31,251 research outputs found
X(1812) in Quarkonia-Glueball-Hybrid Mixing Scheme
Recently a (X(1812)) state with a mass near the threshold of
and has been observed by the BES collaboration in decay. It has been suggested that it is a
state. If it is true, this state fits in a mixing scheme based on quarkonia,
glueball and hybrid (QGH) very nicely where five physical states are predicted.
Together with the known , , , and
states, X(1812) completes the five members in this family. Using known
experimental data on these particles we determine the ranges of the mixing
parameters and predict decay properties for X(1812). We also discuss some
features which may be able to distinguish between four-quark and hybrid mixing
schemes.Comment: 15 pages, 2 figures, 3 table
Local spin polarisation of electrons in Rashba semiconductor nanowires: effects of the bound state
The local spin polarisation (LSP) of electrons in two typical semiconductor
nanowires under the modulation of Rashba spin-orbit interaction (SOI) is
investigated theoretically. The influence of both the SOI- and
structure-induced bound states on the LSP is taken into account via the
spin-resolved lattice Green function method. It is discovered that high
spin-density islands with alternative signs of polarisation are formed inside
the nanowires due to the interaction between the bound states and the Rashba
effective magnetic field. Further study shows that the spin-density islands
caused by the structure-induced bound state exhibit a strong robustness against
disorder. These findings may provide an efficient way to create local magnetic
moments and store information in semiconductors.Comment: 8 pages, 3 figure
Investigation and visualization of internal flow through particle aggregates and microbial flocs using particle image velocimetry
postprin
Investigation of the hydrodynamic behaviour of particles and aggregates by particle image velocimetry (PIV)
Proceedings of the International Symposium on Sustainable and Safe Water Supplies, Hong Kong, China, 15-17 January 2007.An advanced fluid visualisation technique, particle image velocimetry, was employed to investigate the hydrodynamic properties of particles and aggregates. The experiments were conducted in a settling column filled with a suspension of fluorescent polymeric beads as flow tracers. A thin vertical section of the settling column was illuminated by a laser sheet, while the motions of particles were recorded by a high speed CCD camera. Large solid spheres, flocs of latex microspheres and aggregates of marine diatoms were characterised for their hydrodynamic properties. The trajectories of the tracer particles were tracked when a large particle or aggregate settled through the suspension of the tracers, which gave the streamlines surrounding the falling object. The streamlines demonstrate directly the curvilinear feature of the interaction between approaching particles. However, the available curvilinear model underestimates the collision frequency function of particles by one order of magnitude or two. The collision potentials of the flocs and aggregates are more than an order of magnitude greater than the similar-sized solid spheres. Algal aggregates appear to be highly porous and fractal with a fluid collection efficiency of 10-40%, which would significantly enhance the flocculation between particles and the mass transfer into the aggregates. © IWA Publishing 2007.postprin
Cavity QED treatment of scattering-induced efficient free-space excitation and collection in high-Q whispering-gallery microcavities
Whispering-gallery microcavity laser possesses ultralow threshold, whereas
convenient free-space optical excitation and collection suffer from low
efficiencies due to its rotational symmetry. Here we analytically study a
three-dimensional microsphere coupled to a nano-sized scatterer in the
framework of quantum optics. It is found that the scatterer is capable of
coupling light in and out of the whispering-gallery modes (WGMs) without
seriously degrading their high-Q properties, while the microsphere itself plays
the role of a lens to focus the input beam on the scatterer and vice versa. Our
analytical results show that (1) the high-Q WGMs can be excited in free space,
and (2) over 50% of the microcavity laser emission can be collected within less
than . This coupling system holds great potential for low
threshold microlasers free of external couplers.Comment: 10 pages, 8 figure
Strongly enhanced light-matter interaction in a hybrid photonic-plasmonic resonator
We propose a hybrid photonic-plasmonic resonant structure which consists of a
metal nanoparticle (MNP) and a whispering gallery mode (WGM) microcavity. It is
found that the hybrid mode enables a strong interaction between the light and
matter, and the single-atom cooperativity is enhanced by more than two orders
of magnitude compared to that in a bare WGM microcavity. This remarkable
improvement originates from two aspects: (1) the MNP offers a highly enhanced
local field in the vicinity of an emitter, and (2), surprisingly, the
high-\textit{Q} property of WGMs can be maintained in the presence of the MNP.
Thus the present system has great advantages over a single microcavity or a
single MNP, and holds great potential in quantum optics, nonlinear optics and
highly sensitive biosening.Comment: 5 pages, 4 figure
Spinor field realizations of the non-critical string based on the linear algebra
In this paper, we investigate the spinor field realizations of the
algebra, making use of the fact that the algebra can be linearized
through the addition of a spin-1 current. And then the nilpotent BRST charges
of the spinor non-critical string were built with these realizations.Comment: 10 pages, no figures, revtex4 style, accepted by Commun.Theor.Phy
- …