221,099 research outputs found
Simultaneous Monte Carlo analysis of parton densities and fragmentation functions
We perform a comprehensive new Monte Carlo analysis of high-energy
lepton-lepton, lepton-hadron and hadron-hadron scattering data to
simultaneously determine parton distribution functions (PDFs) in the proton and
parton to hadron fragmentation functions (FFs). The analysis includes all
available semi-inclusive deep-inelastic scattering and single-inclusive annihilation data for pions, kaons and unidentified charged hadrons, which
allows the flavor dependence of the fragmentation functions to be constrained.
Employing a new multi-step fitting strategy and more flexible parametrizations
for both PDFs and FFs, we assess the impact of different data sets on sea quark
densities, and confirm the previously observed suppression of the strange quark
distribution. The new fit, which we refer to as "JAM20-SIDIS", will allow for
improved studies of universality of parton correlation functions, including
transverse momentum dependent (TMD) distributions, across a wide variety of
process, and the matching of collinear to TMD factorization descriptions.Comment: 34 pages, 13 figure
Angular Momentum of Phonons and Einstein-de Haas Effect
We study angular momentum of phonons in a magnetic crystal. In the presence
of a spin-phonon interaction, we obtain a nonzero angular momentum of phonons,
which is an odd function of magnetization. At zero temperature, phonon has a
zero-point angular momentum besides a zero-point energy. With increasing
temperature, the total phonon angular momentum diminishes and approaches to
zero in the classical limit. The nonzero phonon angular momentum can have a
significant impact on the Einstein-de Haas effect. To obtain the change of
angular momentum of electrons, the change of phonon angular momentum needs to
be subtracted from the opposite change of lattice angular momentum.
Furthermore, the finding of phonon angular momentum gives a potential method to
study the spin-phonon interaction. Possible experiments on phonon angular
momentum are also discussed.Comment: Accepted by Phys. Rev. Lett. Detailed supplementary file is include
Connecting Angular Momentum and Galactic Dynamics: The complex Interplay between Spin, Mass, and Morphology
The evolution and distribution of the angular momentum of dark matter (DM)
halos have been discussed in several studies over the past decades. In
particular, the idea arose that angular momentum conservation should allow to
infer the total angular momentum of the entire DM halo from measuring the
angular momentum of the baryonic component, which is populating the center of
the halo, especially for disk galaxies. To test this idea and to understand the
connection between the angular momentum of the DM halo and its galaxy, we use
the Magneticum simulations. We successfully produce populations of spheroidal
and disk galaxies self-consistently. Thus, we are able to study the dependence
of galactic properties on their morphology. We find that (1) the specific
angular momentum of stars in disk and spheroidal galaxies as a function of
their stellar mass compares well with observational results; (2) the specific
angular momentum of the stars in disk galaxies is slightly smaller compared to
the specific angular momentum of the cold gas, in good agreement with
observations; (3) simulations including the baryonic component show a dichotomy
in the specific stellar angular momentum distribution when splitting the
galaxies according to their morphological type (this dichotomy can also be seen
in the spin parameter, where disk galaxies populate halos with slightly larger
spin compared to spheroidal galaxies); (4) disk galaxies preferentially
populate halos in which the angular momentum vector of the DM component in the
central part shows a better alignment to the angular momentum vector of the
entire halo; and (5) the specific angular momentum of the cold gas in disk
galaxies is approximately 40 percent smaller than the specific angular momentum
of the total DM halo and shows a significant scatter.Comment: 25 pages, accepted by ApJ, www.magneticum.or
Angular momentum at null infinity in five dimensions
In this paper, using the Bondi coordinates, we discuss the angular momentum
at null infinity in five dimensions and address the Poincare covariance of the
Bondi mass and angular momentum. We also show the angular momentum loss/gain
law due to gravitational waves. In four dimensions, the angular momentum at
null infinity has the supertranslational ambiguity and then it is known that we
cannot construct well-defined angular momentum there. On the other hand, we
would stress that we can define angular momentum at null infinity without any
ambiguity in higher dimensions. This is because of the non-existence of
supertranslations in higher dimensions.Comment: 15 pages, published version in JM
Is the angular momentum of an electron conserved in a uniform magnetic field?
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
Fourier relationship between angular position and optical orbital angular momentum
We demonstrate the Fourier relationship between angular position and angular
momentum for a light mode. In particular we measure the distribution of orbital
angular momentum states of light that has passed through an aperture and verify
that the orbital angular momentum distribution is given by the complex
Fourier-transform of the aperture function. We use spatial light modulators,
configured as diffractive optical components, to define the initial orbital
angular momentum state of the beam, set the defining aperture, and measure the
angular momentum spread of the resulting beam. These measurements clearly
confirm the Fourier relationship between angular momentum and angular position,
even at light intensities corresponding to the single photon level.Comment: 4 pages, 4 figure
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