673,009 research outputs found
Anomalous Currents on Closed Surfaces: Extended Proximity, Partial Quantization, and Qubits
Motivated by the surface of topological insulators, the Dirac anomaly's
discontinuous dependence on sign of the mass, , is investigated on
closed topologies when mass terms are weak or only partially cover the surface.
It is found that, unlike the massive Dirac theory on an infinite plane, there
is a smoothly decreasing current when the mass region is not infinite; also, a
massive finite region fails to exhibit a Hall current edge--exerting an
extended proximity effect, which can, however, be uniformly small--and
oppositely orientated Hall phases are fully quantized while accompanied by
diffuse chiral modes. Examples are computed using Dirac energy eigenstates on a
flat torus (genus one topology) and closed cap cylinder (genus zero topology)
for various mass-term geometries. Finally, from the resulting the properties of
the surface spectra, a potential application for a flux-charge qubit is
presented.Comment: 22 pages, 13 figures. References and focus updated. Added effective
action arguments. Same text as published versio
Effects of nacelle shape on drag and weight of a supersonic cruising aircraft
The quantitive relationship of cruise drag and nacelle shape was investigated for a representative advanced supersonic transport configuration. Nacelle shape parameters were systematically varied, and the effects of these variations on wave and friction drag were determined. The effects of changes in vehicle drag, propulsion weight, and specific fuel consumption on vehicle takeoff gross weight were computed. Generally, it was found that nacelle shapes such that the maximum cross-sectional area occurred at or near the nozzle exit resulted in the lowest wave drag. In fact, nacelle shapes were found that produce favorable interference effects (drag reduction) of such magnitude as to nearly offset the friction drag of the nacelle
Coarsening of a Class of Driven Striped Structures
The coarsening process in a class of driven systems exhibiting striped
structures is studied. The dynamics is governed by the motion of the driven
interfaces between the stripes. When two interfaces meet they coalesce thus
giving rise to a coarsening process in which l(t), the average width of a
stripe, grows with time. This is a generalization of the reaction-diffusion
process A + A -> A to the case of extended coalescing objects, namely, the
interfaces. Scaling arguments which relate the coarsening process to the
evolution of a single driven interface are given, yielding growth laws for
l(t), for both short and long time. We introduce a simple microscopic model for
this process. Numerical simulations of the model confirm the scaling picture
and growth laws. The results are compared to the case where the stripes are not
driven and different growth laws arise
Optical frequency waveguide and transmission system Patent
Optical communication system with gas filled waveguide for laser beam transmissio
Laser machining apparatus Patent
Laser machining device with dielectric functioning as beam waveguide for mechanical and medical application
Shot Noise Enhancement in Resonant Tunneling Structures in a Magnetic Field
We have observed that the shot noise of tunnel current, I, in
GaSb-AlSb-InAs-AlSb-GaSb double-barrier structure under a magnetic field can
exceed 2qI. The measurements were done at T=4K in fields up to 5T parallel to
the current. The noise enhancement occurred at each of the several
negative-differential conductance regions induced by the tunneling of holes
through Landau levels in the InAs quantum well. The amount of the enhancement
increased with the strength of the negative conductance and reached values up
to 8qI. These results are explained qualitatively by fluctuations of the
density of states in the well, but point out the need for a detailed theory of
shot noise enhancement in resonant tunneling devices.Comment: 4 pages, RevTex, 3 figure
Spin Susceptibility of Noncentrosymmetric Heavy-fermion Superconductor CeIrSi3 under Pressure: 29Si-Knight Shift Study on Single Crystal
We report 29Si-NMR study on a single crystal of the heavy-fermion
superconductor CeIrSi3 without an inversion symmetry along the c-axis. The
29Si-Knight shift measurements under pressure have revealed that the spin
susceptibility for the ab-plane decreases slightly below Tc, whereas along the
c-axis it does not change at all. The result can be accounted for by the spin
susceptibility in the superconducting state being dominated by the strong
antisymmetric (Rashba-type) spin-orbit interaction that originates from the
absence of an inversion center along the c-axis and it being much larger than
superconducting condensation energy. This is the first observation which
exhibits an anisotropy of the spin susceptibility below Tc in the
noncentrosymmetric superconductor dominated by strong Rashba-type spin-orbit
interaction.Comment: 4 pages, 4 figures, Accepted for publication in Phys. Rev. Let
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