I is the isospin operator) introduces remarkable simplification in the calculation of matrix elements of operators which do not contain time derivatives of meson fields. The quantum meson contributions turn out to be 3/2/left-angle B|J2|B right-angle times the classical meson-field contributions, with |B right-angle being the hedgehog state. Such operators are encountered in the calculation of nucleon magnetic moments, gA(0) and gπNN(0)/2M. Calculation of charge radii involves operators containing time derivatives of meson fields and requires the knowledge of wave functions of quantum mesons. Proper nonperturbative treatment, even though at the tree level, requires that these wave functions describe the motion of the mesons in the potential generated by the baryon. Fortunately, because of the neglect of the loop terms, one needs only the even-parity, grand-spin-1 states which are purely pionic. The Goldberger-Treiman relations, an exact result for the model, serves as a partial test of the method of calculation discussed here
Measuring the Orbital Angular Momentum of Electron Beams
Guzzinati, Giulio; Béché, Armand; Verbeeck, Jo
2014-01-01
The recent demonstration of electron vortex beams has opened up the new possibility of studying orbital angular momentum (OAM) in the interaction between electron beams and matter. To this aim, methods to analyze the OAM of an electron beam are fundamentally important and a necessary next step. We demonstrate the measurement of electron beam OAM through a variety of techniques. The use of forked holographic masks, diffraction from geometric apertures, diffraction from a knife-edge and the application of an astigmatic lens are all experimentally demonstrated. The viability and limitations of each are discussed with supporting numerical simulations.
Generalized Parton Distributions Describing Partonic Orbital Angular Momentum
Liuti, Simonetta; Engelhardt, Michael; Rajan, Abha; Courtoy, Aurore
2015-04-01
We discuss orbital angular momentum in QCD, in particular, its observability, and its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three Generalized Parton Distributions (GPDs), and it is therefore readily observable in Deeply Virtual Compton Scattering experiments. On the other hand, canonical angular momentum is defined in terms of a Generalized Transverse Momentum Distribution (GTMD) and it can be therefore observed in scattering processes involving an additional hadronic reaction plane. A comparison between the two definitions can be performed by extending to GTMDs the techniques previously developed for lattice calculations of Transverse Momentum Distributions (TMDs) evaluating the matrix elements of quark bilocal operators containing a staple-shaped Wilson connection. This work was funded in part by U.S. D.O.E. Grant DE-FG02-01ER4120.
Generation and detection of orbital angular momentum via metasurface
Jin, Jinjin; Luo, Jun; Zhang, Xiaohu; Gao, Hui; Li, Xiong; Pu, Mingbo; Gao, Ping; Zhao, Zeyu; Luo, Xiangang
2016-04-01
Beams carrying orbital angular momentum possess a significant potential for modern optical technologies ranging from classical and quantum communication to optical manipulation. In this paper, we theoretically design and experimentally demonstrate an ultracompact array of elliptical nanoholes, which could convert the circularly polarized light into the cross-polarized vortex beam. To measure the topological charges of orbital angular momentum in a simple manner, another elliptical nanoholes array is designed to generate reference beam as a reference light. This approach may provide a new way for the generation and detection of orbital angular momentum in a compact device.
Experimental Evidence for Partonic Orbital Angular Momentum at RHIC
Energy Technology Data Exchange (ETDEWEB)
Fields, Douglas E. [University of New Mexico, Department of Physics and Astronomy, Albuquerque, NM 871331 (United States)
2011-12-14
Although one might naively anticipate that the proton, being the lowest baryonic energy state, would be in a L = 0 state, the current theoretical understanding is that it must carry orbital angular momentum in order, for example, to have a non-zero anomalous magnetic moment. I will review the experimental evidence linked theoretically to orbital angular momentum of the proton's constituents from the RHIC experiments and summarize by presenting a challenge to the theory community--to develop a consistent framework which can explain the spin polarization asymmetries seen at RHIC and elsewhere, and give insight to the partonic wave-functions including orbital angular momentum.
Femtosecond dynamics of spin and orbital angular momentum in nickel
Energy Technology Data Exchange (ETDEWEB)
Stamm, Christian; Pontius, Niko; Holldack, Karsten; Quast, Torsten; Kachel, Torsten; Wietstruk, Marko; Mitzner, Rolf; Duerr, Hermann A. [Elektronenspeicherring BESSY II, Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, 12489 Berlin (Germany)
2009-07-01
At the BESSY femtoslicing source we measure X-ray magnetic circular dichroism (XMCD) with 100 fs time resolution. By virtue of the XMCD sum rules, we find that the spin and orbital momenta in a thin nickel film are quenched with a time constant of 150 fs upon excitation with a fs laser pulse. This represents the first unambiguous proof that the total electronic angular momentum is transferred to the lattice on the same ultrafast time scale. The quenching of orbital angular momentum also is a serious constraint for models of angular momentum dissipation.
Experimental Evidence for Partonic Orbital Angular Momentum at RHIC
International Nuclear Information System (INIS)
Although one might naively anticipate that the proton, being the lowest baryonic energy state, would be in a L = 0 state, the current theoretical understanding is that it must carry orbital angular momentum in order, for example, to have a non-zero anomalous magnetic moment. I will review the experimental evidence linked theoretically to orbital angular momentum of the proton's constituents from the RHIC experiments and summarize by presenting a challenge to the theory community--to develop a consistent framework which can explain the spin polarization asymmetries seen at RHIC and elsewhere, and give insight to the partonic wave-functions including orbital angular momentum.
Quark Orbital Angular Momentum and Final State Interactions
Burkardt, Matthias
2014-01-01
Definitions of orbital angular momentum based on Wigner distributions are used to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. The difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.
Coherent detection of orbital angular momentum in radio
Daldorff, L K S; Bergman, J E S; Isham, B; Al-Nuaimi, M K T; Forozesh, K; Carozzi, T D
2015-01-01
The angular momentum propagated by a beam of radiation has two contributions: spin angular momentum (SAM) and orbital angular momentum (OAM). SAM corresponds to wave polarisation, while OAM-carrying beams are characterized by a phase which is a function of azimuth. We demonstrate experimentally that radio beams propagating OAM can be generated and coherently detected using ordinary electric dipole antennas. The results presented here could pave the way for novel radio OAM applications in technology and science, including radio communication, passive remote sensing, and new types of active (continuous or pulsed transmission) electromagnetic measurements.
Electro-optic analyzer of angular momentum hyperentanglement.
Wu, Ziwen; Chen, Lixiang
2016-01-01
Characterizing a high-dimensional entanglement is fundamental in quantum information applications. Here, we propose a theoretical scheme to analyze and characterize the angular momentum hyperentanglement that two photons are entangled simultaneously in spin and orbital angular momentum. Based on the electro-optic sampling with a proposed hyper-entanglement analyzer and the simple matrix operation using Cramer rule, our simulations show that it is possible to retrieve effectively both the information about the degree of polarization entanglement and the spiral spectrum of high-dimensional orbital angular momentum entanglement. PMID:26911530
Squeezing of X waves with orbital angular momentum
Ornigotti, Marco; Szameit, Alexander; Conti, Claudio
2016-01-01
Multi-level quantum protocols may potentially supersede standard quantum optical polarization-encoded protocols in terms of amount of information transmission and security. However, for free space telecomunications, we do not have tools for limiting loss due to diffraction and perturbations, as for example turbulence in air. Here we study propagation invariant quantum X-waves with angular momentum; this representation expresses the electromagnetic field as a quantum gas of weakly interacting bosons. The resulting spatio-temporal quantized light pulses are not subject to diffraction and dispersion, and are intrinsically resilient to disturbances in propagation. We show that spontaneous down-conversion generates squeezed X-waves useful for quantum protocols. Surprisingly the orbital angural momentum affects the squeezing angle, and we predict the existence of a characteristic axicon aperture for maximal squeezing. There results may boost the applications in free space of quantum optical transmission and multi-l...
The origin of angular momentum in dark matter halos
Vitvitska, M; Kravtsov, A V; Bullock, J S; Wechsler, R H; Primack, Joel R
2002-01-01
We propose a new explanation for the origin of angular momentum in galaxies and their dark halos, in which the halos obtain their spin through the cumulative acquisition of angular momentum from satellite accretion. In our model, the build-up of angular momentum is a random walk process associated with the mass assembly history of the halo's major progenitor. We assume no correlation between the angular momenta of accreted objects. Using the extended Press-Schechter approximation, we calculate the growth of mass, angular momentum, and spin parameter $\\lambda$ for many halos. Our random walk model reproduces the key features of the angular momentum of halos found in N-body simulations: a lognormal distribution in $\\lambda$ with an average of $ \\approx 0.04$, independent of mass and redshift. The evolution of the spin parameter in individual halos in this model is quite different from the steady increase with time of angular momentum in the tidal torque picture. We find both in N-body simulations and in our ran...
Cygorek, M.; Tamborenea, P. I.; Axt, V. M.
2015-09-01
We study the spin dynamics of carriers due to the Rashba interaction in semiconductor quantum disks and wells after excitation with light with orbital angular momentum. We find that although twisted light transfers orbital angular momentum to the excited carriers and the Rashba interaction conserves their total angular momentum, the resulting electronic spin dynamics is essentially the same for excitation with light with orbital angular momentum l =+|l | and l =-|l | . The differences between cases with different values of |l | are due to the excitation of states with slightly different energies and not to the different angular momenta per se and vanish for samples with large radii where a k -space quasicontinuum limit can be established. These findings apply not only to the Rashba interaction but also to all other envelope-function-approximation spin-orbit Hamiltonians like the Dresselhaus coupling.
Pluto Moons exhibit Orbital Angular Momentum Quantization per Mass
Potter F.
2012-01-01
The Pluto satellite system of the planet plus five moons is shown to obey the quan- tum celestial mechanics (QCM) angular momentum per mass quantization condition predicted for any gravitationally bound system.
Pluto Moons exhibit Orbital Angular Momentum Quantization per Mass
Directory of Open Access Journals (Sweden)
Potter F.
2012-10-01
Full Text Available The Pluto satellite system of the planet plus five moons is shown to obey the quan- tum celestial mechanics (QCM angular momentum per mass quantization condition predicted for any gravitationally bound system.
Phase-space distributions and orbital angular momentum
Directory of Open Access Journals (Sweden)
Pasquini B.
2014-06-01
Full Text Available We review the concept of Wigner distributions to describe the phase-space distributions of quarks in the nucleon, emphasizing the information encoded in these functions about the quark orbital angular momentum.
Electronic orbital angular momentum and magnetism of graphene
Energy Technology Data Exchange (ETDEWEB)
Luo, Ji, E-mail: ji.luo@upr.edu
2014-10-01
Orbital angular momentum (OAM) of graphene electrons in a perpendicular magnetic field is calculated and corresponding magnetic moment is used to investigate the magnetism of perfect graphene. Variation in magnetization demonstrates its decrease with carrier-doping, plateaus in a large field, and de Haas–van Alphen oscillation. Regulation of graphene's magnetism by a parallel electric field is presented. The OAM originates from atomic-scale electronic motion in graphene lattice, and vector hopping interaction between carbon atomic orbitals is the building element. A comparison between OAM of graphene electrons, OAM of Dirac fermions, and total angular momentum of the latter demonstrates their different roles in graphene's magnetism. Applicability and relation to experiments of the results are discussed. - Highlights: • Orbital angular momentum of graphene electrons is calculated. • Orbital magnetic moment of graphene electrons is obtained. • Variation in magnetization of graphene is calculated. • Roles of different kinds of angular momentum are investigated.
Phase-space distributions and orbital angular momentum
Pasquini B.; Lorcé C.
2014-01-01
We review the concept of Wigner distributions to describe the phase-space distributions of quarks in the nucleon, emphasizing the information encoded in these functions about the quark orbital angular momentum.
Electronic orbital angular momentum and magnetism of graphene
International Nuclear Information System (INIS)
Orbital angular momentum (OAM) of graphene electrons in a perpendicular magnetic field is calculated and corresponding magnetic moment is used to investigate the magnetism of perfect graphene. Variation in magnetization demonstrates its decrease with carrier-doping, plateaus in a large field, and de Haas–van Alphen oscillation. Regulation of graphene's magnetism by a parallel electric field is presented. The OAM originates from atomic-scale electronic motion in graphene lattice, and vector hopping interaction between carbon atomic orbitals is the building element. A comparison between OAM of graphene electrons, OAM of Dirac fermions, and total angular momentum of the latter demonstrates their different roles in graphene's magnetism. Applicability and relation to experiments of the results are discussed. - Highlights: • Orbital angular momentum of graphene electrons is calculated. • Orbital magnetic moment of graphene electrons is obtained. • Variation in magnetization of graphene is calculated. • Roles of different kinds of angular momentum are investigated
Angular Momentum Generation from Holographic Gravitational Chern-Simons Model
Wu, Chaolun
2014-01-01
We study parity-violating effects, particularly the generation of angular momentum density and its relation to the parity-odd and dissipationless transport coefficient Hall viscosity, in strongly-coupled quantum fluid systems in 2+1 dimensions using holographic method. We employ a (3+1)-dimensional holographic model of Einstein-Maxwell system with a gravitational Chern-Simons term coupled to a dynamical scalar field. The scalar can condensate and this breaks the parity spontaneously. We find that when the scalar condensates, a non-vanishing angular momentum density and an associated edge current are generated by the gravitational Chern-Simons term, together with the emergence of Hall viscosity. Both angular momentum density and Hall viscosity acquire membrane paradigm forms and are only determined by the geometry and condensate near the horizon. We present both general analytic results and numeric results which take back-reactions into account. The ratio between Hall viscosity and angular momentum density is ...
A Compact Orbital Angular Momentum Spectrometer Using Quantum Zeno Interrogation
Bierdz, Paul; Deng, Hui
2014-01-01
We present a scheme to measure the orbital angular momentum spectrum of light using a precisely timed optical loop and quantum non-demolition measurements. We also discuss the influence of imperfect optical components.
On the Observability of the Quark Orbital Angular Momentum Distribution
Courtoy, Aurore; Hernandez, J Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha
2013-01-01
We argue that due to Parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions -- the generalized transverse momentum distributions -- that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon, can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated to orbital angular momentum %to deeply virtual Compton scattering provide observables related to orbital angular momentum and are related to the target-spin asymmetry in deeply virtual Compton scattering, already mea...
Generation and detection of orbital angular momentum via metasurface
Jin, Jinjin; Luo, Jun; Zhang, Xiaohu; Gao, Hui; Li, Xiong; Pu, Mingbo; Gao, Ping; Zhao, Zeyu; Luo, Xiangang
2016-01-01
Beams carrying orbital angular momentum possess a significant potential for modern optical technologies ranging from classical and quantum communication to optical manipulation. In this paper, we theoretically design and experimentally demonstrate an ultracompact array of elliptical nanoholes, which could convert the circularly polarized light into the cross-polarized vortex beam. To measure the topological charges of orbital angular momentum in a simple manner, another elliptical nanoholes a...
Mechanical Faraday effect for orbital angular momentum-carrying beams
Wisniewski-Barker, Emma; Gibson, Graham; Franke-Arnold, Sonja; Boyd, Robert W; Padgett, Miles J.
2014-01-01
When linearly polarised light is transmitted through a spinning window, the plane of polarisation is rotated. This rotation arises through a phase change that is applied to the circularly polarised states corresponding to the spin angular momentum (SAM). Here we show an analogous effect for the orbital angular momentum (OAM), where a differential phase between the positive and negative modes (±ℓ) is observed as a rotation of the transmitted image. For normal materials, this rotation is on the...
A quantum memory for orbital angular momentum photonic qubits
Nicolas, A; Veissier, L.; Giner, L.; Giacobino, E.; Maxein, D.; Laurat, J.
2013-01-01
Among the optical degrees of freedom, the orbital angular momentum of light provides unique properties, including mechanical torque action with applications for light manipulation, enhanced sensitivity in imaging techniques and potential high-density information coding for optical communication systems. Recent years have also seen a tremendous interest in exploiting orbital angular momentum at the single-photon level in quantum information technologies. In this endeavor, here we demonstrate t...
Fundamental methods to measure the orbital angular momentum of light
Berkhout, Gregorius Cornelis Gerardus (Joris)
2011-01-01
Light is a ubiquitous carrier of information. This information can be encoded in the intensity, direction, frequency and polarisation of the light and, which was described more recently, in its orbital angular momentum. Although creating light beams with orbital angular momentum is relatively easy, measuring this property has proven to be difficult. In this thesis we present two fundamental methods to solve this problem. First, we show that by analysing the interference pattern behind a multi...
Spin-to-Orbital Angular Momentum Conversion in Semiconductor Microcavities
Manni, Francesco; Lagoudakis, Konstantinos G.; Paraïso, Taofiq; Cerna, Roland; Léger, Yoan; Liew, Timothy Chi Hin; Shelykh, Ivan; Kavokin, Alexey V.; Morier-Genoud, François; Deveaud-Plédran, Benoît
2011-01-01
We experimentally demonstrate a technique for the generation of optical beams carrying orbital angular momentum using a planar semiconductor microcavity. Despite being isotropic systems with no structural gyrotropy, semiconductor microcavities, because of the transverse-electric–transverse-magnetic polarization splitting that they feature, allow for the conversion of the circular polarization of an incoming laser beam into the orbital angular momentum of the transmitted light field. The proce...
Angular Momentum of Electromagnetic Field in Areas of Polarization Singularities
Directory of Open Access Journals (Sweden)
Mokhun I.
2006-06-01
Full Text Available It is shown that physical manifestations of any optical singularity are, in one way or another, related to a specific temporal behaviour of the field, no matter scalar or vector cases are realized. Polarization singularities of the vector field are associated with a presence or absence of angular momentum of electromagnetic field. In the vicinity of -point the orbital angular momentum is observed if the sings of topological charge of the vibration phase and the handedness factor are different.
Continuous Variable Entanglement and Squeezing of Orbital Angular Momentum States
Lassen, Mikael Østergaard; Leuchs, Gerd; Andersen, Ulrik Lund
2009-01-01
We report the first experimental characterization of the first-order continuous variable orbital angular momentum states. Using a spatially nondegenerate optical parametric oscillator (OPO) we produce quadrature entanglement between the two first-order Laguerre-Gauss modes. The family of orbital angular momentum modes is mapped on an orbital Poincaré sphere, where the mode's position on the sphere is spanned by the three orbital parameters. Using a nondegenerate OPO we produce squeezing of th...
Quark Orbital Angular Momentum and Exclusive Processes at HERMES
International Nuclear Information System (INIS)
A first attempt for a model-dependent extraction of the orbital angular momentum of quarks in the nucleon has been made, based on HERMES data on exclusive processes and their description in terms of generalized parton distributions. An overview of the HERMES data on hard exclusive electroproduction of real photons (Deeply-Virtual Compton Scattering) and mesons is given, focusing on the measurements relevant to the extraction of quark orbital angular momentum
Quark Orbital Angular Momentum and Exclusive Processes at HERMES
Ellinghaus, F.
2006-11-01
A first attempt for a model-dependent extraction of the orbital angular momentum of quarks in the nucleon has been made, based on HERMES data on exclusive processes and their description in terms of generalized parton distributions. An overview of the HERMES data on hard exclusive electroproduction of real photons (Deeply-Virtual Compton Scattering) and mesons is given, focusing on the measurements relevant to the extraction of quark orbital angular momentum.
Mechanical memory for photons with orbital angular momentum
Shi, H.; Bhattacharya, M.
2013-01-01
We propose to use an acoustic surface wave as a memory for a photon carrying orbital angular momentum. We clarify the physical mechanism that enables the transfer of information, derive the angular momentum selection rule that must be obeyed in the process, and show how to optimize the optoacoustic coupling. We theoretically demonstrate that high fidelities can be achieved, using realistic parameters, for the transfer of a coherent optical Laguerre-Gaussian state, associated with large angula...
Molecular chirality and the orbital angular momentum of light
Andrews, David L; Romero, Luciana C. Davila; Babiker, Mohamed
2003-01-01
Optical beams with a new and distinctive type of helicity have become the subject of much recent interest. While circularly polarised light comprises photons with spin angular momentum, these optically engineered 'twisted beams' (optical vortices) are endowed with orbital angular momentum. Here, the wave- front surface of the electromagnetic fields assumes helical form. To date, optical vortices have generally been studied only in their interactions with achiral matter. This study assesses wh...
Conservation of orbital angular momentum in air core optical fibers
Gregg, P; Kristensen, P; Ramachandran, S.
2014-01-01
Light's orbital angular momentum (OAM) is a conserved quantity in cylindrically symmetric media; however, it is easily destroyed by free-space turbulence or fiber bends, because anisotropic perturbations impart angular momentum. We observe the conservation of OAM even in the presence of strong bend perturbations, with fibers featuring air cores that appropriately sculpt the modal density of states. In analogy to the classical reasoning for the enhanced stability of spinning tops with increasi...
Relaxation times for angular momentum in damped nuclear reactions
International Nuclear Information System (INIS)
The evolution of the angular momentum distribution in damped nuclear reactions is discussed within the framework of the nucleon exchange transport model. First order equations are derived for the time evolution of the mean values and covariances of the spin variables. Solutions are given for 1400 MeV 165Ho + 165Ho reactions at various values of total angular momentum and total kinetic energy loss. Spin dispersions are well described by the calculations
The angular momentum of baryons and dark matter halos revisited
Kimm, Taysun; Devriendt, Julien; Slyz, Adrianne; Pichon, Christophe; Kassin, Susan A.; Dubois, Yohan
2011-01-01
Recent theoretical studies have shown that galaxies at high redshift are fed by cold, dense gas filaments, suggesting angular momentum transport by gas differs from that by dark matter. Revisiting this issue using high-resolution cosmological hydrodynamics simulations with adaptive mesh refinement, we find that at the time of accretion, gas and dark matter do carry a similar amount of specific angular momentum, but that it is systematically higher than that of the dark matter halo as a whole....
Students' Understanding of the Addition of Angular Momentum
Singh, Chandralekha
2016-01-01
We describe the difficulties advanced undergraduate and graduate students have with concepts related to the addition of angular momentum. We also describe the development and implementation of a research-based learning tool, a Quantum Interactive Learning Tutorial (QuILT), to reduce these difficulties. The preliminary evaluation shows that the QuILT on the addition of angular momentum is helpful in improving students' understanding of these concepts.
Topological defects, geometric phases, and the angular momentum of light
Tiwari, S C
2007-01-01
Recent reports on the intriguing features of vector vortex bearing beams are analyzed using geometric phases in optics. It is argued that the spin redirection phase induced circular birefringence is the origin of topological phase singularities arising in the inhomogeneous polarization patterns. A unified picture of recent results is presented based on this proposition. Angular momentum shift within the light beam (OAM) has exact equivalence with the angular momentum holonomy associated with the geometric phase consistent with our conjecture.
Dynamical birth and thermal death of angular momentum in heavy ion reactions
International Nuclear Information System (INIS)
Dynamical and equilibrium angular momentum fractionation as well as equilibrium angular momentum distributions associated with a variety of collective modes of the intermediate complex are described. (orig.)
Malik, Mehul; Leach, Jonathan; Boyd, Robert W
2012-01-01
We implement an interferometric method using two angular slits to measure the orbital angular momentum (OAM) mode spectrum of a partially coherent field. As the angular separation of the slits changes, an interference pattern for a particular OAM mode is obtained. The visibility of this interference pattern as a function of angular separation is equivalent to the angular correlation function of the field. By Fourier transforming the angular correlation function obtained from the double angular slit interference, we are able to calculate the OAM spectrum of the partially coherent field. This method has potential application for characterizing the OAM spectrum in high-dimensional quantum information protocols.
A new uncertainty relation for angular momentum and angle
International Nuclear Information System (INIS)
An uncertainty relation of the form ΔL2ΔSo >=sup(h/2π)/sub(2) is derived for angular momentum and angle. The non-linear operator So measures angles and has a simple interpretation. Subject to very general conditions of rotational invariance the above relation is unique. Radial momentum is not quantized
Orbital angular momentum exchange in post-collision interaction
Energy Technology Data Exchange (ETDEWEB)
Burgt, P.J.M. van der; Eck, J. van; Heideman, H.G.M.
1985-03-14
The authors have measured the angular distribution of electrons ejected by the He**(2s/sup 2/)/sup 1/S autoionising state after its electron impact excitation via the He/sup -/(2s2p/sup 2/)/sup 2/D resonance. Taking into account interference with electrons from the direct ionisation of helium, analysis of this angular distribution provides evidence for angular momentum exchange between ejected and scattered electrons during the post-collision interaction.
Quark Wigner Distributions and Orbital Angular Momentum
Lorce, Cédric; Pasquini, B.
2011-01-01
We study the Wigner functions of the nucleon which provide multidimensional images of the quark distributions in phase space. These functions can be obtained through a Fourier transform in the transverse space of the generalized transverse-momentum dependent parton distributions. They depend on both the transverse position and the three-momentum of the quark relative to the nucleon, and therefore combine in a single picture all the information contained in the generalized parton distributions...
Spin and orbital angular momentum in the proton
International Nuclear Information System (INIS)
Since the announcement of the proton spin crisis by the European Muon Collaboration there has been considerable progress in unravelling the distribution of spin and orbital angular momentum within the proton. We review the current status of the problem, showing that not only have strong upper limits have been placed on the amount of polarized glue in the proton but that the experimental determination of the spin content has become much more precise. It is now clear that the origin of the discrepancy between experiment and the naive expectation of the fraction of spin carried by the quarks and anti-quarks in the proton lies in the non-perturbative structure of the proton. We explain how the features expected in a modern, relativistic and chirally symmetric description of nucleon structure naturally explain the current data. The consequences of this explanation for the presence of orbital angular momentum on quarks and gluons is reviewed and comparison made with recent results from lattice QCD and experimental data. (author)
Optimization of Angular-Momentum Biases of Reaction Wheels
Lee, Clifford; Lee, Allan
2008-01-01
RBOT [RWA Bias Optimization Tool (wherein RWA signifies Reaction Wheel Assembly )] is a computer program designed for computing angular momentum biases for reaction wheels used for providing spacecraft pointing in various directions as required for scientific observations. RBOT is currently deployed to support the Cassini mission to prevent operation of reaction wheels at unsafely high speeds while minimizing time in undesirable low-speed range, where elasto-hydrodynamic lubrication films in bearings become ineffective, leading to premature bearing failure. The problem is formulated as a constrained optimization problem in which maximum wheel speed limit is a hard constraint and a cost functional that increases as speed decreases below a low-speed threshold. The optimization problem is solved using a parametric search routine known as the Nelder-Mead simplex algorithm. To increase computational efficiency for extended operation involving large quantity of data, the algorithm is designed to (1) use large time increments during intervals when spacecraft attitudes or rates of rotation are nearly stationary, (2) use sinusoidal-approximation sampling to model repeated long periods of Earth-point rolling maneuvers to reduce computational loads, and (3) utilize an efficient equation to obtain wheel-rate profiles as functions of initial wheel biases based on conservation of angular momentum (in an inertial frame) using pre-computed terms.
International Nuclear Information System (INIS)
The angular momentum built up in the fragment nuclei during a damped nuclear reaction is subsequently lost through decay. Since the decay is very fast, the only way to learn about the angular momentum accumulated in the nuclei is to observe the sequential decay products. The present investigation aims at providing precise methods for calculating properties of the sequential decay on the basis of primary spin distributions calculated with the transfer theory
The Angular Momentum of Baryons and Dark Matter Halos Revisited
Kimm, Taysun; Devriendt, Julien; Slyz, Adrianne; Pichon, Christophe; Kassin, Susan A.; Dubois, Yohan
2011-01-01
Recent theoretical studies have shown that galaxies at high redshift are fed by cold, dense gas filaments, suggesting angular momentum transport by gas differs from that by dark matter. Revisiting this issue using high-resolution cosmological hydrodynamics simulations with adaptive-mesh refinement (AMR), we find that at the time of accretion, gas and dark matter do carry a similar amount of specific angular momentum, but that it is systematically higher than that of the dark matter halo as a whole. At high redshift, freshly accreted gas rapidly streams into the central region of the halo, directly depositing this large amount of angular momentum within a sphere of radius r = 0.1R(sub vir). In contrast, dark matter particles pass through the central region unscathed, and a fraction of them ends up populating the outer regions of the halo (r/R(sub vir) > 0.1), redistributing angular momentum in the process. As a result, large-scale motions of the cosmic web have to be considered as the origin of gas angular momentum rather than its virialised dark matter halo host. This generic result holds for halos of all masses at all redshifts, as radiative cooling ensures that a significant fraction of baryons remain trapped at the centre of the halos. Despite this injection of angular momentum enriched gas, we predict an amount for stellar discs which is in fair agreement with observations at z=0. This arises because the total specific angular momentum of the baryons (gas and stars) remains close to that of dark matter halos. Indeed, our simulations indicate that any differential loss of angular momentum amplitude between the two components is minor even though dark matter halos continuously lose between half and two-thirds of their specific angular momentum modulus as they evolve. In light of our results, a substantial revision of the standard theory of disc formation seems to be required. We propose a new scenario where gas efficiently carries the angular momentum generated
Induced Compression of White Dwarfs by Angular Momentum Loss
Boshkayev, Kuantay; Ruffini, Remo; Zhami, Bakytzhan
2016-01-01
We investigate isolated sub- and super-Chandrasekhar white dwarfs which lose angular momentum through magnetic dipole braking. We construct constant rest mass sequences by fulfilling all stability criteria of rotating configurations and show how the main structure of white dwarfs such as the central density, mean radius and angular velocity change with time. We explicitly demonstrate that all isolated white dwarfs regardless of their masses, by angular momentum loss, shrink and increase their central density. We also analyze the effects of the structure parameters on the evolution timescale both in the case of constant magnetic field and constant magnetic flux.
Notes on the quantum theory of angular momentum
Feenberg, Eugene
1999-01-01
This classic, concise text has served a generation of physicists as an exceptionally useful guide to the mysteries of angular momenta and Clebsch-Gordon Coefficients. Derived from notes originally prepared to assist graduate students in reading research papers on atomic, molecular, and nuclear structure, the text first reviews the basic elements of quantum theory. It then examines the development of the fundamental commutation relations for angular momentum components and vector operators, and the ways in which matrix elements and eigenvalues of the angular momentum operators are worked out f
Orbital Angular Momentum in the Chiral Quark Model
Song, Xiaotong
1998-01-01
We developed a new and unified scheme for describing both quark spin and orbital angular momenta in symmetry-breaking chiral quark model. The loss of quark spin in the chiral splitting processes is compensated by the gain of the orbital angular momentum carried by quarks and antiquarks. The sum of both spin and orbital angular momenta carried by quarks and antiquarks is 1/2. The analytic and numerical results for the spin and orbital angular momenta carried by quarks and antiquarks in the nuc...
The angular momentum of baryons and dark matter halos revisited
Kimm, Taysun; Slyz, Adrianne; Pichon, Christophe; Kassin, Susan A; Dubois, Yohan
2011-01-01
Recent theoretical studies have shown that galaxies at high redshift are fed by cold, dense gas filaments, suggesting angular momentum transport by gas differs from that by dark matter. Revisiting this issue using high-resolution cosmological hydrodynamics simulations with adaptive mesh refinement, we find that at the time of accretion, gas and dark matter do carry a similar amount of specific angular momentum, but that it is systematically higher than that of the dark matter halo as a whole. At high redshift, freshly accreted gas rapidly streams into the central region of the halo, directly depositing this large amount of angular momentum within a sphere of radius r=0.1rvir. In contrast, dark matter particles pass through the central region unscathed, and a fraction of them ends up populating the outer regions of the halo (r/rvir>0.1), redistributing angular momentum in the process. As a result, large-scale motions of the cosmic web have to be considered as the origin of gas angular momentum rather than its ...
From transverse angular momentum to photonic wheels
Aiello, Andrea; Banzer, Peter; Neugebauer, Martin; Leuchs, Gerd
2015-12-01
Scientists have known for more than a century that light possesses both linear and angular momenta along the direction of propagation. However, only recent advances in optics have led to the notion of spinning electromagnetic fields capable of carrying angular momenta transverse to the direction of motion. Such fields enable numerous applications in nano-optics, biosensing and near-field microscopy, including three-dimensional control over atoms, molecules and nanostructures, and allowing for the realization of chiral nanophotonic interfaces and plasmonic devices. Here, we report on recent developments of optics with light carrying transverse spin. We present both the underlying principles and the latest achievements, and also highlight new capabilities and future applications emerging from this young yet already advanced field of research.
The Effects of Angular Momentum on Halo Profiles
Lentz, Erik W.; Quinn, Thomas R.; Rosenberg, Leslie J.
2016-05-01
The near universality of DM halo density profiles provided by N-body simulations proved to be robust against changes in total mass density, power spectrum, and some forms of initial velocity dispersion. Here we study the effects of coherently spinning up an isolated DM-only progenitor on halo structure. Halos with spins within several standard deviations of the simulated mean (λ ≲ 0.20) produce profiles with negligible deviations from the universal form. Only when the spin becomes quite large (λ ≳ 0.20) do departures become evident. The angular momentum distribution also exhibits a near universal form, which is also independent of halo spin up to λ ≲ 0.20. A correlation between these epidemic profiles and the presence of a strong bar in the virialized halo is also observed. These bar structures bear resemblance to the radial orbit instability in the rotationless limit.
Tighter spots of light with superposed orbital angular momentum beams
Woźniak, Paweł; Bouchard, Frédéric; Karimi, Ebrahim; Leuchs, Gerd; Boyd, Robert W
2016-01-01
The possibility of focusing light to an ever tighter spot has important implications for many applications and fields of optics research, such as nano-optics and plasmonics, laser-scanning microscopy, optical data storage and many more. The size of lateral features of the field at the focus depends on several parameters, including the numerical aperture of the focusing system, but also the wavelength and polarization, phase and intensity distribution of the input beam. Here, we study the smallest achievable focal feature sizes of coherent superpositions of two co-propagating beams carrying opposite orbital angular momentum. We investigate the feature sizes for this class of beams not only in the scalar limit, but also use a fully vectorial treatment to discuss the case of tight focusing. Both our numerical simulations and our experimental results confirm that lateral feature sizes considerably smaller than those of a tightly focused Gaussian light beam can be observed. These findings may pave the way for impr...
DARK MATTER ANGULAR MOMENTUM PROFILE FROM THE JEANS EQUATION
International Nuclear Information System (INIS)
Cosmological simulations of dark matter (DM) structures have shown that the equilibrated DM structures have a fairly small angular momentum. It appears from these N-body simulations that the radial profile of the angular momentum has an almost universal behavior, even if the different DM structures have experienced very different formation and merger histories. We suggest a perturbed Jeans equation, which includes a rotational term. This is done under a reasonable assumed form of the change in the distribution function. By conjecturing that the (new) subdominant rotation term must be proportional to the (old) dominant mass term, we find a clear connection, which is in rather good agreement with the results of recent high-resolution simulations. We also present a new connection between the radial profiles of the angular momentum and the velocity anisotropy, which is also in fair agreement with numerical findings. Finally, we show how the spin parameter λ increases as a function of radius.
Orbital angular momentum exchange in cylindrical-lens mode converters
Energy Technology Data Exchange (ETDEWEB)
Padgett, M J; Allen, L [Department of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom)
2002-04-01
Cylindrical-lens mode converters (Beijersbergen M W, Allen L, van der Veen H E L O and Woerdman J P 1993 Opt. Commun. 96 123-32) are used to transform between Hermite-Gaussian and Laguerre-Gaussian modes with a resulting transfer of angular momentum to the light beam and a corresponding torque on the lenses. By numerically analysing both the total and local angular momentum of the light beam, we explain the origin of this torque and confirm that is not evenly distributed between the lenses. We also confirm that any vortex contained within the beam may change sign even when the orbital angular momentum of the beam remains constant.
A quantum memory for orbital angular momentum photonic qubits
Nicolas, A; Giner, L; Giacobino, E; Maxein, D; Laurat, J
2013-01-01
Among the optical degrees of freedom, the orbital angular momentum of light provides unique properties, including mechanical torque action with applications for light manipulation, enhanced sensitivity in imaging techniques and potential high-density information coding for optical communication systems. Recent years have also seen a tremendous interest in exploiting orbital angular momentum at the single-photon level in quantum information technologies. In this endeavor, here we demonstrate the implementation of a quantum memory for quantum bits encoded in this optical degree of freedom. We generate various qubits with computer-controlled holograms, store and retrieve them on demand. We further analyse the retrieved states by quantum tomography and thereby demonstrate fidelities exceeding the classical benchmark, confirming the quantum functioning of our storage process. Our results provide an essential capability for future networks exploring the promises of orbital angular momentum of photons for quantum in...
Probing angular momentum coherence in a twin-atom interferometer
de Carvalho, Carlos R; Impens, François; Robert, J; Medina, Aline; Zappa, F; Faria, N V de Castro
2014-01-01
We propose to use a double longitudinal Stern-Gerlach atom interferometer in order to investigate quantitatively the angular momentum coherence of molecular fragments. Assuming that the dissociated molecule has a null total angular momentum, we investigate the propagation of the corresponding atomic fragments in the apparatus. We show that the envisioned interferometer enables one to distinguish unambiguously a spin-coherent from a spin-incoherent dissociation, as well as to estimate the purity of the angular momentum density matrix associated with the fragments. This setup, which may be seen as an atomic analogue of a twin-photon interferometer, can be used to investigate the suitability of molecule dissociation processes -- such as the metastable hydrogen atoms H($2^2 S$)-H($2^2 S$) dissociation - for coherent twin-atom optics.
Generation of Orbital Angular Momentum Carrying Beams in Semiconductor Microcavities
International Nuclear Information System (INIS)
Full text: It is notable that all techniques for the creation of beams with orbital angular momentum, to the best of our knowledge, require an optically inhomogeneous and/or anisotropic material or strong focusing. In this work, we demonstrate that the spin-to-orbital angular momentum (SOAM) conversion can also be achieved in a planar semiconductor microcavity. Despite being an isotropic system, microcavities exhibit a polarization splitting between transverse electric - transverse magnetic (TE-TM) modes, which induces the appearance of an L = +2 orbital angular momentum in one of the circular polarizations, under excitation in the cross-circular polarization [1]. The vertical entities resulting from this conversion process can be regarded as the optical equivalent of a pair of half-quantum vortices. We provide a theoretical model which rigorously derives the principle of the SOAM conversion and quantitatively reproduces the experimental observations. (author)
Valley-contrasting orbital angular momentum in photonic valley crystals
Chen, Xiaodong; Dong, Jianwen
2016-01-01
Valley, as a degree of freedom, has been exploited to realize valley-selective Hall transport and circular dichroism in two-dimensional layered materials. On the other hand, orbital angular momentum of light with helical phase distribution has attracted great attention for its unprecedented opportunity to optical communicagtions, atom trapping, and even nontrivial topology engineering. Here, we reveal valley-contrasting orbital angular momentum in all-dielectric photonic valley crystals. Selective excitation of valley chiral bulk states is realized by sources carrying orbital angular momentum with proper chirality. Valley dependent edge states, predictable by nonzero valley Chern number, enable to suppress the inter-valley scattering along zigzag boundary, leading to broadband robust transmission in Z-shape bend without corner morphological optimization. Our work may open up a new door towards the discovery of novel quantum states and the manipulation of spin-orbit interaction of light in nanophotonics.
A quantum memory for orbital angular momentum photonic qubits
Nicolas, A.; Veissier, L.; Giner, L.; Giacobino, E.; Maxein, D.; Laurat, J.
2014-03-01
Among the optical degrees of freedom, the orbital angular momentum of light provides unique properties, including mechanical torque action, which has applications for light manipulation, enhanced sensitivity in imaging techniques and potential high-density information coding for optical communication systems. Recent years have also seen a tremendous interest in exploiting orbital angular momentum at the single-photon level in quantum information technologies. In pursuing this endeavour, we demonstrate here the implementation of a quantum memory for quantum bits encoded in this optical degree of freedom. We generate various qubits with computer-controlled holograms, store and retrieve them on demand using a dynamic electromagnetically induced transparency protocol. We further analyse the retrieved states by quantum tomography and thereby demonstrate fidelities exceeding the classical benchmark, confirming the quantum functioning of our storage process. Our results provide an essential capability for future networks exploring the promises of orbital angular momentum of photons for quantum information applications.
Angular Momentum Sensitive Two-Center Interference
Ilchen, M.; Glaser, L.; Scholz, F.; Walter, P.; Deinert, S.; Rothkirch, A.; Seltmann, J.; Viefhaus, J.; Decleva, P.; Langer, B.; Knie, A.; Ehresmann, A.; Al-Dossary, O. M.; Braune, M.; Hartmann, G.; Meissner, A.; Tribedi, L. C.; AlKhaldi, M.; Becker, U.
2014-01-01
In quantum mechanics the Young-type double-slit experiment can be performed with electrons either traveling through a double slit or being coherently emitted from two inversion symmetric molecular sites. In the latter one the valence photoionization cross sections of homonuclear diatomic molecules were predicted to oscillate over kinetic energy almost 50 years ago. Beyond the direct proof of the oscillatory behavior of these photoionization cross sections σ, we show that the angular distribution of the emitted electrons reveals hitherto unexplored information on the relative phase shift between the corresponding partial waves through two-center interference patterns.
Yu, Haohai; Zhang, Huaijin; Wang, Yicheng; Han, Shuo; Yang, Haifang; Xu, Xiangang; Wang, Zhengping; Petrov, V.; Wang, Jiyang
2013-01-01
We demonstrate the optical orbital angular momentum conservation during the transfer process from subwavelength plasmonic vortex lens (PVLs) to light and the generating process of surface plasmon polaritons (SPPs). Illuminating plasmonic vortex lenses with beams carrying optical orbital angular momentum, the SP vortices with orbital angular momentum were generated and inherit the optical angular momentum of light beams and PVLs. The angular momentum of twisting SP electromagnetic field is tun...
On the observability of the quark orbital angular momentum distribution
Energy Technology Data Exchange (ETDEWEB)
Courtoy, Aurore, E-mail: aurore.courtoy@ulg.be [IFPA, AGO Department, Université de Liège, Bât. B5, Sart Tilman, B-4000 Liège (Belgium); Laboratori Nazionali di Frascati, INFN, Frascati (Italy); Goldstein, Gary R., E-mail: gary.goldstein@tufts.edu [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Osvaldo Gonzalez Hernandez, J., E-mail: jog4m@virginia.edu [Istituto Nazionale di Fisica Nucleare (INFN) – Sezione di Torino, via P. Giuria, 1, 10125 Torino (Italy); Liuti, Simonetta, E-mail: sl4y@virginia.edu [University of Virginia – Physics Department, 382 McCormick Rd., Charlottesville, VA 22904 (United States); Laboratori Nazionali di Frascati, INFN, Frascati (Italy); Rajan, Abha, E-mail: ar5xc@virginia.edu [University of Virginia – Physics Department, 382 McCormick Rd., Charlottesville, VA 22904 (United States)
2014-04-04
We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions – the generalized transverse momentum distributions – that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light-cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated with orbital angular momentum are related to the target-spin asymmetry in deeply virtual Compton scattering, already measured at HERMES.
On the observability of the quark orbital angular momentum distribution
International Nuclear Information System (INIS)
We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions – the generalized transverse momentum distributions – that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light-cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated with orbital angular momentum are related to the target-spin asymmetry in deeply virtual Compton scattering, already measured at HERMES.
On the observability of the quark orbital angular momentum distribution
Courtoy, Aurore; Goldstein, Gary R.; Osvaldo Gonzalez Hernandez, J.; Liuti, Simonetta; Rajan, Abha
2014-04-01
We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions - the generalized transverse momentum distributions - that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light-cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated with orbital angular momentum are related to the target-spin asymmetry in deeply virtual Compton scattering, already measured at HERMES.
Continuous Variable Entanglement and Squeezing of Orbital Angular Momentum States
DEFF Research Database (Denmark)
Lassen, Mikael Østergaard; Leuchs, Gerd; Andersen, Ulrik Lund
2009-01-01
We report the first experimental characterization of the first-order continuous variable orbital angular momentum states. Using a spatially nondegenerate optical parametric oscillator (OPO) we produce quadrature entanglement between the two first-order Laguerre-Gauss modes. The family of orbital...... angular momentum modes is mapped on an orbital Poincaré sphere, where the mode's position on the sphere is spanned by the three orbital parameters. Using a nondegenerate OPO we produce squeezing of these parameters, and as an illustration, we reconstruct the “cigar-shaped” uncertainty volume on the...... orbital Poincaré sphere....
Quark Spin and Orbital Angular Momentum in the Baryon
Song, X.
1999-01-01
The spin and orbital angular momentum carried by different quark flavors in the nucleon are calculated in the SU(3) chiral quark model with symmetry-breaking. The model is extended to all octet and decuplet baryons. In this model, the reduction of the quark spin, due to the spin dilution in the chiral splitting processes, is transferred into the orbital motion of quarks and antiquarks. The orbital angular momentum for each quark flavor in the proton as function of the partition factor $\\kappa...
Radius of a Photon Beam with Orbital Angular Momentum
Davis, Basil L.; Kaplan, L.
2012-01-01
We analyze the transverse structure of the Gouy phase shift in light beams carrying orbital angular momentum and show that the Gouy radius $r_G$ characterizing the transverse structure grows as $\\sqrt{2p+|\\ell|+1}$ with the nodal number $p$ and photon angular momentum number $\\ell$. The Gouy radius is shown to be closely related to the root-mean-square radius of the beam, and the divergence of the radius away from the focal plane is determined. Finally, we analyze the rotation of the Poynting...
Kinetic description of electron plasma waves with orbital angular momentum
Energy Technology Data Exchange (ETDEWEB)
Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)
2012-11-15
We describe the kinetic theory of electron plasma waves with orbital angular momentum or twisted plasmons. The conditions for a twisted Landau resonance to exist are established, and this concept is introduced for the first time. Expressions for the kinetic dispersion relation and for the electron Landau damping are derived. The particular case of a Maxwellian plasma is examined in detail. The new contributions to wave dispersion and damping due the orbital angular momentum are discussed. It is shown that twisted plasmons can be excited by rotating electron beams.
Undulator radiation carrying spin and orbital angular momentum
Energy Technology Data Exchange (ETDEWEB)
Sasaki, Shigemi [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)], E-mail: sasaki@aps.anl.gov; McNulty, Ian; Dejus, Roger [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)
2007-11-11
We show that the radiation from a helical undulator not only carries spin angular momentum (circular polarization) but also orbital angular momentum. This exotic property of the undulator radiation may be useful in coherent X-ray imaging and scattering experiments and to probe electronic transitions in matter by orbital dichroism spectroscopy. Also, we present that a new magnet configuration, similar to the structure of Figure-8 undulator or the PERA undulator, may generate right- and left-hand circularly polarized off-axis radiation simultaneously.
Undulator radiation carrying spin and orbital angular momentum.
Energy Technology Data Exchange (ETDEWEB)
Sasaki, S.; McNulty, I.; Dejus, R.; X-Ray Science Division
2007-11-11
We show that the radiation from a helical undulator not only carries spin angular momentum (circular polarization) but also orbital angular momentum. This exotic property of the undulator radiation may be useful in coherent X-ray imaging and scattering experiments and to probe electronic transitions in matter by orbital dichroism spectroscopy. Also, we present that a new magnet configuration, similar to the structure of Figure-8 undulator or the PERA undulator, may generate right- and left-hand circularly polarized off-axis radiation simultaneously.
Creation of orbital angular momentum states with chiral polaritonic lenses.
Dall, Robert; Fraser, Michael D; Desyatnikov, Anton S; Li, Guangyao; Brodbeck, Sebastian; Kamp, Martin; Schneider, Christian; Höfling, Sven; Ostrovskaya, Elena A
2014-11-14
Controlled transfer of orbital angular momentum to an exciton-polariton Bose-Einstein condensate spontaneously created under incoherent, off resonant excitation conditions is a long-standing challenge in the field of microcavity polaritonics. We demonstrate, experimentally and theoretically, a simple and efficient approach to the generation of nontrivial orbital angular momentum states by using optically induced potentials-chiral polaritonic lenses. These lenses are produced by a structured optical pump with a spatial distribution of intensity that breaks the chiral symmetry of the system. PMID:25432029
Kinetic description of electron plasma waves with orbital angular momentum
International Nuclear Information System (INIS)
We describe the kinetic theory of electron plasma waves with orbital angular momentum or twisted plasmons. The conditions for a twisted Landau resonance to exist are established, and this concept is introduced for the first time. Expressions for the kinetic dispersion relation and for the electron Landau damping are derived. The particular case of a Maxwellian plasma is examined in detail. The new contributions to wave dispersion and damping due the orbital angular momentum are discussed. It is shown that twisted plasmons can be excited by rotating electron beams.
Effect of Orbital Angular Momentum on Nondiffracting Ultrashort Optical Pulses
Ornigotti, Marco; Conti, Claudio; Szameit, Alexander
2015-09-01
We introduce a new class of nondiffracting optical pulses possessing orbital angular momentum. By generalizing the X -wave solution of the Maxwell equation, we discover the coupling between angular momentum and the temporal degrees of freedom of ultrashort pulses. The spatial twist of propagation invariant light pulse turns out to be directly related to the number of optical cycles. Our results may trigger the development of novel multilevel classical and quantum transmission channels free of dispersion and diffraction. They may also find application in the manipulation of nanostructured objects by ultrashort pulses and for novel approaches to the spatiotemporal measurements in ultrafast photonics.
Spin and Orbital Angular Momentum Distribution Functions of the Nucleon
Wakamatsu, M.; Watabe, T
1999-01-01
A theoretical prediction is given for the spin and orbital angular momentum distribution functions of the nucleon within the framework of an effective quark model of QCD, i.e. the chiral quark soliton model. An outstanding feature of the model is that it predicts fairly small quark spin fraction of the nucleon $\\Delta \\Sigma \\simeq 0.35$, which in turn dictates that the remaining 65% of the nucleon spin is carried by the orbital angular momentum of quarks and antiquarks at the model energy sc...
Photon Orbital Angular Momentum and Mass in a Plasma Vortex
Tamburini, F; Sponselli, A.; Thidé, B.; Mendonça, J. T.
2010-01-01
We analyse the Anderson-Higgs mechanism of photon mass acquisition in a plasma and study the contribution to the mass from the orbital angular momentum acquired by a beam of photons when it crosses a spatially structured charge distribution. To this end we apply Proca-Maxwell equations in a static plasma with a particular spatial distribution of free charges, notably a plasma vortex, that is able to impose orbital angular momentum (OAM) onto light. In addition to the mass acquisition of the c...
On the angular momentum evolution of merged white dwarfs
Gourgouliatos, KN
2006-01-01
We study the angular momentum evolution of binaries containing two white dwarfs (WDs) which merge and become cool helium-rich supergiants. Our object is to compare predicted rotation velocities with observations of highly evolved stars believed to have formed from such a merger, which include the R CrB and extreme He stars. The principal case study involves a short-period binary containing a 0.6-M⊙ carbon–oxygen (CO) WD, and a 0.3-M⊙ He WD. The initial condition for the angular momentum distr...
The evolution of black-hole mass and angular momentum
King, A R
1999-01-01
We show that neither accretion nor angular momentum extraction are likely to lead to significant changes in the mass M_1 or angular momentum parameter a_* of a black hole in a binary system with realistic parameters. Current values of M_1 and a_* therefore probably reflect those at formation. We show further that sufficiently energetic jet ejection powered by the black hole's rotational energy can stabilize mass transfer in systems with large adverse mass ratios, and even reduce the mass transfer rate to the point where the binary becomes transient.
Total Internal Reflection of Orbital Angular Momentum Beams
Loffler W.; Hermosa N.; Aiello A.; Woerdman J.P.
2012-01-01
We investigate how beams with orbital angular momentum (OAM) behave under total internal reflection. This is studied in two complementary experiments: In the first experiment, we study geometric shifts of OAM beams upon total internal reflection (Goos-H\\"anchen and Imbert-Fedorov shifts, for each the spatial and angular variant), and in the second experiment we determine changes in the OAM mode spectrum of a beam, again upon total internal reflection. As a result we find that in the first cas...
Probing Parton Orbital Angular Momentum in Longitudinally Polarized Nucleon
Ji, Xiangdong; Xiong, Xiaonu; Yuan, Feng
2012-01-01
While the total orbital angular momentum (OAM) of a definite quark flavor in a longitudinally-polarized nucleon can be obtained through a sum rule involving twist-two generalized parton distribution (GPDs), its distribution as a function of parton momentum in light-front coordinates is more complicated to define and measure because it involves intrinsically twist-three effects. In this paper, we consider two different parton OAM distributions. The first is manifestly gauge invariant, and its ...
A demonstration of the conservation of the orbital angular momentum of Earth
Pellizza, Leonardo J.; Mayochi, Mariano G.; Ciocci Brazzano, Ligia; Pedrosa, Susana E.
2015-12-01
We describe a simple but quantitative experiment to demonstrate the conservation of angular momentum. We measure the correlation of the apparent radius and angular velocity of the Sun with respect to the stars, due to the conservation of the angular momentum of Earth in its orbit. We also determine the direction of Earth's angular momentum vector and show that it is conserved. The experiment can be performed using a small telescope and a digital camera. It is conceptually simple, allowing students to get direct physical insight from the data. The observations are performed near the resolution limit imposed by the atmosphere, and in the presence of strong competing effects. These effects necessitate a careful experimental setup and allow students to improve their skills in experimentation.
How orbital angular momentum affects beam shifts in optical reflection
International Nuclear Information System (INIS)
It is well known that reflection of a Gaussian light beam (TEM00) by a planar dielectric interface leads to four beam shifts when compared to the geometrical-optics prediction. These are the spatial Goos-Haenchen (GH) shift, the angular GH shift, the spatial Imbert-Fedorov (IF) shift, and the angular IF shift. We report here, theoretically and experimentally, that endowing the beam with orbital angular momentum leads to coupling of these four shifts; this is described by a 4x4 mixing matrix.
Detecting Chiral Orbital Angular Momentum by Circular Dichroism ARPES
Park, Jin-Hong; Kim, Choong H.; Rhim, Jun Won; Han, Jung Hoon
2011-01-01
We show, by way of tight-binding and first-principles calculations, that a one-to-one correspondence between electron's crystal momentum k and non-zero orbital angular momentum (OAM) is a generic feature of surface bands. The OAM forms a chiral structure in momentum space much as its spin counterpart in Rashba model does, as a consequence of the inherent inversion symmetry breaking at the surface but not of spin-orbit interaction. Circular dichroism (CD) angle-resolved photoemission (ARPES) e...
The velocity and angular momentum of a free Dirac electron
Lin, Lu
1998-01-01
It is shown that, in Dirac theory, there is a spatial velocity of a free electron which commutes with the Hamiltonian, so it is a conserved quantity of the motion. Furthermore, there is a spatial orbital angular momentum which also commutes with the Hamiltonian and is a constant of the motion.
Continuous Variable Entanglement of Orbital Angular Momentum States
DEFF Research Database (Denmark)
Lassen, Mikael Østergaard; Leuchs, G.; Andersen, Ulrik Lund
2009-01-01
entanglement is manifested in the squeezing of the rotated modes in the Hermite-Gauss (HG) basis, measured with a specially tailored local oscillator. The most promising application of CV orbital angular momentum (OAM) states is their compatibility with atoms, thus allowing for storage of CV quantum...
Spectra of heavy mesons with nonzero orbital angular momentum
Energy Technology Data Exchange (ETDEWEB)
Boryu, V.Y.; Khokhlachev, S.B. (Institute of Cosmic Research, USSR Academy of Sciences (SU))
1989-06-01
We show that in a number of cases the asymptotic behavior of the Wilson loop average in QCD is sufficient for calculating the interaction Hamiltonian of heavy quarks. In this paper we calculate the levels of mesons with nonzero orbital angular momentum consisting of {ital c} and {ital b} quarks.
Spin-Orbit Coupling and the Conservation of Angular Momentum
Hnizdo, V.
2012-01-01
In nonrelativistic quantum mechanics, the total (i.e. orbital plus spin) angular momentum of a charged particle with spin that moves in a Coulomb plus spin-orbit-coupling potential is conserved. In a classical nonrelativistic treatment of this problem, in which the Lagrange equations determine the orbital motion and the Thomas equation yields the…
Generation of the Stigmatic Beam with Orbital Angular Momentum
Institute of Scientific and Technical Information of China (English)
高春清; 魏光辉; Horst WEBER
2001-01-01
The stigmatic beam with orbital angular momentum is generated by transforming the Hermite-Gaussian beamof a diode-pumped Nd:YAG laser through a rotated cylindrical optical system. Behind the transformation optics,the output beam has an intensity distribution of ring shape and a twist phase. The beam transformation istheoretically calculated and the result has been confirmed in the experiments.
Angular momentum projection of tilted axis rotating states
Energy Technology Data Exchange (ETDEWEB)
Oi, M.; Onishi, N.; Tajima, N. [Tokyo Univ. (Japan); Horibata, T.
1998-03-01
We applied an exact angular momentum projection to three dimensional cranked HFB (3d-CHFB) states. Tilted axis rotating states (TAR) and principal axis rotating states (PAR) are compared. It is shown that TAR is more adequate than PAR for description of the back bending phenomena driven by tilted rotation or wobbling motion. (author)
Exact angular momentum projection based on cranked HFB solution
Energy Technology Data Exchange (ETDEWEB)
Enami, Kenichi; Tanabe, Kosai; Yosinaga, Naotaka [Saitama Univ., Urawa (Japan). Dept. of Physics
1998-03-01
Exact angular momentum projection of cranked HFB solutions is carried out. It is reconfirmed from this calculation that cranked HFB solutions reproduce the intrinsic structure of deformed nucleus. The result also indicates that the energy correction from projection is important for further investigation of nuclear structure. (author)
Dichroism for Orbital Angular Momentum using Stimulated Parametric Down Conversion
Lowney, Joseph; Faccio, Daniele; Wright, Ewan M
2014-01-01
We theoretically analyze stimulated parametric down conversion as a means to produce dichroism based on the orbital angular momentum (OAM) of an incident signal field. The nonlinear interaction is shown to provide differential gain between signal states of differing OAM, the peak gain occurring at half the OAM of the pump field.
Obtaining the Electron Angular Momentum Coupling Spectroscopic Terms, jj
Orofino, Hugo; Faria, Roberto B.
2010-01-01
A systematic procedure is developed to obtain the electron angular momentum coupling (jj) spectroscopic terms, which is based on building microstates in which each individual electron is placed in a different m[subscript j] "orbital". This approach is similar to that used to obtain the spectroscopic terms under the Russell-Saunders (LS) coupling…
Influence of the angular momentum on nuclear fission
Energy Technology Data Exchange (ETDEWEB)
Tanikawa, Masashi [Tokyo Univ. (Japan). Faculty of Science
1996-03-01
The effects of the angular momentum on the mechanism of nuclear fission are studied about the reaction systems of compound nucleus of {sup 210}P and {sup 239}Np by the time-of-flight (TOF) method. The reaction systems in this work are {sup 209}Bi+P, {sup 206}Pb+{alpha}, {sup 206}Po+{alpha}, {sup 198}Pt+{sup 12}C, {sup 238}U+P and {sup 232}Th+{sup 7}Li. Target was prepared by vacuum evaporating of each about 100 {mu}g/cm{sup 2} of {sup 209}Bi, {sup 206}Pb and {sup 198}Pt on 10 {mu}g/cm{sup 2} of carbon film. On compound nucleus {sup 210}Po, {sup 210}Po fissions at Ex=45McV but it fissions after 1 or 2 neutrons emission at higher excited energy (Ex=57 MeV). TKE shows almost the same values except higher value of {sup 209}Bi+P. The decreasing tendency of width of TKE distribution with increasing the angular momentum is found at the first time in this work. The effect of the angular momentum on the fission is small in the case of low angular momentum. On the compound nucleus {sup 239}Np, the effects are shown at the asymmetric fission part of the mass distribution. (S.Y.)
Electronic interaction anisotropy between atoms in arbitrary angular momentum states
Krems, R.V.; Groenenboom, G.C.; Dalgarno, A.
2004-01-01
A general tensorial expansion for the interaction potential between two atoms in arbitrary angular momentum states is derived and the relations between the expansion coefficients and the Born-Oppenheimer potentials of the diatomic molecule are obtained. It is demonstrated that a complete expansion o
Low Angular Momentum in Clumpy, Turbulent Disk Galaxies
Obreschkow, Danail; Glazebrook, Karl; Bassett, Robert; Fisher, David B.; Abraham, Roberto G.; Wisnioski, Emily; Green, Andrew W.; McGregor, Peter J.; Damjanov, Ivana; Popping, Attila; Jørgensen, Inger
2015-12-01
We measure the stellar specific angular momentum {j}s={J}s/{M}s in four nearby (z ≈ 0.1) disk galaxies that have stellar masses {M}s near the break {M}s* of the galaxy mass function but look like typical star-forming disks at z ≈ 2 in terms of their low stability (Q ≈ 1), clumpiness, high ionized gas dispersion (40-50 {km} {{{s}}}-1), high molecular gas fraction (20%-30%), and rapid star formation (˜ 20{M}⊙ {{yr}}-1). Combining high-resolution (Keck-OSIRIS) and large-radius (Gemini-GMOS) spectroscopic maps, only available at low z, we discover that these targets have ˜ 3 times less stellar angular momentum than typical local spiral galaxies of equal stellar mass and bulge fraction. Theoretical considerations show that this deficiency in angular momentum is the main cause of their low stability, while the high gas fraction plays a complementary role. Interestingly, the low {j}s values of our targets are similar to those expected in the {M}s* population at higher z from the approximate theoretical scaling {j}s\\propto {(1+z)}-1/2 at fixed {M}s. This suggests that a change in angular momentum, driven by cosmic expansion, is the main cause for the remarkable difference between clumpy {M}s* disks at high z (which likely evolve into early-type galaxies) and mass-matched local spirals.
Femtosecond Magnetism When the Orbital Angular Momentum is Quenched
Si, M. S.; Yang, D. Z.; Xue, D. S.; Zhang, G. P.
2015-11-01
In femtosecond magnetism, a femtosecond laser pulse affects the spin moment only indirectly through the orbital angular momentum and the spin-orbit coupling. A long-standing puzzle is what happens if the orbital angular momentum itself is quenched. Here, we employ a four-level system to resolve this puzzle. The results show that the quenching of the orbital angular moment in the ground state has no direct relation to the spin moment change. By contrast, the orbital moment can be restored partially after the pulsed optical excitation and can affect the demagnetization. Importantly, this study confirms that the orbital moment indeed responds to the laser field faster than spin if the pulse duration is short, consistent with the recent time-resolved X-ray magnetic circular dichroism experiment. Therefore, our finding shines new light on femtosecond magnetism.
Conservation of orbital angular momentum in air core optical fibers
Gregg, P; Ramachandran, S
2014-01-01
Light's orbital angular momentum (OAM) is a conserved quantity in cylindrically symmetric media; however, it is easily destroyed by free-space turbulence or fiber bends, because anisotropic perturbations impart angular momentum. We observe the conservations of OAM even in the presence of strong bend perturbations, with fibers featuring air cores that appropriately sculpt the modal density of states. In analogy to the classical reasoning for the enhanced stability of spinning tops with increasing angular velocity, these states' lifetimes with OAM magnitude. Consequently, contrary to convention wisdom that ground states of systems are the most stable, OAM longevity in air-core fiber increases with mode order. Aided by conservation of this fundamental quantity, we demonstrate fiber propagation of 12 distinct higher-order OAM modes, of which 8 remain low-loss and >98% pure from near-degenerate coupling after km-length propagation. The first realization of long-lived higher-order OAM states, thus far posited to ex...
Optomechanics based on angular momentum exchange between light and matter
Shi, H.; Bhattacharya, M.
2016-08-01
The subject of optomechanics involves interactions between optical and mechanical degrees of freedom, and is currently of great interest as an enabler of fundamental investigations in quantum mechanics, as well as a platform for ultrasensitive measurement devices. The majority of optomechanical configurations rely on the exchange of linear momentum between light and matter. We will begin this tutorial with a brief description of such systems. Subsequently, we will introduce optomechanical systems based on angular momentum exchange. In this context, optical fields carrying polarization and orbital angular momentum will be considered, while for the mechanics, torsional and free rotational motion will be of relevance. Our overall aims will be to supply basic analyses of some of the existing theoretical proposals, to provide functional descriptions of some of the experiments conducted thus far, and to consider some directions for future research. We hope this tutorial will be useful to both theorists and experimentalists interested in the subject.
Twist Three Generalized Parton Distributions for Orbital Angular Momentum
Rajan, Abha
2016-01-01
We study the orbital angular momentum contribution to the spin structure of the proton. It is well known that the quark and gluon spin contributions do not add up to the proton spin. We motivate the connection between the Generalized Transverse Momentum Distribution (GTMD) $F_{14}$, and orbital angular momentum by exploring the underlying quark proton helicity amplitude structure. The twist three Generalized Parton Distribution (GPD) $\\tilde{E}_{2T}$, was shown to connect to OAM. We study these functions using a diquark model calculation. The GTMD $F_{14}$ is unique in that it can describe both Jaffe-Manohar and Ji OAM depending on choice of gauge link, i.e. whether final state interactions are included or not. We perform a calculation of $F_{14}$ in both scenarios.
Optomechanics based on angular momentum exchange between light and matter
Shi, Hao
2015-01-01
The subject of optomechanics involves interactions between optical and mechanical degrees of freedom, and is currently of great interest as an enabler of fundamental investigations in quantum mechanics, as well as a platform for ultrasensitive measurement devices. The majority of optomechanical configurations rely on the exchange of linear momentum between light and matter. We will begin this tutorial with a brief description of such systems. Subsequently, we will introduce optomechanical systems based on angular momentum exchange. In this context, optical fields carrying polarization and orbital angular momentum will be considered, while for the mechanics, torsional and free rotational motion will be of relevance. Our overall aims will be to supply basic analyses of some of the existing theoretical proposals, to provide functional descriptions of some of the experiments conducted thus far, and to consider some directions for future research. We hope this tutorial will be useful to both theorists and experime...
Yu, Haohai; Zhang, Huaijin; Wang, Yicheng; Han, Shuo; Yang, Haifang; Xu, Xiangang; Wang, Zhengping; Petrov, V.; Wang, Jiyang
2013-01-01
We demonstrate the optical orbital angular momentum conservation during the transfer process from subwavelength plasmonic vortex lens (PVLs) to light and the generating process of surface plasmon polaritons (SPPs). Illuminating plasmonic vortex lenses with beams carrying optical orbital angular momentum, the SP vortices with orbital angular momentum were generated and inherit the optical angular momentum of light beams and PVLs. The angular momentum of twisting SP electromagnetic field is tunable by the twisted metal/dielectric interfaces of PVLs and angular momentum of illuminating singular light. This work may open the door for several possible applications of SP vortices in subwavelength region. PMID:24217130
Ghost imaging with entangled photons and orbital angular momentum
Padgett, Miles
We utilise the position and orbital angular momentum (OAM) correlations between the signal and idler photons generated in the down-conversion process to obtain ghost images of a phase object. By using an OAM phase filter, which is non-local with respect to the object, the ghost images exhibit isotropic edge-enhancement. The strong spatial correlations between the signal and idler photons generated by spontaneous parametric downconversion have been widely utilised in many different imaging systems. The use of a scanning single element detector to recover the spatial information in the signal and idler beams fundamentally limits the detection efficiency of the imaging system to a maximum of 1/N where N is the number of pixels in the image. Our approach overcomes this limitation by replacing the scanning detector by an intensified CCD camera, therefore detecting all photons irrespective of their position within the image. Using a camera in this way, coupled with the OAM edge-enhancement and image reconstruction techniques allows us to obtain images of phase objects with an average of fewer than one photon per image pixel.
Helicon modes in uniform plasmas. III. Angular momentum
International Nuclear Information System (INIS)
Helicons are electromagnetic waves with helical phase fronts propagating in the whistler mode in magnetized plasmas and solids. They have similar properties to electromagnetic waves with angular momentum in free space. Helicons are circularly polarized waves carrying spin angular momentum and orbital angular momentum due to their propagation around the ambient magnetic field B0. These properties have not been considered in the community of researchers working on helicon plasma sources, but are the topic of the present work. The present work focuses on the field topology of helicons in unbounded plasmas, not on helicon source physics. Helicons are excited in a large uniform laboratory plasma with a magnetic loop antenna whose dipole axis is aligned along or across B0. The wave fields are measured in orthogonal planes and extended to three dimensions (3D) by interpolation. Since density and B0 are uniform, small amplitude waves from loops at different locations can be superimposed to generate complex antenna patterns. With a circular array of phase shifted loops, whistler modes with angular and axial wave propagation, i.e., helicons, are generated. Without boundaries radial propagation also arises. The azimuthal mode number m can be positive or negative while the field polarization remains right-hand circular. The conservation of energy and momentum implies that these field quantities are transferred to matter which causes damping or reflection. Wave-particle interactions with fast electrons are possible by Doppler shifted resonances. The transverse Doppler shift is demonstrated. Wave-wave interactions are also shown by showing collisions between different helicons. Whistler turbulence does not always have to be created by nonlinear wave-interactions but can also be a linear superposition of waves from random sources. In helicon collisions, the linear and/or orbital angular momenta can be canceled, which results in a great variety of field topologies. The work will
Helicon modes in uniform plasmas. III. Angular momentum
Energy Technology Data Exchange (ETDEWEB)
Stenzel, R. L.; Urrutia, J. M. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)
2015-09-15
Helicons are electromagnetic waves with helical phase fronts propagating in the whistler mode in magnetized plasmas and solids. They have similar properties to electromagnetic waves with angular momentum in free space. Helicons are circularly polarized waves carrying spin angular momentum and orbital angular momentum due to their propagation around the ambient magnetic field B{sub 0}. These properties have not been considered in the community of researchers working on helicon plasma sources, but are the topic of the present work. The present work focuses on the field topology of helicons in unbounded plasmas, not on helicon source physics. Helicons are excited in a large uniform laboratory plasma with a magnetic loop antenna whose dipole axis is aligned along or across B{sub 0}. The wave fields are measured in orthogonal planes and extended to three dimensions (3D) by interpolation. Since density and B{sub 0} are uniform, small amplitude waves from loops at different locations can be superimposed to generate complex antenna patterns. With a circular array of phase shifted loops, whistler modes with angular and axial wave propagation, i.e., helicons, are generated. Without boundaries radial propagation also arises. The azimuthal mode number m can be positive or negative while the field polarization remains right-hand circular. The conservation of energy and momentum implies that these field quantities are transferred to matter which causes damping or reflection. Wave-particle interactions with fast electrons are possible by Doppler shifted resonances. The transverse Doppler shift is demonstrated. Wave-wave interactions are also shown by showing collisions between different helicons. Whistler turbulence does not always have to be created by nonlinear wave-interactions but can also be a linear superposition of waves from random sources. In helicon collisions, the linear and/or orbital angular momenta can be canceled, which results in a great variety of field
Helicon modes in uniform plasmas. III. Angular momentum
Stenzel, R. L.; Urrutia, J. M.
2015-09-01
Helicons are electromagnetic waves with helical phase fronts propagating in the whistler mode in magnetized plasmas and solids. They have similar properties to electromagnetic waves with angular momentum in free space. Helicons are circularly polarized waves carrying spin angular momentum and orbital angular momentum due to their propagation around the ambient magnetic field B0. These properties have not been considered in the community of researchers working on helicon plasma sources, but are the topic of the present work. The present work focuses on the field topology of helicons in unbounded plasmas, not on helicon source physics. Helicons are excited in a large uniform laboratory plasma with a magnetic loop antenna whose dipole axis is aligned along or across B0. The wave fields are measured in orthogonal planes and extended to three dimensions (3D) by interpolation. Since density and B0 are uniform, small amplitude waves from loops at different locations can be superimposed to generate complex antenna patterns. With a circular array of phase shifted loops, whistler modes with angular and axial wave propagation, i.e., helicons, are generated. Without boundaries radial propagation also arises. The azimuthal mode number m can be positive or negative while the field polarization remains right-hand circular. The conservation of energy and momentum implies that these field quantities are transferred to matter which causes damping or reflection. Wave-particle interactions with fast electrons are possible by Doppler shifted resonances. The transverse Doppler shift is demonstrated. Wave-wave interactions are also shown by showing collisions between different helicons. Whistler turbulence does not always have to be created by nonlinear wave-interactions but can also be a linear superposition of waves from random sources. In helicon collisions, the linear and/or orbital angular momenta can be canceled, which results in a great variety of field topologies. The work will
Angular momentum and linear momentum transfer in intermediate-energy heavy-ion reactions
International Nuclear Information System (INIS)
In order to explore the changing role of angular momentum transfer to the heavy target-like fragment in heavy-ion reactions, the gamma-ray multiplicities associated with projectile residues were measured in the reaction of 20Ne with 181Ta in the energy range of 7.5 to 42 MeV/nucleon. From the gamma-ray multiplicities, the intrinsic spin of the target-like nucleus was determined and corrected for the spin removed by evaporated particles. Comparisons of the measured intrinsic spin with that expected from the missing linear momentum were found to be good at low energies but failed around a bombarding energy of 17 MeV/nucleon. From the results of these studies we infer that angular momentum and therefore linear momentum is being carried away in significant amounts by particles which were not detected
The role of orbital angular momentum in the proton spin
Wakamatsu, M.
2009-01-01
The orbital angular momenta $L^u$ and $L^d$ of up and down quarks in the proton are estimated as functions of the energy scale as model-independently as possible, on the basis of Ji's angular momentum sum rule. This analysis indicates that $L^u - L^d$ is large and negative even at low energy scale of nonperturbative QCD, in contrast to Thomas' similar analysis based on the refined cloudy bag model. We pursuit the origin of this apparent discrepancy and suggest that it may have a connection wi...
Wigner distribution and orbital angular momentum of a proton
Chakrabarti, D.; Maji, T.; Mondal, C.; Mukherjee, A.
2016-01-01
The Wigner distributions for u and d quarks in a proton are calculated using the light front wave functions (LFWFs) of the scalar quark-diquark model for nucleon constructed from the soft-wall AdS/QCD correspondence. We present a detail study of the quark orbital angular momentum(OAM) and its correlation with quark spin and proton spin. The quark density distributions, considering the different polarizations of quarks and proton, in transverse momentum plane as well as in transverse impact pa...
Accessing the quark orbital angular momentum with Wigner distributions
Cedric LorceIPNO and LPT, Orsay; Barbara Pasquini(Pavia U. and INFN, Pavia)
2015-01-01
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wig...
Wigner distribution and orbital angular momentum of a proton
Chakrabarti, D; Mondal, C; Mukherjee, A
2016-01-01
The Wigner distributions for u and d quarks in a proton are calculated using the light front wave functions (LFWFs) of the scalar quark-diquark model for nucleon constructed from the soft-wall AdS/QCD correspondence. We present a detail study of the quark orbital angular momentum(OAM) and its correlation with quark spin and proton spin. The quark density distributions, considering the different polarizations of quarks and proton, in transverse momentum plane as well as in transverse impact parameter plane are presented for both u and d quarks.
Transition radiation from electrons with orbital angular momentum
Konkov, Anatoly S; Polonskaya, Marina S
2013-01-01
Several experimental groups have recently obtained the so called vortex electrons (electrons with orbital angular momentum (OAM) of l = 100h) with energies of 300 keV. The gyromagnetic ratio of such electrons becomes proportional to the OAM value, which leads to the corresponding increase of the electron magnetic moment. In this paper we investigate the transition radiation from the "charge + magnetic moment" system using the theory of classical electrodynamics. The circular polarization of optical transition radiation amounts up to 70%, which allows to use this effect for the independent measurement of the electron orbital momentum value.
Effect of Orbital Angular Momentum on Valence-Quark Helicity Distributions
Avakian, Harut; Brodsky, Stanley J.; Deur, Alexandre; Yuan, Feng
2007-01-01
We study the quark helicity distributions at large x in perturbative QCD, taking into account contributions from the valence Fock states of the nucleon which have nonzero orbital angular momentum. These states are necessary to have a nonzero anomalous magnetic moment. We find that the quark orbital angular momentum contributes a large logarithm to the negative helicity quark distributions in addition to its power behavior, scaling as (1-x)^5\\log^2(1-x) in the limit of x\\to 1. Our analysis sho...
Angular momentum exchange in white dwarf binaries accreting through direct impact
International Nuclear Information System (INIS)
We examine the exchange of angular momentum between the component spins and the orbit in semi-detached double white dwarf binaries undergoing mass transfer through direct impact of the transfer stream. We approximate the stream as a series of discrete massive particles ejected in the ballistic limit at the inner Lagrangian point of the donor toward the accretor. This work improves upon similar earlier studies in a number of ways. First, we self-consistently calculate the total angular momentum of the orbit at all times. This includes changes in the orbital angular momentum during the ballistic trajectory of the ejected mass, as well as changes during the ejection/accretion due to the radial component of the particle's velocity. Second, we calculate the particle's ballistic trajectory for each system, which allows us to determine the precise position and velocity of the particle upon accretion. We can then include specific information about the radius of the accretor as well as the angle of impact. Finally, we ensure that the total angular momentum is conserved, which requires the donor star spin to vary self-consistently. With these improvements, we calculate the angular momentum change of the orbit and each binary component across the entire parameter space of direct impact double white dwarf binary systems. We find a significant decrease in the amount of angular momentum removed from the orbit during mass transfer, as well as cases where this process increases the angular momentum of the orbit at the expense of the spin angular momentum of the donor. We conclude that, unlike earlier claims in the literature, mass transfer through direct impact need not destabilize the binary and that the quantity and sign of the orbital angular momentum transfer depends on the binary properties, particularly the masses of the double white dwarf binary component stars. This stabilization may significantly impact the population synthesis calculations of the expected
Resolving enantiomers using the optical angular momentum of twisted light.
Brullot, Ward; Vanbel, Maarten K; Swusten, Tom; Verbiest, Thierry
2016-03-01
Circular dichroism and optical rotation are crucial for the characterization of chiral molecules and are of importance to the study of pharmaceutical drugs, proteins, DNA, and many others. These techniques are based on the different interactions of enantiomers with circularly polarized components of plane wave light that carries spin angular momentum (SAM). For light carrying orbital angular momentum (OAM), for example, twisted or helical light, the consensus is that it cannot engage with the chirality of a molecular system as previous studies failed to demonstrate an interaction between optical OAM and chiral molecules. Using unique nanoparticle aggregates, we prove that optical OAM can engage with materials' chirality and discriminate between enantiomers. Further, theoretical results show that compared to circular dichroism, mainly based on magnetic dipole contributions, the OAM analog helical dichroism (HD) is critically dependent on fundamentally different chiral electric quadrupole contributions. Our work opens new venues to study chirality and can find application in sensing and chiral spectroscopy. PMID:26998517
Photonic-phononic orbital angular momentum in Brillouin parametric conversion
Zhu, Zhihan; Mu, Chunyuan; Li, Hongwei
2014-01-01
Orbital angular momentum (OAM) is a fundamental photonic degree of freedom, showed by Allen and co-workers. Its most attractive feature is an inherently infinite dimensionality, which in recent years has obtained several ground-breaking demonstrations for high information-density communication and processing, both in classical and quantum. Here, by seeking the reason for photonic OAM non-conservation in stimulated Brillouin amplification, we report the first demonstration of the evolution law for OAM in Brillouin process. The parameter of OAM can conveniently transfer between the phonons and different polarized photons due to the photonic spin angular momentum conservation. Our results have revealed a parametric conversion mechanism of Brillouin process for Photonic-phononic OAM, demonstrated the role of phononic OAM and the vortex acoustic wave in this process, and suggested this mechanism may find important applications in OAM-based information communication and processing.
Resilience of hybrid optical angular momentum qubits to turbulence.
Farías, Osvaldo Jiménez; D'Ambrosio, Vincenzo; Taballione, Caterina; Bisesto, Fabrizio; Slussarenko, Sergei; Aolita, Leandro; Marrucci, Lorenzo; Walborn, Stephen P; Sciarrino, Fabio
2015-01-01
Recent schemes to encode quantum information into the total angular momentum of light, defining rotation-invariant hybrid qubits composed of the polarization and orbital angular momentum degrees of freedom, present interesting applications for quantum information technology. However, there remains the question as to how detrimental effects such as random spatial perturbations affect these encodings. Here, we demonstrate that alignment-free quantum communication through a turbulent channel based on hybrid qubits can be achieved with unit transmission fidelity. In our experiment, alignment-free qubits are produced with q-plates and sent through a homemade turbulence chamber. The decoding procedure, also realized with q-plates, relies on both degrees of freedom and renders an intrinsic error-filtering mechanism that maps errors into losses. PMID:25672667
Trajectory-Based Unveiling of Angular Momentum of Photons
Li, Yongnan; Kong, Ling-Jun; Tu, Chenghou; Wang, Hui-Tian
2015-01-01
The Heisenberg uncertainty principle suggests that it is impossible to determine the trajectory of a quantum particle in the same way as a classical particle. However, we may still yield insight into novel behavior of photons based on the average photon trajectories (APTs). Here we explore the APTs of photons carrying spin angular momentum (SAM) and/or orbital angular momentum (OAM) under the paraxial condition. We define the helicity and differential helicity for unveiling the three-dimensional spiral structures of the APTs of photons. We clarify the novel behaviors of the APTs caused by the SAM and OAM as well as the SAM-OAM coupling. The APT concept is very helpful for profoundly understanding the motion of trapped particles and for elucidating other physical systems. Due to the presence of the helical path caused by the SAM and/or the OAM, the actual traveling distance of the photons might be much longer than the geometric distance.
Angular momentum and torque described with the complex octonion
Weng, Zi-Hua
2015-01-01
The paper aims to adopt the complex octonion to formulate the angular momentum, torque, and force etc in the electromagnetic and gravitational fields. Applying the octonionic representation enables one single definition of angular momentum (or torque, force) to combine some physics contents, which were considered to be independent of each other in the past. J. C. Maxwell used simultaneously two methods, the vector terminology and quaternion analysis, to depict the electromagnetic theory. It motivates the paper to introduce the quaternion space into the field theory, describing the physical feature of electromagnetic and gravitational fields. The spaces of two fields can be chosen as the quaternion spaces, while the coordinate component of quaternion space is able to be the complex number. The quaternion space of electromagnetic field is independent of that of gravitational field. These two quaternion spaces may compose one octonion space. Contrarily, one octonion space can be separated into two subspaces, the...
Efficient polarization of high-angular-momentum systems
Rochester, Simon; Raizen, Mark; Pustelny, Szymon; Auzinsh, Marcis; Budker, Dmitry
2016-01-01
We propose methods of optical pumping that are applicable to open, high-angular-momentum transitions in atoms and molecules, for which conventional optical pumping would lead to significant population loss. Instead of applying circularly polarized cw light, as in conventional optical pumping, we propose to use techniques for coherent population transfer (e.g., adiabatic fast passage) to arrange the atoms so as to increase the entropy removed from the system with each spontaneous decay from the upper state. This minimizes the number of spontaneous-emission events required to produce a stretched state, thus reducing the population loss due to decay to other states. To produce a stretched state in a manifold with angular momentum J, conventional optical pumping requires about 2J spontaneous decays per atom; one of our proposed methods reduces this to about log_2(2J), while another of the methods reduces it to about one spontaneous decay, independent of J.
Institute of Scientific and Technical Information of China (English)
ZHANG Yi-Xin; CANG Ji
2009-01-01
Effects of atmospheric turbulence tilt, defocus, astigmatism and coma aberrations on the orbital angular mo-mentum measurement probability of photons propagating in weak turbulent regime are modeled with Rytov approximation. By considering the resulting wave as a superposition of angular momentum eigenstates, the or-bital angular momentum measurement probabilities of the transmitted digit axe presented. Our results show that the effect of turbulent tilt aberration on the orbital angular momentum measurement probabilities of photons is the maximum among these four kinds of aberrations. As the aberration order increases, the effects of turbulence aberrations on the measurement probabilities of orbital angular momentum generally decrease, whereas the effect of turbulence defoens can be ignored. For tilt aberration, as the difference between the measured orbital angular momentum and the original orbital angular momentum increases, the orbital angular momentum measurement probabifity decreases.
International Nuclear Information System (INIS)
Effects of atmospheric turbulence tilt, defocus, astigmatism and coma aberrations on the orbital angular momentum measurement probability of photons propagating in weak turbulent regime are modeled with Rytov approximation. By considering the resulting wave as a superposition of angular momentum eigenstates, the orbital angular momentum measurement probabilities of the transmitted digit are presented. Our results show that the effect of turbulent tilt aberration on the orbital angular momentum measurement probabilities of photons is the maximum among these four kinds of aberrations. As the aberration order increases, the effects of turbulence aberrations on the measurement probabilities of orbital angular momentum generally decrease, whereas the effect of turbulence defocus can be ignored. For tilt aberration, as the difference between the measured orbital angular momentum and the original orbital angular momentum increases, the orbital angular momentum measurement probability decreases. (fundamental areas of phenomenology (including applications))
Experimental orbital angular momentum based quantum key distribution through turbulence
Goyal, Sandeep; Roux, Filippus S; Konrad, Thomas; Forbes, Andrew
2014-01-01
Using an experimental setup that simulates a turbulent atmosphere, we study the secret key rate for quantum key distribution protocols in orbital angular momentum based free space quantum communication. The quantum key distribution protocols under consideration include the Ekert 91 protocol for different choices of mutually unbiased bases and the six-state protocol. We find that the secret key rate of these protocols decay to zero roughly at the same scale where the entanglement of formation decays to zero.
Angular Momentum Transport in Double White Dwarf Binaries
Motl, Patrick M.; Tohline, J. E.; Frank, J.
2006-12-01
We present numerical simulations of dynamically unstable mass transfer in a double white dwarf binary with initial mass ratio, q = 0.4. The binary components are approximated as polytropes of index n = 3/2 and the synchronously rotating, semi-detached equilibrium binary is evolved hydrodynamically with the gravitational potential being computed through the solution of Poisson's equation. Upon initiating deep contact, the mass transfer rate grows by more than an order of magnitude over approximately ten orbits, as would be expected for dynamically unstable mass transfer. However, the mass transfer rate then reaches a peak value, the binary expands and the mass transfer event subsides. The binary must therefore have crossed the critical mass ratio for stability against dynamical mass transfer. Despite the initial loss of orbital angular momentum into the spin of the accreting star, we find that the accretor's spin saturates and angular momentum is returned to the orbit more efficiently than has been previously suspected for binaries in the direct impact accretion mode. To explore this surprising result, we directly measure the critical mass ratio for stability by imposing artificial angular momentum loss at various rates to drive the binary to an equilibrium mass transfer rate. For one of these driven evolutions, we attain equilibrium mass transfer and deduce that the mass ratio for stability is approximately 2/3. This is consistent with the result for mass transferring binaries that effectively return angular momentum to the orbit through an accretion disk. This work has been supported in part by NSF grants AST 04-07070 and PHY 03-26311 and in part through NASA's ATP program grant NAG5-13430. The computations were performed primarily at NCSA through grant MCA98N043 and at LSU's Center for Computation & Technology.
Orbital angular momentum exchange in an optical parametric oscillator
Martinelli, M.; Huguenin, J. A. O.; Nussenzveig, P.; Khoury, A. Z.
2004-01-01
We present a study of orbital angular momentum transfer from pump to down-converted beams in a type-II Optical Parametric Oscillator. Cavity and anisotropy effects are investigated and demostrated to play a central role in the transverse mode dynamics. While the idler beam can oscillate in a Laguerre-Gauss mode, the crystal birefringence induces an astigmatic effect in the signal beam that prevents the resonance of such mode.
Single beam optical vortex tweezers with tunable orbital angular momentum
International Nuclear Information System (INIS)
We propose a single beam method for generating optical vortices with tunable optical angular momentum without altering the intensity distribution. With the initial polarization state varying from linear to circular, we gradually control the torque transferred to the trapped non-absorbing and non-birefringent silica beads. The continuous transition from the maximum rotation speed to zero without changing the trapping potential gives a way to study the complex tribological interactions.
Colliding particles carrying non-zero orbital angular momentum
Ivanov, I. P.
2011-01-01
Photons carrying non-zero orbital angular momentum (twisted photons) are well-known in optics. Recently, it was suggested to use Compton backscattering to boost optical twisted photons to high energies. Twisted electrons in the intermediate energy range have also been produced recently. Thus, collisions involving energetic twisted particles seem to be feasible and represent a new tool in high-energy physics. Here we discuss some generic features of scattering processes involving twisted parti...
Interplay of Spin and Orbital Angular Momentum in the Proton
Energy Technology Data Exchange (ETDEWEB)
Thomas, Anthony
2008-09-01
We derive the consequences of the Myhrer-Thomas explanation of the proton spin problem for the distribution of orbital angular momentum on the valence and sea quarks. After QCD evolution these results are found to be in very good agreement with both recent lattice QCD calculations and the experimental contraints from Hermes and JLab.
http://dx.doi.org/10.1103/PhysRevLett.101.102003
Spin and Orbital angular momentum propagation in anisotropic media: theory
Picón, Antonio; Benseny, Albert; Mompart, Jordi; Calvo, Gabriel F.
2011-01-01
This paper is devoted to study the propagation of light beams carrying orbital angular momentum in optically anisotropic media. We first review some properties of homogeneous anisotropic media, and describe how the paraxial formalism is modified in order to proceed with a new approach dealing with a general setting of paraxial propagation along uniaxial inhomogeneous media. This approach is suitable for describing the space-variant-optical-axis phase plates.
Self-homodyne detection of the light orbital angular momentum
Belmonte Molina, Aniceto; Pérez Torres, Juan
2012-01-01
A simple optical system for the self-homodyne detection of the orbital angular momentum (OAM) carried by optical beams is introduced. We propose two different schemes based on the use of optical hybrids, which could detect the OAM mode number, even when the input beam might be slightly distorted. A balanced receiver is used to perform a self-homodyne measure of the optical signal from two different locations at the beam wavefront.
Detecting Lateral Motion using Light’s Orbital Angular Momentum
Neda Cvijetic; Giovanni Milione; Ezra Ip; Ting Wang
2015-01-01
Interrogating an object with a light beam and analyzing the scattered light can reveal kinematic information about the object, which is vital for applications ranging from autonomous vehicles to gesture recognition and virtual reality. We show that by analyzing the change in the orbital angular momentum (OAM) of a tilted light beam eclipsed by a moving object, lateral motion of the object can be detected in an arbitrary direction using a single light beam and without object image reconstructi...
Wigner Functions for the Pair Angle and Orbital Angular Momentum
Kastrup, H. A.
2016-01-01
The problem of constructing physically and mathematically well-defined Wigner functions for the canonical pair angle and angular momentum is solved. While a key element for the construction of Wigner functions for the planar phase space is the Heisenberg-Weyl group, the corresponding group for the cylindrical phase space is the Euclidean group of the plane and its unitary representations. Here the angle is replaced by the pair (cos,sin) which determines the points on the unit circle uniquely....
Measuring two-photon orbital angular momentum entanglement
Fernández Calvo, Gabriel; Picón Álvarez, Antonio; Bramon, Albert
2007-01-01
We put forward an approach to estimate the amount of bipartite spatial entanglement of down-converted photon states correlated in orbital angular momentum and the magnitude of the transverse (radial) wave vectors. Both degrees of freedom are properly considered in our framework, which only requires azimuthal local linear optical transformations and mode selection analysis with two fiber detectors. The coincidence distributions predicted by our approach give an excellent fit to the distributio...
Digital coherent receiver for orbital angular momentum demultiplexing
Belmonte A.; Torres J.P.
2013-01-01
We put forward a type of receiver for coherent detection of the photon orbital angular momentum (OAM). A coherent array receiver, consisting of multiple subapertures, with each subaperture coupled to a single-mode fiber, maps the complex optical field in the image plane. Using digital samplers connected to each array element, the local electrical signals resulting from the detection process can be measured coherently, moving the complexity of the full OAM measurement from the optical domain t...
Single beam optical vortex tweezers with tunable orbital angular momentum
Energy Technology Data Exchange (ETDEWEB)
Gecevičius, Mindaugas; Drevinskas, Rokas, E-mail: rd1c12@orc.soton.ac.uk; Beresna, Martynas; Kazansky, Peter G. [Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom)
2014-06-09
We propose a single beam method for generating optical vortices with tunable optical angular momentum without altering the intensity distribution. With the initial polarization state varying from linear to circular, we gradually control the torque transferred to the trapped non-absorbing and non-birefringent silica beads. The continuous transition from the maximum rotation speed to zero without changing the trapping potential gives a way to study the complex tribological interactions.
Measuring the orbital angular momentum of electron beams
Giulio Guzzinati; Laura Clark; Armand B\\xe9ch\\xe9; Jo Verbeeck
2014-01-01
Abstract: The recent demonstration of electron vortex beams has opened up the new possibility of studying orbital angular momentum (OAM) in the interaction between electron beams and matter. To this aim, methods to analyze the OAM of an electron beam are fundamentally important and a necessary next step. We demonstrate the measurement of electron beam OAM through a variety of techniques. The use of forked holographic masks, diffraction from geometric apertures, and diffraction from a knife ed...
Orbital angular momentum driven intrinsic spin Hall effect
Jung, Wonsig; Go, Dongwook; Lee, Hyun-Woo; Kim, Changyoung
2014-01-01
We propose a mechanism of intrinsic spin Hall effect (SHE). In this mechanism, local orbital angular momentum (OAM) induces electron position shift and couples with the bias electric field to generate orbital Hall effect (OHE). SHE then emerges as a concomitant effect of OHE through the atomic spin-orbit coupling. Spin Hall conductivity due to this mechanism is estimated to be comparable to experimental values for heavy metals. This mechanism predicts the sign change of the spin Hall conducti...
Flux enhancement of photons entangled in orbital angular momentum
Palacios S.; Palacios, Silvana; León-Montiel, R. de J.; Leon-Montiel R.D.J.; Hendrych M.; Hendrych, Martin; Valencia, Alejandra; Valencia A.; Torres, Juan P.; Torres J.P.
2011-01-01
Entangled photons are generally collected by detection systems that select their certain spatial modes, for example using single-mode optical fibers. We derive simple and easy-to-use expressions that allow us to maximize the coupling efficiency of entangled photons with specific orbital angular momentum (OAM) correlations generated by means of spontaneous parametric downconversion. Two different configurations are considered: one in which the beams with OAM are generated by conversion from be...
Holographic tool kit for optical communication beyond orbital angular momentum
Trichili, Abderrahmen; Rosales-Guzmán, Carmelo; Dudley, Angela; Ndagano, Bienvenu; Salem, Amine Ben; Zghal, Mourad; Forbes, Andrew
2016-01-01
Mode division multiplexing (MDM) is mooted as a technology to address future bandwidth issues, and has been successfully demonstrated in free space using spatial modes with orbital angular momentum (OAM). To further increase the data transmission rate, more degrees of freedom are required to form a densely packed mode space. Here we move beyond OAM and demonstrate multiplexing and demultiplexing using both the radial and azimuthal degrees of freedom. We achieve this with a holographic approac...
Weak measurements with orbital angular momentum pointer states
Puentes G.; Hermosa N.; Torres J.P.
2012-01-01
Weak measurements are a unique tool for accessing information about weakly interacting quantum systems with minimal back action. Joint weak measurements of single-particle operators with pointer states characterized by a two-dimensional Gaussian distribution can provide, in turn, key information about quantum correlations which can be of relevance for quantum information applications. Here we demonstrate that by employing two-dimensional pointer states endowed with orbital angular momentum (O...
Transition radiation from electrons with orbital angular momentum
Konkov, Anatoly S.; Potylitsyn, Alexander P.; Polonskaya, Marina S.
2013-01-01
Several experimental groups have recently obtained the so called vortex electrons (electrons with orbital angular momentum (OAM) of l = 100h) with energies of 300 keV. The gyromagnetic ratio of such electrons becomes proportional to the OAM value, which leads to the corresponding increase of the electron magnetic moment. In this paper we investigate the transition radiation from the "charge + magnetic moment" system using the theory of classical electrodynamics. The circular polarization of o...
Optical parametric oscillation under injection of orbital angular momentum
Santos, B. Coutinho dos; Souza, C. E. R.; Dechoum, K.; Khoury, A. Z.
2006-01-01
We present a theoretical model for the spatial mode dynamics of an optical parametric oscillator under injection of orbital angular momentum. This process is then interpreted in terms of an interesting picture based on a Poincare representation of first order spatial modes. The spatial properties of the down-converted fields can be easily understood from their symmetries in this geometric representation. By considering the adiabatic mode conversion of the injected signal, we also predict the ...
The orbital angular momentum of down-converted photons
Energy Technology Data Exchange (ETDEWEB)
Ren Xifeng; Guo Guoping; Yu Bo; Li Jian; Guo Guangcan [Key Laboratory of Quantum Information, University of Science and Technology of China, CAS, Hefei 230026 (China)
2004-04-01
We calculate the relative amplitude of the orbital angular momentum (OAM) of entangled photon pairs from the spontaneous parametric down-conversion of a thin quadratic nonlinear crystal. The results show that the amplitude depends on both of the two Laguerre indices l, p. We also discuss the influences of the commonly used holograms and mono-mode fibres for mode analysis. We conclude that only a few dimensions can be explored from the infinite OAM modes of down-converted photon pairs.
Violation of Leggett inequalities in orbital angular momentum subspaces
J. Romero; Leach, J.; Jack, B; Barnett, S. M.; Padgett, M.; Franke-Arnold, S
2010-01-01
We report an experimental test of Leggett's non-local hidden variable theory in an orbital angular momentum (OAM) state space of light. We show that the correlations we observe are in conflict with Leggett's model, thus excluding a particular class of non-local hidden variable theories for the first time in a non-polarization state space. It is known that the violation of the Leggett inequality becomes stronger as more detection settings are used. The required measurements become feasible in ...
Linear Up-conversion of Orbital angular momentum
Ding, Dong-Sheng; Zhou, Zhi-Yuan; Shi, Bao-Sen; Zou, Xu-Bo; Guo, Guang-Can
2012-01-01
We experimentally demonstrated that infrared light imprinted with orbital angular momentum (OAM) was linearly converted into visible light using four-wave mixing (FWM) via a ladder-type configuration in 85Rb atoms. Simultaneously, we theoretically simulated this linear conversion process, and the theoretical analysis was in reasonable agreement with the experimental results. A large single-photon detuning process was used to reduce the absorption of the atoms to the up-converted light and to ...
Tunnelling of orbital angular momentum in parallel optical waveguides
International Nuclear Information System (INIS)
We study the evolution of circularly polarized optical vortices (OVs) in the system of two coupled few-mode optical fibres. We demonstrate that upon propagation OVs tunnel into the adjacent fibre as a complex superposition of OVs that comprise also OVs of opposite polarization and topological charge. The initial OV may tunnel into the other fibre as the same vortex state of lesser energy. The evolution of the orbital angular momentum in coupled fibres is studied
Spin and orbital angular momentum propagation in anisotropic media: theory
International Nuclear Information System (INIS)
This paper is devoted to a study of the propagation of light beams carrying orbital angular momentum in optically anisotropic media. We first review some properties of homogeneous anisotropic media, and describe how the paraxial formalism is modified in order to proceed with a new approach dealing with the general setting of paraxial propagation along uniaxial inhomogeneous media. This approach is suitable for describing space-variant optical-axis phase plates
Chip-Scale Continuously Tunable Optical Orbital Angular Momentum Generator
Sun, Jie; Yaacobi, Ami; Moresco, Michele; Coolbaugh, Douglas; Watts, Michael R.
2014-01-01
Light carrying orbital angular momentum (OAM) has potential to impact a wide variety of applications ranging from optical communications to quantum information and optical forces for the excitation and manipulation of atoms, molecules, and micro-particles. The unique advantage of utilizing OAM in these applications relies, to a large extent, on the use of multiple different OAM states. Therefore, it is desirable to have a device that is able to gen- erate light with freely adjustable OAM stat...
Dynamic interferometry measurement of orbital angular momentum of light
Jianji, Dong; Hailong, Zhou; Xinliang, Zhang
2014-01-01
We present a dynamic interferometry to measure the orbital angular momentum (OAM) of beams. An opaque screen with two air slits is employed, which can be regarded as the Youngs double-pinhole interference. When the OAM beams with an annular intensity distribution vertically incident, the far-field interference patterns depend on the phase difference of the light in the two pinholes. We scan the angle between the two slits, the output intensity at center changes alternatively between darkness ...
Experimental orbital angular momentum based quantum key distribution through turbulence
Goyal, Sandeep; Ibrahim, Alpha Hamadou; Roux, Filippus S.; Konrad, Thomas; Forbes, Andrew
2014-01-01
Using an experimental setup that simulates a turbulent atmosphere, we study the secret key rate for quantum key distribution protocols in orbital angular momentum based free space quantum communication. The quantum key distribution protocols under consideration include the Ekert 91 protocol for different choices of mutually unbiased bases and the six-state protocol. We find that the secret key rate of these protocols decay to zero roughly at the same scale where the entanglement of formation ...
Quantum computer networks with the orbital angular momentum of light
Garcia-Escartin, Juan Carlos; Chamorro-Posada, Pedro
2012-01-01
Inside computer networks, different information processing tasks are necessary to deliver the user data efficiently. This processing can also be done in the quantum domain. We present simple optical quantum networks where the orbital angular momentum of a single photon is used as an ancillary degree of freedom which controls decisions at the network level. Linear optical elements are enough to provide important network primitives like multiplexing and routing. First we show how to build a sim...
Harmonic Oscillator States with Non-Integer Orbital Angular Momentum
Land, Martin
2009-01-01
We study the quantum mechanical harmonic oscillator in two and three dimensions, with particular attention to the solutions as represents of their respective symmetry groups: O(2), O(3), and O(2,1). Solving the Schrodinger equation by separating variables in polar coordinates, we obtain wavefunctions characterized by a principal quantum number, the group Casimir eigenvalue, and one observable component of orbital angular momentum, with eigenvalue $m+s$, for integer $m$ and real constant param...
Intrinsic Spin and Orbital-Angular-Momentum Hall Effect
S. Zhang; Yang, Z.
2004-01-01
A generalized definition of intrinsic and extrinsic transport coefficients is introduced. We show that transport coefficients from the intrinsic origin are solely determined by local electronic structure, and thus the intrinsic spin Hall effect is not a transport phenomenon. The intrinsic spin Hall current is always accompanied by an equal but opposite intrinsic orbital-angular-momentum Hall current. We prove that the intrinsic spin Hall effect does not induce a spin accumulation at the edge ...
Simultaneous demultiplexing and steering of multiple orbital angular momentum modes
Shuhui Li; Jian Wang
2015-01-01
We present a simple scheme to perform simultaneous demultiplexing and steering of multiple orbital angular momentum (OAM) modes using a single complex phase mask. By designing the phase mask, the propagation directions of demultiplexed beams can be arbitrarily steered. System experiments using orthogonal frequency-division multiplexing 32-ary quadrature amplitude modulation (OFDM-32QAM) signals over two OAM modes are carried out by using a two-mode complex phase mask. Moreover, demultiplexing...
Energy and Angular Momentum in Generic F(Riemann) Theories
Senturk, Cetin; Sisman, Tahsin Cagri; Tekin, Bayram(Department of Physics, Middle East Technical University, 06800 Ankara, Turkey)
2012-01-01
We construct the conserved charge of generic gravity theories built on arbitrary contractions of the Riemann tensor (but not on its derivatives) for asymptotically (anti)-de Sitter spacetimes. Our construction is a generalization of the ADT charges of linear and quadratic gravity theories in cosmological backgrounds. As an explicit example we find the energy and angular momentum of the BTZ black hole in the 2+1 dimensional Born-Infeld gravity.
Detection of orbital angular momentum using a photonic integrated circuit
Guanghao Rui; Bing Gu; Yiping Cui; Qiwen Zhan
2016-01-01
Orbital angular momentum (OAM) state of photons offer an attractive additional degree of freedom that has found a variety of applications. Measurement of OAM state, which is a critical task of these applications, demands photonic integrated devices for improved fidelity, miniaturization, and reconfiguration. Here we report the design of a silicon-integrated OAM receiver that is capable of detecting distinct and variable OAM states. Furthermore, the reconfiguration capability of the detector i...
Orbital angular momentum exchange in an optical parametric oscillator
International Nuclear Information System (INIS)
We present a study of orbital angular momentum transfer from pump to down-converted beams in a type-II optical parametric oscillator. Cavity and anisotropy effects are investigated and demonstrated to play a central role in the transverse mode dynamics. While the idler beam can oscillate in a Laguerre-Gauss mode, the crystal birefringence induces an astigmatic effect in the signal beam that prevents the resonance of such a mode
Orbital angular momentum exchange in an optical parametric oscillator
Martinelli, M.; Huguenin, J. A. O.; Nussenzveig, P.; Khoury, A. Z.
2004-07-01
We present a study of orbital angular momentum transfer from pump to down-converted beams in a type-II optical parametric oscillator. Cavity and anisotropy effects are investigated and demonstrated to play a central role in the transverse mode dynamics. While the idler beam can oscillate in a Laguerre-Gauss mode, the crystal birefringence induces an astigmatic effect in the signal beam that prevents the resonance of such a mode.
Formation of disk galaxies: feedback and the angular momentum problem
Sommer-Larsen, J.; Gelato, S.; Vedel, H.
1998-01-01
When only cooling processes are included, smoothed-particle hydrodynamical simulations of galaxy formation in a Cold Dark Matter hierarchical clustering scenario consistently produce collapsed objects that are deficient in angular momentum by a factor of about 25 relative to the disks of observed spiral galaxies. It is widely hoped that proper allowance for star formation feedback effects will resolve this discrepancy. We explore and compare the effects of including two different types of fee...
Angular momentum and the formation of stars and black holes
International Nuclear Information System (INIS)
The formation of compact objects such as stars and black holes is strongly constrained by the requirement that nearly all of the initial angular momentum of the diffuse material from which they form must be removed or redistributed during the formation process. The mechanisms that may be involved and their implications are discussed for (1) low-mass stars, most of which probably form in binary or multiple systems; (2) massive stars, which typically form in clusters and (3) supermassive black holes that form in galactic nuclei. It is suggested that in all cases, gravitational interactions with other stars or mass concentrations in a forming system play an important role in redistributing angular momentum and thereby enabling the formation of a compact object. If this is true, the formation of stars and black holes must be a more complex, dynamic and chaotic process than in standard models. The gravitational interactions that redistribute angular momentum tend to couple the mass of a forming object to the mass of the system, and this may have important implications for mass ratios in binaries, the upper stellar IMF in clusters, and the masses of supermassive black holes in galaxies.
Orbital angular momentum injection in a polariton superfluid.
Boulier, T.; Glorieux, Q.; Cancellieri, E.; Giacobino, E.; Bramati, A.
2015-01-01
We report a new method for injecting angular momentum in a polariton superfluid. Rather than stirring, such as what is done in atomic BECs, we resonantly inject a ring-shaped rotating superfluid in a planar semiconductor cavity. The resonant injection avoids any significant exciton populations and ensures a high level of control in the system. A Spatial Light Modulator is used to create a Laguerre-Gaussian laser beam that pumps the system and creates a rotating polariton population. By using a l = 8 Laguerre-Gaussian mode we have studied the steady-state condition for observing the nucleation of angular momentum in freely propagating polaritons at the center. We find that, likely due to the fixed border conditions, the angular momentum in weak cavity disorder areas does not spontaneously nucleates at the center, and we observe a single l = 8 vortex. For larger cavity disorder vortex-antivortex pairs can nucleate and we present numerical simulations that explain the role of this disorder to observe such a nucleation.
Angular momentum transport via internal gravity waves in evolving stars
International Nuclear Information System (INIS)
Recent asteroseismic advances have allowed for direct measurements of the internal rotation rates of many subgiant and red giant stars. Unlike the nearly rigidly rotating Sun, these evolved stars contain radiative cores that spin faster than their overlying convective envelopes, but slower than they would in the absence of internal angular momentum transport. We investigate the role of internal gravity waves in angular momentum transport in evolving low-mass stars. In agreement with previous results, we find that convectively excited gravity waves can prevent the development of strong differential rotation in the radiative cores of Sun-like stars. As stars evolve into subgiants, however, low-frequency gravity waves become strongly attenuated and cannot propagate below the hydrogen-burning shell, allowing the spin of the core to decouple from the convective envelope. This decoupling occurs at the base of the subgiant branch when stars have surface temperatures of T ≈ 5500 K. However, gravity waves can still spin down the upper radiative region, implying that the observed differential rotation is likely confined to the deep core near the hydrogen-burning shell. The torque on the upper radiative region may also prevent the core from accreting high angular momentum material and slow the rate of core spin-up. The observed spin-down of cores on the red giant branch cannot be totally attributed to gravity waves, but the waves may enhance shear within the radiative region and thus increase the efficacy of viscous/magnetic torques.
Full triaxial angular momentum projection with the Gogny force
International Nuclear Information System (INIS)
Modern beyond mean field methods with effective forces are able to describe many properties of nuclei spread out in the whole nuclear chart like the appearance or degradation of shell closures, shape coexistence, shape transitions, fission barriers, etc. In these methods, the wave functions that describe the ground and excited states of the atomic nucleus are linear combinations of particle number and angular momentum restored product wave functions defined along some collective degrees of freedom. Except of few preliminary cases with Skyrme and Relativistic interactions, most of the calculations has been restricted to angular momentum restoration of axial quadrupole deformed configurations. However, it is well known that there are cases where other collective degrees of freedom, in particular the triaxial deformation, can play an important role in the structure of the nucleus. In this contribution we will show the first results obtained with full triaxial angular momentum restoration with the Gogny force studying some selected cases and comparing the results with the corresponding axial approaches and experimental data. Furthermore, the inclusion of this degree of freedom open new exciting possibilities for understanding the spectroscopy of many nuclei and gives a reliable alternative and/or complement to shell model calculations.
Low Angular Momentum in Clumpy, Turbulent Disk Galaxies
Obreschkow, Danail; Bassett, Robert; Fisher, David B; Abraham, Roberto G; Wisnioski, Emily; Green, Andrew W; McGregor, Peter J; Damjanov, Ivana; Popping, Attila; Jorgensen, Inger
2015-01-01
We measure the stellar specific angular momentum jstar=Jstar/Mstar in four nearby (redshift z~0.1) disk galaxies that have stellar masses Mstar near the break M* of the galaxy mass function, but look like typical star-forming disks at z~2 in terms of their low stability (Q~1), clumpiness, high ionized gas dispersion (40-50 km/s), high molecular gas fraction (20-30%) and rapid star formation (~20 Msun/yr). Combining high-resolution (Keck-OSIRIS) and large-radius (Gemini-GMOS) spectroscopic maps, only available at low z, we discover that these targets have ~3 times less stellar angular momentum than typical local spiral galaxies of equal stellar mass and bulge fraction. Theoretical considerations show that this deficiency in angular momentum is the main cause of their low stability, while the high gas fraction plays a complementary role. Interestingly, the low jstar values of our targets are similar to those expected in the M*-population at higher z from the approximate theoretical scaling jstar~(1+z)^(-1/2) at...
Angular momentum transport within evolved low-mass stars
Energy Technology Data Exchange (ETDEWEB)
Cantiello, Matteo; Bildsten, Lars; Paxton, Bill [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States); Mankovich, Christopher [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Christensen-Dalsgaard, Jørgen, E-mail: matteo@kitp.ucsb.edu [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark)
2014-06-10
Asteroseismology of 1.0-2.0 M {sub ☉} red giants by the Kepler satellite has enabled the first definitive measurements of interior rotation in both first ascent red giant branch (RGB) stars and those on the helium burning clump. The inferred rotation rates are 10-30 days for the ≈0.2 M {sub ☉} He degenerate cores on the RGB and 30-100 days for the He burning core in a clump star. Using the Modules for Experiments in Stellar Evolution code, we calculate state-of-the-art stellar evolution models of low mass rotating stars from the zero-age main sequence to the cooling white dwarf (WD) stage. We include transport of angular momentum due to rotationally induced instabilities and circulations, as well as magnetic fields in radiative zones (generated by the Tayler-Spruit dynamo). We find that all models fail to predict core rotation as slow as observed on the RGB and during core He burning, implying that an unmodeled angular momentum transport process must be operating on the early RGB of low mass stars. Later evolution of the star from the He burning clump to the cooling WD phase appears to be at nearly constant core angular momentum. We also incorporate the adiabatic pulsation code, ADIPLS, to explicitly highlight this shortfall when applied to a specific Kepler asteroseismic target, KIC8366239.
Sakane, E; Sakane, Eisaku; Kawai, Toshiharu
2002-01-01
In an extended, new form of general relativity, which is a teleparallel theory of gravity, we examine the energy-momentum and angular momentum carried by gravitational wave radiated from Newtonian point masses in a weak-field approximation. The resulting wave form is identical to the corresponding wave form in general relativity, which is consistent with previous results in teleparallel theory. The expression for the dynamical energy-momentum density is identical to that for the canonical energy-momentum density in general relativity up to leading order terms on the boundary of a large sphere including the gravitational source, and the loss of dynamical energy-momentum, which is the generator of \\emph{internal} translations, is the same as that of the canonical energy-momentum in general relativity. Under certain asymptotic conditions for a non-dynamical Higgs-type field $\\psi^{k}$, the loss of ``spin'' angular momentum, which is the generator of \\emph{internal} $SL(2,C)$ transformations, is the same as that ...
Magnetic resonance frequencies for ferromagnets with partly frozen orbital angular momentum
International Nuclear Information System (INIS)
The dynamics of angular momentum of a ferromagnet, taking into account both spin and orbital angular momentum is discussed with taking info account the crystalline field and spin-orbit interaction. The spectrum of magnetic oscillations of the magnet consists of three branches of oscillations of various types, among which are one branch of longitudinal oscillations of orbital angular momentum length and two transverse branches, corresponding to coupled oscillations of transverse components of spin and orbital angular momentum
Nature of the Angular Momentum of Light: Rotational Energy and Geometric Phase
S C Tiwari
2006-01-01
The nature of intrinsic/extrinsic character of angular momentum is defined in terms of the kind of the associated rotational energy of the light. The salient features of the spin energy of light and photon are highlighted. Spin angular momentum is intrinsic while orbital angular momentum possesses quasi-intrinsicness only if the vortex-like singularities are present. The claimed spin to orbital angular momentum conversion is interpreted in terms of spin redirection geometric phase. It is poin...
Orbital angular momentum of scalar field generated by gravitational scatterings
Nishikawa, Ryusuke; Masuda, Atsuki; Nambu, Yasusada; Ishihara, Hideki
2016-01-01
It has been expected that astronomical observations to detect the orbital angular momenta of electromagnetic waves may give us a new insight into astrophysics. Previous works pointed out the possibility that a rotating black hole can produce orbital angular momenta of electromagnetic waves through gravitational scattering, and the spin parameter of the black hole can be measured by observing them. However, the mechanism how the orbital angular momentum of the electromagnetic wave is generated by the gravitational scattering has not been clarified sufficiently. In this paper, in order to understand it from a point of view of gravitational lensing effects, we consider an emitter which radiates a spherical wave of the real massless scalar field and study the deformation of the scalar wave by the gravitational scattering due to a black hole by invoking the geometrical optics approximation. We show that the frame dragging caused by the rotating black hole is not a necessary condition for generating the orbital ang...
Q- and Z-dependence of angular momentum transfer in deeply inelastic collisions of 86Kr with 209Bi
International Nuclear Information System (INIS)
The dependence of the in-plane and out-of-plane angular correlations of fragments from fissioning heavy products on the kinetic energy and Z of the light reaction partner have been measured. From the dependence of the angular correlations on Q-value and hence energy loss, together with existing data from which the total angular-integrated cross section as a function of energy loss can be extracted, the dependence of the angular momentum transferred to the heavy product on the initial orbital angular momentum or impact parameter has been determined. The resulting dependence is qualitatively consistent with the sticking limit for a reaction intermediate of touching deformed fragments. More specific nuclear models generally underestimate the angular momentum transfer, although the one-body proximity-friction model accounts for the major fraction of the angular momentum transfer. A recent model incorporating both one-body proximity friction and collective excitations accounts quite well for the observed angular momentum transfer. The Z-dependence of the anisotropy shows the importance of angular momentum fractionation for the less probable events, where the Z of the fissioning system is appreciably less than that of the target. The transferred angular momentum is shown to be fairly strongly aligned along the perpendicular to the reaction plane, with alignment values of 0.6 to 0.8. The component of angular momentum not along the perpendicular to the reaction plane is found to be primarily oriented perpendicular rather than parallel to the recoil directions. The absolute fission probabilities are found to be qualitatively consistent with J-dependent calculations using the J-values deduced from the angular correlations. (Auth.)
Notes on the orbital angular momentum of quarks in the nucleon
Energy Technology Data Exchange (ETDEWEB)
Hatta, Yoshitaka, E-mail: hatta@het.ph.tsukuba.ac.jp [Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571 (Japan)
2012-02-14
We discuss the orbital angular momentum of partons inside a longitudinally polarized proton in the recently proposed framework of spin decomposition. The quark orbital angular momentum defined by Ji can be decomposed into the 'canonical' and the 'potential' angular momentum parts, both of which are represented as the matrix element of a manifestly gauge invariant operator.
Notes on the orbital angular momentum of quarks in the nucleon
Hatta, Yoshitaka
2011-01-01
We discuss the orbital angular momentum of partons inside a longitudinally polarized proton in the recently proposed framework of spin decomposition. The quark orbital angular momentum defined by Ji can be decomposed into the `canonical' and the `potential' angular momentum parts, both of which are represented as the matrix element of a manifestly gauge invariant operator.
Notes on the orbital angular momentum of quarks in the nucleon
International Nuclear Information System (INIS)
We discuss the orbital angular momentum of partons inside a longitudinally polarized proton in the recently proposed framework of spin decomposition. The quark orbital angular momentum defined by Ji can be decomposed into the ‘canonical’ and the ‘potential’ angular momentum parts, both of which are represented as the matrix element of a manifestly gauge invariant operator.
Effects of the angular-momentum projection on cranking wave functions
International Nuclear Information System (INIS)
In this thesis the influence of the angular-momentum projection in cranking Hartree-Fock-Bogolyubov wave functions was studied by the ''variation before projection'' method. This study is equivalent to the question how well the cranking wave function represents an angular-momentum eigenstate because cranking represents an approximate angular-momentum projection. (orig./HSI)
International Nuclear Information System (INIS)
The magnetic confinement in tokamaks is for now the most advanced way towards energy production by nuclear fusion. Both theoretical and experimental studies showed that rotation generation can increase its performance by reducing the turbulent transport in tokamak plasmas. The rotation influence on the heat and particle fluxes is studied along with the angular momentum transport with the quasi-linear gyro-kinetic eigenvalue code QuaLiKiz. For this purpose, the QuaLiKiz code is modified in order to take the plasma rotation into account and compute the angular momentum flux. It is shown that QuaLiKiz framework is able to correctly predict the angular momentum flux including the E*B shear induced residual stress as well as the influence of rotation on the heat and particle fluxes. The major approximations of QuaLiKiz formalisms are reviewed, in particular the ballooning representation at its lowest order and the eigenfunctions calculated in the hydrodynamic limit. The construction of the quasi-linear fluxes is also reviewed in details and the quasi-linear angular momentum flux is derived. The different contributions to the turbulent momentum flux are studied and successfully compared both against non-linear gyro-kinetic simulations and experimental data. (author)
Hay, James G.; Wilson, Barry D.
The angular momentum of a human body derived from both the angular velocity and angular displacement, utilizing cinematographic records has not been adequately assessed, prior to this study. Miller (1970) obtained the angular momentum but only during the airborne phase of activity. The method used by Ramey (1973) involved a force platform, but…
Institute of Scientific and Technical Information of China (English)
Gamal G.L.Nashed
2012-01-01
We apply the energy momentum and angular momentum tensor to a tetrad field,with two unknown functions of radial coordinate,in the framework of a teleparallel equivalent of general relativity (TEGR).The definition of the gravitational energy is used to investigate the energy within the external event horizon of the dyadosphere region for the Reissner-Nordstr(o)m black hole.We also calculate the spatial momentum and angular momentum.
Angular-momentum-dominated electron beams and flat-beam generation
Energy Technology Data Exchange (ETDEWEB)
Sun, Yin-e
2005-06-01
In the absence of external forces, if the dynamics within an electron beam is dominated by its angular momentum rather than other effects such as random thermal motion or self Coulomb-repulsive force (i.e., space-charge force), the beam is said to be angular-momentum-dominated. Such a beam can be directly applied to the field of electron-cooling of heavy ions; or it can be manipulated into an electron beam with large transverse emittance ratio, i.e., a flat beam. A flat beam is of interest for high-energy electron-positron colliders or accelerator-based light sources. An angular-momentum-dominated beam is generated at the Fermilab/NICADD photoinjector Laboratory (FNPL) and is accelerated to an energy of 16 MeV. The properties of such a beam is investigated systematically in experiment. The experimental results are in very good agreement with analytical expectations and simulation results. This lays a good foundation for the transformation of an angular-momentum-dominated beam into a flat beam. The round-to-flat beam transformer is composed of three skew quadrupoles. Based on a good knowledge of the angular-momentum-dominated beam, the quadrupoles are set to the proper strengths in order to apply a total torque which removes the angular momentum, resulting in a flat beam. For bunch charge around 0.5 nC, an emittance ratio of 100 {+-} 5 was measured, with the smaller normalized root-mean-square emittance around 0.4 mm-mrad. Effects limiting the flat-beam emittance ratio are investigated, such as the chromatic effects in the round-to-flat beam transformer, asymmetry in the initial angular-momentum-dominated beam, and space-charge effects. The most important limiting factor turns out to be the uncorrelated emittance growth caused by space charge when the beam energy is low, for example, in the rf gun area. As a result of such emittance growth prior to the round-to-flat beam transformer, the emittance ratio achievable in simulation decreases from orders of thousands to
Orbital angular momentum density of a general Lorentz–Gauss vortex beam
Zhou, Guoquan; Ji, Zhiyue; Ru, Guoyun
2016-07-01
Based on the vectorial Rayleigh–Sommerfeld integral formulae, the analytical expression of a general Lorentz–Gauss vortex beam with an arbitrary topological charge is derived in free space. By using the analytical expressions of the electromagnetic field beyond the paraxial approximation, the orbital angular momentum density of a general Lorentz–Gauss vortex beam can be calculated. The effects of the linearly polarized angle and the topological charge on the three components of the orbital angular momentum density are investigated in the reference plane. The two transversal components of the orbital angular momentum are composed of two lobes with the same areas and opposite signs. The longitudinal component of the orbital angular momentum density is composed of four lobes with the same areas. The sign of the orbital angular momentum density in a pair of lobes is positive, and that of the orbital angular momentum density in the other pair of lobes is negative. Moreover, the negative magnitude of the orbital angular momentum density is larger than the positive magnitude of the orbital angular momentum density. The linearly polarized angle affects not only the shape and the location of the lobes, but also the magnitude of the three components of the orbital angular momentum density. With increasing the topological charge, the distribution of the orbital angular momentum density expands, the magnitude of the orbital angular momentum density increases, and the shape of the lobe also slightly changes.
A Stern-Gerlach-like approach to electron orbital angular momentum measurement
Harvey, Tyler R
2016-01-01
Many methods now exist to prepare free electrons into orbital angular momentum states, and the predicted applications of these electron states as probes of materials and scattering processes are numerous. The development of electron orbital angular momentum measurement techniques has lagged behind. We show that coupling between electron orbital angular momentum and a spatially varying magnetic field produces an angular momentum-dependent focusing effect. We propose a design for an orbital angular momentum measurement device built on this principle. As the method of measurement is non-interferometric, the device works equally well for mixed, superposed and pure final orbital angular momentum states. The energy and orbital angular momentum distributions of inelastically scattered electrons may be simultaneously measurable with this technique.
On the transformations generated by the electromagnetic spin and orbital angular momentum operators
Fernandez-Corbaton, Ivan; Molina-Terriza, Gabriel
2013-01-01
We present a study of the properties of the transversal "spin angular momentum" and "orbital angular momentum" operators. We show that the "spin angular momentum" operators are generators of spatial translations which depend on helicity and frequency and that the "orbital angular momentum" operators generate transformations which are a sequence of this kind of translations and rotations. We give some examples of the use of these operators in light matter interaction problems. Their relationship with the helicity operator allows to involve the electromagnetic duality symmetry in the analysis. We also find that simultaneous eigenstates of the three "spin" operators and parity define a kind of standing modes which have been recently singled out for the interaction of light with chiral molecules. With respect to the relationship between "spin angular momentum", polarization, and total angular momentum, we show that, except for the case of a single plane wave, the total angular momentum of a beam is decoupled from...
Angular momentum and torque described with the complex octonion
Weng, Zi-Hua
2014-08-01
The paper aims to adopt the complex octonion to formulate the angular momentum, torque, and force etc in the electromagnetic and gravitational fields. Applying the octonionic representation enables one single definition of angular momentum (or torque, force) to combine some physics contents, which were considered to be independent of each other in the past. J. C. Maxwell used simultaneously two methods, the vector terminology and quaternion analysis, to depict the electromagnetic theory. It motivates the paper to introduce the quaternion space into the field theory, describing the physical feature of electromagnetic and gravitational fields. The spaces of electromagnetic field and of gravitational field can be chosen as the quaternion spaces, while the coordinate component of quaternion space is able to be the complex number. The quaternion space of electromagnetic field is independent of that of gravitational field. These two quaternion spaces may compose one octonion space. Contrarily, one octonion space can be separated into two subspaces, the quaternion space and S-quaternion space. In the quaternion space, it is able to infer the field potential, field strength, field source, angular momentum, torque, and force etc in the gravitational field. In the S-quaternion space, it is capable of deducing the field potential, field strength, field source, current continuity equation, and electric (or magnetic) dipolar moment etc in the electromagnetic field. The results reveal that the quaternion space is appropriate to describe the gravitational features, including the torque, force, and mass continuity equation etc. The S-quaternion space is proper to depict the electromagnetic features, including the dipolar moment and current continuity equation etc. In case the field strength is weak enough, the force and the continuity equation etc can be respectively reduced to that in the classical field theory.
The vorticity and angular momentum budgets of Asian summer monsoon
Indian Academy of Sciences (India)
P L S Rao; U C Mohanty; P V S Raju; M A Arain
2004-09-01
The study delineates the vorticity and angular momentum balances of Asian summer monsoon during the evolution and established phases. It also elucidates the differences between these balances in the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR) reanalysis and the National Centre for Medium Range Weather Forecasts (NCM- RWF) analysis fields. The NCEP/NCAR reanalysis for a 40 year period (1958-97) and the NCM- RWF analysis for a three year (1994-96) period are made use of for the purpose. The time mean summer monsoon circulation is bifurcated into stable mean and transient eddy components and the mean component is elucidated. The generation of vorticity due to stretching of isobars balances most of the vorticity transported out of the monsoon domain during the evolution period. However, during the established period, the transportation by the relative and planetary vorticity components exceeds the generation due to stretching. The effective balancing mechanism is provided by vorticity generation due to sub-grid scale processes. The flux convergence of omega and relative momenta over the monsoon domain is effectively balanced by pressure torque during the evolution and established phases. Nevertheless, the balance is stronger during the established period due to the increase in the strength of circulation. Both the NCMRWF and NCEP fields indicate the mean features related to vorticity and angular momentum budgets realistically. Apart from the oceanic bias (strong circulation over oceans rather than continents), the summer monsoon circulation indicated by the NCEP is feeble compared to NCMRWF. The significant terms in the large-scale budgets of vorticity and angular momentum enunciate this aspect.
DISTRIBUTION OF ACCRETING GAS AND ANGULAR MOMENTUM ONTO CIRCUMPLANETARY DISKS
International Nuclear Information System (INIS)
We investigate gas accretion flow onto a circumplanetary disk from a protoplanetary disk in detail by using high-resolution three-dimensional nested-grid hydrodynamic simulations, in order to provide a basis of formation processes of satellites around giant planets. Based on detailed analyses of gas accretion flow, we find that most of gas accretion onto circumplanetary disks occurs nearly vertically toward the disk surface from high altitude, which generates a shock surface at several scale heights of the circumplanetary disk. The gas that has passed through the shock surface moves inward because its specific angular momentum is smaller than that of the local Keplerian rotation, while gas near the midplane in the protoplanetary disk cannot accrete to the circumplanetary disk. Gas near the midplane within the planet's Hill sphere spirals outward and escapes from the Hill sphere through the two Lagrangian points L1 and L2. We also analyze fluxes of accreting mass and angular momentum in detail and find that the distributions of the fluxes onto the disk surface are well described by power-law functions and that a large fraction of gas accretion occurs at the outer region of the disk, i.e., at about 0.1 times the Hill radius. The nature of power-law functions indicates that, other than the outer edge, there is no specific radius where gas accretion is concentrated. These source functions of mass and angular momentum in the circumplanetary disk would provide us with useful constraints on the structure and evolution of the circumplanetary disk, which is important for satellite formation.
Angular momentum and torque described with the complex octonion
International Nuclear Information System (INIS)
The paper aims to adopt the complex octonion to formulate the angular momentum, torque, and force etc in the electromagnetic and gravitational fields. Applying the octonionic representation enables one single definition of angular momentum (or torque, force) to combine some physics contents, which were considered to be independent of each other in the past. J. C. Maxwell used simultaneously two methods, the vector terminology and quaternion analysis, to depict the electromagnetic theory. It motivates the paper to introduce the quaternion space into the field theory, describing the physical feature of electromagnetic and gravitational fields. The spaces of electromagnetic field and of gravitational field can be chosen as the quaternion spaces, while the coordinate component of quaternion space is able to be the complex number. The quaternion space of electromagnetic field is independent of that of gravitational field. These two quaternion spaces may compose one octonion space. Contrarily, one octonion space can be separated into two subspaces, the quaternion space and S-quaternion space. In the quaternion space, it is able to infer the field potential, field strength, field source, angular momentum, torque, and force etc in the gravitational field. In the S-quaternion space, it is capable of deducing the field potential, field strength, field source, current continuity equation, and electric (or magnetic) dipolar moment etc in the electromagnetic field. The results reveal that the quaternion space is appropriate to describe the gravitational features, including the torque, force, and mass continuity equation etc. The S-quaternion space is proper to depict the electromagnetic features, including the dipolar moment and current continuity equation etc. In case the field strength is weak enough, the force and the continuity equation etc can be respectively reduced to that in the classical field theory
Angular momentum and torque described with the complex octonion
Energy Technology Data Exchange (ETDEWEB)
Weng, Zi-Hua, E-mail: xmuwzh@xmu.edu.cn [School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005 (China)
2014-08-15
The paper aims to adopt the complex octonion to formulate the angular momentum, torque, and force etc in the electromagnetic and gravitational fields. Applying the octonionic representation enables one single definition of angular momentum (or torque, force) to combine some physics contents, which were considered to be independent of each other in the past. J. C. Maxwell used simultaneously two methods, the vector terminology and quaternion analysis, to depict the electromagnetic theory. It motivates the paper to introduce the quaternion space into the field theory, describing the physical feature of electromagnetic and gravitational fields. The spaces of electromagnetic field and of gravitational field can be chosen as the quaternion spaces, while the coordinate component of quaternion space is able to be the complex number. The quaternion space of electromagnetic field is independent of that of gravitational field. These two quaternion spaces may compose one octonion space. Contrarily, one octonion space can be separated into two subspaces, the quaternion space and S-quaternion space. In the quaternion space, it is able to infer the field potential, field strength, field source, angular momentum, torque, and force etc in the gravitational field. In the S-quaternion space, it is capable of deducing the field potential, field strength, field source, current continuity equation, and electric (or magnetic) dipolar moment etc in the electromagnetic field. The results reveal that the quaternion space is appropriate to describe the gravitational features, including the torque, force, and mass continuity equation etc. The S-quaternion space is proper to depict the electromagnetic features, including the dipolar moment and current continuity equation etc. In case the field strength is weak enough, the force and the continuity equation etc can be respectively reduced to that in the classical field theory.
Angular momentum and torque described with the complex octonion
Directory of Open Access Journals (Sweden)
Zi-Hua Weng
2014-08-01
Full Text Available The paper aims to adopt the complex octonion to formulate the angular momentum, torque, and force etc in the electromagnetic and gravitational fields. Applying the octonionic representation enables one single definition of angular momentum (or torque, force to combine some physics contents, which were considered to be independent of each other in the past. J. C. Maxwell used simultaneously two methods, the vector terminology and quaternion analysis, to depict the electromagnetic theory. It motivates the paper to introduce the quaternion space into the field theory, describing the physical feature of electromagnetic and gravitational fields. The spaces of electromagnetic field and of gravitational field can be chosen as the quaternion spaces, while the coordinate component of quaternion space is able to be the complex number. The quaternion space of electromagnetic field is independent of that of gravitational field. These two quaternion spaces may compose one octonion space. Contrarily, one octonion space can be separated into two subspaces, the quaternion space and S-quaternion space. In the quaternion space, it is able to infer the field potential, field strength, field source, angular momentum, torque, and force etc in the gravitational field. In the S-quaternion space, it is capable of deducing the field potential, field strength, field source, current continuity equation, and electric (or magnetic dipolar moment etc in the electromagnetic field. The results reveal that the quaternion space is appropriate to describe the gravitational features, including the torque, force, and mass continuity equation etc. The S-quaternion space is proper to depict the electromagnetic features, including the dipolar moment and current continuity equation etc. In case the field strength is weak enough, the force and the continuity equation etc can be respectively reduced to that in the classical field theory.
Angular Momentum Transport in Quasi-Keplerian Accretion Disks
Indian Academy of Sciences (India)
Prasad Subramanian; B. S. Pujari; Peter A. Becker
2004-03-01
We reexamine arguments advanced by Hayashi & Matsuda (2001), who claim that several simple, physically motivated derivations based on mean free path theory for calculating the viscous torque in a quasi-Keplerian accretion disk yield results that are inconsistent with the generally accepted model. If correct, the ideas proposed by Hayashi & Matsuda would radically alter our understanding of the nature of the angular momentum transport in the disk, which is a central feature of accretion disk theory. However, in this paper we point out several fallacies in their arguments and show that there indeed exists a simple derivation based on mean free path theory that yields an expression for the viscous torque that is proportional to the radial derivative of the angular velocity in the accretion disk, as expected. The derivation is based on the analysis of the epicyclic motion of gas parcels in adjacent eddies in the disk.
Violation of Angular Momentum Selection Rules in Quantum Gravity
Datta, A; Melé, Barbara; Datta, Anindya; Gabrielli, Emidio; Mele, Barbara
2004-01-01
A simple consequence of the angular momentum conservation in quantum field theories is that the interference of s-channel amplitudes exchanging particles with different spin $J$ vanishes after complete angular integration. We show that, while this rule holds in scattering processes mediated by a massive graviton in Quantum Gravity, a massless graviton s-channel exchange breaks orthogonality when considering its interference with a scalar-particle s-channel exchange, whenever all the external states are massive. To this regard, the Einstein massless graviton propagator behaves as if it was carrying a further scalar degree of freedom. This result reveals new aspects of the well-known van Dam - Veltman - Zakharov discontinuity.
Total internal reflection of orbital angular momentum beams
International Nuclear Information System (INIS)
We investigate how beams with orbital angular momentum (OAM) behave under total internal reflection. This is studied in two complementary experiments: in the first experiment, we study geometric shifts of OAM beams upon total internal reflection (Goos–Hänchen and Imbert–Fedorov shifts, for each the spatial and angular variant), and in the second experiment we determine changes in the OAM mode spectrum of a beam, again upon total internal reflection. As a result we find that, in the first case, the shifts are independent of OAM and beam focusing, while in the second case, modifications in the OAM spectrum occur which depend on the input OAM mode as well as on the beam focusing. This is investigated by experiment and theory. We also show how the two methods, beam shifts on the one hand, and OAM spectrum changes on the other, are related theoretically. (paper)
Total Internal Reflection of Orbital Angular Momentum Beams
Löffler, W; Aiello, Andrea; Woerdman, J P
2012-01-01
We investigate how beams with orbital angular momentum (OAM) behave under total internal reflection. This is studied in two complementary experiments: In the first experiment, we study geometric shifts of OAM beams upon total internal reflection (Goos-H\\"anchen and Imbert-Fedorov shifts, for each the spatial and angular variant), and in the second experiment we determine changes in the OAM mode spectrum of a beam, again upon total internal reflection. As a result we find that in the first case, the shifts are independent of OAM and beam focussing, while in the second case, modifications in the OAM spectrum occur which depend on the input OAM mode as well as on the beam focussing. This is investigated by experiment and theory. We also show how the two methods, beam shifts on the one hand, and OAM spectrum changes on the other, are related theoretically.
Accessing the quark orbital angular momentum with Wigner distributions
Energy Technology Data Exchange (ETDEWEB)
Lorce, Cedric [IPNO, Universite Paris-Sud, CNRS/IN2P3, 91406 Orsay, France and LPT, Universite Paris-Sud, CNRS, 91406 Orsay (France); Pasquini, Barbara [Dipartimento di Fisica, Universita degli Studi di Pavia, Pavia, Italy and Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia (Italy)
2013-04-15
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wigner distributions. We discuss the concept of Wigner distributions in the context of quantum field theory and show how they are related to the GPDs and the TMDs. We summarize the different definitions discussed in the literature for the quark OAM and show how they can in principle be extracted from the Wigner distributions.
An angular momentum conserving Affine-Particle-In-Cell method
Jiang, Chenfanfu; Teran, Joseph
2016-01-01
We present a new technique for transferring momentum and velocity between particles and grid with Particle-In-Cell (PIC) calculations which we call Affine-Particle-In-Cell (APIC). APIC represents particle velocities as locally affine, rather than locally constant as in traditional PIC. We show that this representation allows APIC to conserve linear and angular momentum across transfers while also dramatically reducing numerical diffusion usually associated with PIC. Notably, conservation is achieved with lumped mass, as opposed to the more commonly used Fluid Implicit Particle (FLIP) transfers which require a 'full' mass matrix for exact conservation. Furthermore, unlike FLIP, APIC retains a filtering property of the original PIC and thus does not accumulate velocity modes on particles as FLIP does. In particular, we demonstrate that APIC does not experience velocity instabilities that are characteristic of FLIP in a number of Material Point Method (MPM) hyperelasticity calculations. Lastly, we demonstrate th...
Accessing the quark orbital angular momentum with Wigner distributions
Cedric, Lorce
2012-01-01
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wigner distributions. We discuss the concept of Wigner distributions in the context of quantum field theory and show how they are related to the GPDs and the TMDs. We summarize the different definitions discussed in the literature for the quark OAM and show how they can in principle be extracted from the Wigner distributions.
Accessing the quark orbital angular momentum with Wigner distributions
International Nuclear Information System (INIS)
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wigner distributions. We discuss the concept of Wigner distributions in the context of quantum field theory and show how they are related to the GPDs and the TMDs. We summarize the different definitions discussed in the literature for the quark OAM and show how they can in principle be extracted from the Wigner distributions.
Light beams with orbital angular momentum for free space optics
Institute of Scientific and Technical Information of China (English)
Wu Jing-Zhi; Li Yang-Jun
2007-01-01
The light's orbital angular momentum (OAM) is a consequence of the spiral flow of the electromagnetic energy. In this paper, an analysis of light beams with OAM used for free space optics (FSO) is conducted. The basic description and conception of light's OAM are reviewed. Both encoding information into OAM states of single light beam and encoding information into spatial structure of the mixed optical vortex with OAM are discussed, and feasibility to improve the FSO's performance of security and obstruction of line of sight is examined.
Radio pumping of ionospheric plasma with orbital angular momentum.
Leyser, T B; Norin, L; McCarrick, M; Pedersen, T R; Gustavsson, B
2009-02-13
Experimental results are presented of pumping ionospheric plasma with a radio wave carrying orbital angular momentum (OAM), using the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. Optical emissions from the pumped plasma turbulence exhibit the characteristic ring-shaped morphology when the pump beam carries OAM. Features of stimulated electromagnetic emissions (SEE) that are attributed to cascading Langmuir turbulence are well developed for a regular beam but are significantly weaker for a ring-shaped OAM beam in which case upper hybrid turbulence dominates the SEE. PMID:19257597
Manipulating atomic states via optical orbital angular-momentum
Institute of Scientific and Technical Information of China (English)
2008-01-01
Optical orbital angular-momentum(OAM)has more complex mechanics than the spin degree of photons,and may have a broad range of application.Manipulating atomic states via OAM has become an interesting topic.In this paper,we first review the general theory of generating adiabatic gauge field in ultracold atomic systems by coupling atoms to external optical fields with OAM,and point out the applications of the generated adiabatic gauge field.Then,we review our work in this field,including the generation of macroscopic superposition of vortex-antivortex states and spin Hall effect(SHE)in cold atoms.
Interaction-free generation of orbital angular momentum entanglement
Chen, Yuanyuan; Jiang, Dong; Gu, Xuemei; Xie, Ling; Chen, Lijun
2016-01-01
Due to the infinite range of possibly achievable degrees of freedom, orbital angular momentum (OAM) can tremendously increase the capacity of communication system. Here, we propose a scheme to generate OAM entanglement by using interaction-free measurement (IFM). As the superposition state of the quantum absorption object is not changed after IFM, our scheme can be extended to multiparty easily. The numerical analysis results show that the fidelity of generated OAM entanglement can be arbitrarily close to unity. Besides, the implementation issues are also discussed to evaluate the feasibility in experiment. This OAM entanglement with multiple degrees of freedom will play a key role in distributed entanglement computing and efficient quantum communication.
A Quark Model Analysis of Orbital Angular Momentum
Scopetta, Sergio; Vento Torres, Vicente
1999-01-01
Orbital Angular Momentum (OAM) twist-two parton distributions are studied. At the low energy, hadronic, scale we calculate them for the relativistic MIT bag model and for non-relativistic potential quark models. We reach the scale of the data by leading order evolution using the OPE and perturbative QCD. We confirm that the contribution of quarks and gluons OAM to the nucleon spin grows with $Q^2$, and it can be relevant at the experimental scale, even if it is negligible at the hadronic scal...
Rapid Generation of Light Beams Carrying Orbital Angular Momentum
Mirhosseini, Mohammad; Magana-Loaiza, Omar S.; Chen, Changchen; Rodenburg, Brandon; Malik, Mehul; Boyd, Robert W
2013-01-01
We report a technique for encoding both amplitude and phase variations onto a laser beam using a single digital micro-mirror device (DMD). Using this technique, we generate Laguerre-Gaussian and vortex orbital-angular-momentum (OAM) modes, along with modes in a set that is mutually unbiased with respect to the OAM basis. Additionally, we have demonstrated rapid switching among the generated modes at a speed of 4 kHz, which is much faster than the speed regularly achieved by spatial light modu...
Simultaneous demultiplexing and steering of multiple orbital angular momentum modes
Li, Shuhui; Wang, Jian
2015-01-01
We present a simple scheme to perform simultaneous demultiplexing and steering of multiple orbital angular momentum (OAM) modes using a single complex phase mask. By designing the phase mask, the propagation directions of demultiplexed beams can be arbitrarily steered. System experiments using orthogonal frequency-division multiplexing 32-ary quadrature amplitude modulation (OFDM-32QAM) signals over two OAM modes are carried out by using a two-mode complex phase mask. Moreover, demultiplexing of sixteen OAM modes and arbitrary demultiplexed beam steering are also demonstrated in the experiment. PMID:26503167
Suppression of collapse for matter waves with orbital angular momentum
International Nuclear Information System (INIS)
We explore the influence of the orbital angular momentum on the collapse of vortex-free elliptic clouds of Bose–Einstein condensates with a negative scattering length trapped in a radially symmetric harmonic potential. We show that the number of trapped ultracold atoms corresponding to the collapse threshold can be radically increased for such rotating nonlinear matter waves. Below the threshold the elliptic mode is stable and exhibits periodic oscillations around a stationary rotating state. The frequency of these oscillations is independent of the number of particles and is determined solely by the trapping potential
Simultaneous demultiplexing and steering of multiple orbital angular momentum modes.
Li, Shuhui; Wang, Jian
2015-01-01
We present a simple scheme to perform simultaneous demultiplexing and steering of multiple orbital angular momentum (OAM) modes using a single complex phase mask. By designing the phase mask, the propagation directions of demultiplexed beams can be arbitrarily steered. System experiments using orthogonal frequency-division multiplexing 32-ary quadrature amplitude modulation (OFDM-32QAM) signals over two OAM modes are carried out by using a two-mode complex phase mask. Moreover, demultiplexing of sixteen OAM modes and arbitrary demultiplexed beam steering are also demonstrated in the experiment. PMID:26503167
Orbital Angular Momentum Parton Distributions in Quark Models
Scopetta, S.; Vento, V.
1999-01-01
At the low energy, {\\sl hadronic}, scale we calculate Orbital Angular Momentum (OAM) twist-two parton distributions for the relativistic MIT bag model and for non-relativistic quark models. We reach the scale of the data by leading order evolution in perturbative QCD. We confirm that the contribution of quarks and gluons OAM to the nucleon spin grows with $Q^2$, and it can be relevant at the experimental scale, even if it is negligible at the hadronic scale, irrespective of the model used. Th...
Subwavelength focusing of light with orbital angular momentum.
Heeres, Reinier W; Zwiller, Valery
2014-08-13
The spatial structure of light with Orbital Angular Momentum, or "twisted light", closely resembles the shape of atomic wave functions. It could therefore make symmetry-forbidden transitions possible in quantum dots, or "artificial atoms". However, the vanishing intensity in the center of an OAM beam usually makes this effect weak. Here we show a plasmonic approach to focus OAM light to subwavelength dimensions using metallic nanoscale resonant optical antennas. This allows to increase the field intensity of OAM light at the typical dimensions of quantum dots to an intensity larger than a regular Gaussian beam, which corresponds to increasing the interaction strength by 3 orders of magnitude. PMID:25051525
Unveiling the orbital angular momentum and acceleration of electron beams.
Shiloh, Roy; Tsur, Yuval; Remez, Roei; Lereah, Yossi; Malomed, Boris A; Shvedov, Vladlen; Hnatovsky, Cyril; Krolikowski, Wieslaw; Arie, Ady
2015-03-01
New forms of electron beams have been intensively investigated recently, including vortex beams carrying orbital angular momentum, as well as Airy beams propagating along a parabolic trajectory. Their traits may be harnessed for applications in materials science, electron microscopy, and interferometry, and so it is important to measure their properties with ease. Here, we show how one may immediately quantify these beams' parameters without need for additional fabrication or nonstandard microscopic tools. Our experimental results are backed by numerical simulations and analytic derivation. PMID:25793830
Unveiling the orbital angular momentum and acceleration of electron beams
Shiloh, Roy; Lereah, Yossi; Malomed, Boris A; Shvedov, Vladlen; Hnatovsky, Cyril; Krolikowski, Wieslaw; Arie, Ady
2014-01-01
New forms of electron beams have been intensively investigated recently, including vortex beams carrying orbital angular momentum, as well as Airy beams propagating along a parabolic trajectory. Their traits may be harnessed for applications in materials science, electron microscopy and interferometry, and so it is important to measure their properties with ease. Here we show how one may immediately quantify these beams' parameters without need for additional fabrication or non-standard microscopic tools. Our experimental results are backed by numerical simulations and analytic derivation.
Supermode fiber for orbital angular momentum (OAM) transmission.
Li, Shuhui; Wang, Jian
2015-07-13
We present a multi-orbital-angular-momentum (OAM) multi-core supermode fiber (MOMCSF) to transmit OAM modes. The MOMCSF consists of equally-spaced and circularly-arranged multiple cores, in which the core pitch is small enough to support strong coupling OAM supermodes. The characteristics of OAM modes in MOMCSFs with different core pitches and core numbers are analyzed. The performances of mode coupling and nonlinearity are optimized by designing multiple degrees of freedom of the supermode fiber. The obtained results show that the designed MOMCSF can transmit multiple OAM modes with favorable performance of low mode coupling, low nonlinearity, and low modal dependent loss. PMID:26191933
Optical orbital angular momentum of evanescent Bessel waves.
Yang, Zhenshan
2015-05-18
We show that the orbital angular momentum (OAM) of evanescent light is drastically different from that of traveling light. Specifically, the paraxial contribution (typically the most significant part in a traveling wave) to the OAM vanishes in an evanescent Bessel wave when averaged over the azimuthal angle. Moreover, the OAM per unit energy for the evanescent Bessel field is reduced by a factor of (1+κ2/k2) from the standard result for the corresponding traveling field, where k and κ are the wave number and the evanescent decay rate, respectively. PMID:26074524
Radio Pumping of Ionospheric Plasma with Orbital Angular Momentum
International Nuclear Information System (INIS)
Experimental results are presented of pumping ionospheric plasma with a radio wave carrying orbital angular momentum (OAM), using the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. Optical emissions from the pumped plasma turbulence exhibit the characteristic ring-shaped morphology when the pump beam carries OAM. Features of stimulated electromagnetic emissions (SEE) that are attributed to cascading Langmuir turbulence are well developed for a regular beam but are significantly weaker for a ring-shaped OAM beam in which case upper hybrid turbulence dominates the SEE
Simultaneous demultiplexing and steering of multiple orbital angular momentum modes
Li, Shuhui; Wang, Jian
2015-10-01
We present a simple scheme to perform simultaneous demultiplexing and steering of multiple orbital angular momentum (OAM) modes using a single complex phase mask. By designing the phase mask, the propagation directions of demultiplexed beams can be arbitrarily steered. System experiments using orthogonal frequency-division multiplexing 32-ary quadrature amplitude modulation (OFDM-32QAM) signals over two OAM modes are carried out by using a two-mode complex phase mask. Moreover, demultiplexing of sixteen OAM modes and arbitrary demultiplexed beam steering are also demonstrated in the experiment.
Angular momentum and separation constant in the Kerr metric
International Nuclear Information System (INIS)
Kerr metric admits a Killing tensor which yields a second order constant of motion for classical trajectories. An explicit expression is found for this constant using a particular coordinate system, the oblate spheroidal. Owing to the separability of the Hamilton - Jacobi equation in this system, it is easy to show that the second order constant is in fact the square of the total angular momentum of the particle at infinity, corrected with terms which arise from the non-inertial character of the coordinate system. (Author)
Photons, phonons, and plasmons with orbital angular momentum in plasmas
Chen, Qiang; Liu, Jian
2016-01-01
Exact eigen modes with orbital angular momentum (OAM) in the complex media of unmagnetized homogeneous plasma are studied. Three exact eigen modes with OAM are discovered, i.e., photons, phonons, and plasmons. It is found that an OAM photon can be excited by two familiar Bessel modes without OAM. For the phonons and plasmons, their OAM are carried by the electrons and ions. The OAM modes in plasmas and their characteristics can be explored for various potential applications in plasma physics and accelerator physics.
Modeling Angular-Momentum History in Dark-Matter Halos
Maller, Ariyeh H.; Dekel, Avishai; Somerville, Rachel S.
2001-01-01
We model the acquisition of spin by dark-matter halos in semi-analytic merger trees. We explore two different algorithms; one in which halo spin is acquired from the orbital angular momentum of merging satellites, and another in which halo spin is gained via tidal torquing on shells of material while still in the linear regime. We find that both scenarios produce the characteristic spin distribution of halos found in N-body simulations, namely, a log-normal distribution with mean ~0.04 and st...
Testing angular momentum effects on the space time
Tartaglia, A
2001-01-01
The paper contains a proposed experiment for testing the angular momentum effect on the propagation of light around a rotating mass. The idea is to use a rotating spherical laboratory-scale shell, around which two mutually orthogonal light guides are wound acting as the arms of an interferometer. Numerical estimates show that time of flight differences between the equatorial and polar guides could be in the order of $\\sim 10^{-20}$ s per loop. Using a few thousands loops the time difference is brought in the range of feasible interference measurements.
Nucleon form factors, generalized parton distributions and quark angular momentum
International Nuclear Information System (INIS)
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale μ=2 GeV to be Juv=0.230+0.009-0.024 and Jdv=-0.004+0.010-0.016.
Orbital angular momentum of superposition of identical shifted vortex beams.
Kovalev, A A; Kotlyar, V V
2015-10-01
We have formulated and proven the following theorem: the superposition of an arbitrary number of arbitrarily off-axis, identical nonparaxial optical vortex beams of arbitrary radially symmetric shape, integer topological charge n, and arbitrary real weight coefficients has the normalized orbital angular momentum (OAM) equal to that of individual constituent identical beams. This theorem enables generating vortex laser beams with different (not necessarily radially symmetric) intensity profiles but identical OAM. Superpositions of Bessel, Hankel-Bessel, Bessel-Gaussian, and Laguerre-Gaussian beams with the same OAM are discussed. PMID:26479934
Angular momentum effects in fusion reactions near the Coulomb barrier
International Nuclear Information System (INIS)
Cross sections and γ-ray multiplicities have been measured for neutron evaporation channels in the reactions 16O + 144Nd, 37Cl + 123Sb, 64Ni + 96Zr and 80Se + 80Se leading to the compound system 160Er at common excitation energies. In the near-barrier energy regime average angular momentum transfers depend dramatically on the asymmetry of the entrance channel. The results can be interpreted in terms of barrier fluctuations induced by target and projectile ground-state vibrations
Energy Technology Data Exchange (ETDEWEB)
Thomas, M.S. (Royal Military Coll. of Canada, Kingston, Ontario); Gruber, B. (Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany, F.R.). Inst. fuer Theoretische Physik)
1982-01-01
In this article symmetry chains for the atomic shell model are investigated which lead from the group SO(8l+-5) to the subgroup SOsub(L)(3). The tail group SOsub(L)(3) corresponds to total orbital angular momentum. Along these chains total orbital angular momentum L is a good quantum number, but not total spin S. Total orbital angular momentum can be considered as being made up of four quasi angular momenta.
The effect of scattering on single photon transmission of optical angular momentum
International Nuclear Information System (INIS)
Schemes for the communication and registration of optical angular momentum depend on the fidelity of transmission between optical system components. It is known that electron spin can be faithfully relayed between exciton states in quantum dots; it has also been shown by several theoretical and experimental studies that the use of beams conveying orbital angular momentum can significantly extend the density and efficiency of such information transfer. However, it remains unclear to what extent the operation of such a concept at the single photon level is practicable—especially where this involves optical propagation through a material system, in which forward scattering events can intervene. The possibility of transmitting and decoding angular momentum over nanoscale distances itself raises other important issues associated with near-field interrogation. This paper provides a framework to address these and related issues. A quantum electrodynamical representation is constructed and used to pursue the consequences of individual photons, from a Laguerre–Gaussian beam, undergoing single and multiple scattering events in the course of propagation. In this context, issues concerning orbital angular momentum conservation, and its possible compromise, are tackled by identifying the relevant components of the electromagnetic scattering and coupling tensors, using an irreducible Cartesian basis. The physical interpretation broadly supports the fidelity of quantum information transmission, but it also identifies potential limitations of principle
On angular momentum balance for particle systems with periodic boundary conditions
Kuzkin, Vitaly A.
2013-01-01
The well-known issue with the absence of conservation of angular momentum in classical particle systems with periodic boundary conditions is addressed. It is shown that conventional theory based on Noether's theorem fails to explain the simplest possible example, notably jumps of angular momentum in the case of single particle moving in a periodic cell. It is suggested to consider the periodic cell as an open system, exchanging mass, momentum, angular momentum, and energy with surrounding cel...
Constraining the Angular Momentum Evolution of V455 Andromedae
Mukadam, Anjum S.; Pyrzas, Stylianos; Townsley, D. M.; Gänsicke, B. T.; Hermes, J. J.; Szkody, Paula; Kemp, Jonathan; Patterson, J.; Ding, Claire; Wolf, Katie; Gemma, Marina; Karamehmetoglu, Emir; Rock, John
2016-04-01
Time-series photometry on the cataclysmic variable V455 Andromedae (hereafter V455 And, HS 2331+3905) reveals a rotation period shorter than the orbital period, implying the presence of a magnetic field. We expect that this magnetic field channels the accreted matter from the disk toward the white dwarf poles, classifying it as an Intermediate Polar. The two polar spinning emission areas are visible in the lightcurves at the rotation period of 67.61970396 ± 0.00000072 s, and its harmonic. Using photometric observations of V455 And obtained from 2007 October to 2015, we derive 3σ upper limits to the rate of change of the spin harmonic (SH) with time to be dPSH/dt ≤ ‑7.5 × 10‑15 s s‑1 employing the O–C method, and ‑5.4 × 10‑15 s s‑1 with a direct nonlinear least squares fit. There is no significant detection of a changing spin period for the duration of 2007 October–2015. The 3σ upper limit for the rate of change of spin period with time is dPspin/dt ≤ ‑10.8 × 10‑15 s s‑1 or ‑0.34 μs yr‑1. V455 And underwent a large-amplitude dwarf nova outburst in 2007 September. The pre-outburst data reflect a period 4.8 ± 2.2 μs longer than the best-fit post-outburst spin period. The angular momentum gained by the white dwarf from matter accreted during outburst and its slight subsequent shrinking should both cause the star to spin slightly faster after the outburst. We estimate that the change in spin period due to the outburst should be 5 μs, consistent with the empirical determination of 4.8 ± 2.2 μs (3σ upper limit of 11.4 μs).
Gaffney, Brecca M; Murray, Amanda M; Christiansen, Cory L; Davidson, Bradley S
2016-03-01
Patients with unilateral dysvascular transtibial amputation (TTA) have a higher risk of developing low back pain than their healthy counterparts, which may be related to movement compensations used in the absence of ankle function. Assessing components of segmental angular momentum provides a unique framework to identify and interpret these movement compensations alongside traditional observational analyses. Angular momentum separation indicates two components of total angular momentum: (1) transfer momentum and (2) rotational momentum. The objective of this investigation was to assess movement compensations in patients with dysvascular TTA, patients with diabetes mellitus (DM), and healthy controls (HC) by examining patterns of generating and arresting trunk and pelvis segmental angular momenta during gait. We hypothesized that all groups would demonstrate similar patterns of generating/arresting total momentum and transfer momentum in the trunk and pelvis in reference to the groups (patients with DM and HC). We also hypothesized that patients with amputation would demonstrate different (larger) patterns of generating/arresting rotational angular momentum in the trunk. Patients with amputation demonstrated differences in trunk and pelvis transfer angular momentum in the sagittal and transverse planes in comparison to the reference groups, which indicates postural compensations adopted during walking. However, patients with amputation demonstrated larger patterns of generating and arresting of trunk and pelvis rotational angular momentum in comparison to the reference groups. These segmental rotational angular momentum patterns correspond with high eccentric muscle demands needed to arrest the angular momentum, and may lead to consequential long-term effects such as low back pain. PMID:26979898
Angular momentum budget of the radiational S1 ocean tide
Schindelegger, Michael; Dobslaw, Henryk; Poropat, Lea; Salstein, David; Böhm, Johannes
2016-04-01
The balance of diurnal S1 oceanic angular momentum (OAM) variations through torques at the sea surface and the bottom topography is validated using both a barotropic and a baroclinic numerical tide model. This analysis discloses the extent to which atmosphere-driven S1 forward simulations are reliable for use in studies of high-frequency polar motion and changes in length-of-day. Viscous and dissipative torques associated with wind stress, bottom friction, as well as internal tidal energy conversion are shown to be small, and they are overshadowed by gravitational and pressure-related interaction forces. In particular, the zonal OAM variability of S1 is almost completely balanced by the water pressure torque on the local bathymetry, whereas in the prograde equatorial case also the air pressure torque on the seafloor as well as ellipsoidal contributions from the non-spherical atmosphere and solid Earth must be taken into account. Overall, the OAM budget is well closed in both the axial and the equatorial directions, thus allowing for an identification of the main diurnal angular momentum sinks in the ocean. The physical interaction forces are found to be largest at shelf breaks and continental slopes in low latitudes, with the most dominant contribution coming from the Indonesian archipelago.
Particle beams carrying orbital angular momentum, charge, mass and spin
Tijssen, Teuntje; Hayrapetyan, Armen; Goette, Joerg; Dennis, Mark
Electron beams carrying vortices and angular momentum have been of much experimental and theoretical interest in recent years. In addition, optical vortex beams are a well-established field in optics and photonics. In both cases, the orbital angular momentum associated with the beam's axial vortex has effects on the overall spin of the beam, due to spin-orbit interactions. A simple model of these systems are Bessel beam solutions (of either the Dirac equation or Maxwell equations) with a nonzero azimuthal quantum number, which are found by separation in cylindrical coordinates. Here, we generalize this approach, considering the classical field theory of Bessel beams for particles which are either massive or massless, uncharged or charged and of a variety of different spins (0, 1/2, 1, ⋯). We regard the spin and helicity states and different forms of spin-orbit terms that arise. Moreover, we analyse the induced electromagnetic field when the particles carry charge. Most importantly, this unified field theory approach leads to the prediction of effects for vortex beams of neutrons, mesons and neutrinos.
An Uncertainty Relation for the Orbital Angular Momentum Operator
Fakhri, H.; Sayyah-Fard, M.
2016-01-01
A common reducible representation space of the Lie algebras su(1, 1) and su(2) is equipped with two different types of scalar products. The representation bases are labeled by the azimuthal and magnetic quantum numbers. The generators of su(2) are the x-, y- and z-components of the orbital angular momentum operator. The representation of each of these Lie algebras is unitary with respect to only one of the scalar products. To each positive magnetic quantum number a family of the su(1, 1)-Barut-Girardello coherent states is associated. The normalization and resolution of the identity condition for the coherent states are realized in two different approaches, i.e. the unitary and the non-unitary approaches. For the coherent states of the non-unitary case we calculate the uncertainty relation for the Hermitian x- and y-components of the angular momentum operator. While the unitary case leads to the known uncertainty relation for the Hermitian x- and y-components of su(1, 1) Lie algebra.
Colliding particles carrying non-zero orbital angular momentum
Ivanov, I P
2011-01-01
Photons carrying non-zero orbital angular momentum (twisted photons) are well-known in optics. Recently, it was suggested to use Compton backscattering to boost optical twisted photons to high energies. Twisted electrons in the intermediate energy range have also been produced recently. Thus, collisions involving energetic twisted particles seem to be feasible and represent a new tool in high-energy physics. Here we discuss some features of a generic scattering process in which one (single-twisted case) or both (double-twisted case) initial particles carry orbital angular momentum. We show that the single-twisted cross section allows one to perform a Fourier analysis of the plane wave cross section with respect to the azimuthal angle of the initial particle. For the double-twisted cross section we find an expression that depends not only on the plane wave cross section, but also on the autocorrelation function of the plane wave amplitude. We discuss prospects for experimental study of these effects in the nea...
Angular momentum of disc galaxies with a lognormal density distribution
Marr, John Herbert
2015-01-01
Whilst most galaxy properties scale with galaxy mass, similar scaling relations for angular momentum are harder to demonstrate. A lognormal (LN) density distribution for disc mass provides a good overall fit to the observational data for disc rotation curves for a wide variety of galaxy types and luminosities. In this paper, the total angular momentum J and energy $\\vert{}$E$\\vert{}$ were computed for 38 disc galaxies from the published rotation curves and plotted against the derived disc masses, with best fit slopes of 1.683$\\pm{}$0.018 and 1.643$\\pm{}$0.038 respectively, using a theoretical model with a LN density profile. The derived mean disc spin parameter was $\\lambda{}$=0.423$\\pm{}$0.014. Using the rotation curve parameters V$_{max}$ and R$_{max}$ as surrogates for the virial velocity and radius, the virial mass estimator $M_{disc}\\propto{}R_{max}V_{max}^2$ was also generated, with a log-log slope of 1.024$\\pm{}$0.014 for the 38 galaxies, and a proportionality constant ${\\lambda{}}^*=1.47\\pm{}0.20\\time...
An Uncertainty Relation for the Orbital Angular Momentum Operator
Fakhri, H.; Sayyah-Fard, M.
2016-08-01
A common reducible representation space of the Lie algebras su(1, 1) and su(2) is equipped with two different types of scalar products. The representation bases are labeled by the azimuthal and magnetic quantum numbers. The generators of su(2) are the x-, y- and z-components of the orbital angular momentum operator. The representation of each of these Lie algebras is unitary with respect to only one of the scalar products. To each positive magnetic quantum number a family of the su(1, 1)-Barut-Girardello coherent states is associated. The normalization and resolution of the identity condition for the coherent states are realized in two different approaches, i.e. the unitary and the non-unitary approaches. For the coherent states of the non-unitary case we calculate the uncertainty relation for the Hermitian x- and y-components of the angular momentum operator. While the unitary case leads to the known uncertainty relation for the Hermitian x- and y-components of su(1, 1) Lie algebra.
Drell-Yan Lepton Angular Distribution at Small Transverse Momentum
Boer, D; Boer, Daniel; Vogelsang, Werner
2006-01-01
We investigate the dependence of the Drell-Yan cross section on lepton polar and azimuthal angles, as generated by the lowest-order QCD annihilation and Compton processes. We focus in particular on the azimuthal-angular distributions, which are of the form cos(phi) and cos(2phi). At small transverse momentum q_T of the lepton pair, q_T << Q, with Q the pair mass, these terms are known to be suppressed relative to the phi-independent part of the Drell-Yan cross section by one or two powers of the transverse momentum. Nonetheless, as we show, like the phi-independent part they are subject to large logarithmic corrections, whose precise form however depends on the reference frame chosen. These logarithmic contributions ultimately require resummation to all orders in the strong coupling. We discuss the potential effects of resummation on the various angular terms in the cross section and on the Lam-Tung relation.
Hancox, Cindy I; Doret, S Charles; Hummon, Matthew T; Krems, Roman V; Doyle, John M
2005-01-14
The Zeeman relaxation rate in cold collisions of Ti(3d(2)4s(2) 3F2) with He is measured. We find that collisional transfer of angular momentum is dramatically suppressed due to the presence of the filled 4s(2) shell. The degree of electronic interaction anisotropy, which is responsible for Zeeman relaxation, is estimated to be about 200 times smaller in the Ti-He complex than in He complexes with typical non-S-state atoms. PMID:15698077
Orbital angular momentum of the laser beam and the second order intensity moments
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
From the wave equation of a generalized beam the orbital angular momentum is studied. It is shown that the orbital angular momentum exists not only in the Laguerre_Gaussian beam,but in any beam with an angular_dependent structure. By calculating the second order intensity moments of the beam the relation between the orbital angular momentum and the second order moments 〈xθy〉, 〈yθx〉 is given. As an example the orbital angular momentum of the general astigmatic Gaussian beam is studied.
Orbital angular momentum of the laser beam and the second order intensity moments
Institute of Scientific and Technical Information of China (English)
高春清[1; 魏光辉[2; HorstWeber[3
2000-01-01
From the wave equation of a generalized beam the orbital angular momentum is studied. It is shown that the orbital angular momentum exists not only in the Laguerre-Gaussian beam, but in any beam with an angular-dependent structure. By calculating the second order intensity moments of the beam the relation between the orbital angular momentum and the second order moments 〈xθy〉, 〈yθx〉 is given. As an example the orbital angular momentum of the general astigmatic Gaussian beam is studied.
Statistical mechanics of collisionless orbits. IV. Distribution of angular momentum
International Nuclear Information System (INIS)
It has been shown in previous work that DARKexp, which is a theoretically derived, maximum entropy, one shape parameter model for isotropic collisionless systems, provides very good fits to simulated and observed dark matter halos. Specifically, it fits the energy distribution, N(E), and the density profiles, including the central cusp. Here, we extend DARKexp N(E) to include the distribution in angular momentum, L 2, for spherically symmetric systems. First, we argue, based on theoretical, semi-analytical, and simulation results, that while dark matter halos are relaxed in energy, they are not nearly as relaxed in angular momentum, which precludes using maximum entropy to uniquely derive N(E, L 2). Instead, we require that when integrating N(E, L 2) over squared angular momenta one retrieves the DARKexp N(E). Starting with a general expression for N(E, L 2) we show how the distribution of particles in L 2 is related to the shape of the velocity distribution function, VDF, and velocity anisotropy profile, β(r). We then demonstrate that astrophysically realistic halos, as judged by the VDF shape and β(r), must have linear or convex distributions in L 2, for each separate energy bin. The distribution in energy of the most bound particles must be nearly flat, and become more tilted in favor of radial orbits for less bound particles. These results are consistent with numerical simulations and represent an important step toward deriving the full distribution function for spherically symmetric dark matter halos.
Statistical mechanics of collisionless orbits. IV. Distribution of angular momentum
Energy Technology Data Exchange (ETDEWEB)
Williams, Liliya L. R. [School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Hjorth, Jens; Wojtak, Radosław, E-mail: llrw@astro.umn.edu, E-mail: jens@dark-cosmology.dk, E-mail: wojtak@dark-cosmology.dk [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark)
2014-03-01
It has been shown in previous work that DARKexp, which is a theoretically derived, maximum entropy, one shape parameter model for isotropic collisionless systems, provides very good fits to simulated and observed dark matter halos. Specifically, it fits the energy distribution, N(E), and the density profiles, including the central cusp. Here, we extend DARKexp N(E) to include the distribution in angular momentum, L {sup 2}, for spherically symmetric systems. First, we argue, based on theoretical, semi-analytical, and simulation results, that while dark matter halos are relaxed in energy, they are not nearly as relaxed in angular momentum, which precludes using maximum entropy to uniquely derive N(E, L {sup 2}). Instead, we require that when integrating N(E, L {sup 2}) over squared angular momenta one retrieves the DARKexp N(E). Starting with a general expression for N(E, L {sup 2}) we show how the distribution of particles in L {sup 2} is related to the shape of the velocity distribution function, VDF, and velocity anisotropy profile, β(r). We then demonstrate that astrophysically realistic halos, as judged by the VDF shape and β(r), must have linear or convex distributions in L {sup 2}, for each separate energy bin. The distribution in energy of the most bound particles must be nearly flat, and become more tilted in favor of radial orbits for less bound particles. These results are consistent with numerical simulations and represent an important step toward deriving the full distribution function for spherically symmetric dark matter halos.
International Nuclear Information System (INIS)
The energy–momentum tensor, which is coordinate-independent, is used to calculate energy, momentum and angular momentum of two different tetrad fields. Although, the two tetrad fields reproduce the same space-time their energies are different. Therefore, a regularized expression of the gravitational energy–momentum tensor of the teleparallel equivalent of general relativity (TEGR), is used to make the energies of the two tetrad fields equal. The definition of the gravitational energy–momentum is used to investigate the energy within the external event horizon. The components of angular momentum associated with these space–times are calculated. In spite of using a static space–time, we get a non-zero component of angular momentum! Therefore, we derive the Killing vectors associated with these space–times using the definition of the Lie derivative of a second rank tensor in the framework of the TEGR to make the picture more clear. (general)
Effect of Orbital Angular Momentum on Valence-Quark Helicity Distributions
Energy Technology Data Exchange (ETDEWEB)
Harut Avakian; Stanley J. Brodsky; Alexandre Deur; Feng Yuan
2007-08-01
We study the quark helicity distributions at large x in perturbative QCD, taking into account contributions from the valence Fock states of the nucleon which have nonzero orbital angular momentum. These states are necessary to have a nonzero anomalous magnetic moment. We find that the quark orbital angular momentum contributes a large logarithm to the negative helicity quark distributions in addition to its power behavior, scaling as (1-x)^5\\log^2(1-x) in the limit of x\\to 1. Our analysis shows that the ratio of the polarized over unpolarized down quark distributions, \\Delta d/d, will still approach 1 in this limit. By comparing with the experimental data, we find that this ratio should cross zero at x\\approx 0.75.
Mode density of orbital angular momentum modes in a cylindrical cavity and in free space
Andersson, Mauritz; Björk, Gunnar
2015-01-01
In this short note we derive an approximate expression for the mode density of modes carrying orbital angular momentum (OAM) in a cylindrical cavity which is large compared to the inverse wavevector in any direction. We argue that in the large cavity limit the modes asymptotically converges to the corresponding OAM modes in free space. We compare the result to Weyl's law. It is found, as expected, that the mode density does not depend on whether or not the modes carry OAM.
/sup 3/He-A versus bose liquid: orbital angular momentum and orbital dynamics
Energy Technology Data Exchange (ETDEWEB)
Volovik, G.S.; Mineev, V.P. (AN SSSR, Moscow. Inst. Teoreticheskoj Fiziki)
1981-09-01
At T=0 are obtained general expressions for the superfluid current and orbital angular momentum in a superfluid liquid with the structure of the /sup 3/He A-phase which in the limit ..delta..<
Competition between spin and orbital photon angular momentum transfer in liquid crystals
Energy Technology Data Exchange (ETDEWEB)
Piccirillo, B; Vella, A; Santamato, E [Istituto Nazionale di Fisica della Materia, Dipartimento di Scienze Fisiche, via Cintia, 80126 Naples (Italy)
2002-04-01
We present a theoretical and experimental study on the transfer of angular momentum from a light beam to a nematic liquid crystal film. In the angular momentum transfer process photons are not destroyed, but scattered in a different angular momentum state: a process known as self-induced stimulated light scattering (Santamato E, Daino B, Romagnoli M, Settembre M and Shen Y R 1988 Phys. Rev. Lett. 61 113-16). Each photon in the incident beam transfers to the material only the change of its angular momentum, producing a torque on the body. Under the action of this torque, the body starts to rotate, changing, in turn, the amount of angular momentum extracted from the light beam. The process is intrinsically nonlinear and, as proved by the experiments reported in this paper, it can be initiated by a light beam carrying no angular momentum at all.
Numerical Solution of the Evolution Equation for Orbital Angular Momentum of Partons in the Nucleon
Martin, O.; Hagler, P.; Schafer, A.
1998-01-01
The evolution of orbital angular momentum distributions within the radiative parton model is studied. We use different scenarios for the helicity weighted parton distributions and consider a broad range of input distributions for orbital angular momentum. In all cases we are lead to the conclusion that the absolute value of the average angular momentum per parton peaks at relatively large $x\\approx 0.1$ for perturbatively accessible scales. Furthermore, in all scenarios considered here the av...
High-capacity millimetre-wave communications with orbital angular momentum multiplexing
Yan, Yan; Xie, Guodong; Lavery, Martin P. J.; Huang, Hao; Ahmed, Nisar; Bao, Changjing; Ren, Yongxiong; Cao, Yinwen; Li, Long; Zhao, Zhe; Molisch, Andreas F; Tur, Moshe; Padgett, Miles J.; Willner, Alan E.
2014-01-01
One property of electromagnetic waves that has been recently explored is the ability to multiplex multiple beams, such that each beam has a unique helical phase front. The amount of phase front ‘twisting’ indicates the orbital angular momentum state number, and beams with different orbital angular momentum are orthogonal. Such orbital angular momentum based multiplexing can potentially increase the system capacity and spectral efficiency of millimetre-wave wireless communication links with a ...
Spin-to-orbital angular momentum conversion and spin-polarization filtering in electron beams
Karimi E.; Marrucci L.; Grillo V.; Santamato E.
2012-01-01
We propose the design of a space-variant Wien filter for electron beams that induces a spin half-turn and converts the corresponding spin angular momentum variation into orbital angular momentum of the beam itself by exploiting a geometrical phase arising in the spin manipulation. When applied to a spatially coherent input spin-polarized electron beam, such a device can generate an electron vortex beam, carrying orbital angular momentum. When applied to an unpolarized input beam, the proposed...
Beam moments and angular momentum in non-uniformly polarized beams
Serna, Julio; Piquero, Gemma
2009-05-01
The angular momentum of non-uniformly totally polarized beams is investigated using methods from the beam characterization approach. The relationship between the elements of the beam matrix for the two components of the field and the angular momentum is given. The unconventional distribution of the polarization across the beam profile could result in contributions to both the spin and orbital terms of the angular momentum. To illustrate this, a particular example with a vortex beam is considered.
Proposals for the generation of angular momentum from non-uniformly polarized beams
Alonso, Mara; Piquero, Gemma; Serna, Julio
2012-04-01
Several optical arrangements using non-uniformly polarized fields are proposed for generating beams with spin and/or orbital angular momentum. By choosing adequately the input beam polarization and the characteristics of the different proposed set-ups we can control the overall angular momentum of the output beam at will. The orbital angular momentum is analyzed with the beam moments theory and the spin term is evaluated using the averaged s3 Stokes parameter.
Angular momentum dynamics and the intrinsic drift of monopolar vortices on a rotating sphere
van Toorn, R.; Zimmerman, J.T.F.
2010-01-01
On the basis of the angular momentum equation for a fluid shell on a rotating planet, we analyze the intrinsic drift of a monopolar vortex in the shell. Central is the development of a general angular momentum equation for Eulerian fluid mechanics based on coordinate-free, general tensorial representations of the underlying fluid dynamics on the one hand, and an appropriate representation of the Lie algebra so(3) of rotations on the other hand. We show that angular momentum fluid dynamics con...
The angular momentum transport by unstable toroidal magnetic fields
Ruediger, G; Spada, F; Tereshin, I
2014-01-01
We demonstrate with a nonlinear MHD code that angular momentum can be transported due to the magnetic instability of toroidal fields under the influence of differential rotation, and that the resulting effective viscosity may be high enough to explain the almost rigid-body rotation observed in radiative stellar cores. The fields are assumed strong enough and the density stratification weak enough that the influence of the 'negative' buoyancy in the radiative zones can be neglected. Only permanent current-free fields and only those combinations of rotation rates and magnetic field amplitudes which provide maximal numerical values of the viscosity are considered. We find that the dimensionless ratio of the turbulent over molecular viscosity, \
Orbital angular momentum loss in PSR 1957 + 20
Banit, Menashe; Shaham, Jacob
1992-01-01
It is suggested that the companion winds, excited by the radiation from the neutron star in PSR 1957 + 20 form only through the combined action of the radiation heat on the companion's atmosphere and the radiation force on the slowly lifting wind. Ballistic simulations suggest that these winds leave only from selected areas of the illuminated surface of the companion; surface currents channel into these regions relatively hot (but altogether cooler than the companion escape velocity) 'coronal' matter from the whole illuminated area. Under suitable conditions, wind particles spend some time trailing the companion at close distances before taking off to escape from the system. This can torque the binary into angular momentum loss that will be as efficient as the one recently observed in PSR 1957 + 20 if the companion is bloated to dimensions close to that of the Roche lobe.
Observation of Four-Photon Orbital Angular Momentum Entanglement
Hiesmayr, B. C.; de Dood, M. J. A.; Löffler, W.
2016-02-01
We demonstrate genuine multipartite quantum entanglement of four photons in their orbital angular momentum degrees of freedom, where a high-dimensional discrete Hilbert space is attached to each photon. This can encode more quantum information compared to the qubit case, but it is a long-standing problem to entangle more than two such photons. In our experiment we use pulsed spontaneous parametric down-conversion to produce the photon quadruplets, which allows us to detect about one four-photon event per second. By means of quantum state reconstruction and a suitable witness operator we find that the photon quadruplets form a genuine multipartite entangled symmetric Dicke state. This opens a new tool for addressing foundational questions in quantum mechanics, and for exploration of novel high-dimensional multiparty quantum information applications such as secret sharing.
Detecting Lateral Motion using Light’s Orbital Angular Momentum
Cvijetic, Neda; Milione, Giovanni; Ip, Ezra; Wang, Ting
2015-01-01
Interrogating an object with a light beam and analyzing the scattered light can reveal kinematic information about the object, which is vital for applications ranging from autonomous vehicles to gesture recognition and virtual reality. We show that by analyzing the change in the orbital angular momentum (OAM) of a tilted light beam eclipsed by a moving object, lateral motion of the object can be detected in an arbitrary direction using a single light beam and without object image reconstruction. We observe OAM spectral asymmetry that corresponds to the lateral motion direction along an arbitrary axis perpendicular to the plane containing the light beam and OAM measurement axes. These findings extend OAM-based remote sensing to detection of non-rotational qualities of objects and may also have extensions to other electromagnetic wave regimes, including radio and sound. PMID:26493681
Creating High-Harmonic Beams with Controlled Orbital Angular Momentum
Boyd, Robert W.
A beam of light with an angle-dependent phase Φ = lϕ , where ϕ is the azimuthal coordinate, about the beam axis carries an orbital angular momentum (OAM) of lℏ per photon. Such beams have been exploited to provide superresolution in visible-light microscopy. The ability to create extreme ultraviolet or soft-x-ray beams with controllable OAM would be a critical step towards extending superresolution methods to extremely small feature size. Here we show that OAM is conserved during the process of high-harmonic generation (HHG). Experimentally, we use a fundamental beam with l = 1 and interferometrically determine that the q-th harmonic has an OAM quantum number l equal to its harmonic order q. We also show theoretically how to couple an arbitrary low value of the OAM quantum number l to any harmonic order q in a controlled manner. Our results open a route to microscopy on the molecular, or even submolecular, scale.
Violation of Leggett inequalities in orbital angular momentum subspaces
Energy Technology Data Exchange (ETDEWEB)
Romero, J; Leach, J; Jack, B; Padgett, M J; Franke-Arnold, S [School of Physics and Astronomy, SUPA, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Barnett, S M, E-mail: s.franke-arnold@physics.gla.ac.u [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 ONG (United Kingdom)
2010-12-15
We report an experimental test of Leggett's non-local hidden variable theory in an orbital angular momentum (OAM) state space of light. We show that the correlations we observe are in conflict with Leggett's model, thus excluding a particular class of non-local hidden variable theories for the first time in a non-polarization state space. It is known that the violation of the Leggett inequality becomes stronger as more detection settings are used. The required measurements become feasible in an OAM subspace, and we demonstrate this by testing the inequality using three and four settings. We observe excellent agreement with quantum predictions and a violation of five and six standard deviations, respectively, compared to Leggett's non-local hidden variable theory.
Generation of Electromagnetic Waves with Arbitrary Orbital Angular Momentum Modes
Cheng, Li; Hong, Wei; Hao, Zhang-Cheng
2014-01-01
Recently, much attention has been focused on beams carrying orbital angular momentum (OAM) for radio communication. Here we experimentally demonstrate a planar-spiral phase plate (planar-SPP) for generating arbitrary mixed OAM beams. This proposed planar-SPP uses the concept of transmit array antenna having a perforated substrate to control the outputting phase for generating beams carrying OAM with arbitrary modes. As demonstrations, three planar-SPPs with a single OAM mode and two mixed OAM modes around 94 GHz have been investigated with design and experiments in this paper, respectively. The typical experimental intensity and phase patterns show that the proposed method of generating OAM beams really works. PMID:24770669
Calculations of angular momentum coupling coefficients on a computer code
International Nuclear Information System (INIS)
In this study, Clebsch-Gordan coefficients, 3j symbols, Racah coefficients, Wigner's 6j and 9j symbols were calculated by a prepared computer code of COEFF. The computer program COEFF is described which calculates angular momentum coupling coefficients and expresses them as quotient of two integers multiplied by the square root of the quotient of two integers. The program includes subroutines to encode an integer into its prime factors, to decode of prime factors back into an integer , to perform basic arithmetic operations on prime-coded numbers, as well as subroutines which calculate the coupling coefficients themselves. The computer code COEFF had been prepared to run on a VAX. In this study we rearranged the code to run on PC and tested it successfully. The obtained values in this study, were compared with the values of other computer programmes. A pretty good agreement is obtained between our prepared computer code and other computer programmes
Narrow band amplification of light carrying orbital angular momentum.
Borba, G C; Barreiro, S; Pruvost, L; Felinto, D; Tabosa, J W R
2016-05-01
We report on the amplification of an optical vortex beam carrying orbital angular momentum via induced narrow Raman gain in an ensemble of cold cesium atoms. A 20% single-pass Raman gain of a weak vortex signal field is observed with a spectral width of order of 1 MHz, much smaller than the natural width, demonstrating that the amplification process preserves the phase structure of the vortex beam. The gain is observed in the degenerated two-level system associated with the hyperfine transition 6S1/2(F = 3) ↔ 6P3/2(F' = 2) of cesium. Our experimental observations are explained with a simple theoretical model based on a three-level Λ system interacting coherently with the weak Laguerre-Gauss field and a strong coupling field, including an incoherent pumping rate between the two degenerate ground-states. PMID:27137618
Non-collinear interaction of photons with orbital angular momentum
Roger, Thomas; Wright, Ewan M; Faccio, Daniele
2013-01-01
We elucidate the consequences of a phase-matching theory that describes second-harmonic generation of two non-collinear incident light beams that carry orbital angular momentum (OAM). More specifically, the two incident beams generate a third that, depending on the incident OAM, may experience a significantly smaller conversion efficiency in comparison to that based on the conventional phase-matching theory. This is the case even for incident angles substantially less than those required for non-conservation of OAM in the nonlinear interaction. Experiments are performed under different conditions and are in excellent agreement with the theory. Our results have implications beyond the specific case studied here of second-harmonic generation, in particular for parametric down-conversion of photons.
Detecting Lateral Motion using Light’s Orbital Angular Momentum
Cvijetic, Neda; Milione, Giovanni; Ip, Ezra; Wang, Ting
2015-10-01
Interrogating an object with a light beam and analyzing the scattered light can reveal kinematic information about the object, which is vital for applications ranging from autonomous vehicles to gesture recognition and virtual reality. We show that by analyzing the change in the orbital angular momentum (OAM) of a tilted light beam eclipsed by a moving object, lateral motion of the object can be detected in an arbitrary direction using a single light beam and without object image reconstruction. We observe OAM spectral asymmetry that corresponds to the lateral motion direction along an arbitrary axis perpendicular to the plane containing the light beam and OAM measurement axes. These findings extend OAM-based remote sensing to detection of non-rotational qualities of objects and may also have extensions to other electromagnetic wave regimes, including radio and sound.
Detecting Lateral Motion using Light's Orbital Angular Momentum.
Cvijetic, Neda; Milione, Giovanni; Ip, Ezra; Wang, Ting
2015-01-01
Interrogating an object with a light beam and analyzing the scattered light can reveal kinematic information about the object, which is vital for applications ranging from autonomous vehicles to gesture recognition and virtual reality. We show that by analyzing the change in the orbital angular momentum (OAM) of a tilted light beam eclipsed by a moving object, lateral motion of the object can be detected in an arbitrary direction using a single light beam and without object image reconstruction. We observe OAM spectral asymmetry that corresponds to the lateral motion direction along an arbitrary axis perpendicular to the plane containing the light beam and OAM measurement axes. These findings extend OAM-based remote sensing to detection of non-rotational qualities of objects and may also have extensions to other electromagnetic wave regimes, including radio and sound. PMID:26493681
Dynamic interferometry measurement of orbital angular momentum of light
Jianji, Dong; Xinliang, Zhang
2014-01-01
We present a dynamic interferometry to measure the orbital angular momentum (OAM) of beams. An opaque screen with two air slits is employed, which can be regarded as the Youngs double-pinhole interference. When the OAM beams with an annular intensity distribution vertically incident, the far-field interference patterns depend on the phase difference of the light in the two pinholes. We scan the angle between the two slits, the output intensity at center changes alternatively between darkness and brightness. Utilizing this characteristic, we can measure the OAM of light. This scheme is very simple and low-cost. In addition, it can measure very large topological charge of OAM beams due to the continuously scanning.
Chip-Scale Continuously Tunable Optical Orbital Angular Momentum Generator
Sun, Jie; Moresco, Michele; Coolbaugh, Douglas; Watts, Michael R
2014-01-01
Light carrying orbital angular momentum (OAM) has potential to impact a wide variety of applications ranging from optical communications to quantum information and optical forces for the excitation and manipulation of atoms, molecules, and micro-particles. The unique advantage of utilizing OAM in these applications relies, to a large extent, on the use of multiple different OAM states. Therefore, it is desirable to have a device that is able to gen- erate light with freely adjustable OAM states in an integrated form for large- scale integration. We propose and demonstrate a compact silicon photonic integrated circuit to generate a free-space optical beam with OAM state con- tinuously tuned from a single electrical input signal, realizing both integer and non-integer OAM states. The compactness and flexibility of the device and its compatibility with complementary metal-oxide-semiconductor (CMOS) pro- cessing hold promise for integration with other silicon photonic components for wide-ranging applications.
Violation of Leggett inequalities in orbital angular momentum subspaces
International Nuclear Information System (INIS)
We report an experimental test of Leggett's non-local hidden variable theory in an orbital angular momentum (OAM) state space of light. We show that the correlations we observe are in conflict with Leggett's model, thus excluding a particular class of non-local hidden variable theories for the first time in a non-polarization state space. It is known that the violation of the Leggett inequality becomes stronger as more detection settings are used. The required measurements become feasible in an OAM subspace, and we demonstrate this by testing the inequality using three and four settings. We observe excellent agreement with quantum predictions and a violation of five and six standard deviations, respectively, compared to Leggett's non-local hidden variable theory.
Dynamic interferometry measurement of orbital angular momentum of light.
Zhou, Hailong; Shi, Lei; Zhang, Xinliang; Dong, Jianji
2014-10-15
We present a dynamic interferometry to measure the orbital angular momentum (OAM) of beams. An opaque screen with two nonparallel air slits is employed that can be regarded as the Young's double-pinhole interference. When the OAM beams with an annular intensity distribution vertically incident, the far-field interference patterns depend on the phase difference of the light in the two pinholes. We scan the angle between the two slits, and the output intensity at center changes alternatively between darkness and brightness. Utilizing this characteristic, we can measure the OAM of light. This scheme is very simple and low-cost. In addition, it can measure very large topological charge of OAM beams due to continuous scanning. PMID:25361155
Information Transferring between a Photon's Orbital Angular Momentum and Frequency
International Nuclear Information System (INIS)
A photon's orbital angular momentum (OAM) offers a promising resource for the higher-dimensional quantum information process, which is due to the infinite values of OAM. One of the obstacles for its application is that it is difficult to transmit information encoded in OAM space in long distance quantum communication, e.g., photons with different OAMs are unsupported in optical fiber transmitting. We propose an efficient scheme to transform the information from OAM to frequency. Then the information encoded in frequency freedom can be used in fiber transmission and finally be recovered to OAM from frequency. Our scheme can be easily extended to higher-dimensional quantum information transferring between OAM and frequency
Rapid Generation of Light Beams Carrying Orbital Angular Momentum
Mirhosseini, Mohammad; Chen, Changchen; Rodenburg, Brandon; Malik, Mehul; Boyd, Robert W
2013-01-01
We report a technique for encoding both amplitude and phase variations onto a laser beam using a single digital micro-mirror device (DMD). Using this technique, we generate Laguerre-Gaussian and vortex orbital-angular-momentum (OAM) modes, along with modes in a set that is mutually unbiased with respect to the OAM basis. Additionally, we have demonstrated rapid switching among the generated modes at a speed of 4 kHz, which is much faster than the speed regularly achieved by spatial light modulators (SLMs). The dynamic control of both phase and amplitude of a laser beam is an enabling technology for classical communication and quantum key distribution (QKD) systems that employ spatial mode encoding.
Object Identification Using Correlated Orbital Angular Momentum States
Uribe-Patarroyo, Nestor; Simon, David S; Minaeva, Olga; Sergienko, Alexander V
2012-01-01
Using spontaneous parametric down conversion as a source of entangled photon pairs, correlations are measured between the orbital angular momentum (OAM) in a target beam (which contains an unknown object) and that in an empty reference beam. Unlike previous studies, the effects of the object on off-diagonal elements of the OAM correlation matrix are examined. Due to the presence of the object, terms appear in which the signal and idler OAM do not add up to that of the pump. Using these off-diagonal correlations, the potential for high-efficiency object identification by means of correlated OAM states is experimentally demonstrated for the first time. The higher-dimensional OAM Hilbert space enhances the information capacity of this approach, while the presence of the off-diagonal correlations allows for recognition of specific spatial signatures present in the object. In particular, this allows the detection of discrete rotational symmetries and the efficient evaluation of multiple azimuthal Fourier coefficie...
Controllable all-fiber orbital angular momentum mode converter.
Li, Shuhui; Mo, Qi; Hu, Xiao; Du, Cheng; Wang, Jian
2015-09-15
We present a scheme to realize a controllable, scalable, low-cost, and versatile all-fiber orbital angular momentum (OAM) converter. The converter consists of a two-mode fiber (TMF) with its input terminal welded with a single-mode fiber, a mechanical long-period grating (LPG), a mechanical rotator, metal flat slabs, and a fiber polarization controller. The LPG is employed to convert the fundamental fiber mode to higher-order modes and the flat slabs are used to stress the TMF to adjust the relative phase difference between two orthogonal higher-order modes. Selective conversion from the LP(01) mode to the LP(11a), LP(11b), OAM(-1), or OAM(+1) mode is demonstrated in the experiment. PMID:26371940
Catenary optics for achromatic generation of perfect optical angular momentum.
Pu, Mingbo; Li, Xiong; Ma, Xiaoliang; Wang, Yanqin; Zhao, Zeyu; Wang, Changtao; Hu, Chenggang; Gao, Ping; Huang, Cheng; Ren, Haoran; Li, Xiangping; Qin, Fei; Yang, Jing; Gu, Min; Hong, Minghui; Luo, Xiangang
2015-10-01
The catenary is the curve that a free-hanging chain assumes under its own weight, and thought to be a "true mathematical and mechanical form" in architecture by Robert Hooke in the 1670s, with nevertheless no significant phenomena observed in optics. We show that the optical catenary can serve as a unique building block of metasurfaces to produce continuous and linear phase shift covering [0, 2π], a mission that is extremely difficult if not impossible for state-of-the-art technology. Via catenary arrays, planar optical devices are designed and experimentally characterized to generate various kinds of beams carrying orbital angular momentum (OAM). These devices can operate in an ultra-broadband spectrum because the anisotropic modes associated with the spin-orbit interaction are almost independent of the incident light frequency. By combining the optical and topological characteristics, our approach would allow the complete control of photons within a single nanometric layer. PMID:26601283
The decay of massive closed superstrings with maximum angular momentum
International Nuclear Information System (INIS)
We study the decay of a very massive closed superstring (i.e. α'M2 >> 1) in the unique state of maximum angular momentum. This is done in flat ten-dimensional spacetime and in the regime of weak string coupling, where the dominant decay channel is into two states of masses M1, M2. We find that the lifetime surprisingly grows with the first power of the mass M: T=cα'M. We also compute the decay rate for each values of M1, M2. We find that, for large M, the dynamics selects only special channels of decay: modulo processes which are exponentially suppressed, for every decay into a state of given mass M1, the mass M2 of the other state is uniquely determined. (author)
Holographic tool kit for optical communication beyond orbital angular momentum
Trichili, Abderrahmen; Dudley, Angela; Ndagano, Bienvenu; Salem, Amine Ben; Zghal, Mourad; Forbes, Andrew
2016-01-01
Mode division multiplexing (MDM) is mooted as a technology to address future bandwidth issues, and has been successfully demonstrated in free space using spatial modes with orbital angular momentum (OAM). To further increase the data transmission rate, more degrees of freedom are required to form a densely packed mode space. Here we move beyond OAM and demonstrate multiplexing and demultiplexing using both the radial and azimuthal degrees of freedom. We achieve this with a holographic approach that allows over 100 modes to be encoded on a single hologram, across a wide wavelength range, in a wavelength independent manner. Our results offer a new tool that will prove useful in realising higher bit rates for next generation optical networks.
Do all BPS black hole microstates carry zero angular momentum?
Chowdhury, Abhishek; Garavuso, Richard S.; Mondal, Swapnamay; Sen, Ashoke
2016-04-01
From the analysis of the near horizon geometry and supersymmetry algebra it has been argued that all the microstates of single centered BPS black holes with four unbroken supersymmetries carry zero angular momentum in the region of the moduli space where the black hole description is valid. A stronger form of the conjecture would be that the result holds for any sufficiently generic point in the moduli space. In this paper we set out to test this conjecture for a class of black hole microstates in type II string theory on T 6, represented by four stacks of D-branes wrapped on various cycles of T 6. For this system the above conjecture translates to the statement that the moduli space of classical vacua must be a collection of points. Explicit analysis of systems carrying a low number of D-branes supports this conjecture.
Nucleon form factors, generalized parton distributions and quark angular momentum
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kroll, Peter [Bergische Univ., Wuppertal (Germany). Fachbereich Physik; Regensburg Univ. (Germany). Institut fuer Theoretische Physik
2013-02-15
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale {mu}=2 GeV to be J{sup u}{sub v}=0.230{sup +0.009}{sub -0.024} and J{sup d}{sub v}=-0.004{sup +0.010}{sub -0.016}.
Narrow band amplification of light carrying orbital angular momentum
Borba, G C; Pruvost, L; Felinto, D; Tabosa, J W R
2016-01-01
We report on the amplification of an optical vortex beam carrying orbital angular momentum via induced narrow Raman gain in an ensemble of cold cesium atoms. A 20\\% single-pass Raman gain of a weak vortex signal field is observed with a spectral width of order of 1 MHz, much smaller than the natural width, demonstrating that the amplification process preserves the phase structure of the vortex beam. The gain is observed in the degenerated two-level system associated with the hyperfine transition $6S_{1/2}(F=3)\\leftrightarrow 6P_{3/2}(F^{\\prime}=2)$ of cesium. Our experimental observations are explained with a simple theoretical model based on a three-level $\\Lambda$ system interacting coherently with the weak Laguerre-Gauss field and a strong coupling field, including an incoherent pumping rate between the two degenerate ground-states.
Detection of orbital angular momentum using a photonic integrated circuit
Rui, Guanghao; Gu, Bing; Cui, Yiping; Zhan, Qiwen
2016-01-01
Orbital angular momentum (OAM) state of photons offer an attractive additional degree of freedom that has found a variety of applications. Measurement of OAM state, which is a critical task of these applications, demands photonic integrated devices for improved fidelity, miniaturization, and reconfiguration. Here we report the design of a silicon-integrated OAM receiver that is capable of detecting distinct and variable OAM states. Furthermore, the reconfiguration capability of the detector is achieved by applying voltage to the GeSe film to form gratings with alternate states. The resonant wavelength for arbitrary OAM state is demonstrated to be tunable in a quasi-linear manner through adjusting the duty cycle of the gratings. This work provides a viable approach for the realization of a compact integrated OAM detection device with enhanced functionality that may find important applications in optical communications and information processing with OAM states. PMID:27321916
Observation of Four-Photon Orbital Angular Momentum Entanglement.
Hiesmayr, B C; de Dood, M J A; Löffler, W
2016-02-19
We demonstrate genuine multipartite quantum entanglement of four photons in their orbital angular momentum degrees of freedom, where a high-dimensional discrete Hilbert space is attached to each photon. This can encode more quantum information compared to the qubit case, but it is a long-standing problem to entangle more than two such photons. In our experiment we use pulsed spontaneous parametric down-conversion to produce the photon quadruplets, which allows us to detect about one four-photon event per second. By means of quantum state reconstruction and a suitable witness operator we find that the photon quadruplets form a genuine multipartite entangled symmetric Dicke state. This opens a new tool for addressing foundational questions in quantum mechanics, and for exploration of novel high-dimensional multiparty quantum information applications such as secret sharing. PMID:26943533
Time division multiplexed orbital angular momentum access system
Shi, Jianyang; Fang, Yuan; Chi, Nan
2016-03-01
We propose and experimentally demonstrate time division multiplexed orbital angular momentum (OAM) access system to increase transmission capacity and spectral efficiency. In this system, data carried on different time tributaries share the same OAM mode. Multiple time division multiplexed OAM modes are multiplexed to realize two-dimensional (time dimension and OAM dimension) multiplexing. Therefore, the capacity and spectral efficiency of the access system will increase. The orthogonality between optical time division multiplexing (OTDM) and OAM techniques is also verified in our experiment. In a proof-of-concept experiment, 2×5-Gbps return-to-zero signal over OAM mode +4 is transmitted and investigated. The bit error ratio performance after transmission in this system can be smaller than 1×10-9. Results show that the proposed time division multiplexed OAM access system is suitable for future broadband access network.
Catenary optics for achromatic generation of perfect optical angular momentum
Pu, Mingbo; Li, Xiong; Ma, Xiaoliang; Wang, Yanqin; Zhao, Zeyu; Wang, Changtao; Hu, Chenggang; Gao, Ping; Huang, Cheng; Ren, Haoran; Li, Xiangping; Qin, Fei; Yang, Jing; Gu, Min; Hong, Minghui; Luo, Xiangang
2015-01-01
The catenary is the curve that a free-hanging chain assumes under its own weight, and thought to be a “true mathematical and mechanical form” in architecture by Robert Hooke in the 1670s, with nevertheless no significant phenomena observed in optics. We show that the optical catenary can serve as a unique building block of metasurfaces to produce continuous and linear phase shift covering [0, 2π], a mission that is extremely difficult if not impossible for state-of-the-art technology. Via catenary arrays, planar optical devices are designed and experimentally characterized to generate various kinds of beams carrying orbital angular momentum (OAM). These devices can operate in an ultra-broadband spectrum because the anisotropic modes associated with the spin-orbit interaction are almost independent of the incident light frequency. By combining the optical and topological characteristics, our approach would allow the complete control of photons within a single nanometric layer. PMID:26601283
Angular momentum and orientation effects in excitation-ionization collisions
Harris, A. L.; Esposito, T. P.
2016-08-01
We present theoretical fully differential cross sections (FDCS) for electron-impact excitation-ionization of helium in which the final state He+ ion is oriented in a particular direction. Specifically, we study the process for He+ ions in the 2p0 state. Using our 4-body distorted wave model, we show a strong dependence of the FDCS on the ion’s orientation and trace some unexpected structures in the FDCS to the L = 2 term in the partial wave expansion for the ionized electron. A comparison is drawn to the ionization of oriented Mg (3p0) atoms, and unlike that process, we find that for excitation-ionization angular momentum must be transferred from either the projectile or the target atom.
Energy Technology Data Exchange (ETDEWEB)
Hazak, G.; Zarmi, Y.; Zinamon, Z.
1981-06-01
The detailed structure of electron momentum distribution in relativistic diodes is studied. It is proven that in most of the diode region the momentum distribution is isotropic in fluid rest frame, with azimuthal temperature which, in general, is much larger than the cathode temperature. A diode model based on these conclusions is presented. The model allows for a continuum of electron trajectories at each point. In various limits the results are reduced to well-known cold fluid model results.
Is the angular momentum of a ferromagnetic sample after exposure to a fs laser pulse conserved?
International Nuclear Information System (INIS)
In the theories of fs demagnetization of a ferromagnetic sample after exposure to a fs laser pulse it is assumed that the angular momentum of the sample is conserved. It is shown that this is not strictly valid. However, it is argued that the effect of the deviations from strict angular momentum conservation is very small. - Highlights: • Theory of fs-demagnetization after laser pulse excitation. • Angular momentum transfer out of the electronic spin system. • Non-isolated system, non-central forces, angular momentum conservation
Spin-to-orbital angular momentum conversion for Bessel light beams in crystals
International Nuclear Information System (INIS)
We have studied the spatial dynamics of spin-to-orbital angular momentum conversion for zero-order and higherorder circularly polarized Bessel light beams, propagating along the optic axes of uniaxial and biaxial crystals. We have established that interaction of the Bessel beam with a uniaxial crystal slab makes possible practically complete conversion of the optical spin [angular] momentum to [orbital] angular [momentum]. In a biaxial crystal slab, during such a conversion the angular momentum is partially transferred to the medium, and as a result the slab undergoes rotation. (author)
On the natures of the spin and orbital parts of optical angular momentum
Barnett, Stephen M.; Allen, L.; Cameron, Robert P.; Gilson, Claire R.; Padgett, Miles J.; Speirits, Fiona C.; Yao, Alison M.
2016-06-01
The modern field of optical angular momentum began with the realisation by Allen et al in 1992 that, in addition to the spin associated with polarisation, light beams with helical phase fronts carry orbital angular momentum. There has been much confusion and debate, however, surrounding the intricacies of the field and, in particular, the separation of the angular momentum into its spin and orbital parts. Here we take the opportunity to state the current position as we understand it, which we present as six perspectives: (i) we start with a reprise of the 1992 paper in which it was pointed out that the Laguerre–Gaussian modes, familiar from laser physics, carry orbital angular momentum. (ii) The total angular momentum may be separated into spin and orbital parts, but neither alone is a true angular momentum. (iii) The spin and orbital parts, although not themselves true angular momenta, are distinct and physically meaningful, as has been demonstrated clearly in a range of experiments. (iv) The orbital part of the angular momentum in the direction of propagation of a beam is not simply the azimuthal component of the linear momentum. (v) The component of spin in the direction of propagation is not the helicity, although these are related quantities. (vi) Finally, the spin and orbital parts of the angular momentum correspond to distinct symmetries of the free electromagnetic field and hence are separately conserved quantities.
Wave mediated angular momentum transport in astrophysical boundary layers
Hertfelder, Marius
2015-01-01
Context. Disk accretion onto weakly magnetized stars leads to the formation of a boundary layer (BL) where the gas loses its excess kinetic energy and settles onto the star. There are still many open questions concerning the BL, for instance the transport of angular momentum (AM) or the vertical structure. Aims. It is the aim of this work to investigate the AM transport in the BL where the magneto-rotational instability (MRI) is not operating owing to the increasing angular velocity $\\Omega(r)$ with radius. We will therefore search for an appropriate mechanism and examine its efficiency and implications. Methods. We perform 2D numerical hydrodynamical simulations in a cylindrical coordinate system $(r, \\varphi)$ for a thin, vertically inte- grated accretion disk around a young star. We employ a realistic equation of state and include both cooling from the disk surfaces and radiation transport in radial and azimuthal direction. The viscosity in the disk is treated by the {\\alpha}-model; in the BL there is no v...
Generalized ray optics and orbital angular momentum carrying beams
Potoček, Václav; Barnett, Stephen M.
2015-10-01
In classical optics the Wolf function is the natural analogue of the quantum Wigner function and like the latter it may be negative in some regions. We discuss the implications this negativity has on the generalized ray interpretation of free-space paraxial wave evolution. Important examples include two classes of beams carrying optical orbital angular momentum—Laguerre-Gaussian (LG) and Bessel beams. We formulate their defining eigenfunction properties as phase-space symmetries of their Wolf functions, whose analytical form is shown, and discuss their interpretation in the ray picture. By moving to a more general picture of partly coherent fields, we find that new solutions displaying the same symmetries appear. In particular, we find that mixtures of Gaussian beams (thus fully describable using classical ray optics) can mimic the basic properties of LG beams without the need for negativity, and are not restricted to quantized values of angular momentum. The quantization of both the l and p parameters and negativity of the Wolf function are both inevitable and, indeed, arise naturally when a requirement on the purity of the solution is added. This work is supplemented by a set of computer animations, graphically illustrating the interpretative aspects of the described model.
Jian-Zu, Zhang; Wei, Cao; Ke-Lin, Gao
2012-01-01
An approach to solve the critical problem of testing quantum effects of spatial noncommutativity is proposed. Magnetic hyperfine structures in a Rydberg system induced by fractional angular momentum originated from spatial noncommutativity are discussed. The orders of the corresponding magnetic hyperfine splitting of spectrum $\\sim 10^{-7} - 10^{-8} eV$ lie within the limits of accuracy of current experimental measurements. Experimental tests of physics beyond the standard model are the focus of broad interest. We note that the present approach is reasonable achievable with current technology. The proof is based on very general arguments involving only the deformed Heisenberg-Weyl algebra and the fundamental property of angular momentum. Its experimental verification would constitute an advance in understanding of fundamental significance, and would be a key step towards a decisive test of spatial noncommutativity.
Energy, momentum and angular momentum conservations in de Sitter special relativity
Lu, Jia-An
2016-01-01
In de Sitter (dS) special relativity (SR), two kinds of conserved currents are derived. The first kind is a 5-dimensional dS-covariant angular momentum (AM) current, which unites the energy-momentum (EM) and 4d AM current in an inertial-type coordinate system. The second kind is a dS-invariant AM current, which can be generalized to a conserved current for the coupling system of the matter field and gravitational field in dS gravity. Moreover, an inherent EM tensor is predicted, which comes from the spin part of the dS-covariant current. All the above results are compared to the ordinary SR with Lorentz invariance.
Orbital angular momentum mode-demultiplexing scheme with partial angular receiving aperture.
Zheng, Shilie; Hui, Xiaonan; Zhu, Jiangbo; Chi, Hao; Jin, Xiaofeng; Yu, Siyuan; Zhang, Xianmin
2015-05-01
For long distance orbital angular momentum (OAM) based transmission, the conventional whole beam receiving scheme encounters the difficulty of large aperture due to the divergence of OAM beams. We propose a novel partial receiving scheme, using a restricted angular aperture to receive and demultiplex multi-OAM-mode beams. The scheme is theoretically analyzed to show that a regularly spaced OAM mode set remain orthogonal and therefore can be de-multiplexed. Experiments have been carried out to verify the feasibility. This partial receiving scheme can serve as an effective method with both space and cost savings for the OAM communications. It is applicable to both free space OAM optical communications and radio frequency (RF) OAM communications. PMID:25969311
Angular Momentum Evolution of Solar-type Stars and Implications for Gyrochronology
Terndrup, Donald M.; Somers, Garrett; Tayar, Jamie; Pinsonneault, Marc H.
2016-01-01
A detailed understanding of the assembly history and rate of chemical enrichment in the Milky Way requires accurate ages for vast numbers of stars. Standard age-dating techniques have significant degeneracies and other limitations, and in any case are mostly limited to the tiny minority of stars in bound clusters.Data from the Kepler and K2 surveys, along with ground-based studies, show that stellar rotation rates could potentially be exploited to determine ages of field stars since rotation declines with age; this method is called gyrochronology. Several groups have advocated a purely empirical gyrochronology, essentially fitting simple mathematical expressions to rotation/age data, but here we argue that the power of rotation studies lies in their use for calibrating (or rejecting) proposed physical mechanisms for internal angular momentum transport and angular momentum loss through magnetized winds.We will review the available data and discuss several important selection biases, and will present the results of a detailed Bayesian modeling exercise to show how well a gyrochronology might work in the most favorable cases. We will also discuss whether evidence for saturation of wind loss or of internal angular momentum transfer is properly justified in a statistical sense.
Defining the Observables for Quarks and Gluons Orbital Angular Momentum Distributions
International Nuclear Information System (INIS)
We present a critical discussion of the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term, generally associated with the Ji decomposition, and a canonical term from the Jaffe Manohar decomposition. Orbital angular momentum has been connected to a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and to a twist three Generalized Parton Distribution for the kinetic term. We argue that while the latter appears as an azimuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments. (author)