1,138 research outputs found
The SPIRIT collection: an overview of a large web collection
A large scale collection of web pages has been essential for research in information retrieval and related areas. This paper provides an overview of a large web collection used in the SPIRIT project for the design and testing of spatially-aware retrieval systems. Several statistics are derived and presented to show the characteristics of the collection
Low scale gravity mediation with warped extra dimension and collider phenomenology on the hidden sector
We propose a scenario of gravity mediated supersymmetry breaking (gravity
mediation) in a supersymmetric Randall-Sundrum model. In our setup, both of the
visible sector and the hidden sector co-exist on the infrared (IR) brane. We
introduce the Polonyi model as a simple hidden sector. Due to the warped
metric, the effective cutoff scale on the IR brane is ``warped down'', so that
the gravity mediation occurs at a low scale. As a result, the gravitino is
naturally the lightest superpartner (LSP) and contact interactions between the
hidden and the visible sector fields become stronger. We address
phenomenologies for various IR cutoff scales. In particular, we investigate
collider phenomenology involving a scalar field (Polonyi field) in the hidden
sector for the case with the IR cutoff around 10 TeV. We find a possibility
that the hidden sector scalar can be produced at the LHC and the International
Linear Collider (ILC). Interestingly, the scalar behaves like the Higgs boson
of the standard model in the production process, while its decay process is
quite different and, once produced, it will provide us with a very clean
signature. The hidden sector may be no longer hidden.Comment: 18 pages, 4 figures. typographical errors have been corrected and a
few new comments have been adde
LaCo2B2: A Co-based layered superconductor with a ThCr2Si2-type structure
LaCo2B2 with a ThCr2Si2-type structure composed of alternately stacked La and
CoB layers exhibits metallic electrical conductivity and Pauli paramagnetic
behavior down to 2K. Bulk superconductivity with a Tc of ~4K emerges upon
substitution with dopant elements; i.e., isovalent substitution to form
(La1-xYx)Co2B2, or aliovalent substitution to form La(Co1-xFex)2B2. Highly
covalent bonding between Co 3d and B 2p levels in the CoB layers, which is
caused by the B 2p level being shallower than the Fermi level, removes magnetic
ordering from Co 3d electrons even in the undoped samples.Comment: 3 figure
Infrared features of unquenched finite temperature lattice Landau gauge QCD
The color diagonal and color antisymmetric ghost propagators slightly above
of MILC lattices are measured and compared with
zero temperature unquenched MILC and MILC
lattices and zero temperature quenched and
6.45 lattices. The expectation value of the color antisymmetric ghost
propagator is zero but its Binder cumulant, which is consistent
with that of dimensional Gaussian distribution below , decreases
above . Although the color diagonal ghost propagator is temperature
independent, the norm of the color antisymmetric ghost propagator is
temperature dependent. The expectation value of the ghost condensate observed
at zero temperature unquenched configuration is consistent with 0 in .
We also measure transverse, magnetic and electric gluon propagator and
extract gluon screening masses. The running coupling measured from the product
of the gluon dressing function and the ghost dressing function are almost
temperature independent but the effect of condensate observed at zero
temperature is consistent with 0 in .
The transverse gluon dressing function at low temperature has a peak in the
infrared but it becomes flatter at high temperature. Its absolute value in the
high momentum is larger for high temperature and similar to the magnetic gluon
dressing function. The electric gluon propagator at high momentum is
temperature independent. These data imply that the magnetic gluon propagator
and the color antisymmetric ghost propagator are affected by the presence of
dynamical quarks and there are strong non-perturbative effects through the
temperature dependent color anti-symmetric ghost propagator.Comment: 11 pages 16 figures, version accepted for publication in Phys. Rev.
Dynamical scaling analysis of the optical Hall conductivity in the quantum Hall regime
Dynamical scaling analysis is theoretically performed for the ac (optical)
Hall conductivity as a function of Fermi
energy and frequency for the two-dimensional electron
gas and for graphene. In both systems, results based on exact diagonalization
show that displays a well-defined dynamical
scaling, for which the dynamical critical exponent as well as the localization
exponent are fitted and plugged in. A crossover from the dc-like bahavior to
the ac regime is identified. The dynamical scaling analysis has enabled us to
quantify the plateau in the ac Hall conductivity previously obtained, and to
predict that the plateaux structure in ac is robust enough to be observed in
the THz regime.Comment: 5 pages, 3 figure
Time evolution of a thin black ring via Hawking radiation
Black objects lose their mass and angular momenta through evaporation by
Hawking radiation, and the investigation of their time evolution has a long
history. In this paper, we study this problem for a five-dimensional doubly
spinning black ring. The black ring is assumed to emit only massless scalar
particles. We consider a thin black ring with a small thickness parameter,
, which can be approximated by a boosted Kerr string locally. We
show that a thin black ring evaporates with fixing its thickness parameter
. Further, in the case of an Emparan-Reall black ring, we derive
analytic formulas for the time evolution, which has one parameter to be
evaluated numerically. We find that the lifetime of a thin black ring is
shorter by a factor of compared to a five-dimensional
Schwarzschild black hole with the same initial mass. We also study detailed
properties of the Hawking radiation from the thin black ring, including the
energy and angular spectra of emitted particles.Comment: 28 pages, 6 figure
Hidden particle production at the ILC
In a class of new physics models, new physics sector is completely or partly
hidden, namely, singlet under the Standard Model (SM) gauge group. Hidden
fields included in such new physics models communicate with the Standard Model
sector through higher dimensional operators. If a cutoff lies in the TeV range,
such hidden fields can be produced at future colliders. We consider a scalar
filed as an example of the hidden fields. Collider phenomenology on this hidden
scalar is similar to that of the SM Higgs boson, but there are several features
quite different from those of the Higgs boson. We investigate productions of
the hidden scalar at the International Linear Collider (ILC) and study the
feasibility of its measurements, in particular, how well the ILC distinguishes
the scalar from the Higgs boson, through realistic Monte Carlo simulations.Comment: the version to be published in PR
Mott Relation for Anomalous Hall and Nernst effects in Ga1-xMnxAs Ferromagnetic Semiconductors
The Mott relation between the electrical and thermoelectric transport
coefficients normally holds for phenomena involving scattering. However, the
anomalous Hall effect (AHE) in ferromagnets may arise from intrinsic spin-orbit
interaction. In this work, we have simultaneously measured AHE and the
anomalous Nernst effect (ANE) in Ga1-xMnxAs ferromagnetic semiconductor films,
and observed an exceptionally large ANE at zero magnetic field. We further show
that AHE and ANE share a common origin and demonstrate the validity of the Mott
relation for the anomalous transport phenomena
Blue light-emitting diode based on ZnO
A near-band-edge bluish electroluminescence (EL) band centered at around 440
nm was observed from ZnO p-i-n homojunction diodes through a semi-transparent
electrode deposited on the p-type ZnO top layer. The EL peak energy coincided
with the photoluminescence peak energy of an equivalent p-type ZnO layer,
indicating that the electron injection from the n-type layer to the p-type
layer dominates the current, giving rise to the radiative recombination in the
p-type layer. The imbalance in charge injection is considered to originate from
the lower majority carrier concentration in the p-type layer, which is one or
two orders of magnitude lower than that in the n-type one. The current-voltage
characteristics showed the presence of series resistance of several hundreds
ohms, corresponding to the current spread resistance within the bottom n-type
ZnO. The employment of conducting ZnO substrates may solve the latter problem.Comment: 13 pages, 4 figures. Jpn. J. Appl. Phys. in pres
Evolution of Cosmological Perturbations in the Long Wavelength Limit
The relation between the long wavelength limit of solutions to the
cosmological perturbation equations and the perturbations of solutions to the
exactly homogeneous background equations is investigated for scalar
perturbations on spatially flat cosmological models. It is shown that a
homogeneous perturbation coincides with the long wavelength limit of some
inhomogeneous perturbation only when the former satisfies an additional
condition corresponding to the momentum constraint if the matter consists only
of scalar fields. In contrast, no such constraint appears if the fundamental
variables describing the matter contain a vector field as in the case of a
fluid. Further, as a byproduct of this general analysis, it is shown that there
exist two universal exact solutions to the perturbation equations in the long
wavelength limit, which are expressed only in terms of the background
quantities. They represent adiabatic growing and decaying modes, and correspond
to the well-known exact solutions for perfect fluid systems and scalar field
systems.Comment: 16 pages, no figure, submitted to PR
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