150 research outputs found
A supersymmetric black ring
A new supersymmetric black hole solution of five-dimensional supergravity is
presented. It has an event horizon of topology S1xS2. This is the first example
of a supersymmetric, asymptotically flat black hole of non-spherical topology.
The solution is uniquely specified by its electric charge and two independent
angular momenta. These conserved charges can be arbitrarily close, but not
exactly equal, to those of a supersymmetric black hole of spherical topology.Comment: 4 pages, 1 figure. v2: Comment about chiral null models remove
Non-BPS D8-branes and Dynamic Domain Walls in Massive IIA Supergravities
We study the D8-branes of the Romans massive IIA supergravity theory using
the coupled supergravity and worldvolume actions. D8 branes can be regarded as
domain walls with the jump in the extrinsic curvature at the brane given by the
Israel matching conditions. We examine the restrictions that these conditions
place on extreme and non-extreme solutions and find that they rule out some of
the supersymmetric solutions given by Bergshoeff {\em et al}. We consider what
happens when the dilaton varies on the worldvolume of the brane, which implies
that the brane is no longer static. We obtain a family of D8-brane solutions
parametrized by a non-extremality term on each side of the brane and the
asymptotic values of the 10-form field. The non-extremality parameters can be
related to the velocity of the brane. We also study 8-brane solutions of a
massive IIA supergravity theory introduced by Howe, Lambert and West. This
theory also admits a 10-form formulation, but the 10-form is not a R-R sector
field and so these 8-branes are not D-branes.Comment: 23 pages REVTeX, 2 .eps figures. This paper completely replaces and
extends an earlier paper (hep-th/9712112) by Chamblin and Perr
Perturbations of higher-dimensional spacetimes
We discuss linearized gravitational perturbations of higher dimensional
spacetimes. For algebraically special spacetimes (e.g. Myers-Perry black
holes), we show that there exist local gauge invariant quantities linear in the
metric perturbation. These are the higher dimensional generalizations of the 4d
Newman-Penrose scalars that (in an algebraically special vacuum spacetime)
satisfy decoupled equations of motion. We show that decoupling occurs in more
than four dimensions if, and only if, the spacetime admits a null geodesic
congruence with vanishing expansion, rotation and shear. Decoupling of
electromagnetic perturbations occurs under the same conditions. Although these
conditions are not satisfied in black hole spacetimes, they are satisfied in
the near-horizon geometry of an extreme black hole.Comment: 21 pages (v2:Minor corrections, accepted by CQG.
How hairy can a black ring be?
It has been shown recently that there is a large class of supersymmetric
solutions of five-dimensional supergravity which generalize the supersymmetric
black ring solution of Elvang et al. This class involves arbitrary functions.
We show that most of these solutions do not have smooth event horizons, so they
do not provide examples of black objects with infinite amounts of "hair".Comment: 19 pages. v2: minor change
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