256 research outputs found
General Supersymmetric Solutions of Five-Dimensional Supergravity
The classification of 1/4-supersymmetric solutions of five dimensional gauged
supergravity coupled to arbitrary many abelian vector multiplets, which was
initiated in hep-th/0401129, is completed. The structure of all solutions for
which the Killing vector constructed from the Killing spinor is null is
investigated in both the gauged and the ungauged theories and some new
solutions are constructed.Comment: 24 pages, references added, uses JHEP3.cl
Geometries with Killing Spinors and Supersymmetric AdS Solutions
The seven and nine dimensional geometries associated with certain classes of
supersymmetric and solutions of type IIB and D=11 supergravity,
respectively, have many similarities with Sasaki-Einstein geometry. We further
elucidate their properties and also generalise them to higher odd dimensions by
introducing a new class of complex geometries in dimensions, specified
by a Riemannian metric, a scalar field and a closed three-form, which admit a
particular kind of Killing spinor. In particular, for , we show that
when the geometry in dimensions is a cone we obtain a class of
geometries in dimensions, specified by a Riemannian metric, a scalar
field and a closed two-form, which includes the seven and nine-dimensional
geometries mentioned above when , respectively. We also consider various
ansatz for the geometries and construct infinite classes of explicit examples
for all .Comment: 28 page
CELLS v1.0 : updated and parallelized version of an electrical scheme to simulate multiple electrified clouds and flashes over large domains.
International audienceThe paper describes the fully parallelized electrical scheme CELLS which is suitable to simulate explicitly electrified storm systems on parallel computers. Our motivation here is to show that a cloud electricity scheme can be developed for use on large grids with complex terrain. Large computational domains are needed to perform real case meteorological simulations with many independent convective cells. The scheme computes the bulk electric charge attached to each cloud particle and hydrometeor. Positive and negative ions are also taken into account. Several parametrizations of the dominant non-inductive charging process are included and an inductive charging process as well. The electric field is obtained by inverting the Gauss equation with an extension to terrain-following coordinates. The new feature concerns the lightning flash scheme which is a simplified version of an older detailed sequential scheme. Flashes are composed of a bidirectional leader phase (vertical extension from the triggering point) and a phase obeying a fractal law (with horizontal extension on electrically charged zones). The originality of the scheme lies in the way the branching phase is treated to get a parallel code. The complete electrification scheme is tested for the 10 July 1996 STERAO case and for the 21 July 1998 EULINOX case. Flash characteristics are analysed in detail and additional sensitivity experiments are performed for the STERAO case. Although the simulations were run for flat terrain conditions, they show that the model behaves well on multiprocessor computers. This opens a wide area of application for this electrical scheme with the next objective of running real meterological case on large domains
On a class of 4D Kahler bases and AdS_5 supersymmetric Black Holes
We construct a class of toric Kahler manifolds, M_4, of real dimension four,
a subset of which corresponds to the Kahler bases of all known 5D
asymptotically AdS_5 supersymmetric black-holes. In a certain limit, these
Kahler spaces take the form of cones over Sasaki spaces, which, in turn, are
fibrations over toric manifolds of real dimension two. The metric on M_4 is
completely determined by a single function H(x), which is the conformal factor
of the two dimensional space. We study the solutions of minimal five
dimensional gauged supergravity having this class of Kahler spaces as base and
show that in order to generate a five dimensional solution H(x) must obey a
simple sixth order differential equation. We discuss the solutions in detail,
which include all known asymptotically AdS_5 black holes as well as other
spacetimes with non-compact horizons. Moreover we find an infinite number of
supersymmetric deformations of these spacetimes with less spatial isometries
than the base space. These deformations vanish at the horizon, but become
relevant asymptotically.Comment: 34 pages, 3 figures. v2: formula (8.35) and other minor typos
corrected; references added; accepted for publication in JHE
UV-divergences of Wilson Loops for Gauge/Gravity Duality
We analyze the structure of the UV divergences of the Wilson loop for a
general gauge/gravity duality. We find that, due to the presence of a
nontrivial NSNS B-field and metric, new divergences that cannot be subtracted
out by the conventional Legendre transform may arise. We also derive conditions
on the B-field and the metric, which when satisfied, the leading UV divergence
will become linear, and can be cancelled out by choosing the boundary condition
of the string appropriately. Our results, together with the recent result of
arXiv:0807.5127, where the effect of a nontrivial dilaton on the structure of
UV divergences in Wilson loop is analysed, allow us to conclude that Legendre
transform is at best capable of cancelling the linear UV divergences arising
from the area of the worldsheet, but is incapable to handle the divergences
associated with the dilaton or the B-field in general. We also solve the
conditions for the cancellation of the leading linear divergences generally and
find that many well-known supergravity backgrounds are of these kinds,
including examples such as the Sakai-Sugimoto QCD model or N=1 duality with
Sasaki-Einstein spaces. We also point out that Wilson loop in the
Klebanov-Strassler background have a divergence associated with the B-field
which cannot be cancelled away with the Legendre transform. Finally we end with
some comments on the form of the Wilson loop operator in the ABJM
superconformal Chern-Simons theory.Comment: 26 pages. LaTeX. v2: reference added. version to appear in JHE
Relationship between dynamical heterogeneities and stretched exponential relaxation
We identify the dynamical heterogeneities as an essential prerequisite for
stretched exponential relaxation in dynamically frustrated systems. This
heterogeneity takes the form of ordered domains of finite but diverging
lifetime for particles in atomic or molecular systems, or spin states in
magnetic materials. At the onset of the dynamical heterogeneity, the
distribution of time intervals spent in such domains or traps becomes stretched
exponential at long time. We rigorously show that once this is the case, the
autocorrelation function of the renewal process formed by these time intervals
is also stretched exponential at long time.Comment: 8 pages, 4 figures, submitted to PR
Comparing health workforce forecasting approaches for healthcare planning: The case for ophthalmologists
Health workforce planning is essential in the provision of quality healthcare. Several approaches to planning are customarily used
and advocated, each with unique underlying assumptions. Thus, a thorough understanding of each assumption is required in
order to make an informed decision on the choice of forecasting approach to be used. For illustration, we compare results for
eye care requirements in Singapore using three established workforce forecasting approaches â workforce-to-population-ratio,
needs based approach, utilization based approach â and a proposed robust integrated approach to discuss the appropriateness of
each approach under various scenarios. Four simulation models using the systems modeling methodology of system dynamics
were developed for use in each approach. These models were initialized and simulated using the example of eye care workforce
planning in Singapore, to project the number of ophthalmologists required up to the year 2040 under the four different approaches.
We found that each approach projects a different number of ophthalmologists required over time. The needs based approach tends
to project the largest number of required ophthalmologists, followed by integrated, utilization based and workforce-to-population
ratio approaches in descending order. The four different approaches vary widely in their forecasted workforce requirements and
reinforce the need to be discerning of the fundamental differences of each approach in order to choose the most appropriate
one. Further, health workforce planning should also be approached in a comprehensive and integrated manner that accounts for
developments in demographic and healthcare systems
Scale-free static and dynamical correlations in melts of monodisperse and Flory-distributed homopolymers: A review of recent bond-fluctuation model studies
It has been assumed until very recently that all long-range correlations are
screened in three-dimensional melts of linear homopolymers on distances beyond
the correlation length characterizing the decay of the density
fluctuations. Summarizing simulation results obtained by means of a variant of
the bond-fluctuation model with finite monomer excluded volume interactions and
topology violating local and global Monte Carlo moves, we show that due to an
interplay of the chain connectivity and the incompressibility constraint, both
static and dynamical correlations arise on distances . These
correlations are scale-free and, surprisingly, do not depend explicitly on the
compressibility of the solution. Both monodisperse and (essentially)
Flory-distributed equilibrium polymers are considered.Comment: 60 pages, 49 figure
Density-functional calculation of ionization energies of current-carrying atomic states
Current-density-functional theory is used to calculate ionization energies of
current-carrying atomic states. A perturbative approximation to full
current-density-functional theory is implemented for the first time, and found
to be numerically feasible. Different parametrizations for the
current-dependence of the density functional are critically compared. Orbital
currents in open-shell atoms turn out to produce a small shift in the
ionization energies. We find that modern density functionals have reached an
accuracy at which small current-related terms appearing in open-shell
configurations are not negligible anymore compared to the remaining difference
to experiment.Comment: 7 pages, 2 tables, accepted by Phys. Rev.
The holographic superconductors in higher-dimensional AdS soliton
We explore the behaviors of the holographic superconductors at zero
temperature for a charged scalar field coupled to a Maxwell field in
higher-dimensional AdS soliton spacetime via analytical way. In the probe
limit, we obtain the critical chemical potentials increase linearly as a total
dimension grows up. We find that the critical exponent for condensation
operator is obtained as 1/2 independently of , and the charge density is
linearly related to the chemical potential near the critical point.
Furthermore, we consider a slightly generalized setup the
Einstein-Power-Maxwell field theory, and find that the critical exponent for
condensation operator is given as in terms of a power parameter
of the Power-Maxwell field, and the charge density is proportional to the
chemical potential to the power of .Comment: LaTeX, 16 pages, 5 figures, typos corrected, one reference added,
version to appear in European Physical Journal
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