39,969 research outputs found
Quark Orbital Angular Momentum in the Baryon
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 and the
chiral splitting probability is shown. The cancellation between the spin
and orbital contributions in the spin sum rule and in the baryon magnetic
moments is discussed.Comment: 26 pages, 3 figures, revised version with minor eq. no and ref. no.
corrections. Discussion on the spin and a new ref. are adde
Atomic Entanglement vs Photonic Visibility for Quantum Criticality of Hybrid System
To characterize the novel quantum phase transition for a hybrid system
consisting of an array of coupled cavities and two-level atoms doped in each
cavity, we study the atomic entanglement and photonic visibility in comparison
with the quantum fluctuation of total excitations. Analytical and numerical
simulation results show the happen of quantum critical phenomenon similar to
the Mott insulator to superfluid transition. Here, the contour lines
respectively representing the atomic entanglement, photonic visibility and
excitation variance in the phase diagram are consistent in the vicinity of the
non-analytic locus of atomic concurrences.Comment: 4 pages, 2 figure
Nucleon spin-flavor structure in SU(3) breaking chiral quark model
The SU(3) symmetric chiral quark model, which describes interactions between
quarks, gluons and the Goldstone bosons, explains reasonably well many aspects
of the flavor and spin structure of the proton, except for the values of
and . Introducing the SU(3)-breaking effect
suggested by the mass difference between the strange and nonstrange quarks, we
find that this discrepancy can be removed and better overall agreement
obtained.Comment: 18 pages, Latex, 4 tables. Phys. Rev. D (in press, submitted/revised
in June/Nov 1996
Effect of inter-subsystem couplings on the evolution of composite systems
The effect of inter-subsystem coupling on the adiabaticity of composite
systems and that of its subsystems is investigated. Similar to the adiabatic
evolution defined for pure states, non-transitional evolution for mixed states
is introduced; conditions for the non-transitional evolution are derived and
discussed. An example that describes two coupled qubits is presented to detail
the general presentation. The effects due to non-adiabatic evolution on the
geometric phase are also presented and discussed.Comment: 5 pages, 1 figur
Wetting and bonding characteristics of selected liquid-metals with a high power diode laser treated alumina bioceramic
Changes in the wettability characteristics of an alumina bioceramic occasioned by high power diode laser (HPDL) surface treatment were apparent from the observed reduction in the contact angle. Such changes were due to the HPDL bringing about reductions the surface roughness, increases in the surface O2 content and increases in the polar component of the surface energy. Additionally, HPDL treatment of the alumina bioceramic surface was found to effect an improvement in the bonding characteristics by increasing the work of adhesion. An electronic approach was used to elucidate the bonding characteristics of the alumina bioceramic before and after HPDL treatment. It is postulated that HPDL induced changes to the alumina bioceramic produced a surface with a reduced bandgap energy which consequently increased the work of adhesion by increasing the electron transfer at the metal/oxide interface and thus the metal-oxide interactions. Furthermore, it is suggested that the increase in the work of adhesion of the alumina bioceramic after HPDL treatment was due to a correlation existing between the wettability and ionicity of the alumina bioceramic; for it is believed that the HPDL treated surface is less ionic in nature than the untreated surface and therefore exhibits better wettability characteristics
Very Long Baseline Array observations of the Intraday Variable source J1128+592
Short time-scale flux density variations of flat spectrum radio sources are
often explained by the scattering of radio waves in the turbulent, ionized
Interstellar Matter of the Milky Way. One of the most convincing observational
arguments in favor of this is the annual modulation of the variability
time-scale caused by the Earth orbital motion around the Sun. J1128+592 is an
IDV source with a possible annual modulation in its variability time-scale. We
observed the source in 6 epochs with the VLBA at 5, 8 and 15 GHz in total
intensity and polarization. The VLBA observations revealed an east-west
oriented core-jet structure. Its position angle agrees with the angle of
anisotropy derived from the annual modulation model. No significant long-term
structural changes were observed with VLBI on mas-scales, however, compared to
archival data, the VLBI core size is expanded. This expansion offers a possible
explanation to the observed decrease of the strength of IDV. VLBI polarimetry
revealed significant changes in the electric vector position angle and Rotation
Measure of the core and jet. Part of the observed RM variability could be
attributed to a scattering screen (37 pc distance), which covers the source
(core and jet) and which may be responsible for the IDV. Superposition of
polarized sub-components below the angular resolution limit may affect the
observed RM as well.Comment: accepted for A&A (11 pages, 11 figures
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