16,069 research outputs found
Curvature-induced radiation of surface plasmon polaritons propagating around bends
We present a theoretical study of the curvature-induced radiation of surface
plasmon polaritons (SPPs) propagating around bends at metal-dielectric
interfaces. We explain qualitatively how the curvature leads to distortion of
the phase front, causing the fields to radiate energy away from the
metal-dielectric interface. We then quantify, both analytically and
numerically, radiation losses and energy transmission efficiencies of SPPs
propagating around bends with varying radii- as well as sign-of-curvature.Comment: 9 pages, 8 figures, submitted to Physical Review
Decoherence modes of entangled qubits within neutron interferometry
We study two different decoherence modes for entangled qubits by considering
a Liouville - von Neumann master equation. Mode A is determined by projection
operators onto the eigenstates of the Hamiltonian and mode B by projectors onto
rotated states. We present solutions for general and for Bell diagonal states
and calculate for the later the mixedness and the amount of entanglement given
by the concurrence.
We propose a realization of the decoherence modes within neutron
interferometry by applying fluctuating magnetic fields. An experimental test of
the Kraus operator decomposition describing the evolution of the system for
each mode is presented.Comment: 15 pages, 5 figure
The Spin Mass of an Electron Liquid
We show that in order to calculate correctly the {\it spin current} carried
by a quasiparticle in an electron liquid one must use an effective "spin mass"
, that is larger than both the band mass, , which determines the
charge current, and the quasiparticle effective mass , which determines
the heat capacity. We present microscopic calculations of in a
paramagnetic electron liquid in three and two dimensions, showing that the mass
enhancement can be a very significant effect.Comment: 10 pages, 1 figur
PCAC and the Deficit of Forward Muons in pi^+ Production by Neutrinos
The K2K experiment, using a fine-grained detector in a neutrino beam of
energy has observed two-track events that can be
interpreted as a coherent reaction or an incoherent process , the final nucleon being unobserved. The data show a significant
deficit of forward-going muons in the interval ,
where a sizeable coherent signal is expected. We attempt an explanantion of
this effect, using a PCAC formula that includes the effect of the non-vanishing
muon mass. A suppression of about 25 % is caused by a destructive interference
of the axial vector and pseudoscalar (pion-exchange) amplitudes. The incoherent
background is also reduced by 10 - 15 %. As a consequence the discrepancy
between theory and observation is significantly reduced.Comment: 4 pages including 1 figure, changes in abstract and text; version to
appear in Phys.Lett.
Proton Activation Analysis of Several Trace Impurities in Standard Steel Samples
開始ページ、終了ページ: 冊子体のページ付
Solitary Waves Bifurcated from Bloch Band Edges in Two-dimensional Periodic Media
Solitary waves bifurcated from edges of Bloch bands in two-dimensional
periodic media are determined both analytically and numerically in the context
of a two-dimensional nonlinear Schr\"odinger equation with a periodic
potential. Using multi-scale perturbation methods, envelope equations of
solitary waves near Bloch bands are analytically derived. These envelope
equations reveal that solitary waves can bifurcate from edges of Bloch bands
under either focusing or defocusing nonlinearity, depending on the signs of
second-order dispersion coefficients at the edge points. Interestingly, at edge
points with two linearly independent Bloch modes, the envelope equations lead
to a host of solitary wave structures including reduced-symmetry solitons,
dipole-array solitons, vortex-cell solitons, and so on -- many of which have
never been reported before. It is also shown analytically that the centers of
envelope solutions can only be positioned at four possible locations at or
between potential peaks. Numerically, families of these solitary waves are
directly computed both near and far away from band edges. Near the band edges,
the numerical solutions spread over many lattice sites, and they fully agree
with the analytical solutions obtained from envelope equations. Far away from
the band edges, solitary waves are strongly localized with intensity and phase
profiles characteristic of individual families.Comment: 23 pages, 15 figures. To appear in Phys. Rev.
Weak-Light Ultraslow Vector Optical Solitons via Electromagnetically Induced Transparency
We propose a scheme to generate temporal vector optical solitons in a
lifetime broadened five-state atomic medium via electromagnetically induced
transparency. We show that this scheme, which is fundamentally different from
the passive one by using optical fibers, is capable of achieving
distortion-free vector optical solitons with ultraslow propagating velocity
under very weak drive conditions. We demonstrate both analytically and
numerically that it is easy to realize Manakov temporal vector solitons by
actively manipulating the dispersion and self- and cross-phase modulation
effects of the system.Comment: 4 pages, 4 figure
Theory of Magnetic Short--Range Order for High-T_c Superconductors
A theory of magnetic short--range order for high-- cuprates is presented
on the basis of the one--band ----Hubbard model combining the
four--field slave--boson functional integral technique with the Bethe cluster
method. The ground--state phase diagram evaluated self--consistently at the
saddle--point and pair--approximation levels shows the experimentally observed
suppression of magnetic long--range order in the favour of a paraphase with
antiferromagnetic short--range order. In this phase the uniform static spin
susceptibility consists of interrelated itinerant and local parts and increases
upon doping up to the transition to the Pauli paraphase. Using realistic values
of the Hubbard interaction we obtain the cusp position and the doping
dependence of the zero--temperature susceptibility in reasonable agreement with
experiments on .Comment: 3 pages, 2 Postscript figure, Proc. Int. Conf. SCES Zuerich
Switzerland Aug. 96, to appear in Physica
Spontaneous soliton formation and modulational instability in Bose-Einstein condensates
The dynamics of an elongated attractive Bose-Einstein condensate in an
axisymmetric harmonic trap is studied. It is shown that density fringes caused
by self-interference of the condensate order parameter seed modulational
instability. The latter has novel features in contradistinction to the usual
homogeneous case known from nonlinear fiber optics. Several open questions in
the interpretation of the recent creation of the first matter-wave bright
soliton train [Strecker {\it et al.} Nature {\bf 417} 150 (2002)] are
addressed. It is shown that primary transverse collapse, followed by secondary
collapse induced by soliton--soliton interactions, produce bursts of hot atoms
at different time scales.Comment: 4 pages, 3 figures. Phys. Rev. Lett. in pres
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