356 research outputs found
Kaehler forms and cosmological solutions in type II supergravities
We consider cosmological solutions to type II supergravity theories where the
spacetime is split into a FRW universe and a K\"ahler space, which may be taken
to be Calabi-Yau. The various 2-forms present in the theories are taken to be
proportional to the K\"ahler form associated to the K\"ahler space.Comment: 6 pages, LaTeX2
Performance-based financing as a health system reform : mapping the key dimensions for monitoring and evaluation
Peer reviewedPublisher PD
Black holes and black strings of N=2, d=5 supergravity in the H-FGK formalism
We study general classes and properties of extremal and non-extremal static
black-hole solutions of N=2, d=5 supergravity coupled to vector multiplets
using the recently proposed H-FGK formalism, which we also extend to static
black strings. We explain how to determine the integration constants and
physical parameters of the black-hole and black-string solutions. We derive
some model-independent statements, including the transformation of non-extremal
flow equations to the form of those for the extremal flow. We apply our methods
to the construction of example solutions (among others a new extremal string
solution of heterotic string theory on K_3 \times S^1). In the cases where we
have calculated it explicitly, the product of areas of the inner and outer
horizon of a non-extremal solution coincides with the square of the
moduli-independent area of the horizon of the extremal solution with the same
charges.Comment: 33 pages. Revised version: references added. No other change
Solutions of Minimal Four Dimensional de Sitter Supergravity
Pseudo-supersymmetric solutions of minimal , de Sitter
supergravity are classified using spinorial geometry techniques. We find three
classes of solutions. The first class of solution consists of geometries which
are fibrations over a 3-dimensional manifold equipped with a Gauduchon-Tod
structure. The second class of solution is the cosmological Majumdar-Papapetrou
solution of Kastor and Traschen, and the third corresponds to gravitational
waves propagating in the Nariai cosmology.Comment: 17 Pages. Minor correction to section 4; equation (4.21) corrected
and (old) equation (4.26) deleted; the final result is unchange
Analysis and design of a slotless tubular permanent magnet actuator for high acceleration applications
This paper presents the design of a linear actuator for high acceleration applications. In the analysis, a slotless tubular permanent magnet actuator is modeled by means of semianalytical field solutions. Several slotless topologies are modeled and compared to achieve the highest acceleration. A design has been proposed and built, and measurements are conducted to verify the model
Three-Dimensional Magnetic Field Modeling of a Cylindrical Halbach Array
A semi-analytical description of the 3-D magnetic field distribution of a cylindrical quasi-Halbach permanent magnet array is derived. This model avoids the necessity of time-consuming finite element analyses and allows for fast parameterization to investigate the influence of the number of segments on the magnetic flux density distribution. The segmented magnet is used to approximate an ideal radial magnetized ring in a cylindrical quasi-Halbach array. The model is obtained by solving the Maxwell equations using the magnetic scalar potential and describes the magnetic fields by a Fourier series
Homogeneity and plane-wave limits
We explore the plane-wave limit of homogeneous spacetimes. For plane-wave
limits along homogeneous geodesics the limit is known to be homogeneous and we
exhibit the limiting metric in terms of Lie algebraic data. This simplifies
many calculations and we illustrate this with several examples. We also
investigate the behaviour of (reductive) homogeneous structures under the
plane-wave limit.Comment: In memory of Stanley Hobert, 33 pages. Minor corrections and some
simplification of Section 4.3.
Extensions of AdS_5 x S^5 and the Plane-wave Superalgebras and Their Realization in the Tiny Graviton Matrix Theory
In this paper we consider all consistent extensions of the AdS_5 x S^5
superalgebra, psu(2,2|4), to incorporate brane charges by introducing both
bosonic and fermionic (non)central extensions. We study the Inonu-Wigner
contraction of the extended psu(2,2|4) under the Penrose limit to obtain the
most general consistent extension of the plane-wave superalgebra and compare
these extensions with the possible BPS (flat or spherical) brane configurations
in the plane-wave background. We give an explicit realization of some of these
extensions in terms of the Tiny Graviton Matrix Theory (TGMT)[hep-th/0406214]
which is the 0+1 dimensional gauge theory conjectured to describe the DLCQ of
strings on the AdS_5 x S^5 and/or the plane-wave background.Comment: 27 pages, LaTe
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