47,693 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
Trace forms of Galois extensions in the presence of a fourth root of unity
We study quadratic forms that can occur as trace forms of Galois field
extensions L/K, under the assumption that K contains a primitive 4th root of
unity. M. Epkenhans conjectured that any such form is a scaled Pfister form. We
prove this conjecture and classify the finite groups G which admit a G-Galois
extension L/K with a non-hyperbolic trace form. We also give several
applications of these results.Comment: 19 pages, to appear in International Math Research Notice
Compact, fiber-compatible, cascaded Raman laser
Cascaded Raman Stokes lasing in an ultrahigh-Q silica microsphere resonator coupled to a tapered fiber is demonstrated and analyzed. With less than 900 μW of pump power near 980 nm, five cascaded Stokes lasing lines are generated. In addition, a threshold power of 56.4 μW for the first-order Stokes lasing is achieved. The Stokes lasing lines exhibit distinct characteristics depending on their order, as predicted by theoretical analysis
Luminosity Profiles of Merger Remnants
Using published luminosity and molecular gas profiles of the late-stage
mergers NGC 3921, NGC 7252 and Arp 220, we examine the expected luminosity
profiles of the evolved merger remnants, especially in light of the massive CO
complexes that are observed in their nuclei. For NGC 3921 and NGC 7252 we
predict that the resulting luminosity profiles will be characterized by an
r^{1/4} law. In view of previous optical work on these systems, it seems likely
that they will evolve into normal ellipticals as regards their optical
properties. Due to a much higher central molecular column density, Arp 220
might not evolve such a ``seamless'' light profile. We conclude that
ultraluminous infrared mergers such as Arp 220 either evolve into ellipticals
with anomalous luminosity profiles, or do not produce many low-mass stars out
of their molecular gas complexes.Comment: Final refereed version. Note new title. 4 pages, 2 encapsulated color
figures, uses emulateapj.sty. Accepted to ApJL. Also available at
http://www.cv.nrao.edu/~jhibbard/Remnants/remnants.htm
Heavy Flavor at the Large Hadron Collider in a Strong Coupling Approach
Employing nonperturbative transport coefficients for heavy-flavor (HF)
diffusion through quark-gluon plasma (QGP), hadronization and hadronic matter,
we compute - and -meson observables in Pb+Pb (=2.76\,TeV)
collisions at the LHC. Elastic heavy-quark scattering in the QGP is evaluated
within a thermodynamic -matrix approach, generating resonances close to the
critical temperature which are utilized for recombination into and
mesons, followed by hadronic diffusion using effective hadronic scattering
amplitudes. The transport coefficients are implemented via Fokker-Planck
Langevin dynamics within hydrodynamic simulations of the bulk medium in nuclear
collisions. The hydro expansion is quantitatively constrained by
transverse-momentum spectra and elliptic flow of light hadrons. Our approach
thus incorporates the paradigm of a strongly coupled medium in both bulk and HF
dynamics throughout the thermal evolution of the system.Comment: 7 pages, 7 figures Representation of experimental data is update
Ideal Hydrodynamics for Bulk and Multistrange Hadrons in =200\,AGeV Au-Au Collisions
We revisit the use of ideal hydrodynamics to describe bulk- and
multistrange-hadron observables in nuclear collisions at the Relativistic Heavy
Ion Collider. Toward this end we augment the 2+1-dimensional code "AZHYDRO" by
employing (a) an equation of state based on recent lattice-QCD computations
matched to a hadron-resonance gas with chemical decoupling at 160\,MeV, (b) a compact initial density profile, (c) an initial-flow
field including azimuthal anisotropies, and (d) a sequential kinetic decoupling
of bulk (, , ) and multistrange (, , ) hadrons at
\,MeV and 160\,MeV, respectively. We find that this scheme allows
for a consistent description of the observed chemistry, transverse-momentum
spectra and elliptic flow of light and strange hadrons.Comment: 9 pages, 5 figure
Large anisotropy in the optical conductivity of YNi2B2C
The optical properties of YNiBC are studied by using the
first-principles full-potential linearized augmented plane wave (FLAPW) method
within the local density approximation. Anisotropic behavior is obtained in the
optical conductivity, even though the electronic structure shows 3D character.
A large peak in is obtained at 2.4 eV. The anisotropic optical
properties are analyzed in terms of interband transitions between energy levels
and found that the Ni site plays an important role. The electronic energy loss
spectroscopy (EELS) spectra are also calculated to help elucidate the
anisotropic properties in this system.Comment: revtex4, 4 pages, 5 figures, to appear in PR
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