5,425 research outputs found
Air-core photonic band-gap fibers: the impact of surface modes
We study the dispersion and leakage properties for the recently reported
low-loss photonic band-gap fiber by Smith et al. [Nature 424, 657 (2003)]. We
find that surface modes have a significant impact on both the dispersion and
leakage properties of the fundamental mode. Our dispersion results are in
qualitative agreement with the dispersion profile reported recently by Ouzounov
et al. [Science 301, 1702 (2003)] though our results suggest that the observed
long-wavelength anomalous dispersion is due to an avoided crossing (with
surface modes) rather than band-bending caused by the photonic band-gap
boundary of the cladding.Comment: 7 pages including 4 figures. Accepted for Optics Expres
Spin-current injection and detection in strongly correlated organic conductor
Spin-current injection into an organic semiconductor
film induced by the spin
pumping from an yttrium iron garnet (YIG) film. When magnetization dynamics in
the YIG film is excited by ferromagnetic or spin-wave resonance, a voltage
signal was found to appear in the
film.
Magnetic-field-angle dependence measurements indicate that the voltage signal
is governed by the inverse spin Hall effect in
. We found that the
voltage signal in the /YIG
system is critically suppressed around 80 K, around which magnetic and/or glass
transitions occur, implying that the efficiency of the spin-current injection
is suppressed by fluctuations which critically enhanced near the transitions
Tidal disruption of dark matter halos around proto-globular clusters
Tidal disruption of dark matter halos around proto-globular clusters in a
halo of a small galaxy is studied in the context of the hierarchical clustering
scenario by using semi-cosmological N-body/SPH simulations assuming the
standard cold dark matter model (). Our analysis on formation and
evolution of the galaxy and its substructures archives until . In such
a high-redshift universe, the Einstein-de Sitter universe is still a good
approximation for a recently favored -dominated universe, and then our
results does not depend on the choice of cosmology. In order to resolve small
gravitationally-bound clumps around galaxies and consider radiative cooling
below , we adopt a fine mass resolution (m_{\rm SPH} = 1.12 \times
10^3 \Msun). Because of the cooling, each clump immediately forms a
`core-halo' structure which consists of a baryonic core and a dark matter halo.
The tidal force from the host galaxy mainly strips the dark matter halo from
clumps and, as a result, theses clumps get dominated by baryons. Once a clump
is captured by the host halo, its mass drastically decreases each pericenter
passage. At , more than half of the clumps become baryon dominated
systems (baryon mass/total mass ). Our results support the tidal
evolution scenario of the formation of globular clusters and baryon dominated
dwarf galaxies in the context of the cold dark matter universe.Comment: 9page, 13 figures. Accepted for publication in ApJ. A high-resolution
PDF of the paper can be obtained from http://th.nao.ac.jp/~takayuki/ApJ05
Population-only decay map for n-qubit n-partite inseparability detection
We introduce a new positive linear map for a single qubit. This map is a
decay only in populations of a single-qubit density operator. It is shown that
an n-fold product of this map may be used for a detection of n-partite
inseparability of an n-qubit density operator (i.e., detection of impossibility
of representing a density operator in the form of a convex combination of
products of density operators of individual qubits). This product map is also
investigated in relation to a variant of the entanglement detection method
mentioned by Laskowski and Zukowski.Comment: 5 pages, 1 figure, RevTex4, v2 minor grammatical changes, typos
correcte
Effects of a Supermassive Black Hole Binary on a Nuclear Gas Disk
We study influence of a galactic central supermassive black hole (SMBH)
binary on gas dynamics and star formation activity in a nuclear gas disk by
making three-dimensional Tree+SPH simulations. Due to orbital motions of SMBHs,
there are various resonances between gas motion and the SMBH binary motion. We
have shown that these resonances create some characteristic structures of gas
in the nuclear gas disk, for examples, gas elongated or filament structures,
formation of gaseous spiral arms, and small gas disks around SMBHs. In these
gaseous dense regions, active star formations are induced. As the result, many
star burst regions are formed in the nuclear region.Comment: 19 pages, 11 figures, accepted for publication in Ap
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Simulation of premixed combustion with varying equivalence ratio in gas turbine combustor
RANS simulation of a gas turbine combustor with complex geometry is performed. The turbulence is modelled using a two-equation approach. The scalar mixing and combustion is modelled using a flamelet based approach for partially premixed combustion. In this approach transport equations to described scalar mixing and reacting fields and their statistical interactions are solved along with standard conservation equations. The boundary conditions are specified using measured values. The computed spatial variations of averaged temperature and dry mole fractions of various scalars, including CO and NOx, compared quite well with measured values. The results of this combustion model are compared to the eddy-dissipation-concept (EDC) model commonly used for gas turbine combustion calculation and this comparison showed that the results of partially premixed combustion model is improved considerably.This is the author accepted manuscript. The final version is available from the American Institute of Aeronautics and Astronautics via http://dx.doi.org/10.2514/1.B3551
Nonclassical correlation in a multipartite quantum system: two measures and evaluation
There is a commonly recognized paradigm in which a multipartite quantum
system described by a density matrix having no product eigenbasis is considered
to possess nonclassical correlation. Supporting this paradigm, we define two
entropic measures of nonclassical correlation of a multipartite quantum system.
One is defined as the minimum uncertainty about a joint system after we collect
outcomes of particular local measurements. The other is defined by taking the
maximum over all local systems about the minimum distance between a genuine set
and a mimic set of eigenvalues of a reduced density matrix of a local system.
The latter measure is based on an artificial game to create mimic eigenvalues
of a reduced density matrix of a local system from eigenvalues of a density
matrix of a global system. Numerical computation of these measures for several
examples is performed.Comment: v1: 10 pages, 8 figures, IOPART, v2: introduction modified, figure 7
replaced, v3: 10 pages, 10 figures, RevTeX4, major revision with an
additional measure introduced, title changed (previous title: Non-classical
correlation in a multi-partite quantum system reconsidered), to appear in
Phys. Rev.
N\'eel and singlet RVB orders in the t-J model
The N\'eel and the singlet RVB orders of the {\it t-J} model in a 2D square
lattice are studied in the slave-boson mean-field approximation. It is shown
that the N\'eel order parameter takes the maximum value at the finite
temperature and disappear at the lower temperature for a certain range of
doping. It is also shown that the N\'eel and the singlet RVB orders coexist at
low temperature. This suggests the possibility of the coexistence of the N\'eel
and the superconducting orders.Comment: RevTeX, 8 pages, 1 postscript figure. To appear in Physica C, Volume
257, issue 38
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