10,024 research outputs found
Ballistic transport in induced one-dimensional hole systems
We have fabricated and studied a ballistic one-dimensional p-type quantum
wire using an undoped AlGaAs/GaAs heterostructure. The absence of modulation
doping eliminates remote ionized impurity scattering and allows high mobilities
to be achieved over a wide range of hole densities, and in particular, at very
low densities where carrier-carrier interactions are strongest. The device
exhibits clear quantized conductance plateaus with highly stable gate
characteristics. These devices provide opportunities for studying spin-orbit
coupling and interaction effects in mesoscopic hole systems in the strong
interaction regime where rs > 10.Comment: 6 pages, 4 figures (accepted to Applied Physics Letters
Independent analysis of the orbits of Pioneer 10 and 11
Independently developed orbit determination software is used to analyze the
orbits of Pioneer 10 and 11 using Doppler data. The analysis takes into account
the gravitational fields of the Sun and planets using the latest JPL
ephemerides, accurate station locations, signal propagation delays (e.g., the
Shapiro delay, atmospheric effects), the spacecrafts' spin, and maneuvers. New
to this analysis is the ability to utilize telemetry data for spin, maneuvers,
and other on-board systematic effects. Using data that was analyzed in prior
JPL studies, the anomalous acceleration of the two spacecraft is confirmed. We
are also able to put limits on any secondary acceleration (i.e., jerk) terms.
The tools that were developed will be used in the upcoming analysis of recently
recovered Pioneer 10 and 11 Doppler data files.Comment: 22 pages, 5 figures; accepted for publication in IJMP
Production of a sterile species: quantum kinetics
Production of a sterile species is studied within an effective model of
active-sterile neutrino mixing in a medium in thermal equilibrium. The quantum
kinetic equations for the distribution functions and coherences are obtained
from two independent methods: the effective action and the quantum master
equation. The decoherence time scale for active-sterile oscillations is
, but the evolution of the distribution functions
is determined by the two different time scales associated with the damping
rates of the quasiparticle modes in the medium: \Gamma_1=\Gamma_{aa}\cos^2\tm
; \Gamma_2=\Gamma_{aa}\sin^2\tm where is the interaction rate of
the active species in absence of mixing and \tm the mixing angle in the
medium. These two time scales are widely different away from MSW resonances and
preclude the kinetic description of active-sterile production in terms of a
simple rate equation. We give the complete set of quantum kinetic equations for
the active and sterile populations and coherences and discuss in detail the
various approximations. A generalization of the active-sterile transition
probability \emph{in a medium} is provided via the quantum master equation. We
derive explicitly the usual quantum kinetic equations in terms of the
``polarization vector'' and show their equivalence to those obtained from the
quantum master equation and effective action.Comment: To appear in Phys. Rev.
Branes from a non-Abelian (2,0) tensor multiplet with 3-algebra
In this paper, we study the equations of motion for non-Abelian N=(2,0)
tensor multiplets in six dimensions, which were recently proposed by Lambert
and Papageorgakis. Some equations are regarded as constraint equations. We
employ a loop extension of the Lorentzian three-algebra (3-algebra) and examine
the equations of motion around various solutions of the constraint equations.
The resultant equations take forms that allow Lagrangian descriptions. We find
various (5+d)-dimensional Lagrangians and investigate the relation between them
from the viewpoint of M-theory duality.Comment: 44+1 pages, reference added, typos corrected, and several discussions
added; v3, reference added, many typos corrected, the language improved; v4,
some typos and references corrected, final version to appear in J. Phys.
Nonlinear Transport and Current Fluctuation in an AB Ring with a Quantum Dot
Nonequilibrium steady states are explicitly constructed for a noninteracting
electron model of an Aharonov-Bohm (AB) ring with a quantum dot (QD) with the
aid of asymptotic fields. The Fano line shapes and AB oscillations are shown to
strongly depend on the bias voltage. Current fluctuations are studied as well.Comment: 4pages, 6figure
Dp-branes, NS5-branes and U-duality from nonabelian (2,0) theory with Lie 3-algebra
We derive the super Yang-Mills action of Dp-branes on a torus T^{p-4} from
the nonabelian (2,0) theory with Lie 3-algebra. Our realization is based on Lie
3-algebra with pairs of Lorentzian metric generators. The resultant theory then
has negative norm modes, but it results in a unitary theory by setting VEV's of
these modes. This procedure corresponds to the torus compactification,
therefore by taking a transformation which is equivalent to T-duality, the
Dp-brane action is obtained. We also study type IIA/IIB NS5-brane and
Kaluza-Klein monopole systems by taking other VEV assignments. Such various
compactifications can be realized in the nonabelian (2,0) theory, since both
longitudinal and transverse directions can be compactified, which is different
from the BLG theory. We finally discuss U-duality among these branes, and show
that most of the moduli parameters in U-duality group are recovered. Especially
in D5-brane case, the whole U-duality relation is properly reproduced.Comment: 1+26 page
What Opportunities from the “One Belt, One Road” Initiative for Manufacturing? The Case of Hong Kong\u27s Textiles and Clothing Sectors
Past studies have investigated the trade relationship between countries by analysing economic and political related factors using gravity models. Numerous factors have been empirically tested in the literature which are proposed to be important contributors in determining trade flow. This study addresses the research questions, what are the key factors and dimensions that influence bilateral trade. It focuses on identifying the key factors and dimensions for the expansion of Textile and Clothing (T&C) manufacturing by Chinese manufacturers to other countries, in light of China’s recent One Belt One Road (OBOR) initiative. This paper will critically review bilateral trade and international business literature that uses the gravity model from 1960 to 2017 to discuss factors previously investigated by researchers. The review reflects on the factors commonly explored in the literature, but also highlights the absence of sustainability factors given the importance of sustainability and CSR issues in today’s global T&C industry. This study will contribute to the wider literature of international business and trade, particularly for the expansion of Chinese T&C manufacturing to other countries which are promoted through China’s OBOR initiative
Theory for the Ultrafast Structural Response of optically excited small clusters: Time-dependence of the Ionization Potential
Combining an electronic theory with molecular dynamics simulations we present
results for the ultrafast structural changes in small clusters. We determine
the time scale for the change from the linear to a triangular structure after
the photodetachment process Ag. We show that the
time-dependent change of the ionization potential reflects in detail the
internal degrees of freedom, in particular coherent and incoherent motion, and
that it is sensitive to the initial temperature. We compare with experiment and
point out the general significance of our results.Comment: 10 pages, Revtex, 3 postscript figure
Interference scheme to measure light-induced nonlinearities in Bose-Einstein condensates
Light-induced nonlinear terms in the Gross-Pitaevskii equation arise from the
stimulated coherent exchange of photons between two atoms. For atoms in an
optical dipole trap this effect depends on the spatial profile of the trapping
laser beam. Two different laser beams can induce the same trapping potential
but very different nonlinearities. We propose a scheme to measure light-induced
nonlinearities which is based on this observation.Comment: 2 figure
Gamma rays and neutrinos from the Crab Nebula produced by pulsar accelerated nuclei
We investigate the consequences of the acceleration of heavy nuclei (e.g.
iron nuclei) by the Crab pulsar. Accelerated nuclei can photodisintegrate in
collisions with soft photons produced in the pulsar's outer gap, injecting
energetic neutrons which decay either inside or outside the Crab Nebula. The
protons from neutron decay inside the nebula are trapped by the Crab Nebula
magnetic field, and accumulate inside the nebula producing gamma-rays and
neutrinos in collisions with the matter in the nebula. Neutrons decaying
outside the Crab Nebula contribute to the Galactic cosmic rays. We compute the
expected fluxes of gamma-rays and neutrinos, and find that our model could
account for the observed emission at high energies and may be tested by
searching for high energy neutrinos with future neutrino telescopes currently
in the design stage.Comment: 8 pages, 4 figures, LaTeX uses revtex.sty, submitted to Phys. Rev.
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