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

Supersymmetry of Massive D=9 Supergravity

By applying generalized dimensional reduction on the type IIB supersymmetry variations, we derive the supersymmetry variations for the massive 9-dimensional supergravity. We use these variations and the ones for massive type IIA to derive the supersymmetry transformation of the gravitino for the proposed massive 11-dimensional supergravity.Comment: 13 page

The FGK formalism for black p-branes in d dimensions

We present a generalization to an arbitrary number of spacetime (d) and worldvolume (p+1) dimensions of the formalism proposed by Ferrara, Gibbons and Kallosh to study black holes (p=0) in d=4 dimensions. We include the special cases in which there can be dyonic and self- or anti-self-dual black branes. Most of the results valid for 4-dimensional black holes (relations between temperature, entropy and non-extremality parameter, and between entropy and black-hole potential on the horizon) are straightforwardly generalized. We apply the formalism to the case of black strings in N=2,d=5 supergravity coupled to vector multiplets, in which the black-string potential can be expressed in terms of the dual central charge and work out an explicit example with one vector multiplet, determining supersymmetric and non-supersymmetric attractors and constructing the non-extremal black-string solutions that interpolate between them.Comment: 28 pages no figures; v2: some references adde

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

Type 0 T-Duality and the Tachyon Coupling

We consider the T-duality relations between Type 0A and 0B theories, and show that this constraints the possible couplings of the tachyon to the RR-fields. Due to the `doubling' of the RR sector in Type 0 theories, we are able to introduce a democratic formulation for the Type 0 effective actions, in which there is no Chern-Simons term in the effective action. Finally we discuss how to embed Type II solutions into Type 0 theories.Comment: some misprints corrected and a reference adde

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.

A geometrical calibration method for the PIXSCAN micro-CT scanner

Reconstruction in Cone-Beam Tomography can suffer from artifacts due to geometrical misalignments of the source-detector system. They can be avoided by a complete and precise description of the system. We present a high precision method for the geometric calibration for the PIXSCAN, a small animal X-ray CT scanner demonstrator based on hybrid pixel detectors (XPAD2). The specificities of the XPAD2 detectors (dead pixels, tilts and gaps between modules...) made the calibration of the PIXSCAN quite difficult. The method uses a calibration object consisting of a hollow cylinder of polycarbonate on which we positioned four metallic balls. It requires 360 X-ray images (1° increments). An analytic expression of the 3 image ellipses has been derived. It is used for a least square regression of the 13 alignment parameters after a correction of the internal XPAD2 geometry. Our method is fast and completely automated, achieving a precision of about 30 μm

Solutions of Minimal Four Dimensional de Sitter Supergravity

Pseudo-supersymmetric solutions of minimal $N=2$, $D=4$ 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