Shakur, Asif; Sinatra, Taylor
2013-01-01
The gyroscope in a smartphone was employed in a physics laboratory setting to verify the conservation of angular momentum and the nonconservation of rotational kinetic energy. As is well-known, smartphones are ubiquitous on college campuses. These devices have a panoply of built-in sensors. This creates a unique opportunity for a new paradigm in…
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.
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...
Schwinger, J.
1952-01-26
The commutation relations of an arbitrary angular momentum vector can be reduced to those of the harmonic oscillator. This provides a powerful method for constructing and developing the properties of angular momentum eigenvectors. In this paper many known theorems are derived in this way, and some new results obtained. Among the topics treated are the properties of the rotation matrices; the addition of two, three, and four angular momenta; and the theory of tensor operators.
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
Parker, G. W.
1978-01-01
Discusses, classically and quantum mechanically, the angular momentum induced in the bound motion of an electron by an external magnetic field. Calculates the current density and its magnetic moment, and then uses two methods to solve the first-order perturbation theory equation for the required eigenfunction. (Author/GA)
Quantum Heuristics of Angular Momentum
Levy-Leblond, Jean-Marc
1976-01-01
Discusses the quantization of angular momentum components, Heisenberg-type inequalities for their spectral dispersions, and the quantization of the angular momentum modulus, without using operators or commutation relations. (MLH)
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.
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
Intrinsic Angular Momentum of Light.
Santarelli, Vincent
1979-01-01
Derives a familiar torque-angular momentum theorem for the electromagnetic field, and includes the intrinsic torques exerted by the fields on the polarized medium. This inclusion leads to the expressions for the intrinsic angular momentum carried by the radiation traveling through a charge-free medium. (Author/MA)
Angular momentum evolution for galaxies
Pedrosa, Susana
2015-01-01
Using cosmological hydrodynamics simulations we study the angular momentum content of the simulated galaxies in relation with their morphological type. We found that not only the angular momentum of the disk component follow the expected theoretical relation, Mo, Mao & Whiye (1998), but also the spheroidal one, with a gap due to its lost of angular momentum, in agreement with Fall & Romanowsky (2013),. We also found that the galaxy size can plot in one general relation, despite the morphological type, as found by Kravtsov (2013).
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...
Angular momentum in human walking.
Herr, Hugh; Popovic, Marko
2008-02-01
Angular momentum is a conserved physical quantity for isolated systems where no external moments act about a body's center of mass (CM). However, in the case of legged locomotion, where the body interacts with the environment (ground reaction forces), there is no a priori reason for this relationship to hold. A key hypothesis in this paper is that angular momentum is highly regulated throughout the walking cycle about all three spatial directions [|Lt| approximately 0], and therefore horizontal ground reaction forces and the center of pressure trajectory can be explained predominantly through an analysis that assumes zero net moment about the body's CM. Using a 16-segment human model and gait data for 10 study participants, we found that calculated zero-moment forces closely match experimental values (Rx2=0.91; Ry2=0.90). Additionally, the centroidal moment pivot (point where a line parallel to the ground reaction force, passing through the CM, intersects the ground) never leaves the ground support base, highlighting how closely the body regulates angular momentum. Principal component analysis was used to examine segmental contributions to whole-body angular momentum. We found that whole-body angular momentum is small, despite substantial segmental momenta, indicating large segment-to-segment cancellations ( approximately 95% medio-lateral, approximately 70% anterior-posterior and approximately 80% vertical). Specifically, we show that adjacent leg-segment momenta are balanced in the medio-lateral direction (left foot momentum cancels right foot momentum, etc.). Further, pelvis and abdomen momenta are balanced by leg, chest and head momenta in the anterior-posterior direction, and leg momentum is balanced by upper-body momentum in the vertical direction. Finally, we discuss the determinants of gait in the context of these segment-to-segment cancellations of angular momentum.
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
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...
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
Whole-body angular momentum during stair ascent and descent.
Silverman, Anne K; Neptune, Richard R; Sinitski, Emily H; Wilken, Jason M
2014-04-01
The generation of whole-body angular momentum is essential in many locomotor tasks and must be regulated in order to maintain dynamic balance. However, angular momentum has not been investigated during stair walking, which is an activity that presents a biomechanical challenge for balance-impaired populations. We investigated three-dimensional whole-body angular momentum during stair ascent and descent and compared it to level walking. Three-dimensional body-segment kinematic and ground reaction force (GRF) data were collected from 30 healthy subjects. Angular momentum was calculated using a 13-segment whole-body model. GRFs, external moment arms and net joint moments were used to interpret the angular momentum results. The range of frontal plane angular momentum was greater for stair ascent relative to level walking. In the transverse and sagittal planes, the range of angular momentum was smaller in stair ascent and descent relative to level walking. Significant differences were also found in the ground reaction forces, external moment arms and net joint moments. The sagittal plane angular momentum results suggest that individuals alter angular momentum to effectively counteract potential trips during stair ascent, and reduce the range of angular momentum to avoid falling forward during stair descent. Further, significant differences in joint moments suggest potential neuromuscular mechanisms that account for the differences in angular momentum between walking conditions. These results provide a baseline for comparison to impaired populations that have difficulty maintaining dynamic balance, particularly during stair ascent and descent.
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.
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 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.
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.
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.
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...
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.
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...
Whole-body angular momentum in incline and decline walking.
Silverman, Anne K; Wilken, Jason M; Sinitski, Emily H; Neptune, Richard R
2012-04-01
Angular momentum is highly regulated over the gait cycle and is important for maintaining dynamic stability and control of movement. However, little is known regarding how angular momentum is regulated on irregular surfaces, such as slopes, when the risk of falling is higher. This study examined the three-dimensional whole-body angular momentum patterns of 30 healthy subjects walking over a range of incline and decline angles. The range of angular momentum was either similar or reduced on decline surfaces and increased on incline surfaces relative to level ground, with the greatest differences occurring in the frontal and sagittal planes. These results suggest that angular momentum is more tightly controlled during decline walking when the risk of falling is greater. In the frontal plane, the range of angular momentum was strongly correlated with the peak hip and knee abduction moments in early stance. In the transverse plane, the strongest correlation occurred with the knee external rotation peak in late stance. In the sagittal plane, all external moment peaks were correlated with the range of angular momentum. The peak ankle plantarflexion, knee flexion and hip extension moments were also strongly correlated with the sagittal-plane angular momentum. These results highlight how able-bodied subjects control angular momentum differently on sloped surfaces relative to level walking and provide a baseline for comparison with pathological populations that are more susceptible to falling. PMID:22325978
Whole-body angular momentum in incline and decline walking.
Silverman, Anne K; Wilken, Jason M; Sinitski, Emily H; Neptune, Richard R
2012-04-01
Angular momentum is highly regulated over the gait cycle and is important for maintaining dynamic stability and control of movement. However, little is known regarding how angular momentum is regulated on irregular surfaces, such as slopes, when the risk of falling is higher. This study examined the three-dimensional whole-body angular momentum patterns of 30 healthy subjects walking over a range of incline and decline angles. The range of angular momentum was either similar or reduced on decline surfaces and increased on incline surfaces relative to level ground, with the greatest differences occurring in the frontal and sagittal planes. These results suggest that angular momentum is more tightly controlled during decline walking when the risk of falling is greater. In the frontal plane, the range of angular momentum was strongly correlated with the peak hip and knee abduction moments in early stance. In the transverse plane, the strongest correlation occurred with the knee external rotation peak in late stance. In the sagittal plane, all external moment peaks were correlated with the range of angular momentum. The peak ankle plantarflexion, knee flexion and hip extension moments were also strongly correlated with the sagittal-plane angular momentum. These results highlight how able-bodied subjects control angular momentum differently on sloped surfaces relative to level walking and provide a baseline for comparison with pathological populations that are more susceptible to falling.
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.
Magnetic Modulation of Stellar Angular Momentum Loss
Garraffo, Cecilia; Cohen, Ofer
2014-01-01
Angular Momentum Loss is important for understanding astrophysical phenomena such as stellar rotation, magnetic activity, close binaries, and cataclysmic variables. Magnetic breaking is the dominant mechanism in the spin down of young late-type stars. We have studied angular momentum loss as a function of stellar magnetic activity. We argue that the complexity of the field and its latitudinal distribution are crucial for angular momentum loss rates. In this work we discuss how angular momentum is modulated by magnetic cycles, and how stellar spin down is not just a simple function of large scale magnetic field strength.
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.
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
Angular Momentum Distribution in the Transverse Plane
Adhikari, Lekha
2016-01-01
Several possibilities to relate the $t$-dependence of Generalized Parton Distributions (GPDs) to the distribution of angular momentum in the transverse plane are discussed. Using a simple spectator model we demonstrate that non of them correctly describes the orbital angular momentum distribution that for a longitudinally polarized nucleon obtained directly from light-front wavefunctions.
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.
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.
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
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.
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...
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...
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.
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.
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...
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...
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.
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.
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...
Angular Momentum Eigenstates for Equivalent Electrons.
Tuttle, E. R.; Calvert, J. B.
1981-01-01
Simple and efficient methods for adding angular momenta and for finding angular momentum eigenstates for systems of equivalent electrons are developed. Several different common representations are used in specific examples. The material is suitable for a graduate course in quantum mechanics. (SK)
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...
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...
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.
Olympic Wrestling and Angular Momentum.
Carle, Mark
1988-01-01
Reported is the use of a wrestling photograph in a noncalculus introductory physics course. The photograph presents a maneuver that could serve as an example for a discussion on equilibrium, forces, torque, and angular motion. Provided are some qualitative thoughts as well as quantitative calculations. (YP)
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.
Parton transverse momentum and orbital angular momentum distributions
Rajan, Abha; Courtoy, Aurore; Engelhardt, Michael; Liuti, Simonetta
2016-08-01
The quark orbital angular momentum component of proton spin, Lq, 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 Lq 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.
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.
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...
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...
Surface angular momentum of light beams.
Ornigotti, Marco; Aiello, Andrea
2014-03-24
Traditionally, the angular momentum of light is calculated for "bullet-like" electromagnetic wave packets, although in actual optical experiments "pencil-like" beams of light are more commonly used. The fact that a wave packet is bounded transversely and longitudinally while a beam has, in principle, an infinite extent along the direction of propagation, renders incomplete the textbook calculation of the spin/orbital separation of the angular momentum of a light beam. In this work we demonstrate that a novel, extra surface part must be added in order to preserve the gauge invariance of the optical angular momentum per unit length. The impact of this extra term is quantified by means of two examples: a Laguerre-Gaussian and a Bessel beam, both circularly polarized.
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.
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.
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.
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.
Ultrafast angular momentum transfer in multisublattice ferrimagnets.
Bergeard, N; López-Flores, V; Halté, V; Hehn, M; Stamm, C; Pontius, N; Beaurepaire, E; Boeglin, C
2014-03-11
Femtosecond laser pulses can be used to induce ultrafast changes of the magnetization in magnetic materials. However, one of the unsolved questions is that of conservation of the total angular momentum during the ultrafast demagnetization. Here we report the ultrafast transfer of angular momentum during the first hundred femtoseconds in ferrimagnetic Co0.8Gd0.2 and Co0.74Tb0.26 films. Using time-resolved X-ray magnetic circular dichroism allowed for time-resolved determination of spin and orbital momenta for each element. We report an ultrafast quenching of the magnetocrystalline anisotropy and show that at early times the demagnetization in ferrimagnetic alloys is driven by the local transfer of angular momenta between the two exchange-coupled sublattices while the total angular momentum stays constant. In Co0.74Tb0.26 we have observed a transfer of the total angular momentum to an external bath, which is delayed by ~150 fs.
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)
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
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
Angular Momentum Transport in Accretion Disks
DEFF Research Database (Denmark)
E. Pessah, Martin; Chan, Chi-kwan; Psaltis, Dimitrios;
2007-01-01
if the resolution were set equal to the natural dissipation scale in astrophysical disks. We conclude that, in order for MRI-driven turbulent angular momentum transport to be able to account for the large value of the effective alpha viscosity inferred observationally, the disk must be threaded by a significant...
On the quantisation of the angular momentum
Ho, V B
1994-01-01
When a hydrogen-like atom is treated as a two dimensional system whose configuration space is multiply connected, then in order to obtain the same energy spectrum as in the Bohr model the angular momentum must be half-integral.
Angular and linear momentum of excited ferromagnets
Yan, P.; Kamra, A.; Cao, Y.; Bauer, G.E.W.
2013-01-01
The angular momentum vector of a Heisenberg ferromagnet with isotropic exchange interaction is conserved, while under uniaxial crystalline anisotropy the projection of the total spin along the easy axis is a constant of motion. Using Noether's theorem, we prove that these conservation laws persist i
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.
Optical angular momentum conversion in a nanoslit
Chimento, P.F.; Alkemade, P.F.A.; T Hooft, G.W.; Eliel, E.R.
2012-01-01
We demonstrate partial conversion of circularly polarized light into orbital angular momentum-carrying vortex light with opposite-handed circular polarization. This conversion is accomplished in a novel manner using the birefringent properties of a circular subwavelength slit in a thin metal film. O
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.
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.
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 ...
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.
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 Sharing in Dissipative Collisions
Casini, G.; Poggi, G.; Bini, M.; Calamai, S.; Maurenzig, P. R.; Olmi, A.; Pasquali, G.; Stefanini, A. A.; Taccetti, N.; Steckmeyer, J. C.; Laforest, R.; Saint-Laurent, F.
1999-09-01
Light charged particles emitted by the projectilelike fragment were measured in the direct and reverse collision of 93Nb and 116Sn at 25A MeV. The experimental multiplicities of hydrogen and helium particles as a function of the primary mass of the emitting fragment show evidence for a correlation with net mass transfer. The ratio of hydrogen and helium multiplicities points to a dependence of the angular momentum sharing on the net mass transfer.
Angular momentum sharing in dissipative collisions
Casini, G; Bini, M; Calamai, S; Maurenzig, P R; Olmi, A; Pasquali, G; Stefanini, A A; Taccetti, N; Steckmeyer, J C; Laforest, R; Saint-Laurent, F
1999-01-01
Light charged particles emitted by the projectile-like fragment were measured in the direct and reverse collision of $^{93}$Nb and $^{116}$Sn at 25 AMeV. The experimental multiplicities of Hydrogen and Helium particles as a function of the primary mass of the emitting fragment show evidence for a correlation with net mass transfer. The ratio of Hydrogen and Helium multiplicities points to a dependence of the angular momentum sharing on the net mass transfer.
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...
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...
Localization of angular momentum in optical waves propagating through turbulence.
Sanchez, Darryl J; Oesch, Denis W
2011-12-01
This is the first in a series of papers demonstrating that photons with orbital angular momentum can be created in optical waves propagating through distributed turbulence. The scope of this first paper is much narrower. Here, we demonstrate that atmospheric turbulence can impart non-trivial angular momentum to beams and that this non-trivial angular momentum is highly localized. Furthermore, creation of this angular momentum is a normal part of propagation through atmospheric turbulence.
Angular momentum of a brane-world model
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
In this paper we discuss the properties of the general covariant angular momentum of a fivedimensional brane-world model. Through calculating the total angular momentum of this model, we are able to analyze the properties of the total angular momentum in the inflationary RS model. We show that the space-like components of the total angular momentum of the inflationary RS model are all zero while the others are non-zero, which agrees with the results from ordinary RS model.
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...
Angular Momentum of a Brane-world Model
Jia, Bei; Zhang, Peng-Ming
2008-01-01
In this paper we discuss the properties of the general covariant angular momentum of a five-dimensional brane-world model. Through calculating the total angular momentum of this model, we are able to analyze the properties of the total angular momentum in the inflationary RS model. We show that the space-like components of the total angular momentum of are all zero while the others are non-zero, which agrees with the results from ordinary RS model.
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.
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.
ANGULAR MOMENTUM AND GALAXY FORMATION REVISITED
Energy Technology Data Exchange (ETDEWEB)
Romanowsky, Aaron J. [University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Fall, S. Michael [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2012-12-15
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{sub *} and mass M{sub *} (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{sub *} reliably. Our results contravene suggestions that ellipticals could harbor large reservoirs of hidden j{sub *} 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 {approx}100 nearby bright galaxies of all types, placing them on a diagram of j{sub *} versus M{sub *}. The ellipticals and spirals form two parallel j{sub *}-M{sub *} tracks, with log-slopes of {approx}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 {approx}3-4 if mass-to-light ratio variations are neglected for simplicity, and {approx}7 if they are included. We decompose the spirals into disks and bulges and find that these subcomponents follow j{sub *}-M{sub *} 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
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.
Linear Upconversion of Orbit Angular Momentum
Ding, Dong-Sheng; Shi, Bao-Sen; Zou, Xu-Bo; Guo, Guang-Can
2012-01-01
We experimentally demonstrate that an infrared light imprinted the orbit angular momentum is linearly converted into a visible light using Four-wave mixing (FWM) via a Ladder-type configuration in Rb85 atoms. Simultaneously, we theoretically simulate this linear conversion process, and theoretical analysis is in reasonable agreement with the experimental result. A large single-photon detuning is used to reduce the absorption of the atoms to the up-converted light and to avoid the pattern formation in FWM process. The multi-mode image linear conversion is important for applications in image communications, astrophysics and quantum information so on.
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.
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 Transfer in Catastrophic Asteroid Impacts
Love, S. G.; Ahrens, T. J.
1996-09-01
Incomplete knowledge of angular momentum transfer in asteroid impacts has hampered efforts to deduce asteroid collisional histories from their rotation rates. This problem traditionally has been investigated using impact experiments on cm-scale, strength-dominated targets. Recent evidence, however, indicates that impacts on asteroids of km size and larger may be controlled by gravity rather than strength, and that the analogy to laboratory impacts may not hold. Accordingly, we have modelled catastrophic impacts on gravitating asteroids to better understand angular momentum transfer in such events. We employ a 3--D, strengthless, gravitating SPH computer code. Target bodies are 10 to 1000 km in diameter and do not initially rotate. Impact speeds are 3--7 km/s; impact angles are 15--75(deg) . Each target is composed of 1791 mass elements: spatial resolution is coarse but acceptable for large scale energy transfer. We simulate the hydrodynamic phase of each impact, after which particle motions are ballistic and treated analytically. Escaping particles have kinetic energy greater than the gravitational energy binding them to the rest of the system; the others reaccrete to form a ``rubble pile'' which is assumed spherical. The rubble pile's size, mass, and angular momentum define its rotation rate. Spin rates for ejected fragments cannot be determined. The target's final spin period depends on the impact angle and the fraction of target mass ejected, but not on impact speed or target size in the ranges tested. The lack of size dependence cannot explain the observed excess of slowly rotating asteroids of ~ 100 km diameter. The fraction of projectile angular momentum retained by the target varies dramatically with impact speed and angle and with target size and fraction of mass removed, complicating its use in models where collision geometry varies. The final spin period of an asteroid losing 50% of its mass is 6--10 hours, comparable to the asteroidal mean of 8 hours
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 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...
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.
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
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.
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.
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
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.
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...
Orbital angular momentum photonic quantum interface
Institute of Scientific and Technical Information of China (English)
Zhi-Yuan Zhou; Yan Li; Dong-Sheng Ding; Wei Zhang; Shuai Shi; Bao-Sen Shi; Guang-Can Guo
2016-01-01
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 OAM-carried light has not been realized yet.Here,we report the first experimental realization of a quantum interface for a heralded single photon carrying OAM using a nonlinear crystal in an optical cavity.The spatial structures of input and output photons exhibit strong similarity.More importantly,single-photon coherence is preserved during up-conversion as demonstrated.
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.
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
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.
Ideal linear-chain polymers with fixed angular momentum.
Brunner, Matthew; Deutsch, J M
2011-07-01
The statistical mechanics of a linear noninteracting polymer chain with a large number of monomers is considered with fixed angular momentum. The radius of gyration for a linear polymer is derived exactly by functional integration. This result is then compared to simulations done with a large number of noninteracting rigid links at fixed angular momentum. The simulation agrees with the theory up to finite-size corrections. The simulations are also used to investigate the anisotropic nature of a spinning polymer. We find universal scaling of the polymer size along the direction of the angular momentum, as a function of rescaled angular momentum.
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.
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}
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.
Creating high-harmonic beams with controlled orbital angular momentum.
Gariepy, Genevieve; Leach, Jonathan; Kim, Kyung Taec; Hammond, T J; Frumker, E; Boyd, Robert W; Corkum, P B
2014-10-10
A beam with an angular-dependant phase Φ = ℓϕ about the beam axis carries an orbital angular momentum of ℓℏ per photon. Such beams are exploited to provide superresolution in microscopy. Creating extreme ultraviolet or soft-x-ray beams with controllable orbital angular momentum is a critical step towards extending superresolution to much higher spatial resolution. We show that orbital angular momentum is conserved during high-harmonic generation. Experimentally, we use a fundamental beam with |ℓ| = 1 and interferometrically determine that the harmonics each have orbital angular momentum equal to their harmonic number. Theoretically, we show how any small value of orbital angular momentum can be coupled to any harmonic in a controlled manner. Our results open a route to microscopy on the molecular, or even submolecular, scale.
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...
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
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,
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.
Evolution equations for higher moments of angular momentum distributions
Hägler, P
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.
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.
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; 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...
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.
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
2016-09-01
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 photon's 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 to 525 nm for OAM qubits, OAM-polarization 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 between different quantum systems operating in a photon's OAM degrees of freedom, which will be of great importance in building a high-capacity OAM quantum network.
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
Orbital angular momentum divider of light
Dong, Hailong Zhou Jianji; Cai, Xinlun; Yu, SiYuan; Zhang, Xinliang
2016-01-01
Manipulation of orbital angular momentum (OAM) of light is essential in OAM-based optical systems. Especially, OAM divider, which can convert the incoming OAM mode into one or several new smaller modes in proportion at different spatial paths, is very useful in OAM-based optical networks. However, this useful tool was never reported yet. For the first time, we put forward a passive OAM divider based on coordinate transformation. The device consists of a Cartesian to log-polar coordinate converter and an inverse converter. The first converter converts the OAM light into a rectangular-shaped plane light with a transverse phase gradient. And the second converter converts the plane light into multiple diffracted light. The OAM of zeroth-order diffracted light is the product of the input OAM and the scaling parameter. The residual light is output from other diffracted orders. Furthermore, we extend the scheme to realize equal N-dividing of OAM and arbitrary dividing of OAM. The ability of dividing OAM shows huge p...
Angular momentum and galaxy formation revisited
Romanowsky, Aaron J
2012-01-01
Motivated by new kinematic data in the outer parts of early-type galaxies (ETGs), we re-examine angular momentum (AM) in all galaxy types. We present methods for estimating the specific AM j, focusing on ETGs, to derive relations between stellar j_* and mass M_* (after Fall 1983). We perform analyses of 8 galaxies out to ~10 R_e, finding that data at 2 R_e are sufficient to estimate total j_*. Our results contravene suggestions that ellipticals (Es) harbor large reservoirs of hidden j_* from AM transport in major mergers. We carry out a j_*-M_* analysis of literature data for ~100 nearby bright galaxies of all types. The Es and spirals form parallel j_*-M_* tracks, which for spirals is like the Tully-Fisher relation, but for Es derives from a mass-size-rotation conspiracy. The Es contain ~3-4 times less AM than equal-mass spirals. We decompose the spirals into disks+bulges and find similar j_*-M_* trends to spirals and Es overall. The S0s are intermediate, and we propose that morphological types reflect disk/...
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
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 ...
Nuclear Level Density with Non-zero Angular Momentum
Institute of Scientific and Technical Information of China (English)
A.N. Behkami; M. Gholami; M. Kildir; M. Soltani
2006-01-01
The statistical properties of interacting fermions have been studied for various angular momentum with the inclusion of pairing interaction. The dependence of the critical temperature on angular momentum for several nuclei,have been studied. The yrast energy as a function of angular momentum for 28 Si and 24Mg nuclei have been calculated up to 60.0 MeV of excitation energy. The computed limiting angular momenta are compared with the experimental results for 26Al produced by 12C + 14N reaction. The relevant nuclear level densities for non-zero angular momentum have been computed for 44Ti and l36Ba nuclei. The results are compared with their corresponding values obtained from the approximateformulas.
Orbital angular momentum in optical waves propagating through distributed turbulence.
Sanchez, Darryl J; Oesch, Denis W
2011-11-21
This is the second of two papers demonstrating that photons with orbital angular momentum can be created in optical waves propagating through distributed turbulence. In the companion paper, it is shown that propagation through atmospheric turbulence can create non-trivial angular momentum. Here, we extend the result and demonstrate that this momentum is, at least in part, orbital angular momentum. Specifically, we demonstrate that branch points (in the language of the adaptive optic community) indicate the presence of photons with non-zero OAM. Furthermore, the conditions required to create photons with non-zero orbital angular momentum are ubiquitous. The repercussions of this statement are wide ranging and these are cursorily enumerated.
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.
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
2016-02-25
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.
Detection of a spinning object using light's orbital angular momentum.
Lavery, Martin P J; Speirits, Fiona C; Barnett, Stephen M; Padgett, Miles J
2013-08-01
The linear Doppler shift is widely used to infer the velocity of approaching objects, but this shift does not detect rotation. By analyzing the orbital angular momentum of the light scattered from a spinning object, we observed a frequency shift proportional to product of the rotation frequency of the object and the orbital angular momentum of the light. This rotational frequency shift was still present when the angular momentum vector was parallel to the observation direction. The multiplicative enhancement of the frequency shift may have applications for the remote detection of rotating bodies in both terrestrial and astronomical settings.
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
2016-04-07
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.
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 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. PMID:27052796
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.
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...
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.
Uncertainty Relation between Angular Momentum and Angle Variable.
Roy, C. L.; Sannigrahi, A. B.
1979-01-01
Discusses certain pitfalls regarding the uncertainty relation between angular momentum and the angle variable from a pedagogic point of view. Further, an uncertainty relation has been derived for these variables in a simple and consistant manner. (Author/HM)
Effect of angular momentum conservation on hydrodynamic simulations of colloids.
Yang, Mingcheng; Theers, Mario; Hu, Jinglei; Gompper, Gerhard; Winkler, Roland G; Ripoll, Marisol
2015-07-01
In contrast to most real fluids, angular momentum is not a locally conserved quantity in some mesoscopic simulation methods. Here we quantify the importance of this conservation in the flow fields associated with different colloidal systems. The flow field is analytically calculated with and without angular momentum conservation for the multiparticle collision dynamics (MPC) method, and simulations are performed to verify the predictions. The flow field generated around a colloidal particle moving under an external force with slip boundary conditions depends on the conservation of angular momentum, and the amplitude of the friction force is substantially affected. Interestingly, no dependence on the angular momentum conservation is found for the flow fields generated around colloids under the influence of phoretic forces. Moreover, circular Couette flow between a no-slip and a slip cylinder is investigated, which allows us to validate one of the two existing expressions for the MPC stress tensor.
General covariant conservative angular momentum as internal charges
Institute of Scientific and Technical Information of China (English)
赵德品
1996-01-01
The usual approach to internal conservative charges is used to obtain the conservation laws of angular-momentum in both Einstein gravity and gravitational anyons.The results are in complete agreement with those of references.
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
"Angle" Operator Conjugate to Photon's Intrinsic Angular Momentum
Institute of Scientific and Technical Information of China (English)
范洪义
2001-01-01
We find the correct "angle" operator conjugate to the intrinsic angular momentum of the photon by introducing a suitable representation which involves both left-handed and right-handed polarization photon operators.
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...
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....
Angular momentum and torque described with the complex octonion
Zi-Hua Weng
2014-01-01
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 m...
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
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.
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...
Relativistic electron ring equilibrium with angular momentum spread
Energy Technology Data Exchange (ETDEWEB)
Croitoru, M.; Grecu, D. (Institutul de Fizica si Inginerie Nucleara, Bucharest (Romania))
1980-01-01
The equilibrium properties of a relativistic electron ring are determined by solving in a consistent way the Vlasov-Maxwell equations for a distribution function with an angular momentum spread. In the thin ring approximation there have been deduced general formulae for the electron density and the current density. A general theorem concerning the sharp form in space of the electron density is also obtained for the case of a microcanonical distribution function both in energy and angular momentum.
Modelling black holes with angular momentum in loop quantum gravity
Frodden, Ernesto; Perez, Alejandro; Pranzetti, Daniele; Röken, Christian
2014-12-01
We construct a connection formulation of Kerr isolated horizons. As in the non-rotating case, the model is based on a Chern-Simons theory describing the degrees of freedom on the horizon. The presence of a non-vanishing angular momentum modifies the admissibility conditions for spin network states. Physical states of the system are in correspondence with open intertwiners with total spin matching the angular momentum of the spacetime.
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.
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.
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...
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...
Domínguez-Tenreiro, R; Saiz, A
1998-01-01
We report results on the formation of disk-like structures in two cosmological hydrodynamical simulations in a hierarchical clustering scenario, sharing the same initial conditions. In the first one, a simple and generic implementation of star formation has allowed galaxy-like objects with stellar bulges and extended, populated disks to form. Gas in the disk comes from both, particles that survive mergers keeping in part their angular momentum content, and new gas supply by infall, once the merger process is over, with global specific angular momentum conservation. The stellar bulge forms from gas that has lost most of its angular momentum. In the second simulation, no star formation has been included. In this case, objects consist of an overpopulated central gas concentration, and an extended, underpopulated disk. The central concentration forms from particles that suffer an important angular momentum loss in violent events, and it often contains more than 70% of the object's baryonic mass. The external disk...
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
Relevance of angular momentum conservation in mesoscale hydrodynamics simulations.
Götze, Ingo O; Noguchi, Hiroshi; Gompper, Gerhard
2007-10-01
The angular momentum is conserved in fluids with a few exceptions such as ferrofluids. However, it can be violated locally in fluid simulations to reduce computational costs. The effects of this violation are investigated using a particle-based simulation method, multiparticle collision dynamics, which can switch on or off angular-momentum conservation. To this end, we study circular Couette flows between concentric and eccentric cylinders, where nonphysical torques due to the lack of the angular-momentum conservation are found whereas the velocity field is not affected. In addition, in simulations of fluids with different viscosities in contact and star polymers in solvent, incorrect angular velocities occur. These results quantitatively agree with the theoretical predictions based on the macroscopic stress tensor.
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.
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...
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
2009-10-12
The orbital angular momentum of photons, being defined in an infinite-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 orbital angular momentum of single photons and vice versa. All our schemes exploit a newly developed optical device, the so-called "q-plate", which enables the manipulation of the photon orbital angular momentum driven by the polarization degree of freedom. By stacking several q-plates in a suitable sequence, one can also have access to higher-order angular momentum subspaces. In particular, we demonstrate the control of the orbital angular momentum m degree of freedom within the subspaces of |m| = 2h and |m| = 4h per photon.
Is the angular momentum of an electron conserved in a uniform magnetic field?
Greenshields, Colin R; Stamps, Robert L; Franke-Arnold, Sonja; Barnett, Stephen M
2014-12-12
We show that an electron moving in a uniform magnetic field possesses a time-varying "diamagnetic" angular momentum. Surprisingly this means that the kinetic angular momentum of the electron may vary with time, despite the rotational symmetry of the system. This apparent violation of angular momentum conservation is resolved by including the angular momentum of the surrounding fields.
Transfer of optical orbital angular momentum to a bound electron
Schmiegelow, Christian T.; Schulz, Jonas; Kaufmann, Henning; Ruster, Thomas; Poschinger, Ulrich G.; Schmidt-Kaler, Ferdinand
2016-10-01
Photons can carry angular momentum, not only due to their spin, but also due to their spatial structure. This extra twist has been used, for example, to drive circular motion of microscopic particles in optical tweezers as well as to create vortices in quantum gases. Here we excite an atomic transition with a vortex laser beam and demonstrate the transfer of optical orbital angular momentum to the valence electron of a single trapped ion. We observe strongly modified selection rules showing that an atom can absorb two quanta of angular momentum from a single photon: one from the spin and another from the spatial structure of the beam. Furthermore, we show that parasitic ac-Stark shifts from off-resonant transitions are suppressed in the dark centre of vortex beams. These results show how light's spatial structure can determine the characteristics of light-matter interaction and pave the way for its application and observation in other systems.
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.
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.
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.
Fractional angular momentum in cold-atom systems.
Zhang, Yuhe; Sreejith, G J; Gemelke, N D; Jain, J K
2014-10-17
The quantum statistics of bosons or fermions are manifest through the even or odd relative angular momentum of a pair. We show theoretically that, under certain conditions, a pair of certain test particles immersed in a fractional quantum Hall state possesses, effectively, a fractional relative angular momentum, which can be interpreted in terms of fractional braid statistics. We propose that the fractionalization of the angular momentum can be detected directly through the measurement of the pair correlation function in rotating ultracold atomic systems in the fractional quantum Hall regime. Such a measurement will also provide direct evidence for the effective magnetic field resulting from Berry phases arising from attached vortices, and of excitations with a fractional particle number, analogous to the fractional charge of the electron fractional quantum Hall effect.
On-chip noninterference angular momentum multiplexing of broadband light.
Ren, Haoran; Li, Xiangping; Zhang, Qiming; Gu, Min
2016-05-13
Angular momentum division has emerged as a physically orthogonal multiplexing method in high-capacity optical information technologies. However, the typical bulky elements used for information retrieval from the overall diffracted field, based on the interference method, impose a fundamental limit toward realizing on-chip multiplexing. We demonstrate noninterference angular momentum multiplexing by using a mode-sorting nanoring aperture with a chip-scale footprint as small as 4.2 micrometers by 4.2 micrometers, where nanoring slits exhibit a distinctive outcoupling efficiency on tightly confined plasmonic modes. The nonresonant mode-sorting sensitivity and scalability of our approach enable on-chip parallel multiplexing over a bandwidth of 150 nanometers in the visible wavelength range. The results offer the possibility of ultrahigh-capacity and miniaturized nanophotonic devices harnessing angular momentum division.
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.
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.
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.
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.
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.
Unveiling pseudospin and angular momentum in photonic graphene.
Song, Daohong; Paltoglou, Vassilis; Liu, Sheng; Zhu, Yi; Gallardo, Daniel; Tang, Liqin; Xu, Jingjun; Ablowitz, Mark; Efremidis, Nikolaos K; Chen, Zhigang
2015-02-17
Pseudospin, an additional degree of freedom inherent in graphene, plays a key role in understanding many fundamental phenomena such as the anomalous quantum Hall effect, electron chirality and Klein paradox. Unlike the electron spin, the pseudospin was traditionally considered as an unmeasurable quantity, immune to Stern-Gerlach-type experiments. Recently, however, it has been suggested that graphene pseudospin is a real angular momentum that might manifest itself as an observable quantity, but so far direct tests of such a momentum remained unfruitful. Here, by selective excitation of two sublattices of an artificial photonic graphene, we demonstrate pseudospin-mediated vortex generation and topological charge flipping in otherwise uniform optical beams with Bloch momentum traversing through the Dirac points. Corroborated by numerical solutions of the linear massless Dirac-Weyl equation, we show that pseudospin can turn into orbital angular momentum completely, thus upholding the belief that pseudospin is not merely for theoretical elegance but rather physically measurable.
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 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...
Molecular chirality and the orbital angular momentum of light
Andrews, D L; Babiker, M; 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 what new features, if any, can be expected when such beams are used to interrogate a chiral system.
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.
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.
Efficient Sorting of Free Electron Orbital Angular Momentum
McMorran, Benjamin J; Lavery, Martin P J
2016-01-01
We propose a method for sorting electrons by orbital angular momentum (OAM). Several methods now exist to prepare electron wavefunctions in OAM states, but no technique has been developed for efficient, parallel measurement of pure and mixed electron OAM states. The proposed technique draws inspiration from the recent demonstration of the sorting of OAM through modal transformation. We show that the same transformation can be performed with electrostatic electron optical elements. Specifically, we show that a charged needle and an array of electrodes perform the transformation and phase correction necessary to sort orbital angular momentum states. This device may enable the analysis of the spatial mode distribution of inelastically scattered electrons.
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...
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.
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
Evolution of Angular Momentum Distribution during Star Formation
Tomisaka, K
1999-01-01
If the angular momentum of the molecular cloud core were conserved during the star formation process, a new-born star would rotate much faster than its fission speed. This constitutes the angular momentum problem of new-born stars. In this paper, the angular momentum transfer in the contraction of a rotating magnetized cloud is studied with axisymmetric MHD simulations. Owing to the large dynamic range covered by the nested-grid method, the structure of the cloud in the range from 10 AU to 0.1 pc is explored. First, the cloud experiences a run-away collapse, and a disk forms perpendicularly to the magnetic field, in which the central density increases greatly in a finite time-scale. In this phase, the specific angular momentum j of the disk decreases to $\\simeq 1/3$ of the initial cloud. After the central density of the disk exceeds $\\sim 10^{10}{\\rm cm}^{-3}$, the infall on to the central object develops. In this accretion stage, the rotation motion and thus the toroidal magnetic field drive the outflow. The...
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…
Optical angular momentum conversion in a nanoslit: reply
Chimento, P.F.; Alkemade, P.F.A.; T Hooft, G.W.; Eliel, E.R.
2013-01-01
We respond to a Comment on our Letter [Opt. Lett. 37, 4946 (2012)], in which we reported on the spin-to-orbital optical angular momentum conversion of a circular nanoslit in a thin metal layer. We claimed, in an unfortunately worded sentence, that the conversion efficiency was independent of the sli
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.
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…
The operator method for angular momentum and SU3
Eekelen, H.A.M. van; Ruijgrok, Th.W.
1966-01-01
It is well known how Schwinger's1) operator method can be used to construct all representations of the angular momentum operators. We give a brief account of this method and show that it is very convenient for a short derivation of the general Clebsch-Gordan coefficients. The method is then applied
Remarks on the Total Angular Momentum in General Relativity
Institute of Scientific and Technical Information of China (English)
ZHANG Xiao
2003-01-01
We verify that the total angular momentum 3-vector defined by the author [X. Zhang, Commun. Math.Phys. 206 (1999) 137] is equal to (0, 0, ma) forany time slice in both the Kerr and the Kerr-Newman spacetimes.
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...
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.
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.
The Gravitomagnetic measurement of the angular momentum of celestial bodies
Tartaglia, Angelo; Ruggiero, Matteo Luca
2004-01-01
The asymmetry in the time delay for light rays propagating on opposite sides of a spinning body is analyzed. A frequency shift in the perceived signals is found. A practical procedure is proposed for evidencing the asymmetry, allowing for a measurement of the specific angular momentum of the rotating mass. Orders of magnitude are discussed.
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.)
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)
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)
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.
Simplified Generation of High-Angular-Momentum Light Beams
Savchenkov, Anatoliy; Maleki, Lute; Matsko, Andrey; Strekalov, Dmitry; Grudinin, Ivan
2007-01-01
A simplified method of generating a beam of light having a relatively high value of angular momentum (see figure) involves the use of a compact apparatus consisting mainly of a laser, a whispering- gallery-mode (WGM) resonator, and optical fibers. The method also can be used to generate a Bessel beam. ( Bessel beam denotes a member of a class of non-diffracting beams, so named because their amplitudes are proportional to Bessel functions of the radii from their central axes. High-order Bessel beams can have high values of angular momentum.) High-angular-momentum light beams are used in some applications in biology and nanotechnology, wherein they are known for their ability to apply torque to make microscopic objects rotate. High-angular-momentum light beams could also be used to increase bandwidths of fiber-optic communication systems. The present simplified method of generating a high-angular-momentum light beam was conceived as an alternative to prior such methods, which are complicated and require optical setups that include, variously, holograms, modulating Fabry-Perot cavities, or special microstructures. The present simplified method exploits a combination of the complex structure of the electromagnetic field inside a WGM resonator, total internal reflection in the WGM resonator, and the electromagnetic modes supported by an optical fiber. The optical fiber used to extract light from the WGM resonator is made of fused quartz. The output end of this fiber is polished flat and perpendicular to the fiber axis. The input end of this fiber is cut on a slant and placed very close to the WGM resonator at an appropriate position and orientation. To excite the resonant whispering- gallery modes, light is introduced into the WGM resonator via another optical fiber that is part of a pigtailed fiber-optic coupler. Light extracted from the WGM resonator is transformed into a high-angular- momentum beam inside the extraction optical fiber and this beam is emitted from the
Yu, Haohai; Zhang, Huaijin; Wang, Yicheng; Han, Shuo; Yang, Haifang; Xu, Xiangang; Wang, Zhengping; Petrov, V; Wang, Jiyang
2013-11-12
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.
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
The gait of children with and without cerebral palsy: work, energy, and angular momentum.
Russell, Shawn; Bennett, Bradford; Sheth, Pradip; Abel, Mark
2011-05-01
This paper describes a method to characterize gait pathologies like cerebral palsy using work, energy, and angular momentum. For a group of 24 children, 16 with spastic diplegic cerebral palsy and 8 typically developed, kinematic data were collected at the subjects self selected comfortable walking speed. From the kinematics, the work-internal, external, and whole body; energy-rotational and relative linear; and the angular momentum were calculated. Our findings suggest that internal work represents 53% and 40% respectively of the whole body work in gait for typically developed children and children with cerebral palsy. Analysis of the angular momentum of the whole body, and other subgroupings of body segments, revealed a relationship between increased angular momentum and increased internal work. This relationship allows one to use angular momentum to assist in determining the kinetics and kinematics of gait which contribute to increased internal work. Thus offering insight to interventions which can be applied to increase the efficiency of bipedal locomotion, by reducing internal work which has no direct contribution to center of mass motion, in both normal and pathologic populations.
Three in one go: consequential angular momentum loss can solve major problems of CV evolution
Schreiber, Matthias R; Wijnen, Thomas P G
2015-01-01
The average white dwarf (WD) masses in cataclysmic variables (CVs) have been measured to significantly exceed those of single WDs, which is the opposite of what is theoretically expected. We present the results of binary population synthesis models taking into account consequential angular momentum loss (CAML) that is assumed to increase with decreasing WD mass. This approach can not only solve the WD mass problem, but also brings in agreement theoretical predictions and observations of the orbital period distribution and the space density of CVs. We speculate that frictional angular momentum loss following nova eruptions might cause such CAML and could thus be the missing ingredient of CV evolution.
Injection of Orbital Angular Momentum and Storage of Quantized Vortices in Polariton Superfluids.
Boulier, T; Cancellieri, E; Sangouard, N D; Glorieux, Q; Kavokin, A V; Whittaker, D M; Giacobino, E; Bramati, A
2016-03-18
We report the experimental investigation and theoretical modeling of a rotating polariton superfluid relying on an innovative method for the injection of angular momentum. This novel, multipump injection method uses four coherent lasers arranged in a square, resonantly creating four polariton populations propagating inwards. The control available over the direction of propagation of the superflows allows injecting a controllable nonquantized amount of optical angular momentum. When the density at the center is low enough to neglect polariton-polariton interactions, optical singularities, associated with an interference pattern, are visible in the phase. In the superfluid regime resulting from the strong nonlinear polariton-polariton interaction, the interference pattern disappears and only vortices with the same sign are persisting in the system. Remarkably, the number of vortices inside the superfluid region can be controlled by controlling the angular momentum injected by the pumps.
Injection of Orbital Angular Momentum and Storage of Quantized Vortices in Polariton Superfluids
Boulier, T.; Cancellieri, E.; Sangouard, N. D.; Glorieux, Q.; Kavokin, A. V.; Whittaker, D. M.; Giacobino, E.; Bramati, A.
2016-03-01
We report the experimental investigation and theoretical modeling of a rotating polariton superfluid relying on an innovative method for the injection of angular momentum. This novel, multipump injection method uses four coherent lasers arranged in a square, resonantly creating four polariton populations propagating inwards. The control available over the direction of propagation of the superflows allows injecting a controllable nonquantized amount of optical angular momentum. When the density at the center is low enough to neglect polariton-polariton interactions, optical singularities, associated with an interference pattern, are visible in the phase. In the superfluid regime resulting from the strong nonlinear polariton-polariton interaction, the interference pattern disappears and only vortices with the same sign are persisting in the system. Remarkably, the number of vortices inside the superfluid region can be controlled by controlling the angular momentum injected by the pumps.
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
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
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
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
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
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...
Zhang, Zijing; Qiao, Tianyuan; Ma, Kun; Cen, Longzhu; Zhang, Jiandong; Wang, Feng; Zhao, Yuan
2016-08-15
Photon orbital angular momentum has led to many novel insights and applications in quantum measurement. Photon orbital angular momentum can increase the resolution and sensitivity of angular rotation measurement. However, quantum measurement strategy can further surpass this limit and improve the resolution of angular rotation measurement. This Letter proposes and demonstrates a parity measurement method in angular rotation measurement scheme for the first time. Parity measurement can make the resolution superior to the limit of the existing method. The sensitivity can be improved with higher orbital angular momentum photons. Moreover, this Letter gives a detailed discussion of the change of resolution and sensitivity in the presence of photon loss.
Zhang, Zijing; Qiao, Tianyuan; Ma, Kun; Cen, Longzhu; Zhang, Jiandong; Wang, Feng; Zhao, Yuan
2016-08-15
Photon orbital angular momentum has led to many novel insights and applications in quantum measurement. Photon orbital angular momentum can increase the resolution and sensitivity of angular rotation measurement. However, quantum measurement strategy can further surpass this limit and improve the resolution of angular rotation measurement. This Letter proposes and demonstrates a parity measurement method in angular rotation measurement scheme for the first time. Parity measurement can make the resolution superior to the limit of the existing method. The sensitivity can be improved with higher orbital angular momentum photons. Moreover, this Letter gives a detailed discussion of the change of resolution and sensitivity in the presence of photon loss. PMID:27519107
Angular Momentum Transport via Internal Gravity Waves in Evolving Stars
Fuller, Jim; Cantiello, Matteo; Brown, Ben
2014-01-01
Recent asteroseismic advances have allowed for direct measurements of the internal rotation rates of many sub-giant 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 sub-giants, 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 sub-giant branch when stars have surface temperatures of roughly 5500 K. However, gravity waves can s...
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.
Scalable orbital-angular-momentum sorting without destroying photon states
Wang, Fang-Xiang; Yin, Zhen-Qiang; Wang, Shuang; Guo, Guang-Can; Han, Zheng-Fu
2016-01-01
Single photons with orbital angular momentum (OAM) have attracted substantial attention from researchers. A single photon can carry infinite OAM values theoretically. Thus, OAM photon states have been widely used in quantum information and fundamental quantum mechanics. Although there have been many methods for sorting quantum states with different OAM values, the nondestructive and efficient sorter of high-dimensional OAM remains a fundamental challenge. Here, we propose a scalable OAM sorter which can categorize different OAM states simultaneously, meanwhile, preserving both OAM and spin angular momentum. Fundamental elements of the sorter are composed of symmetric multiport beam splitters (BSs) and Dove prisms with cascading structure, which in principle can be flexibly and effectively combined to sort arbitrarily high-dimensional OAM photons. The scalable structures proposed here greatly reduce the number of BSs required for sorting high-dimensional OAMstates. In view of the nondestructive and extensible ...
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...
Atmosphere-earth angular momentum exchange and ENSO cycle
Institute of Scientific and Technical Information of China (English)
钱维宏; 丑纪范
1996-01-01
The time series of the earth’s rotation rate, eastern equatorial Pacific sea surface temperature (Tss), sea level pressure (Psl) and atmospheric angular momentum (Maa) during 1976 -1989 are used to study the relation between atmosphere-earth angular momentum exchange and ENSO cycle. The result shows that (i) there are synergetic relationships among the variations of solid earth’s rotation, eastern equatorial Pacific T,, Psl, different latitude zonal Maa and global Maa; (ii) local atmosphere-ocean interaction over low-latitude area can form ENSO-like cycle through Hadley circulation; (iii) the solid earth and global atmosphere-ocean interaction can form some aperiodic behavior and asynchronous oscillations by mountain torque and earth spin anomalous friction torque acting on each component of solid earth-ocean-atmosphere system; and (iv) actual ENSO cycle is a phenomenon reflecting in Pacific basin through interaction among solid earth, global ocean and the atmosphere.
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.
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
2015-02-12
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.
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.
Hydrodynamic turbulence cannot transport angular momentum effectively in astrophysical disks
Ji, H; Schartman, E; Goodman, J; Ji, Hantao; Burin, Michael J.; Schartman, Ethan; Goodman, Jeremy
2006-01-01
The most efficient energy sources known in the Universe are accretion disks. Those around black holes convert 5 -- 40 per cent of rest-mass energy to radiation. Like water circling a drain, inflowing mass must lose angular momentum, presumably by vigorous turbulence in disks, which are essentially inviscid. The origin of the turbulence is unclear. Hot disks of electrically conducting plasma can become turbulent by way of the linear magnetorotational instability. Cool disks, such as the planet-forming disks of protostars, may be too poorly ionized for the magnetorotational instability to occur, hence essentially unmagnetized and linearly stable. Nonlinear hydrodynamic instability often occurs in linearly stable flows (for example, pipe flows) at sufficiently large Reynolds numbers. Although planet-forming disks have extreme Reynolds numbers, Keplerian rotation enhances their linear hydrodynamic stability, so the question of whether they can be turbulent and thereby transport angular momentum effectively is con...
Temperature dependence of angular momentum transport across interfaces
Chen, Kai; Lin, Weiwei; Chien, C. L.; Zhang, Shufeng
2016-08-01
Angular momentum transport in magnetic multilayered structures plays a central role in spintronic physics and devices. The angular momentum currents or spin currents are carried by either quasiparticles such as electrons and magnons, or by macroscopic order parameters such as local magnetization of ferromagnets. Based on the generic interface exchange interaction, we develop a microscopic theory that describes interfacial spin conductance for various interfaces among nonmagnetic metals, ferromagnetic insulators, and antiferromagnetic insulators. Spin conductance and its temperature dependence are obtained for different spin batteries including spin pumping, temperature gradient, and spin Hall effect. As an application of our theory, we calculate the spin current in a trilayer made of a ferromagnetic insulator, an antiferromagnetic insulator, and a nonmagnetic heavy metal. The calculated results on the temperature dependence of spin conductance quantitatively agree with the existing experiments.
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.
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.
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 ...
Shape evolution with angular momentum in Lu isotopes
Kardan, Azam; Sayyah, Sepideh
2016-06-01
The nuclear potential energies of Lu isotopes with neutron number N = 90 - 98 up to high spins are computed within the framework of the unpaired cranked Nilsson-Strutinsky method. The potential and the macroscopic Lublin-Strasbourg drop (LSD) energy-surface diagrams are analyzed in terms of quadrupole deformation and triaxiality parameter. The shape evolution of these isotopes with respect to angular momentum, as well as the neutron number is studied.
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...
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.
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...
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...
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 ...
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.
Angular Momentum in the Formation of Disk Galaxies
Institute of Scientific and Technical Information of China (English)
LUO Zhi-Jian; SHU Cheng-Gang
2004-01-01
@@ Within the current framework of disk galaxy formation, we discuss the resulted surface-density profiles according to the theoretical angular momentum distributions (AMDs) presented by Bullock et al. [Astrophys. J.555 (2001) 240(B01)] for the ACDM cosmology in both spherical and cylindric coordinates. It is found that the derived surface density distribution of a disk in the outer region is in general similar to an exponential disk for both the theoretical AMDs. In the central region, the results from both the theoretical AMDs are inconsistent with observations whatever the disk bar-instability is taken into account or not. The cylindric form of the theoretical AMD leads to the bar-instability more easily for a give galaxy than that for spherical AMD, which could result in a more massive bulge. After comparing the model predictions with our Milky Way galaxy, we find that the theoretical AMDs predict larger mass fractions of baryons with low angular momentum than the observed ones, which would lead to the disk sizes to be smaller. Two possible processes which could solve the angular momentum problem are discussed.
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.
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.
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
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 ...
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...
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.
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.
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.
Statistical mechanics of collisionless orbits. IV. Distribution of angular momentum
Williams, Liliya L R; Wojtak, Radoslaw
2014-01-01
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^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, \\beta(...
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.
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
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.
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.
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.
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.
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.
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...
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
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.
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
Engineering of orbital angular momentum supermodes in coupled optical waveguides
Turpin, A; Polo, J; Mompart, J; Ahufinger, V
2016-01-01
In this work we demonstrate the existence of orbital angular momentum (OAM) bright and dark supermodes in a three-evanescent coupled cylindrical waveguides system. Bright and dark supermodes are characterized by its coupling and decoupling from one of the waveguides, respectively. In addition, we demonstrate that complex couplings between modes of different waveguides appear naturally due to the characteristic spiral phase-front of OAM modes in two-dimensional configurations where the waveguides are arranged forming a triangle. Finally, by adding dissipation to the waveguide uncoupled to the dark supermode, we are able to filter it out, allowing for the design of OAM mode clonners and inverters.
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
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 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)
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.
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.
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.
Energy and angular momentum sharing in dissipative collisions
Casini, G; Calamai, S; Laforest, R; Maurenzig, P R; Olmi, A; Pasquali, G; Piantelli, S; Poggi, G; Saint-Laurent, F; Steckmeyer, J C; Stefanini, A A; Taccetti, N
2000-01-01
Primary and secondary masses of heavy reaction products have been deduced from kinematics and E-ToF measurements, respectively, for the direct and reverse collisions of 93Nb and 116Sn at 25 AMeV. Light charged particles have also been measured in coincidence with the heavy fragments. Direct experimental evidence of the correlation of energy-sharing with net mass transfer has been found using the information from both the heavy fragments and the light charged particles. The ratio of Hydrogen and Helium multiplicities points to a further correlation of angular momentum sharing with net mass transfer.
Energy and angular momentum sharing in dissipative collisions
Casini, G.; Bini, M.; Calamai, S.; Laforest, R.; Maurenzig, P. R.; Olmi, A.; Pasquali, G.; Piantelli, S.; Poggi, G.; Saint-Laurent, F.; Steckmeyer, J. C.; Stefanini, A. A.; Taccetti, N.
Primary and secondary masses of heavy reaction products have been deduced from kinematics and E-ToF measurements, respectively, for the direct and reverse collisions of 93Nb and 116Sn at 25 AMeV. Light charged particles have also been measured in coincidence with the heavy fragments. Direct experimental evidence of the correlation of energy-sharing with net mass transfer has been found using information from both the heavy fragments and the light charged particles. The ratio of hydrogen and helium multiplicities points to a further correlation of angular momentum sharing with net mass transfer.
Energy and angular momentum sharing in dissipative collisions
Energy Technology Data Exchange (ETDEWEB)
Casini, G.; Bini, M.; Calamai, S.; Maurenzig, P.R.; Olmi, A.; Pasquali, G.; Piantelli, S.; Poggi, G.; Stefanini, A.A.; Taccetti, N. [Istituto Nazionale di Fisica Nucleare, Florence (Italy); Laforest, R.; Steckmeyer, J.C. [Caen Univ., 14 (France). Lab. de Physique Corpusculaire; Saint-Laurent, F. [Grand Accelerateur National d' Ions Lourds (GANIL), 14 - Caen (France)
2000-12-01
Primary and secondary masses of heavy reaction products have been deduced from kinematics and E-ToF measurements, respectively, for the direct and reverse collisions of {sup 93}Nb and {sup 116}Sn at 25 AMeV. Light charged particles have also been measured in coincidence with the heavy fragments. Direct experimental evidence of the correlation of energy-sharing with net mass transfer has been found using information from both the heavy fragments and the light charged particles. The ratio of hydrogen and helium multiplicities points to a further correlation of angular momentum sharing with net mass transfer. (orig.)
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
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.
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.
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...
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.
Odd–even effect in fragment angular momentum in low-energy fission of actinides
Indian Academy of Sciences (India)
B S Tomar; R Tripathi; A Goswami
2007-01-01
Quantitative explanation for the odd–even effect on fragment angular momenta in the low-energy fission of actinides have been provided by taking into account the single particle spin of the odd proton at the fragment's scission point deformation in the case of odd- fragments along with the contribution from the population of angular momentum bearing collective vibrations of the fissioning nucleus at scission point. The calculated fragment angular momenta have been found to be in very good agreement with the experimental data for fragments in the mass number region of 130–140. The odd–even effect observed in the fragment angular momenta in the low-energy fission of actinides has been explained quantitatively for the first 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.
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...
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.
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 transport and evolution of lopsided galaxies
Saha, Kanak
2014-01-01
The surface brightness distribution in the majority of stellar galactic discs falls off exponentially. Often what lies beyond such a stellar disc is the neutral hydrogen gas whose distribution also follows a nearly exponential profile at least for a number of nearby disc galaxies. Both the stars and gas are commonly known to host lopsided asymmetry especially in the outer parts of a galaxy. The role of such asymmetry in the dynamical evolution of a galaxy has not been explored so far. Following Lindblad's original idea of kinematic density waves, we show that the outer part of an exponential disc is ideally suitable for hosting lopsided asymmetry. Further, we compute the transport of angular momentum in the combined stars and gas disc embedded in a dark matter halo. We show that in a pure star and gas disc, there is a transition point where the free precession frequency of a lopsided mode, $\\Omega -\\kappa $, changes from retrograde to prograde and this in turn reverses the direction of angular momentum flow i...
Extraordinary Light-Induced Local Angular Momentum near Metallic Nanoparticles.
Alabastri, Alessandro; Yang, Xiao; Manjavacas, Alejandro; Everitt, Henry O; Nordlander, Peter
2016-04-26
The intense local field induced near metallic nanostructures provides strong enhancements for surface-enhanced spectroscopies, a major focus of plasmonics research over the past decade. Here we consider that plasmonic nanoparticles can also induce remarkably large electromagnetic field gradients near their surfaces. Sizeable field gradients can excite dipole-forbidden transitions in nearby atoms or molecules and provide unique spectroscopic fingerprinting for chemical and bimolecular sensing. Specifically, we investigate how the local field gradients near metallic nanostructures depend on geometry, polarization, and wavelength. We introduce the concept of the local angular momentum (LAM) vector as a useful figure of merit for the design of nanostructures that provide large field gradients. This quantity, based on integrated fields rather than field gradients, is particularly well-suited for optimization using numerical grid-based full wave electromagnetic simulations. The LAM vector has a more compact structure than the gradient matrix and can be straightforwardly associated with the angular momentum of the electromagnetic field incident on the plasmonic structures.
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)
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.
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.
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)
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.
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.
Angular momentum properties of haloes and their baryon content in the Illustris simulation
Zjupa, Jolanta; Springel, Volker
2016-01-01
The angular momentum properties of virialised dark matter haloes have been measured with good statistics in collisionless N-body simulations, but an equally accurate analysis of the baryonic spin is still missing. We employ the Illustris simulation suite, one of the first simulations of galaxy formation with full hydrodynamics that produces a realistic galaxy population in a sizeable volume, to quantify the baryonic spin properties for more than $\\sim$ 320,000 haloes. We first compare the sys...
Is angular momentum in the horizontal plane during gait a controlled variable?
Thielemans, Valerie; Meyns, Pieter; Bruijn, Sjoerd M
2014-04-01
It has been suggested that angular momentum in the horizontal plane during human gait is controlled (i.e., kept minimal). However, this has not been explored in conditions when angular momentum of different segments is manipulated explicitly. In order to examine the behavior of angular momentum, 12 participants walked in 17 conditions in which angular momentum of either the arms or legs was manipulated. Subjects walked at different step lengths, different speeds and with an additional weight on either the wrist or ankle. Angular momentum of total body, arms and legs was calculated from gait kinematics. Increasing step length increased total body and leg angular momentum. When weight was added to the limbs, arm and leg angular momentum were affected and counteracted each other, so that total body angular momentum did not change. Moreover, increasing walking speed increased arm, leg and total body angular momentum. Thus, it may be concluded that if angular momentum is controlled (which only seems to be the case for conditions when weights are added), it is not strictly controlled in all gait conditions (as it may increase by walking faster/with larger steps).
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.
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.
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)
Population momentum across vertebrate life histories
Koons, D.N.; Grand, J.B.; Arnold, J.M.
2006-01-01
Population abundance is critically important in conservation, management, and demographic theory. Thus, to better understand how perturbations to the life history affect long-term population size, we examined population momentum for four vertebrate classes with different life history strategies. In a series of demographic experiments we show that population momentum generally has a larger effect on long-term population size for organisms with long generation times than for organisms with short generation times. However, patterns between population momentum and generation time varied across taxonomic groups and according to the life history parameter that was changed. Our findings indicate that momentum may be an especially important aspect of population dynamics for long-lived vertebrates, and deserves greater attention in life history studies. Further, we discuss the importance of population momentum in natural resource management, pest control, and conservation arenas. ?? 2006 Elsevier B.V. All rights reserved.
Numerical Solution of the Evolution Equation for Orbital Angular Momentum of Partons in the Nucleon
Martin, O; Schäfer, A
1999-01-01
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 average orbital angular momentum per parton is several times larger for gluons than for quarks which favours gluon initiated reactions to measure orbital angular momentum. The large gluon polarization typically obtained in NLO-fits to DIS data is primarily canceled by the gluon orbital angular momentum.
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.
Angular momentum: understanding spatial aspects in chemistry and physics
Zare, Richard N.
2013-01-01
Designed as a learning tool for those with limited background in quantum mechanics, this book provides comprehensive coverage of angular momentum in quantum mechanics and its applications to chemistry and physics. Based on class-tested material, this presentation offers clear explanations of theory while giving equal attention to solving real problems. Theoretical considerations are made concrete and accessible through extensive examples and applications at the end of each chapter. Problem sets, designed as both individual and group exercises, are treated as an integral part of the text in order to stimulate student interest and clarify the abstract principles discussed. Examples are drawn primarily from atomic and molecular phenomena, and include many intermediate steps (often left out of other texts) to ensure complete mastery of the material, and to lay the groundwork for understanding photon and particle collision phenomena, and more advanced studies.
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.
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
Measuring an electron beam's orbital angular momentum spectrum
Grillo, incenzo; Venturi, Federico; Larocque, Hugo; Balboni, Roberto; Gazzadi, Gian Carlo; Frabboni, Stefano; Lu, Peng-Han; Mafakheri, Erfan; Bouchard, Frédéric; Dunin-Borkowski, Rafal E; Boyd, Robert W; Lavery, Martin P J; Padgett, Miles J; Karimi, Ebrahim
2016-01-01
Quantum complementarity states that particles, e.g. electrons, can exhibit wave-like properties such as diffraction and interference upon propagation. \\textit{Electron waves} defined by a helical wavefront are referred to as twisted electrons~\\cite{uchida:10,verbeeck:10,mcmorran:11}. These electrons are also characterised by a quantized and unbounded magnetic dipole moment parallel to their propagation direction, as they possess a net charge of $-|e|$~\\cite{bliokh:07}. When interacting with magnetic materials, the wavefunctions of twisted electrons are inherently modified~\\cite{lloyd:12b,schattschneider:14a,asenjo:14}. Such variations therefore motivate the need to analyze electron wavefunctions, especially their wavefronts, in order to obtain information regarding the material's structure~\\cite{harris:15}. Here, we propose, design, and demonstrate the performance of a device for measuring an electron's azimuthal wavefunction, i.e. its orbital angular momentum (OAM) content. Our device consists of nanoscale h...
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.
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
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
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.
Weak measurements with orbital-angular-momentum pointer states.
Puentes, G; Hermosa, N; Torres, J P
2012-07-27
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 that can be relevant for quantum information applications. Here we demonstrate that by employing two-dimensional pointer states endowed with orbital angular momentum (OAM), it is possible to extract weak values of the higher order moments of single-particle operators, an inaccessible quantity with Gaussian pointer states only. We provide a specific example that illustrates the advantages of our method both in terms of signal enhancement and information retrieval. PMID:23006067
Weak measurements with orbital angular momentum pointer states
Puentes, G; 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. In this paper, we demonstrate that by employing two-dimensional pointer states endowed with orbital angular momentum (OAM), it is possible to extract second-order weak values of single particle operators, an unaccessible quantity with Gaussian pointer states only. An important application of the results presented here is in the non-destructive measurement of single-particle operator weak variances, via two-dimensional pointer displacements.
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.
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.
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...
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.
Rapid generation of light beams carrying orbital angular momentum.
Mirhosseini, Mohammad; Magaña-Loaiza, Omar S; Chen, Changchen; Rodenburg, Brandon; Malik, Mehul; Boyd, Robert W
2013-12-16
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 phase-only 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.
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.
Radial and angular-momentum Regge trajectories: a systematic approach
Directory of Open Access Journals (Sweden)
Arriola E.R.
2012-12-01
Full Text Available We present the analysis of Ref. [1] of the radial (n and angular-momentum (J Regge trajectories for all light-quark meson states listed in the Particle Data Tables. The parameters of the trajectories are obtained with linear regression, with weight of each resonance inversely proportional to its half-width squared, (Γ/22. The joint analysis in the (n, J, M2 Regge plane indicates, at the 4.5 standard deviation level, that the slopes in n are larger from the slopes in J. Thus no strict universality of slopes occurs in the light non-strange meson sector. We also extend our analysis to the kaon sector.
Detection of orbital angular momentum using a photonic integrated circuit
Rui, Guanghao; Gu, Bing; Cui, Yiping; Zhan, Qiwen
2016-06-01
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.
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)
Nondestructive Measurement of Orbital Angular Momentum for an Electron Beam
Larocque, Hugo; Bouchard, Frédéric; Grillo, Vincenzo; Sit, Alicia; Frabboni, Stefano; Dunin-Borkowski, Rafal E.; Padgett, Miles J.; Boyd, Robert W.; Karimi, Ebrahim
2016-10-01
Free electrons with a helical phase front, referred to as "twisted" electrons, possess an orbital angular momentum (OAM) and, hence, a quantized magnetic dipole moment along their propagation direction. This intrinsic magnetic moment can be used to probe material properties. Twisted electrons thus have numerous potential applications in materials science. Measuring this quantity often relies on a series of projective measurements that subsequently change the OAM carried by the electrons. In this Letter, we propose a nondestructive way of measuring an electron beam's OAM through the interaction of this associated magnetic dipole with a conductive loop. Such an interaction results in the generation of induced currents within the loop, which are found to be directly proportional to the electron's OAM value. Moreover, the electron experiences no OAM variations and only minimal energy losses upon the measurement, and, hence, the nondestructive nature of the proposed technique.
Continuous Variable Entanglement of Orbital Angular Momentum States
DEFF Research Database (Denmark)
Lassen, Mikael Østergaard; Leuchs, G.; Andersen, Ulrik Lund
2009-01-01
We have generated a new quantum state of light composed of quadrature entangled Laguerre-Gaussian (LG) modes. For the generation we used an OPO operating in a new regime where all field parameters are degenerate except for its spatial degree of freedom for which it is two-fold degenerate. The ent......We have generated a new quantum state of light composed of quadrature entangled Laguerre-Gaussian (LG) modes. For the generation we used an OPO operating in a new regime where all field parameters are degenerate except for its spatial degree of freedom for which it is two-fold degenerate....... The 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...
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}.
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
Detection of orbital angular momentum using a photonic integrated circuit.
Rui, Guanghao; Gu, Bing; Cui, Yiping; Zhan, Qiwen
2016-06-20
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.
Multi-channel orbital angular momentum detection with metahologram.
Rui, Guanghao; Ma, Yanbao; Gu, Bing; Zhan, Qiwen; Cui, Yiping
2016-09-15
Orbital angular momentum (OAM) is an intrinsic property of light that has attracted increasing attention recently. In a wide range of applications that involve OAM, it is often crucial to discern the OAM states with high fidelity. In this Letter, we propose a novel method to extend the detectable range of the OAM states by adopting a multi-sector metahologram. The incident light carrying OAM would be focused by the metahologram into surface plasmon waves with separated propagation directions that are spatially sampled by multiple subwavelength detectors. Through quantizing and mapping the detector signals into a lookup table, a wide range of OAM states could be distinguished. The principle reported in this Letter may find important applications in optical communications and information processing with the OAM states. PMID:27628402
Coronal Mass Ejections and Angular Momentum Loss in Young Stars
Aarnio, Alicia; Matt, Sean
2014-01-01
In our own solar system, the necessity of understanding space weather is readily evident. Fortunately for Earth, our nearest stellar neighbor is relatively quiet, exhibiting activity levels several orders of magnitude lower than young, solar-type stars. In protoplanetary systems, stellar magnetic phenomena observed are analogous to the solar case, but dramatically enhanced on all physical scales: bigger, more energetic, more frequent. While coronal mass ejections (CMEs) could play a signi?cant role in the evolution of protoplanets, they could also a?ffect the evolution of the central star itself. To assess the consequences of prominence eruption/CMEs, we have invoked the solar-stellar connection to estimate, for young, solar-type stars, how frequently stellar CMEs may occur and their attendant mass and angular momentum loss rates. We will demonstrate the necessary conditions under which CMEs could slow stellar rotation.
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, \
Semiclassical decay of strings with maximum angular momentum
Iengo, R; Iengo, Roberto; Russo, Jorge G.
2003-01-01
A highly excited (closed or open) string state on the leading Regge trajectory can be represented by a rotating soliton solution. There is a semiclassical probability per unit cycle that this string can spontaneously break into two pieces. Here we find the resulting solutions for the outgoing two pieces, which describe two specific excited string states, and show that this semiclassical picture reproduces very accurately the features of the quantum calculation of decay in the large mass M limit. In particular, this picture prescribes the precise analytical relation of the masses M_1 and M_2 of the decay products, and indicates that the lifetime of these string states grows with the mass as T= const. a' M, in agreement with the quantum calculation. Thus, surprisingly, a string with maximum angular momentum becomes more stable for larger masses. We also point out some interesting features of the evolution after the splitting process.
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.
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.
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
Quasi-Local Energy-Momentum and Angular Momentum in General Relativity
Directory of Open Access Journals (Sweden)
Szabados László B.
2009-06-01
Full Text Available The present status of the quasi-local mass, energy-momentum and angular-momentum constructions in general relativity is reviewed. First, the general ideas, concepts, and strategies, as well as the necessary tools to construct and analyze the quasi-local quantities, are recalled. Then, the various specific constructions and their properties (both successes and deficiencies are discussed. Finally, some of the (actual and potential applications of the quasi-local concepts and specific constructions are briefly mentioned.This review is based on talks given at the Erwin Schrödinger Institute, Vienna in July 1997, at the Universität Tübingen in May 1998, and at the National Center for Theoretical Sciences in Hsinchu, Taiwan and at the National Central University, Chungli, Taiwan, in July 2000.
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)
Muscle contributions to whole-body sagittal plane angular momentum during walking.
Neptune, R R; McGowan, C P
2011-01-01
Walking is a complex dynamic task that requires the regulation of whole-body angular momentum to maintain dynamic balance while performing walking subtasks such as propelling the body forward and accelerating the leg into swing. In human walking, the primary mechanism to regulate angular momentum is muscle force generation. Muscles accelerate body segments and generate ground reaction forces that alter angular momentum about the body's center-of-mass to restore and maintain dynamic stability. In addition, gravity contributes to whole-body angular momentum through its contribution to the ground reaction forces. The purpose of this study was to generate a muscle-actuated forward dynamics simulation of normal walking to quantify how individual muscles and gravity contribute to whole-body angular momentum in the sagittal plane. In early stance, the uniarticular hip and knee extensors (GMAX and VAS), biarticular hamstrings (HAM) and ankle dorsiflexors (TA) generated backward angular momentum while the ankle plantar flexors (SOL and GAS) generated forward momentum. In late stance, SOL and GAS were the primary contributors and generated angular momentum in opposite directions. SOL generated primarily forward angular momentum while GAS generated backward angular momentum. The difference between muscles was due to their relative contributions to the horizontal and vertical ground reaction forces. Gravity contributed to the body's angular momentum in early stance and to a lesser extent in late stance, which was counteracted primarily by the plantar flexors. These results may provide insight into balance and movement disorders and provide a basis for developing locomotor therapies that target specific muscle groups.
Galaxy S-Stars Exhibit Orbital Angular Momentum Quantization per Unit Mass
Directory of Open Access Journals (Sweden)
Potter F.
2012-10-01
Full Text Available The innermost stars of our Galaxy, called S-stars, are in Keplerian orbits. Quantum celestial mechanics (QCM predicts orbital angular momentum quantization per unit mass for each of them. I determine the quantization integers for the 27 well-measured S-stars and the total angular momentum of this nearly isolated QCM system within the Galactic bulge.
Angular momentum dynamics and the intrinsic drift of monopolar vortices on a rotating sphere
Van der 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 represen
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
2014-09-16
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 single aperture pair by transmitting multiple coaxial data streams. Here we demonstrate a 32-Gbit s(-1) millimetre-wave link over 2.5 metres with a spectral efficiency of ~16 bit s(-1) Hz(-1) using four independent orbital-angular momentum beams on each of two polarizations. All eight orbital angular momentum channels are recovered with bit-error rates below 3.8 × 10(-3). In addition, we demonstrate a millimetre-wave orbital angular momentum mode demultiplexer to demultiplex four orbital angular momentum channels with crosstalk less than -12.5 dB and show an 8-Gbit s(-1) link containing two orbital angular momentum beams on each of two polarizations.
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 single aperture pair by transmitting multiple coaxial data streams. Here we demonstrate a 32-Gbit s−1 millimetre-wave link over 2.5 metres with a spectral efficiency of ~16 bit s−1 Hz−1 using four independent orbital–angular momentum beams on each of two polarizations. All eight orbital angular momentum channels are recovered with bit-error rates below 3.8 × 10−3. In addition, we demonstrate a millimetre-wave orbital angular momentum mode demultiplexer to demultiplex four orbital angular momentum channels with crosstalk less than −12.5 dB and show an 8-Gbit s−1 link containing two orbital angular momentum beams on each of two polarizations. PMID:25224763
Excitation of high orbital angular momentum Rydberg states with Laguerre-Gauss beams
Rodrigues, J D; Mendonça, J T
2015-01-01
We consider the excitation of Rydberg states through photons carrying an intrinsic orbital angular momentum degree of freedom. Laguerre-Gauss modes, with a helical wave-front structure, correspond to such a set of laser beams, which carry some units of orbital angular momentum in their propagation direction. We demonstrate that, in a proper geometrical setting, this orbital angular momentum can be transferred to the internal degrees of freedom of the atoms, thus violating the standard dipolar selection rules. Higher orbital angular momentum states become accessible through a single photon excitation process. We investigate how the spacial structure of the Laguerre-Gauss beam affects the radial coupling strength, assuming the simplest case of hydrogen-like wavefunctions. Finally we discuss a generalization of the angular momentum coupling, in order to include the effects of the fine and hyperfine splitting, in the context of the Wigner-Eckart theorem.
Specific Angular Momentum Distribution of Disc Galaxies Formed in Preheated Intergalactic Media
Institute of Scientific and Technical Information of China (English)
LUO Zhi-Jian; FU Li-Ping; SHU Cheng-Gang
2004-01-01
Assuming that baryons within a galactic halo have the same specific angular momentum as the dark matter where they locate initially and a disc forms due to the gas cooling and condensation with the conservation of angular momentum, we investigate the angular momentum distribution in a resulting galactic disc under the new preheated galaxy formation model suggested by Mo and Mao (Mon. Not. R. Astron. Soc. 333 (2002) 768).Compared with the observational results, it can be concluded that the preheated galaxy formation model can match current observations. This model can be a good approach to solve the problems of both the angular momentum catastrophe and the mismatch of angular-momentum profiles in current disc galaxy formation models.
Excitation of high orbital angular momentum Rydberg states with Laguerre-Gauss beams
Rodrigues, J. D.; Marcassa, L. G.; Mendonça, J. T.
2016-04-01
We consider the excitation of Rydberg states through photons carrying an intrinsic orbital angular momentum degree of freedom. Laguerre-Gauss modes, with a helical wave-front structure, correspond to such a set of laser beams, which carry {{\\ell }}0 units of orbital angular momentum in their propagation direction, with ℓ 0 the winding number. We demonstrate that, in a proper geometry setting, this orbital angular momentum can be transferred to the internal degrees of freedom of the atoms, thus violating the standard dipole selection rules. Higher orbital angular momentum states become accessible through a single photon excitation process. We investigate how the spacial structure of the Laguerre-Gauss beam affects the radial coupling strength, assuming the simplest case of hydrogen-like wavefunctions. Finally we discuss a generalization of the angular momentum coupling, in order to include the effects of the fine and hyperfine splitting, in the context of the Wigner-Eckart theorem.
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.-
He, Li; Li, Mo
2016-01-01
Photons carry linear momentum, and spin angular momentum when circularly or elliptically polarized. During light-matter interaction, transfer of linear momentum leads to optical forces, while angular momentum transfer induces optical torque. Optical forces including radiation pressure and gradient forces have long been utilized in optical tweezers and laser cooling. In nanophotonic devices optical forces can be significantly enhanced, leading to unprecedented optomechanical effects in both classical and quantum regimes. In contrast, to date, the angular momentum of light and the optical torque effect remain unexplored in integrated photonics. Here, we demonstrate the measurement of the spin angular momentum of photons propagating in a birefringent waveguide and the use of optical torque to actuate rotational motion of an optomechanical device. We show that the sign and magnitude of the optical torque are determined by the photon polarization states that are synthesized on the chip. Our study reveals the mecha...
Modeling Angular-Momentum History in Dark-Matter Halo
Maller, A H; Somerville, R S; Maller, Ariyeh H.; Dekel, Avishai; Somerville, Rachel S.
2002-01-01
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 standard deviation ~0.5 in the log. A perfect match requires fine-tuning of two free parameters. Both algorithms also reproduce the general insensitivity of the spin distribution to halo mass, redshift and cosmology seen in N-body simulations. The spin distribution can be made strictly constant by physically motivated scalings of the free parameters. In addition, both schemes predict that halos which have had recent major mergers have systematically larger spin values. These algorithms can be implemented within semi-analyti...
The angular momentum transport by unstable toroidal magnetic fields
Rüdiger, G.; Gellert, M.; Spada, F.; Tereshin, I.
2015-01-01
We demonstrate with a nonlinear magnetohydrodynamic (MHD) code that angular momentum can be transported because of 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. We only consider stationary, current-free fields, and only those combinations of rotation rates and magnetic field amplitudes which provide maximal numerical values of the viscosity. We find that the dimensionless ratio of the effective over molecular viscosity, νT/ν, linearly grows with the Reynolds number of the rotating fluid multiplied by the square-root of the magnetic Prandtl number, which is approximately unity for the considered red subgiant star KIC 7341231. For the interval of magnetic Reynolds numbers considered - which is restricted by numerical constraints of the nonlinear MHD code - the magnetic Prandtl number has a remarkable influence on the relative importance of the contributions of the Reynolds stress and the Maxwell stress to the total viscosity, which is magnetically dominated only for Pm ≳ 0.5. We also find that the magnetized plasma behaves as a non-Newtonian fluid, i.e., the resulting effective viscosity depends on the shear in the rotation law. The decay time of the differential rotation thus depends on its shear and becomes longer and longer during the spin-down of a stellar core.
A QUANTUM MULTIPLE ACCESS COMMUNICATIONS SCHEME USING ORBITAL ANGULAR MOMENTUM
Institute of Scientific and Technical Information of China (English)
Dong Xiaoliang; Zhao Shengmei; Zheng Baoyu
2013-01-01
We propose a quantum multiple access communications scheme using Orbital Angular Momentum (OAM) sector states in the paper.In the scheme,each user has an individual modified Poincare Bloch sphere and encodes his information with his own corresponding sector OAM states.A prepared entangled photon pairs are separated at transmitter and receiver.At the transmitter,each user encodes his information with the sector OAM states on the photons and the superposition of the different sector OAM states is carried by the photons.Then the photons are transmitted through quantum noiseless channel to the receiver.At the receiver,each user could retrieve his information by coincidently measuring the transmitted photons with the receiver side photons which are modulated by a special prepared measurement basis.The theoretical analysis and the numerical simulations show that each user could get his information from the superposition state without error.It seems that this scheme provides a novel method for quantum multiple users communications.
New Treatment of Systems of Compounded Angular Momentum
Mweene, H V
1999-01-01
The approach to quantum mechanics which we hav used to derive the matrix treatment of spin from first principles is now employed to treat systems of compounded angular momentum. A general treatment is first given, which is then applied to the concrete cases of a spin-0 and a spin-1 system obtained by adding the spins of two spin-1/2 systems. Thus, the probability amplitudes for measurements on the systems are derived, as well as the matrix vectors and operators corresponding to the systems. The matrix operators and states thereby resulting are different from the standard forms and are much more generalized. The formulas so derived are applied to the case of joint measurements on the subsystems of such a system, a problem made very topical by the great interest in quantum foundations now obtaining. As a consequence of the insights arising from this treatment, we show that the Clebsch-Gordan coefficients are amenable to generalization, and we give the generalized forms for these cases.
Polarized Structure Function of Nucleon and Orbital Angular Momentum
Arash, Firooz; Taghavi-Shahri, Fatemeh
2007-06-01
We have utilized the concept of valon model to calculate the spin structure function of a constituent quark. This structure is universal and arises from perturbative dressing of a valence quark in QCD. With a convolution method the polarized structure functions of proton, neutron, and deuteron are obtained. Our results agree rather well with all available experimental data. It suggests that the sea quark contribution to the spin of nucleon is consistent with zero, in agreement with HERMES data. It also reveals that while the total quark contribution to the spin of a constituent quark, or valon, is almost constant and equal to one, the gluon contribution grows with the increase of Q2, and hence, requiring a sizable negative angular momentum contribution. This component, as well as singlet and non-singlet parts are calculated in the Next-to-Leading order in QCD. We speculate that the gluon contribution to the spin of proton is in the order of 50%. Furthermore, we have determined the polarized valon distribution in a nucleon.
Polarization radiation of vortex electrons with large orbital angular momentum
Ivanov, Igor P
2013-01-01
Vortex electrons, i.e. freely propagating electrons whose wavefunction has helical wavefronts, could emerge as a novel tool for the physics of electromagnetic (EM) radiation. They carry non-zero intrinsic orbital angular momentum (OAM) $\\ell$ and, for $\\ell \\gg 1$, a large OAM-induced magnetic moment, $\\mu \\approx \\ell \\mu_B$ ($\\mu_B$ is the Bohr magneton), which affects the radiation of EM waves. Here, we consider in detail its influence on two forms of polarization radiation, namely on Cherenkov and transition radiation. Due to large $\\ell$, we can neglect quantum or spin-induced effects, which are of order $\\hbar \\omega/E_e \\ll 1$, but retain the magnetic moment contribution $\\ell \\hbar \\omega/E_e \\lesssim 1$, which makes the quasiclassical approach to polarization radiation applicable. We discuss magnetic moment contribution to polarization radiation, which has never been experimentally observed, and study how its visibility depends on kinematical parameters and permittivity of the medium. In particular, ...
Non-collinear interaction of photons with orbital angular momentum
Roger, Thomas; Heitz, Julius J. F.; Wright, Ewan M.; Faccio, Daniele
2013-01-01
We study the nonlinear interaction between two non-collinear light beams that carry orbital angular momentum (OAM). More specifically, two incident beams interact at an angle in a medium with a second order nonlinearity and thus generate a third, non-collinear beam at the second harmonic frequency that experiences a reduced conversion efficiency in comparison to that expected based on conventional phase-matching theory. This reduction scales with the input beam OAM and, differently from previous spiral bandwidth calculations, is due to a geometric effect whereby the input OAM is projected along the non-collinear interaction direction. The effect is relevant even at small interaction angles and is further complicated at large angles by a non-conservation of the total 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 or in general for phase-matched non-collinear interactions between beams with different OAM. PMID:24336441
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.
Adaptive power-controllable orbital angular momentum (OAM) multicasting
Li, Shuhui; Wang, Jian
2015-01-01
We report feedback-assisted adaptive multicasting from a single Gaussian mode to multiple orbital angular momentum (OAM) modes using a single phase-only spatial light modulator loaded with a complex phase pattern. By designing and optimizing the complex phase pattern through the adaptive correction of feedback coefficients, the power of each multicast OAM channel can be arbitrarily controlled. We experimentally demonstrate power-controllable multicasting from a single Gaussian mode to two and six OAM modes with different target power distributions. Equalized power multicasting, “up-down” power multicasting and “ladder” power multicasting are realized in the experiment. The difference between measured power distributions and target power distributions is assessed to be less than 1 dB. Moreover, we demonstrate data-carrying OAM multicasting by employing orthogonal frequency-division multiplexing 64-ary quadrature amplitude modulation (OFDM 64-QAM) signal. The measured bit-error rate curves and observed optical signal-to-noise ratio penalties show favorable operation performance of the proposed adaptive power-controllable OAM multicasting. PMID:25989251
Angular Momentum Regulates Atomic Gas Fractions of Galactic Disks
Obreschkow, Danail; Kilborn, Virginia; Lutz, Katharina
2016-01-01
We show that the mass fraction f_atm = 1.35*MHI/M of neutral atomic gas (HI and He) in isolated local disk galaxies of baryonic mass M is well described by a straightforward stability model for flat exponential disks. In the outer disk parts, where gas at the characteristic dispersion of the Warm Neutral Medium is stable in the sense of Toomre (1964), the disk consists of neutral atomic gas; conversely the inner part where this medium would be Toomre-unstable, is dominated by stars and molecules. Within this model, f_atm only depends on a global stability parameter q=j*sigma/(GM), where j is the baryonic specific angular momentum of the disk and sigma the velocity dispersion of the atomic gas. The analytically derived first-order solution f_atm = min{1,2.5q^1.12} provides a good fit to all plausible rotation curves. This model, with no free parameters, agrees remarkably well (+-0.2 dex) with measurements of f_atm in isolated local disk galaxies, even with galaxies that are extremely HI-rich or HI-poor for the...
Influence of angular momentum on evaporation residue cross section as a probe of nuclear dissipation
Institute of Scientific and Technical Information of China (English)
YE Wei; WU Feng
2008-01-01
By calculating the excess of the evaporation residue cross sections of the 200pb nucleus over that predicted by the standard statistical model as a function of nuclear viscosity coefficient using a Langevin equation combined with a statistical decay model, it is found that high angular momentum not only amplifies the dissipation effects on the excess of the evaporation residue cross sections, but also considerably increases the sensitivity of this excess to the nuclear viscosity coefficient. These results suggest that on the experimental side, to accurately obtain the information of nuclear dissipation inside the saddle point by measuring the evaporation residue cross section, it had better populate those compound systems with high spins.
Angular momentum loss of primordial gas in Lyman-alpha radiation field
Yajima, Hidenobu
2013-01-01
We present results on the radiation drag exerted by an isotropic and homogenous background of Lya photons on neutral gas clouds orbiting within HII regions around Population III stars of different masses. The Doppler shift causes a frequency difference between photons moving in the direction of the cloud and opposite to it resulting in a net momentum loss of the cloud in the direction of motion. We find that half of the angular momentum of gas with v_theta 10^8 yr even for low velocity clouds. Our results suggest that a sweet spot exists for the loss of angular momentum by radiation drag for gas clouds at z > 10 and with v ~ 20 km/s. Comparison to dynamical friction forces acting on typical gas clouds suggest that radiation drag is the dominant effect impacting the orbit. We propose that this effect can suppress the formation of extended gas discs in the first galaxies and help gas accretion near galactic centres and central black holes.
Effect of stride length on overarm throwing delivery: Part II: An angular momentum response.
Ramsey, Dan K; Crotin, Ryan L
2016-04-01
This is the second component of a two-part series investigating 3D momentum profiles specific to overhand throwing, where altering stride reportedly influences throwing mechanics resulting in significantly different physiologic outcomes and linear momentum profiles. Using a randomized cross-over design, nineteen pitchers (15 collegiate and 4 high school) were assigned to pitch two simulated 80-pitch games at ±25% of their desired stride length. An 8-camera motion capture system (240Hz) integrated with two force plates (960Hz) and radar gun tracked each overhand throw. Segmental angular momentums were summed yielding throwing arm and total body momentums, from which compensation ratio's (relative contribution between the two) were derived. Pairwise comparisons at hallmark events and phases identified significantly different angular momentum profiles, in particular total body, throwing arm, and momentum compensation ratios (P⩽0.05) as a result of manipulating stride length. Sagittal, frontal, and transverse angular momentums were affected by stride length changes. Transverse magnitudes showed greatest effects for total body, throwing arm, and momentum compensation ratios. Since the trunk is the main contributor to linear and angular momentum, longer strides appear to better regulate transverse trunk momentum in double support, whereas shorter strides show increased momentum prior to throwing arm acceleration.
Spin and orbital angular momentum and their conversion in cylindrical vector vortices.
Zhu, Jiangbo; Chen, Yujie; Zhang, Yanfeng; Cai, Xinlun; Yu, Siyuan
2014-08-01
The generation of light beams carrying orbital angular momentum (OAM) has been greatly advanced with the emergence of the recently reported integrated optical vortex emitters. Generally, optical vortices emitted by these devices possess cylindrically symmetric states of polarization and spiral phase fronts, and they can be defined as cylindrical vector vortices (CVVs). Using the radiation of angularly arranged dipoles to model the CVVs, these beams as hybrid modes of two circularly polarized scalar vortices are theoretically demonstrated to own well-defined total angular momentum. Moreover, the effect of spin-orbit interactions of angular momentum is identified in the CVVs when the size of the emitting structure varies. This effect results in the diminishing spin component of angular momentum and purer OAM states at large structure radii.
Angular Momentum Regulates Atomic Gas Fractions of Galactic Disks
Obreschkow, D.; Glazebrook, K.; Kilborn, V.; Lutz, K.
2016-06-01
We show that the mass fraction {f}{{atm}}=1.35{M}{{H}{{I}}}/M of neutral atomic gas (H i and He) in isolated local disk galaxies of baryonic mass M is well described by a straightforward stability model for flat exponential disks. In the outer disk parts, where gas at the characteristic dispersion of the warm neutral medium is stable in the sense of Toomre, the disk consists of neutral atomic gas; conversely, the inner part where this medium would be Toomre-unstable, is dominated by stars and molecules. Within this model, {f}{{atm}} only depends on a global stability parameter q\\equiv jσ /({GM}), where j is the baryonic specific angular momentum of the disk and σ the velocity dispersion of the atomic gas. The analytically derived first-order solution {f}{{atm}}={min}\\{1,2.5{q}1.12\\} provides a good fit to all plausible rotation curves. This model, with no free parameters, agrees remarkably well (±0.2 dex) with measurements of {f}{{atm}} in isolated local disk galaxies, even with galaxies that are extremely H i-rich or H i-poor for their mass. The finding that {f}{{atm}} increasing monotonically with q for pure stability reasons offers a powerful intuitive explanation for the mean variation of {f}{{atm}} with M: in a cold dark matter universe, galaxies are expected to follow j\\propto {M}2/3, which implies the average scaling q\\propto {M}-1/3 and hence {f}{{atm}}\\propto {M}-0.37, in agreement with the observations.
Mediolateral angular momentum changes in persons with amputation during perturbed walking.
Sheehan, Riley C; Beltran, Eduardo J; Dingwell, Jonathan B; Wilken, Jason M
2015-03-01
Over 50% of individuals with lower limb amputation fall at least once each year. These individuals also exhibit reduced ability to effectively respond to challenges to frontal plane stability. The range of whole body angular momentum has been correlated with stability and fall risk. This study determined how lateral walking surface perturbations affected the regulation of whole body and individual leg angular momentum in able-bodied controls and individuals with unilateral transtibial amputation. Participants walked at fixed speed in a Computer Assisted Rehabilitation Environment with no perturbations and continuous, pseudo-random, mediolateral platform oscillations. Both the ranges and variability of angular momentum for both the whole body and both legs were significantly greater (pangular momentum range or variability during unperturbed walking. The range of frontal plane angular momentum was significantly greater for those with amputation than for controls for all segments (pangular momentum ranges were greater for patients with amputation. However, for the prosthetic leg, angular momentum ranges were less for patients than controls. Patients with amputation were significantly more affected by the perturbations. Though patients with amputation were able to maintain similar patterns of whole body angular momentum during unperturbed walking, they were more highly destabilized by the walking surface perturbations. Individuals with transtibial amputation appear to predominantly use altered motion of the intact limb to maintain mediolateral stability.
Simple method for evaluating Goldstone diagrams in an angular momentum coupled representation
Energy Technology Data Exchange (ETDEWEB)
Kuo, T.T.S.; Shurpin, J.; Tam, K.C.; Osnes, E.; Ellis, P.J.
1981-04-01
A simple and convenient method is derived for evaluating linked Goldstone diagrams in an angular momentum coupled representation. Our method is general, and can be used to evaluate any effective interaction and/or effective operator diagrams for both closed-shell nuclei (vacuum to vacuum linked diagrams) and open-shell nuclei (valence linked diagrams). The techniques of decomposing diagrams into ladder diagrams, cutting open internal lines and cutting off one-body insertions are introduced. These enable us to determine angular momentum factors associated with diagrams in the coupled representation directly, without the need for carrying out complicated angular momentum algebra. A summary of diagram rules is given.
Tidal contribution of planets to removing angular momentum from the Sun
International Nuclear Information System (INIS)
The angle between the solar equatorial plane and the Laplace invariable plane of the Solar System was computed (5.84deg). This phenomenon is to be considered not accidental. The well known idea arises about a fast-spinning early Sun, the angular momentum of which was mostly shared by the surrounding close disc which gave rise to the planets. The tidal removal of the angular momentum from the Sun by Jupiter, Venus and Mercury was estimated. It is concluded that the explanation of the present small angular momentum of the Sun would require the planetary orbits to have been much closer to the Sun during their past evolution. (author)
Olabarrieta, I.; Ventrella, J.; Choptuik, M.; Unruh, W.
2007-01-01
We study the critical collapse of a massless scalar field with angular momentum in spherical symmetry. In order to mimic the effects of angular momentum we perform a sum of the stress-energy tensors for all the scalar fields with the same eigenvalue, l, of the angular momentum operator and calculate the equations of motion for the radial part of these scalar fields. We have found that the critical solutions for different values of l are discretely self-similar (as in the original l=0 case). T...
Angular Momentum-Phase Coherent State for an Electron in Uniform Magnetic Field
Institute of Scientific and Technical Information of China (English)
FAN Hong-Yi; FAN Yue
2001-01-01
Based on the newly constructed state ｜l, r》 [Fan et al., Chin. Phys. Lett. 16(1999)706], where l is the angular momentum quantum number and r denotes the electron's orbit radius in a uniform magnetic field, we propose a new angular momentum-phase coherent state by introducing a new operator A. A and A+ are annihilation and creation operators in the ｜l, r》 space, respectively. The coherent state is A's eigenket and possesses non-orthonormal and overcomplete properties. It is constructed on the certain superposition of zero-angular momentum states along the radius direction.
Angular Momentum of Twisted Radiation from an Electron in Spiral Motion
Katoh, M; Kawaguchi, H; Tsuchiya, K; Ohmi, K; Kaneyasu, T; Taira, Y; Hosaka, M; Mochihashi, A; Takashima, Y
2016-01-01
We theoretically demonstrate for the first time that a single free electron in circular/spiral motion emits twisted photons carrying well defined orbital angular momentum along the axis of the electron circulation, in adding to spin angular momentum. We show that, when the electron velocity is relativistic, the radiation field contains harmonic components and the photons of l-th harmonic carry lhbar total angular momentum for each. This work indicates that twisted photons are naturally emitted by free electrons and more ubiquitous in laboratories and in nature than ever been thought.
Orbital Angular Momentum in Noncollinear Second Harmonic Generation by off-axis vortex beams
Bovino, Fabio Antonio; Giardina, Maurizio; Sibilia, Concita
2011-01-01
We experimentally study the behavior of orbital angular momentum (OAM) of light in a noncollinear second harmonic generation (SHG) process. The experiment is performed by using a type I BBO crystal under phase matching conditions with femtosecond pumping fields at 830 nm. Two specular off-axis vortex beams carrying fractional orbital angular momentum at the fundamental frequency (FF) are used. We analyze the behavior of the OAM of the SH signal when the optical vortex of each input field at the FF is displaced from the beam's axis. We obtain different spatial configurations of the SH field, always carrying the same zero angular momentum.
Orbital angular momentum control by a multihelicoidal fibre with a twist defect
International Nuclear Information System (INIS)
We have theoretically demonstrated that by creating a controllable twist defect in an l-helicoidal fibre one can control the orbital angular momentum of the generated beam at a constant power. We have studied the passage of the Gaussian beam through such a defect fibre and shown that by varying the twist defect angle one can change the total orbital angular momentum of the generated optical field from 0 to l (in dimensionless units). We have also studied the distribution of the angular momentum density in the cross-section of the generated optical field. (paper)
Orbital angular momentum of a high-order Bessel light beam
Energy Technology Data Exchange (ETDEWEB)
Volke-Sepulveda, K [Instituto Nacional de Astrofisica, Optica y Electronica, Apdo. Postal 51/216, Puebla, Pue., Mexico 72000 (Mexico); Garces-Chavez, V [School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, Scotland (United Kingdom); Chavez-Cerda, S [Instituto Nacional de Astrofisica, Optica y Electronica, Apdo. Postal 51/216, Puebla, Pue., Mexico 72000 (Mexico); Arlt, J [School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, Scotland (United Kingdom); Dholakia, K [School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, Scotland (United Kingdom)
2002-04-01
The orbital angular momentum density of Bessel beams is calculated explicitly within a rigorous vectorial treatment. This allows us to investigate some aspects that have not been analysed previously, such as the angular momentum content of azimuthally and radially polarized beams. Furthermore, we demonstrate experimentally the mechanical transfer of orbital angular momentum to trapped particles in optical tweezers using a high-order Bessel beam. We set transparent particles of known dimensions into rotation, where the sense of rotation can be reversed by changing the sign of the singularity. Quantitative results are obtained for rotation rates. This paper's animations are available from the Multimedia Enhancements page.
Unique role of orbital angular momentum in subshell-resolved photoionization of C{sub 60}
Energy Technology Data Exchange (ETDEWEB)
McCune, Matthew A; Chakraborty, Himadri S [Department of Chemistry and Physics, Northwest Missouri State University, Maryville, MO 64468 (United States); Madjet, Mohamed E [Institute of Chemistry and Biochemistry, Free University, Fabeckstrasse 36a, D-14195 Berlin (Germany)], E-mail: himadri@nwmissouri.edu
2008-10-28
We predict that the oscillations in the subshell photoionization of C{sub 60} evolve with the orbital angular momentum of the bound electrons such that the structures of the highest and the lowest angular momentum subshell cross sections differ dramatically. The effect results from a decrease in the photoelectron production at the molecular inner edge due to the angular momentum generated repulsion on the electron. Fourier analysis of the cross sections at energies below the carbon K-shell continuum indicates that the effect can be observed by photoelectron spectroscopy. The phenomenon should be generic in the photoionization of nanoparticles containing delocalized electrons. (fast track communication)
Separation of spin angular momentum in space-variant linearly polarized beam
Chen, Hao; Yu, Zhongliang; Hao, Jingjing; Chen, Zhaozhong; Xu, Ji; Ding, Jianping; Wang, Hui-Tian
2014-03-01
We show that the spin angular momentum (SAM) flux in a space-variant linearly polarized beam can be separated in the focal plane. Such a beam carries only orbital angular momentum (OAM) and develops a net SAM flux upon focusing. The radial splitting of the SAM flux density is mediated by the phase vortex (or OAM) and can be controlled by the topological charge of the phase vortex. Optical trapping experiments verify the separation of the SAM flux density. The proposed approach enriches the manipulation of the angular momentum of light fields and inspires more designs of focus engineering, which would benefit optical micromanipulation of microscopic particles.
CONSTRAINING THE ANGULAR MOMENTUM EVOLUTION OF V455 ANDROMEDAE
Energy Technology Data Exchange (ETDEWEB)
Mukadam, Anjum S.; Szkody, Paula [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Pyrzas, Stylianos [Qatar Environment and Energy Research Institute (QEERI), HBKU, Qatar Foundation, P.O. Box 5825, Doha (Qatar); Townsley, D. M. [Department of Physics and Astronomy, The University of Alabama, Tuscaloosa, AL 35487 (United States); Gänsicke, B. T. [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Hermes, J. J. [Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599-3255 (United States); Kemp, Jonathan [Department of Physics, Middlebury College, Middlebury, VT 05753 (United States); Patterson, J.; Ding, Claire; Wolf, Katie; Gemma, Marina; Karamehmetoglu, Emir [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Rock, John [CBA-Wilts, 2 Spa Close, Highworth, Swindon, Wilts SN6 7PJ (United Kingdom)
2016-04-10
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 dP{sub SH}/dt ≤ −7.5 × 10{sup −15} s s{sup −1} employing the O–C method, and −5.4 × 10{sup −15} s s{sup −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 dP{sub spin}/dt ≤ −10.8 × 10{sup −15} s s{sup −1} or −0.34 μs yr{sup −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)
Interannual signals in length of day and atmospheric angular momentum
Directory of Open Access Journals (Sweden)
R. Abarco del Rio
Full Text Available Atmospheric angular momentum (AAM and length of day (LOD series are investigated for their characteristics on interannual time scales during the half-century period 1949 to 1998. During this epoch, the interannual variability in LOD can be separated naturally into three bands: a quasi-biennial, a triennial-quadrennial and one at six-seven years. The atmosphere appears to excite the first two bands, while it does not contribute to the last. Considering the quasi-biennial (QB band alone, the atmosphere appears to excite most of its signal in LOD, but it arises from separate fluctuations with stratospheric and tropospheric origin. Thus, although close in frequency, stratospheric and tropospheric processes differ in their amplitude and phase variability. The time shift can be noted especially during the strong El Niño events of 1982-83 and 1997-98 when both processes have positive phase and thus combine to help produce particularly strong peak in AAM and LOD. In addition, we have reconfirmed the downward propagation in the stratosphere and upward propagation in the troposphere of AAM observed in earlier studies for other variables. In the triennial-quadrennial (TQ band, time-variable spectral analyses reveal that LOD and AAM contain strong variability, with periods shorter than four years before 1975 and longer thereafter. This signal originates mainly within the troposphere and propagates upwards from the lower to the higher layers of the troposphere. According to a zonal analysis, an equatorial poleward mode, strongly linked to the SOI, explains more than 60% of the total variability at these ranges. In addition, this study also indicates that an equatorward mode, originating within polar latitudes, explains, on average, more than 15% of the triennial-quadrennial oscillation (TQO variability in AAM, and up to 30% at certain epochs. Finally, a six year period in LOD noted in earlier studies, as well as in lengthier series covering much of the
Davis, D. R.; Greenberg, R.; Hebert, F.
1985-01-01
Models of lunar origin in which the Moon accretes in orbit about the Earth from material approaching the Earth from heliocentric orbits must overcome a fundamental problem: the approach orbits of such material would be, in the simplest approximation, equally likely to be prograde or retrograde about the Earth, with the result that accretion of such material adds mass but not angular momentum to circumterrestrial satellites. Satellite orbits would then decay due to the resulting drag, ultimately impacting onto the Earth. One possibility for adding both material and angular momentum to Earth orbit is investigated: imbalance in the delivered angular momentum between pro and retrograde Earth passing orbits which arises from the three body dynamics of planetesimals approaching the Earth from heliocentric space. In order to study angular momentum delivery to circumterrestrial satellites, the near Earth velocities were numerically computed as a function of distance from the Earth for a large array of orbits systematically spanning heliocentric phase space.
Circumbinary disk, an efficient medium extracting orbital angular momentum in close binaries
Institute of Scientific and Technical Information of China (English)
CHEN WenCong; ZENG QingGuo
2009-01-01
The loss of orbital angular momentum plays an important role in the mass transfer and orbital evolution of close binaries. The traditional mechanisms of orbital angular momentum loss consist of gravitational wave radiation, mass loss and magnetic braking. However, a small fraction of the mass outflow may form a thin circumbinary disk (CB disk) located in the orbital plane of the binary during mass exchange. The tide torques caused by the gravitational interaction between a CB disk and a binary system brake binary effectively, and extract the orbital angular momentum from the binary system. In this study, numerical calculations for the evolution of the white dwarf binary show that a CB disk is an efficient medium extracting orbital angular momentum even if the mass loss is very small. Finally, some theo-retical research and observational progress on CB disks are presented.
Strain, Michael J; Cai, Xinlun; Wang, Jianwei; Zhu, Jiangbo; Phillips, David B; Chen, Lifeng; Lopez-Garcia, Martin; O'Brien, Jeremy L; Thompson, Mark G; Sorel, Marc; Yu, Siyuan
2014-09-17
The ability to rapidly switch between orbital angular momentum modes of light has important implications for future classical and quantum systems. In general, orbital angular momentum beams are generated using free-space bulk optical components where the fastest reconfiguration of such systems is around a millisecond using spatial light modulators. In this work, an extremely compact optical vortex emitter is demonstrated with the ability to actively tune between different orbital angular momentum modes. The emitter is tuned using a single electrically contacted thermo-optical control, maintaining device simplicity and micron scale footprint. On-off keying and orbital angular momentum mode switching are achieved at rates of 10 μs and 20 μs respectively.
Energy dissipation and angular momentum transfer within a magnetically torqued accretion disc
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
We discuss transportation and redistribution of energy and angular momentum in the magnetic connection(MC) process and Blandford-Payne(BP) process.MC results in readjusting the interior viscous torque,and its effects are operative not only in but also beyond the MC region.The BP process is invoked to transfer the "excessive" angular momentum from an accretion disc.In addition,we derive a criterion for the interior viscous torque to resolve the puzzle of the overall equilibrium of angular momentum in disc accretion.It turns out that the efficiency of BP at extracting angular momentum and the intensity of the outflow are required to be greater than some critical values.
Stevens, Adam R H; Mutch, Simon J
2016-01-01
We present the new semi-analytic model of galaxy evolution, DARK SAGE, a heavily modified version of the publicly available SAGE code. The model is designed for detailed evolution of galactic discs. We evolve discs in a series of annuli with fixed specific angular momentum, which allows us to make predictions for the radial and angular-momentum structure of galaxies. Most physical processes, including all channels of star formation and associated feedback, are performed in these annuli. We present the surface density profiles of our model spiral galaxies, both as a function of radius and specific angular momentum, and find the discs naturally build a pseduobulge-like component. Our main results are focussed on predictions relating to the integrated mass--specific angular momentum relation of stellar discs. The model produces a distinct sequence between these properties in remarkable agreement with recent observational literature. We investigate the impact Toomre disc instabilities have on shaping this sequenc...
Precisely measuring the orbital angular momentum of beams via weak measurement
Qiu, Jiangdong; Ren, Changliang; Zhang, Zhiyou
2016-06-01
We proposed and analyzed a scheme of precisely measuring orbital angular momentum (OAM) of the vortex beams with the help of weak measurement process. The orbital angular momentum information l of the unknown OAM state can be obtained by its spatial displacements. The valid condition of precisely measuring orbital angular momentum was completely discussed. Interestingly, it is shown that the measurement by using the two-dimensional spatial displacements jointly is very useful for precisely measuring the OAM state with a large orbital angular momentum l . The signal-to-noise ratio of the measurement can be enhanced by increasing the weak-coupling γ linearly as the valid condition is still satisfied. For fixed γ , the maximal signal-to-noise ratio for each weak value increases with the decrease of the weak value.
Large Quantum imaging of nonlocal spatial correlations induced by orbital angular momentum
Altman, A; Corndorf, E; Kumar, P; Barbosa, G A; Altman, Adam R.; K\\"{o}pr\\"{u}l\\"{u}, Kahraman G.; Corndorf, Eric; Kumar, Prem; Barbosa, Geraldo A.
2004-01-01
Through scanned coincidence counting, we probe the quantum image produced by parametric down conversion with a pump beam carrying orbital angular momentum. Nonlocal spatial correlations are manifested through splitting of the coincidence spot into two.
Angular momentum transport efficiency in post-main sequence low-mass stars
Spada, F; Arlt, R; Deheuvels, S
2016-01-01
Context. Using asteroseismic techniques, it has recently become possible to probe the internal rotation profile of low-mass (~1.1-1.5 Msun) subgiant and red giant stars. Under the assumption of local angular momentum conservation, the core contraction and envelope expansion occurring at the end of the main sequence would result in a much larger internal differential rotation than observed. This suggests that angular momentum redistribution must be taking place in the interior of these stars. Aims. We investigate the physical nature of the angular momentum redistribution mechanisms operating in stellar interiors by constraining the efficiency of post-main sequence rotational coupling. Methods. We model the rotational evolution of a 1.25 Msun star using the Yale Rotational stellar Evolution Code. Our models take into account the magnetic wind braking occurring at the surface of the star and the angular momentum transport in the interior, with an efficiency dependent on the degree of internal differential rotati...
Resolving flows around black holes: the impact of gas angular momentum
Curtis, Michael; Sijacki, Debora
2016-01-01
Cosmological simulations almost invariably estimate the accretion of gas onto supermassive black holes using a Bondi-Hoyle-like prescription. Doing so ignores the effects of the angular momentum of the gas, which may prevent or significantly delay accreting material falling directly onto the black hole. We outline a black hole accretion rate prescription using a modified Bondi-Hoyle formulation that takes into account the angular momentum of the surrounding gas. Meaningful implementation of t...
Subwave spikes of the orbital angular momentum of the vortex-beams in a uniaxial crystal
Fadeyeva, T; Rubass, A; Zinov'ev, A; Konovalenko, V; Volyar, A
2011-01-01
We have theoretically predicted the gigantic spikes of the orbital angular momentum caused by the conversion processes of the centered optical vortex in the circularly polarized components of the elliptic vortex beam propagating perpendicular to the crystal optical axis. We have experimentally observed the conversion process inside the subwave deviations of the crystal length. We have found that the total orbital angular momentum of the wave beam is conserved.
Whole-body angular momentum during stair walking using passive and powered lower-limb prostheses.
Pickle, Nathaniel T; Wilken, Jason M; Aldridge, Jennifer M; Neptune, Richard R; Silverman, Anne K
2014-10-17
Individuals with a unilateral transtibial amputation have a greater risk of falling compared to able-bodied individuals, and falling on stairs can lead to serious injuries. Individuals with transtibial amputations have lost ankle plantarflexor muscle function, which is critical for regulating whole-body angular momentum to maintain dynamic balance. Recently, powered prostheses have been designed to provide active ankle power generation with the goal of restoring biological ankle function. However, the effects of using a powered prosthesis on the regulation of whole-body angular momentum are unknown. The purpose of this study was to use angular momentum to evaluate dynamic balance in individuals with a transtibial amputation using powered and passive prostheses relative to able-bodied individuals during stair ascent and descent. Ground reaction forces, external moment arms, and joint powers were also investigated to interpret the angular momentum results. A key result was that individuals with an amputation had a larger range of sagittal-plane angular momentum during prosthetic limb stance compared to able-bodied individuals during stair ascent. There were no significant differences in the frontal, transverse, or sagittal-plane ranges of angular momentum or maximum magnitude of the angular momentum vector between the passive and powered prostheses during stair ascent or descent. These results indicate that individuals with an amputation have altered angular momentum trajectories during stair walking compared to able-bodied individuals, which may contribute to an increased fall risk. The results also suggest that a powered prosthesis provides no distinct advantage over a passive prosthesis in maintaining dynamic balance during stair walking.
Song, Xinbing; Sun, Yifan; Li, Pengyun; Qin, Hongwei; Zhang, Xiangdong
2015-09-15
We perform Bell's measurement for the non-separable correlation between polarization and orbital angular momentum from the same classical vortex beam. The violation of Bell's inequality for such a non-separable classical correlation has been demonstrated experimentally. Based on the classical vortex beam and non-quantum entanglement between the polarization and the orbital angular momentum, the Hadamard gates and conditional phase gates have been designed. Furthermore, a quantum Fourier transform has been implemented experimentally.
Fractional angular momentum in noncommutative generalized Chern-Simons quantum mechanics
Zhang, Xi-Lun; Sun, Yong-Li; Wang, Qing; Long, Zheng-Wen; Jing, Jian
2016-07-01
The noncommutative generalized Chern-Simons quantum mechanics, i.e., the Chern-Simons quantum mechanics on the noncommutative plane in the presence of Aharonov-Bohm magnetic vector potentials, is studied in this paper. We focus our attention on the canonical orbital angular momentum and show that there are two different approaches to produce the fractional angular momentum in the noncommutative generalized Chern-Simons quantum mechanics.
On matrix elements of phase-angular momentum commutator in Hilbert space of arbitrary dimensions
Johal, Ramandeep S.
2002-01-01
We discuss correspondence between the predictions of quantum theories for rotation angle formulated in infinite and finite dimensional Hilbert spaces, taking as example, the calculation of matrix elements of phase-angular momentum commutator. A new derivation of the matrix elements is presented in infinite space, making use of a unitary transformation that maps from the state space of periodic functions to non-periodic functions, over which the spectrum of angular momentum operator is in gene...
Observation of Interaction of Spin and Intrinsic Orbital Angular Momentum of Light
Vitullo, Dashiell L P; Gregg, Patrick; Smith, Roger A; Reddy, Dileep V; Ramachandran, Siddharth; Raymer, Michael G
2016-01-01
Spin and intrinsic orbital angular momentum interaction of light is observed, as evidenced by length-dependent rotations of both spatial patterns and optical polarization in an isotropic optical fiber. The distinction between intrinsic and extrinsic orbital angular momentum (as seen in helically coiled fiber) is made clear by controllable excitation of a small number of optical modes in a straight, few-mode fiber.
Orbital Angular Momentum in Noncollinear Second Harmonic Generation by off-axis vortex beams
Bovino, Fabio Antonio; Braccini, Matteo; Giardina, Maurizio; Sibilia, Concita
2011-01-01
We experimentally study the behavior of orbital angular momentum (OAM) of light in a noncollinear second harmonic generation (SHG) process. The experiment is performed by using a type I BBO crystal under phase matching conditions with femtosecond pumping fields at 830 nm. Two specular off-axis vortex beams carrying fractional orbital angular momentum at the fundamental frequency (FF) are used. We analyze the behavior of the OAM of the SH signal when the optical vortex of each input field at t...
Balint-Kurti, Gabriel G; Vasyutinskii, Oleg S
2009-12-31
A general reactive collision of the type A + B --> C + D is considered where both the collision partners (A and B) or the products (C and D) may possess internal, i.e., spin, orbital or rotational, angular momenta. Compact expressions are derived using a rigorous quantum mechanical analysis for the angular momentum anisotropy of either of the products (C or D) arising from an initially polarized distribution of the reactant angular momentum. The angular momentum distribution of the product is expressed in terms of canonical spherical tensors multiplied by anisotropy-transforming coefficients c(K(i)q(k))(K)(K(r),L). These coefficients act as transformation coefficients between the angular momentum anisotropy of the reactants and that of the product. They are independent of scattering angle but depend on the details of the scattering dynamics. The relationship between the coefficients c(K(i)q(k))(K)(K(r),L) and the body-fixed scattering S matrix is given and the methodology for the quantum mechanical calculation of the anisotropy-transforming coefficients is clearly laid out. The anisotropy-transforming coefficients are amenable to direct experimental measurement in a similar manner to vector correlation and alignment parameters in photodissociation processes. A key aspect of the theory is the use of projections of both reactant and product angular momenta onto the product recoil vector direction. An important new conservation rule is revealed through the analysis, namely that if the state multipole for reactant angular momentum distribution has a projection q(k) onto the product recoil vector the state multipoles for the product angular momentum distribution all have this same projection. Expressions are also presented for the distribution of the product angular momentum when its components are evaluated relative to the space-fixed Z-axis. Notes with detailed derivations of all the formulas are available as Supporting Information. PMID:19642631
Balint-Kurti, Gabriel G; Vasyutinskii, Oleg S
2009-12-31
A general reactive collision of the type A + B --> C + D is considered where both the collision partners (A and B) or the products (C and D) may possess internal, i.e., spin, orbital or rotational, angular momenta. Compact expressions are derived using a rigorous quantum mechanical analysis for the angular momentum anisotropy of either of the products (C or D) arising from an initially polarized distribution of the reactant angular momentum. The angular momentum distribution of the product is expressed in terms of canonical spherical tensors multiplied by anisotropy-transforming coefficients c(K(i)q(k))(K)(K(r),L). These coefficients act as transformation coefficients between the angular momentum anisotropy of the reactants and that of the product. They are independent of scattering angle but depend on the details of the scattering dynamics. The relationship between the coefficients c(K(i)q(k))(K)(K(r),L) and the body-fixed scattering S matrix is given and the methodology for the quantum mechanical calculation of the anisotropy-transforming coefficients is clearly laid out. The anisotropy-transforming coefficients are amenable to direct experimental measurement in a similar manner to vector correlation and alignment parameters in photodissociation processes. A key aspect of the theory is the use of projections of both reactant and product angular momenta onto the product recoil vector direction. An important new conservation rule is revealed through the analysis, namely that if the state multipole for reactant angular momentum distribution has a projection q(k) onto the product recoil vector the state multipoles for the product angular momentum distribution all have this same projection. Expressions are also presented for the distribution of the product angular momentum when its components are evaluated relative to the space-fixed Z-axis. Notes with detailed derivations of all the formulas are available as Supporting Information.
Stevens, Adam R. H.; Croton, Darren J.; Mutch, Simon J.
2016-09-01
We present the new semi-analytic model of galaxy evolution, DARK SAGE, a heavily modified version of the publicly available SAGE code. The model is designed for detailed evolution of galactic discs. We evolve discs in a series of annuli with fixed specific angular momentum, which allows us to make predictions for the radial and angular-momentum structure of galaxies. Most physical processes, including all channels of star formation and associated feedback, are performed in these annuli. We present the surface density profiles of our model spiral galaxies, both as a function of radius and specific angular momentum, and find that the discs naturally build a pseudo-bulge-like component. Our main results are focused on predictions relating to the integrated mass-specific angular momentum relation of stellar discs. The model produces a distinct sequence between these properties in remarkable agreement with recent observational literature. We investigate the impact Toomre disc instabilities have on shaping this sequence and find they are crucial for regulating both the mass and spin of discs. Without instabilities, high-mass discs would be systematically deficient in specific angular momentum by a factor of ˜2.5, with increased scatter. Instabilities also appear to drive the direction in which the mass-spin sequence of spiral galaxy discs evolves. With them, we find galaxies of fixed mass have higher specific angular momentum at later epochs.
Martin, Caroline; Kulpa, Richard; Delamarche, Paul; Bideau, Benoit
2013-03-01
The purpose of the study was to identify the relationships between segmental angular momentum and ball velocity between the following events: ball toss, maximal elbow flexion (MEF), racket lowest point (RLP), maximal shoulder external rotation (MER), and ball impact (BI). Ten tennis players performed serves recorded with a real-time motion capture. Mean angular momentums of the trunk, upper arm, forearm, and the hand-racket were calculated. The anteroposterior axis angular momentum of the trunk was significantly related with ball velocity during the MEF-RLP, RLP-MER, and MER-BI phases. The strongest relationships between the transverse-axis angular momentums and ball velocity followed a proximal-to-distal timing sequence that allows the transfer of angular momentum from the trunk (MEF-RLP and RLP-MER phases) to the upper arm (RLP-MER phase), forearm (RLP-MER and MER-BI phases), and the hand-racket (MER-BI phase). Since sequence is crucial for ball velocity, players should increase angular momentums of the trunk during MEF-MER, upper arm during RLP-MER, forearm during RLP-BI, and the hand-racket during MER-BI. PMID:23724603
He, Li; Li, Huan; Li, Mo
2016-09-01
Photons carry linear momentum and spin angular momentum when circularly or elliptically polarized. During light-matter interaction, transfer of linear momentum leads to optical forces, whereas transfer of angular momentum induces optical torque. Optical forces including radiation pressure and gradient forces have long been used in optical tweezers and laser cooling. In nanophotonic devices, optical forces can be significantly enhanced, leading to unprecedented optomechanical effects in both classical and quantum regimes. In contrast, to date, the angular momentum of light and the optical torque effect have only been used in optical tweezers but remain unexplored in integrated photonics. We demonstrate the measurement of the spin angular momentum of photons propagating in a birefringent waveguide and the use of optical torque to actuate rotational motion of an optomechanical device. We show that the sign and magnitude of the optical torque are determined by the photon polarization states that are synthesized on the chip. Our study reveals the mechanical effect of photon's polarization degree of freedom and demonstrates its control in integrated photonic devices. Exploiting optical torque and optomechanical interaction with photon angular momentum can lead to torsional cavity optomechanics and optomechanical photon spin-orbit coupling, as well as applications such as optomechanical gyroscopes and torsional magnetometry.
He, Li; Li, Huan; Li, Mo
2016-01-01
Photons carry linear momentum and spin angular momentum when circularly or elliptically polarized. During light-matter interaction, transfer of linear momentum leads to optical forces, whereas transfer of angular momentum induces optical torque. Optical forces including radiation pressure and gradient forces have long been used in optical tweezers and laser cooling. In nanophotonic devices, optical forces can be significantly enhanced, leading to unprecedented optomechanical effects in both classical and quantum regimes. In contrast, to date, the angular momentum of light and the optical torque effect have only been used in optical tweezers but remain unexplored in integrated photonics. We demonstrate the measurement of the spin angular momentum of photons propagating in a birefringent waveguide and the use of optical torque to actuate rotational motion of an optomechanical device. We show that the sign and magnitude of the optical torque are determined by the photon polarization states that are synthesized on the chip. Our study reveals the mechanical effect of photon’s polarization degree of freedom and demonstrates its control in integrated photonic devices. Exploiting optical torque and optomechanical interaction with photon angular momentum can lead to torsional cavity optomechanics and optomechanical photon spin-orbit coupling, as well as applications such as optomechanical gyroscopes and torsional magnetometry. PMID:27626072
He, Li; Li, Huan; Li, Mo
2016-09-01
Photons carry linear momentum and spin angular momentum when circularly or elliptically polarized. During light-matter interaction, transfer of linear momentum leads to optical forces, whereas transfer of angular momentum induces optical torque. Optical forces including radiation pressure and gradient forces have long been used in optical tweezers and laser cooling. In nanophotonic devices, optical forces can be significantly enhanced, leading to unprecedented optomechanical effects in both classical and quantum regimes. In contrast, to date, the angular momentum of light and the optical torque effect have only been used in optical tweezers but remain unexplored in integrated photonics. We demonstrate the measurement of the spin angular momentum of photons propagating in a birefringent waveguide and the use of optical torque to actuate rotational motion of an optomechanical device. We show that the sign and magnitude of the optical torque are determined by the photon polarization states that are synthesized on the chip. Our study reveals the mechanical effect of photon's polarization degree of freedom and demonstrates its control in integrated photonic devices. Exploiting optical torque and optomechanical interaction with photon angular momentum can lead to torsional cavity optomechanics and optomechanical photon spin-orbit coupling, as well as applications such as optomechanical gyroscopes and torsional magnetometry. PMID:27626072
Angular momentum analysis of rotational transfer of superthermal relative velocity distributions
Energy Technology Data Exchange (ETDEWEB)
Whiteley, T.W.J.; McCaffery, A.J. [Sussex Univ., Brighton (United Kingdom). School of Molecular Sciences
1996-12-02
An angular momentum (AM) theory is developed to calculate the relative populations of final rotational states after collision between a diatomic molecule and an atom having a narrow, superthermal velocity distribution as produced by, e.g. photolysis of a precursor species. Probability densities are derived from semiclassical expressions for energy and angular momentum assuming the classically impulsive limit with the repulsive wall modelled by a hard ellipsoid. The treatment given is general and therefore applies to molecules in which the centre-of-mass does not coincide with the centre of the potential coordinates. A transfer function for RT is derived and applied to the H + CO system. Analysis of the data allows the anisotropy to be extracted which is in good agreement with an ab initio potential surface. The method described allows one to rapidly assess the contributions from the elliptical core of the potential and from other features of the potential, and would permit more sophisticated representations of the topology to be incorporated. (Author).
A new method for verifying the law of conservation of angular momentum
International Nuclear Information System (INIS)
A new method has been proposed for verifying the law of conservation of angular momentum by measuring the linear velocity, which is in contrast to the conventional method in which the angular velocity is measured. Using the proposed method, systematic and random errors can be greatly reduced. It has been found that the relative experimental error can be reduced to 1.4%. (paper)
Demonstrating the Conservation of Angular Momentum Using Model Cars Moving along a Rotating Rod
Abdul-Razzaq, Wathiq; Golubovic, Leonardo
2013-01-01
We have developed an exciting non-traditional experiment for our introductory physics laboratories to help students to understand the principle of conservation of angular momentum. We used electric toy cars moving along a long rotating rod. As the cars move towards the centre of the rod, the angular velocity of this system increases.…
Quark orbital angular momentum: can we learn about it from GPDs and TMDs?
Energy Technology Data Exchange (ETDEWEB)
H.Avakian, A.V.Efremov, P.Schweitzer, O.V.Teryaev, P.Zavada
2011-05-01
It is known how to access information on quark orbital angular momentum from generalized parton distribution functions, in a certain specified framework. It is intuitively expected, that such information can be accessed also through transverse momentum dependent distribution functions, but not known how. Now quark models provide promising hints. Recent results are reviewed.
Quark orbital angular momentum: can we learn about it from GPDs and TMDs?
Avakian, H; Schweitzer, P; Teryaev, O V; Zavada, P
2010-01-01
It is known how to access information on quark orbital angular momentum from generalized parton distribution functions, in a certain specified framework. It is intuitively expected, that such information can be accessed also through transverse momentum dependent distribution functions, but not known how. Now quark models provide promising hints. Recent results are reviewed.
Excited Landau levels, orbital angular momentum and axial anomaly
International Nuclear Information System (INIS)
The IR cutoff via the exclusion of the high orbital momentum components for the excited Landau levels leads to the physical interpretation of the cancellation between the explicity and anomalous chiral symmetry breaking. 21 refs
Microscopic analysis of angular momentum projected HFB-states in terms of interacting bosons
International Nuclear Information System (INIS)
Angular momentum- and number-projected Hartree-Fock-Bogoliubov (HFB) wavefunctions for transitional and deformed Rare Earth nuclei are analyzed in terms of Fermion pairs coupled to angular momenta L = 0(S), 2(D), 4(G), ... The Fermion space is truncated to contain only S-D or S-D-G pairs. The variation is carried out before and after angular momentum projection and with different truncations. The influence of the truncation on physical quantities such as moments of inertia, quadrupole moments or pair transfer matrix elements is discussed. 21 references
Gauge-Invariant Spin and Orbital Angular Momentum of Laguerre-Gaussian Laser
Institute of Scientific and Technical Information of China (English)
LIANG Wen-Feng; WU Ming; LIU Hui; CHEN Xiang-Song
2008-01-01
@@ We adopt a gauge-invariant definition to calculate the spin and orbital angular momenta of a so-called Ith order Laguerre-Gaussian laser.The results reveal that photons on the axis of the beam may carry an orbital angular momentum of (l - 1)h besides lh per photon.For the spin, we obtain a more reasonable expression proportional to the beam intensity instead of the gradient of the intensity as previously derived.We also discuss how to experimentally discriminate the angular momentum expressions given here and those commonly accepted in the literature.
Yang, W M
2008-01-01
The purpose of this work was to obtain diffusion coefficient for the magnetic angular momentum transport and material transport in a rotating solar model. We assumed that the transport of both angular momentum and chemical elements caused by magnetic fields could be treated as a diffusion process. The diffusion coefficient depends on the stellar radius, angular velocity, and the configuration of magnetic fields. By using of this coefficient, it is found that our model becomes more consistent with the helioseismic results of total angular momentum, angular momentum density, and the rotation rate in a radiative region than the one without magnetic fields. Not only can the magnetic fields redistribute angular momentum efficiently, but they can also strengthen the coupling between the radiative and convective zones. As a result, the sharp gradient of the rotation rate is reduced at the bottom of the convective zone. The thickness of the layer of sharp radial change in the rotation rate is about 0.036 $R_{\\odot}$ ...
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.
Al-Jarro, Ahmed; Biris, Claudiu G; Panoiu, Nicolae C
2016-04-01
We present an in-depth analysis of the resonant intermixing between optical orbital and spin angular momentum of Laguerre-Gaussian (LG) beams, mediated by chiral clusters made of silicon nanospheres. In particular, we establish a relationship between the spin and orbital quantum numbers characterizing the LG beam and the order q of the rotation symmetry group q of the cluster of nanospheres for which resonantly enhanced coupling between the two components of the optical angular momentum is observed. Thus, similar to the case of diffraction grating-mediated transfer of linear momentum between optical beams, we demonstrate that clusters of nanospheres that are invariant to specific rotation transformations can efficiently transfer optical angular momentum between LG beams with different quantum numbers. We also discuss the conditions in which the resonant interaction between LG beams and a chiral cluster of nanospheres leads to the generation of superchiral light.
Al-Jarro, Ahmed; Biris, Claudiu G; Panoiu, Nicolae C
2016-04-01
We present an in-depth analysis of the resonant intermixing between optical orbital and spin angular momentum of Laguerre-Gaussian (LG) beams, mediated by chiral clusters made of silicon nanospheres. In particular, we establish a relationship between the spin and orbital quantum numbers characterizing the LG beam and the order q of the rotation symmetry group q of the cluster of nanospheres for which resonantly enhanced coupling between the two components of the optical angular momentum is observed. Thus, similar to the case of diffraction grating-mediated transfer of linear momentum between optical beams, we demonstrate that clusters of nanospheres that are invariant to specific rotation transformations can efficiently transfer optical angular momentum between LG beams with different quantum numbers. We also discuss the conditions in which the resonant interaction between LG beams and a chiral cluster of nanospheres leads to the generation of superchiral light. PMID:27136989
Classical and quantum equations of motion for tensor of angular momentum
International Nuclear Information System (INIS)
In the frame of the Hamiltonian-Jacoby theory the tensor of angular momentum is defined through the vector-function of action. The principle of least action for a vector-function is formulated. Hamilton equations for the tensor of angular momentum are derived from the principle of least action by means of proving the opposite. The equations for the vector-function action are obtained analogous to the Hamilton-Jacoby's equation. Quantum-mechanical equations of motion for the tensor of angular momentum are derived traditionally, replacing the Hamiltonian and momentum of the system for corresponding operator. The nonrelativistic and relativistic cases are considered. It has been shown that equations describe systems with spin equal to one. In relativistic case the obtained equations generalize well-known Proca equations; in the nonrelativistic one, Pauli's equations for the spin one
Polarization of molecular angular momentum in the chemical reactions Li + HF and F + HD.
Krasilnikov, Mikhail B; Popov, Ruslan S; Roncero, Octavio; De Fazio, Dario; Cavalli, Simonetta; Aquilanti, Vincenzo; Vasyutinskii, Oleg S
2013-06-28
The quantum mechanical approach to vector correlation of angular momentum orientation and alignment in chemical reactions [G. Balint-Kurti and O. S. Vasyutinskii, J. Phys. Chem. A 113, 14281 (2009)] is applied to the molecular reagents and products of the Li + HF [L. Gonzalez-Sanchez, O. S. Vasyutinskii, A. Zanchet, C. Sanz-Sanz, and O. Roncero, Phys. Chem. Chem. Phys. 13, 13656 (2011)] and F + HD [D. De Fazio, J. Lucas, V. Aquilanti, and S. Cavalli, Phys. Chem. Chem. Phys. 13, 8571 (2011)] reactions for which accurate scattering information has become recently available through time-dependent and time-independent approaches. Application of the theory to two important particular cases of the reactive collisions has been considered: (i) the influence of the angular momentum polarization of reactants in the entrance channel on the spatial distribution of the products in the exit channel and (ii) angular momentum polarization of the products of the reaction between unpolarized reactants. In the former case, the role of the angular momentum alignment of the reactants is shown to be large, particularly when the angular momentum is perpendicular to the reaction scattering plane. In the latter case, the orientation and alignment of the product angular momentum was found to be significant and strongly dependent on the scattering angle. The calculation also reveals significant differences between the vector correlation properties of the two reactions under study which are due to difference in the reaction mechanisms. In the case of F + HD reaction, the branching ratio between HF and DF production points out interest in the insight gained into the detailed dynamics, when information is available either from exact quantum mechanical calculations or from especially designed experiments. Also, the geometrical arrangement for the experimental determination of the product angular momentum orientation and alignment based on a compact and convenient spherical tensor expression for
The angular momentum of condensations within elephant trunks
Lora, V; Esquivel, A
2009-01-01
The radiation from newly born stars photoevaporates their parental neutral cloud, leading to the formation of dense clumps that will eventually form stars. We present 3D simulations of the interaction of a neutral cloud with an external ionising radiation field, and compute the angular momenta of these collapsing clumps. The angular momenta of these collapsing clumps show that they have preferential orient mostly perpendicular to the direction of the incident ionising photon field. Therefore, the axes of the jet systems that will be eventually ejected (from the star + accretion disk systems that will form) will be oriented approximately perpendicular to the direction to the photoionising source.
Energy and angular momentum of dilaton black holes
Directory of Open Access Journals (Sweden)
Marcelo Samuel Berman
2008-01-01
Full Text Available Dando seguimiento a un art culo previo, revisamos los resultados para la energ a y momento angular de un hoyo negro de Kerr-Newman, y extendemos el c alculo para el caso de un dilaton en rotaci on, obtenido a partir del modelo de Gar nkle et al. (1991, 1992. Mostramos que hay, en lo que se re ere solamente a la energ a y momento angular, una interacci on entre los campos, de forma que, el gravitacional y el electromagn etico pueden ser ocultados por la intensidad del campo escalar.
Skab, Ihor; Vlokh, Rostyslav
2012-04-01
Acousto-optic diffraction of light in optically active cubic crystals is analyzed from the viewpoint of conservation of optical angular momentum. It is shown that the availability of angular momentum in the diffracted optical beam can be necessarily inferred from the requirements of angular momentum conservation law. As follows from our analysis, a circularly polarized diffracted wave should bear an orbital angular momentum. The efficiency of the spin-to-orbit momentum conversion is governed by the efficiency of acousto-optic diffraction.
Casuso, E.; Beckman, J. E.
2015-05-01
We present here a theoretical model which can at least contribute to the observed relation between the specific angular momenta of galaxies and their masses. This study offers prima facie evidence that the origin of an angular momentum of galaxies could be somewhat more complex than previously proposed. The most recent observations point to a scenario in which, after recombination, matter was organized around bubbles (commonly termed voids), which acquired rotation by tidal torque interaction. Subsequently, a combination of the effects of the gravitational collapse of gas in protogalaxies and the Coriolis force due to the rotation of the voids could produce the rotation of spiral galaxies. Thereafter, the tidal interaction between the objects populating the quasi-spherical voids, in which the galaxies far away from the rotation axes (populating the sheet forming the surface of a void) interact with higher probability with others similarly situated in a neighbouring void, offers a mechanism for transforming some of the galaxies into ellipticals, breaking their spin and yielding galaxies with low net angular momentum, as observed. This model gives an explanation for those observations which suggest a tendency of galactic spins to align along the radius vectors pointing towards the centres of the voids for ellipticals/SO and parallel to filaments and sheets for the spirals. Furthermore, while in simple tidal torque theory the angular momentum supplied to galaxies diminishes drastically with the cosmic expansion, in our approximation for which the Coriolis force acts in addition to tidal torques, the Coriolis force due to void rotation ensures almost continuous angular momentum supply.
Large angular momentum closed strings colliding with D-branes
Imamura, Yosuke
2002-01-01
We investigate colliding processes of closed strings with large angular momenta with D-branes. We give explicit CFT calculations for closed string states with an arbitrary number of bosonic excitations and no or one fermion excitation. The results reproduce the correspondence between closed string states and single trace operators in the boundary gauge theory recently suggested by Berenstein, Maldacena and Nastase.
The parton orbital angular momentum: Status and prospects
Liu, Keh-Fei; Lorcé, Cédric
2016-06-01
Theoretical progress on the formulation and classification of the quark and gluon orbital angular momenta (OAM) is reviewed. Their relation to parton distributions and open questions and puzzles are discussed. We give a status report on the lattice calculation of the parton kinetic and canonical OAM and point out several strategies to calculate the quark and gluon canonical OAM on the lattice.
Angular Momentum of Supersymmetric Non-isotropic Traps
Institute of Scientific and Technical Information of China (English)
XU Qiang
2001-01-01
A simple way to explain quantum behavior of supersymmetric non-isotropic traps is proposed in the framework of sermiunitary formulation of supersymmetric quantum mechanics. Using semiunitary formulation we can simultaneously supersymmetrize the complete set of observables, especially including angular moment.
Long-time tails in angular momentum correlations
Lowe, C.P.; Frenkel, D.; Masters, A.J.
1995-01-01
We compare computer simulation results for the angular velocity autocorrelation function (AVACF) of a colloidal particle with theoretical predictions. We consider both spherical and nonspherical particles in two and three dimensions. The theoretical prediction for the long-time decay of the AVACF in
The Parton Orbital Angular Momentum: Status and Prospects
Liu, Keh-Fei; Lorce, Cedric
2015-01-01
Theoretical progress on the formulation and classification of the quark and gluon orbital angular momenta (OAM) is reviewed. Their relation to parton distributions and open questions and puzzles are discussed. We give a status report on the lattice calculation of the parton kinetic and canonical OAM and point out several strategies to calculate the quark and gluon canonical OAM on the lattice.
Angular momentum properties of haloes and their baryon content in the Illustris simulation
Zjupa, Jolanta
2016-01-01
The angular momentum properties of virialised dark matter haloes have been measured with good statistics in collisionless N-body simulations, but an equally accurate analysis of the baryonic spin is still missing. We employ the Illustris simulation suite, one of the first simulations of galaxy formation with full hydrodynamics that produces a realistic galaxy population in a sizeable volume, to quantify the baryonic spin properties for more than $\\sim$ 320,000 haloes. We first compare the systematic differences between different spin parameter and halo definitions, and the impact of sample selection criteria on the derived properties. We confirm that dark matter only haloes exhibit a close to self-similar spin distribution in mass and redshift of lognormal form. However, the physics of galaxy formation radically changes the baryonic spin distribution. While the dark matter component remains largely unaffected, strong trends with mass and redshift appear for the spin of diffuse gas and the formed stellar compo...
Angular momentum flux of nonparaxial acoustic vortex beams and torques on axisymmetric objects.
Zhang, Likun; Marston, Philip L
2011-12-01
An acoustic vortex in an inviscid fluid and its radiation torque on an axisymmetric absorbing object are analyzed beyond the paraxial approximation to clarify an analogy with an optical vortex. The angular momentum flux density tensor from the conservation of angular momentum is used as an efficient description of the transport of angular momentum. Analysis of a monochromatic nonparaxial acoustic vortex beam indicates that the local ratio of the axial (or radial) flux density of axial angular momentum to the axial (or radial) flux density of energy is exactly equal to the ratio of the beam's topological charge l to the acoustic frequency ω. The axial radiation torque exerted by the beam on an axisymmetric object centered on the beam's axis due to the transfer of angular momentum is proportional to the power absorbed by the object with a factor l/ω, which can be understood as a result of phonon absorption from the beam. Depending on the vortex's helicity, the torque is parallel or antiparallel to the beam's axis.