923 research outputs found
Dynamical symmetry enhancement near N=2, D=4 gauged supergravity horizons
We show that all smooth Killing horizons with compact horizon sections of
4-dimensional gauged N=2 supergravity coupled to any number of vector
multiplets preserve supersymmetries, where
is a pull-back of the Hodge bundle of the special K\"ahler manifold on the
horizon spatial section. We also demonstrate that all such horizons with
exhibit an SL(2,R) symmetry and preserve either 4 or 8
supersymmetries. If the orbits of the SL(2,R) symmetry are 2-dimensional, the
horizons are warped products of AdS2 with the horizon spatial section.
Otherwise, the horizon section admits an isometry which preserves all the
fields. The proof of these results is centered on the use of index theorem in
conjunction with an appropriate generalization of the Lichnerowicz theorem for
horizons that preserve at least one supersymmetry. In all
cases, we specify the local geometry of spatial horizon sections and
demonstrate that the solutions are determined by first order non-linear
ordinary differential equations on some of the fields.Comment: 60 pages, late
Bubbling 1/2 BPS solutions of minimal six-dimensional supergravity
We continue our previous analysis (hep-th/0412045) of 1/2 BPS solutions to
minimal 6d supergravity of bubbling form. We show that, by turning on an axion
field in the T^2 torus reduction, the constraint F \wedge F, present in the
case of an S^1 x S^1 reduction, is relaxed. We prove that the four-dimensional
reduction to a bosonic field theory, whose content is the metric, a gauge
field, two scalars and a pseudo-scalar (the axion), is consistent. Moreover,
these reductions when lifted to the six-dimensional minimal supergravity
represent the sought-after family of 1/2 BPS bubbling solutions.Comment: 17 pages, late
Mapping the G-structures and supersymmetric vacua of five-dimensional N=4 supergravity
We classify the supersymmetric vacua of N=4, d=5 supergravity in terms of
G-structures. We identify three classes of solutions: with R^3, SU(2) and
generic SO(4) structure. Using the Killing spinor equations, we fully
characterize the first two classes and partially solve the latter. With the N=4
graviton multiplet decomposed in terms of N=2 multiplets: the graviton, vector
and gravitino multiplets, we obtain new supersymmetric solutions corresponding
to turning on fields in the gravitino multiplet. These vacua are described in
terms of an SO(5) vector sigma-model coupled with gravity, in three or four
dimensions. A new feature of these N=4 vacua, which is not seen from an N=2
point of view, is the possibility for preserving more exotic fractions of
supersymmetry. We give a few concrete examples of these new supersymmetric
(albeit singular) solutions. Additionally, we show how by truncating the N=4,
d=5 set of fields to minimal supergravity coupled with one vector multiplet we
recover the known two-charge solutions.Comment: 31 pages, late
Five-dimensional Nernst branes from special geometry
We construct Nernst brane solutions, that is black branes with zero entropy
density in the extremal limit, of FI-gauged minimal five-dimensional
supergravity coupled to an arbitrary number of vector multiplets. While the
scalars take specific constant values and dynamically determine the value of
the cosmological constant in terms of the FI-parameters, the metric takes the
form of a boosted AdS Schwarzschild black brane. This metric can be brought to
the Carter-Novotny-Horsky form that has previously been observed to occur in
certain limits of boosted D3-branes. By dimensional reduction to four
dimensions we recover the four-dimensional Nernst branes of arXiv:1501.07863
and show how the five-dimensional lift resolves all their UV singularities. The
dynamics of the compactification circle, which expands both in the UV and in
the IR, plays a crucial role. At asymptotic infinity, the curvature singularity
of the four-dimensional metric and the run-away behaviour of the
four-dimensional scalar combine in such a way that the lifted solution becomes
asymptotic to AdS5. Moreover, the existence of a finite chemical potential in
four dimensions is related to fact that the compactification circle has a
finite minimal value. While it is not clear immediately how to embed our
solutions into string theory, we argue that the same type of dictionary as
proposed for boosted D3-branes should apply, although with a lower amount of
supersymmetry.Comment: 59 pages, 1 figure. Revised version: references added, typos
corrected. Final version, accepted by JHEP: two references adde
Cosmological Solutions, a New Wick-Rotation, and the First Law of Thermodynamics
We present a modified implementation of the Euclidean action formalism suitable for studying the thermodynamics of a class of cosmological solutions containing Killing horizons. To obtain a real metric of definite signature, we perform a `triple Wick-rotation' by analytically continuing all space-like directions. The resulting Euclidean geometry is used to calculate the Euclidean on-shell action, which defines a thermodynamic potential. We show that for the vacuum de Sitter solution, planar solutions of Einstein-Maxwell theory and a previously found class of cosmological solutions of N = 2 supergravity, this thermodynamic potential can be used to define an internal energy which obeys the first law of thermodynamics. Our approach is complementary to, but consistent with the isolated horizon formalism. For planar Einstein-Maxwell solutions, we find dual solutions in Einstein-anti-Maxwell theory where the sign of the Maxwell term is reversed. These solutions are planar black holes, rather than cosmological solutions, but give rise, upon a standard Wick-rotation to the same Euclidean action and thermodynamic relations
Three Charge Supertubes in Type IIB Plane Wave Backgrounds
We deform the supersymmetric black ring of five dimensional supergravity
coupled to N-1 vector multiplets to obtain an asymptotically Goedel
supersymmetric black ring. For the U(1)^3 model we lift this solution to obtain
a three charge D1-D5-P supertube which asymptotes to a 1/2 supersymmetric plane
wave of Type IIB supergravity. Further, we also show how one may deform the
asymptotically flat three charge supertube of type IIB, in the special case of
vanishing KK dipole charge, to a three charge supertube which asymptotes to the
maximally supersymmetric plane wave.Comment: 1+14 pages, JHEP
The Geometry of D=11 Null Killing Spinors
We determine the necessary and sufficient conditions on the metric and the
four-form for the most general bosonic supersymmetric configurations of D=11
supergravity which admit a null Killing spinor i.e. a Killing spinor which can
be used to construct a null Killing vector. This class covers all
supersymmetric time-dependent configurations and completes the classification
of the most general supersymmetric configurations initiated in hep-th/0212008.Comment: 30 pages, typos corrected, reference added, new solution included in
section 5.1; uses JHEP3.cl
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
M-Horizons
We solve the Killing spinor equations and determine the near horizon
geometries of M-theory that preserve at least one supersymmetry. The M-horizon
spatial sections are 9-dimensional manifolds with a Spin(7) structure
restricted by geometric constraints which we give explicitly. We also provide
an alternative characterization of the solutions of the Killing spinor
equation, utilizing the compactness of the horizon section and the field
equations, by proving a Lichnerowicz type of theorem which implies that the
zero modes of a Dirac operator coupled to 4-form fluxes are Killing spinors. We
use this, and the maximum principle, to solve the field equations of the theory
for some special cases and present some examples.Comment: 36 pages, latex. Reference added, minor typos correcte
Designers' unified cost model
The Structures Technology Program Office (STPO) at NASA LaRC has initiated development of a conceptual and preliminary designers' cost prediction model. The model will provide a technically sound method for evaluating the relative cost of different composite structural designs, fabrication processes, and assembly methods that can be compared to equivalent metallic parts or assemblies. The feasibility of developing cost prediction software in a modular form for interfacing with state-of-the-art preliminary design tools and computer aided design programs is being evaluated. The goal of this task is to establish theoretical cost functions that relate geometric design features to summed material cost and labor content in terms of process mechanics and physics. The output of the designers' present analytical tools will be input for the designers' cost prediction model to provide the designer with a database and deterministic cost methodology that allows one to trade and synthesize designs with both cost and weight as objective functions for optimization. This paper presents the team members, approach, goals, plans, and progress to date for development of COSTADE (Cost Optimization Software for Transport Aircraft Design Evaluation)
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