63,963 research outputs found
Cylindrical Superlens by a Coordinate Transformation
Cylinder-shaped perfect lens deduced from the coordinate transformation
method is proposed. The previously reported perfect slab lens is noticed to be
a limiting form of the cylindrical lens when the inner radius approaches
infinity with respect to the lens thickness. Connaturality between a
cylindrical lens and a slab lens is affirmed by comparing their eigenfield
transfer functions. We numerically confirm the subwavelength focusing
capability of such a cylindrical lens with consideration of material
imperfection. Compared to a slab lens, a cylindrical lens has several
advantages, including finiteness in cross-section, and ability in lensing with
magnification or demagnification. Immediate applications of such a cylindrical
lens can be in high-resolution imaging and lithography technologies. In
addition, its invisibility property suggests that it may be valuable for
non-invasive electromagnetic probing.Comment: Minor changes to conform with the published versio
WZW action in odd dimensional gauge theories
It is shown that Wess-Zumino-Witten (WZW) type actions can be constructed in
odd dimensional space-times using Wilson line or Wilson loop. WZW action
constructed using Wilson line gives anomalous gauge variations and the WZW
action constructed using Wilson loop gives anomalous chiral transformation. We
show that pure gauge theory including Yang-Mills action, Chern-Simons action
and the WZW action can be defined in odd dimensional space-times with even
dimensional boundaries. Examples in 3D and 5D are given. We emphasize that this
offers a way to generalize gauge theory in odd dimensions. The WZW action
constructed using Wilson line can not be considered as action localized on
boundary space-times since it can give anomalous gauge transformations on
separated boundaries. We try to show that such WZW action can be obtained in
the effective theory when making localized chiral fermions decouple.Comment: 19 pages, text shortened, reference added. Version to appear in PR
A Monte Carlo study of the triangular lattice gas with the first- and the second-neighbor exclusions
We formulate a Swendsen-Wang-like version of the geometric cluster algorithm.
As an application,we study the hard-core lattice gas on the triangular lattice
with the first- and the second-neighbor exclusions. The data are analyzed by
finite-size scaling, but the possible existence of logarithmic corrections is
not considered due to the limited data. We determine the critical chemical
potential as and the critical particle density as
. The thermal and magnetic exponents
and , estimated from Binder ratio and
susceptibility , strongly support the general belief that the model is in
the 4-state Potts universality class. On the other hand, the analyses of
energy-like quantities yield the thermal exponent ranging from
to . These values differ significantly from the expected value 3/2,
and thus imply the existence of logarithmic corrections.Comment: 4 figures 2 table
Flow-distributed spikes for Schnakenberg kinetics
This is the post-print version of the final published paper. The final publication is available at link.springer.com by following the link below. Copyright @ 2011 Springer-Verlag.We study a system of reaction–diffusion–convection equations which combine a reaction–diffusion system with Schnakenberg kinetics and the convective flow equations. It serves as a simple model for flow-distributed pattern formation. We show how the choice of boundary conditions and the size of the flow influence the positions of the emerging spiky patterns and give conditions when they are shifted to the right or to the left. Further, we analyze the shape and prove the stability of the spikes. This paper is the first providing a rigorous analysis of spiky patterns for reaction-diffusion systems coupled with convective flow. The importance of these results for biological applications, in particular the formation of left–right asymmetry in the mouse, is indicated.RGC of Hong Kon
Strong Pinning Enhancement in MgB2 Using Very Small Dy2O3 Additions
0.5 to 5.0 wt.% Dy2O3 was in-situ reacted with Mg + B to form pinned MgB2.
While Tc remained largely unchanged, Jc was strongly enhanced. The best sample
(only 0.5 wt.% Dy2O3) had a Jc of 6.5 x 10^5 A/cm^2 at 6K, 1T and 3.5 x 10^5
A/cm^2 at 20K, 1T, around a factor of 4 higher compared to the pure sample, and
equivalent to hot-pressed or nano-Si added MgB2 at below 1T. Even distributions
of nano-scale precipitates of DyB4 and MgO were observed within the grains. The
room temperature resistivity decreased with Dy2O3 indicative of improved grain
connectivity.Comment: 13 pages, 4 figures and 1 tabl
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