124 research outputs found
AdS and Lifshitz Black Holes in Conformal and Einstein-Weyl Gravities
We study black hole solutions in extended gravities with higher-order
curvature terms, including conformal and Einstein-Weyl gravities. In addition
to the usual AdS vacuum, the theories admit Lifshitz and Schr\"odinger vacua.
The AdS black hole in conformal gravity contains an additional parameter over
and above the mass, which may be interpreted as a massive spin-2 hair. By
considering the first law of thermodynamics, we find that it is necessary to
introduce an associated additional intensive/extensive pair of thermodynamic
quantities. We also obtain new Liftshitz black holes in conformal gravity and
study their thermodynamics. We use a numerical approach to demonstrate that AdS
black holes beyond the Schwarzschild-AdS solution exist in Einstein-Weyl
gravity. We also demonstrate the existence of asymptotically Lifshitz black
holes in Einstein-Weyl gravity. The Lifshitz black holes arise at the boundary
of the parameter ranges for the AdS black holes. Outside the range, the
solutions develop naked singularities. The asymptotically AdS and Lifshitz
black holes provide an interesting phase transition, in the corresponding
boundary field theory, from a relativistic Lorentzian system to a
non-relativistic Lifshitz system.Comment: typos corrected, references adde
Instanton Moduli and Brane Creation
We obtain new intersecting 5-brane, string and pp-wave solutions in the
heterotic string on a torus and on a K3 manifold. In the former case the
5-brane is supported by Yang-Mills instantons, and in the latter case both the
5-brane and the string are supported by the instantons. The instanton moduli
are parameterised by the sizes and locations of the instantons. We exhibit two
kinds of phase transition in which, for suitable choices of the instanton
moduli, a 5-brane and/or a string can be created. One kind of phase transition
occurs when the size of an instanton vanishes, while the other occurs when a
pair of Yang-Mills instantons coalesce. We also study the associated
five-dimensional black holes and the implications of these phase transitions
for the black-hole entropy. Specifically, we find that the entropy of the
three-charge black holes is zero when the instantons are separated and of
non-zero scale size, but becomes non-zero (which can be counted miscrospically)
after either of the phase transitions.Comment: 18 pages, Late
PP-waves in AdS Gauged Supergravities and Supernumerary Supersymmetry
Purely gravitational pp-waves in AdS backgrounds are described by the
generalised Kaigorodov metrics, and they generically preserve 1/4 of the
maximum supersymmetry allowed by the AdS spacetimes. We obtain 1/2
supersymmetric purely gravitational pp-wave solutions, in which the Kaigorodov
component is set to zero. We construct pp-waves in AdS gauged supergravities
supported by a vector field. We find that the solutions in D=4 and D=5 can then
preserve 1/2 of the supersymmetry. Like those in ungauged supergravities, the
supernumerary supersymmetry imposes additional constraints on the harmonic
function associated with the pp-waves. These new backgrounds provide
interesting novel features of the supersymmetry enhancement for the dual
conformal field theory in the infinite-momentum frame.Comment: Latex, 27 pages, minor typos corrected and reference added, to appear
in Phys. Rev.
Generalized solutions of the kundt class for the einstein equations with the cosmological constant
Vacuum solutions of type III and N in the Kundt class are completely known (W. Kundt, Z. Phys., No. 163, 77 (1961)). In this paper, we present two classes of solutions for the case of the Einstein vacuum equations with cosmological constant A. Each class of solutions is characterized by the fact that the wave 2-surface is a space of constant curvature with K = 6A and K = 2A. © 1997 Plenum Publishing Corporation
New Supersymmetric Solutions in N=2 Matter Coupled AdS_3 Supergravities
We construct new 1/2 supersymmetric solutions in D=3, N=2, matter coupled,
U(1) gauged supergravities and study some of their properties. We do this by
employing a quite general supersymmetry breaking condition, from which we also
redrive some of the already known solutions. Among the new solutions, we have
an explicit non-topological soliton for the non-compact sigma model, a locally
flat solution for the compact sigma model and a string-like solution for both
types of sigma models. The last one is smooth for the compact scalar manifold.Comment: 1+21 pages, 2 figures, LaTeX2e, JHEP style; v2: added one reference +
made minor changes and added a few comments to clarify the presentatio
Algebraically special gravitational fields with single-parameter motion groups
The Newman-Penrose equations for the general class of algebraically special gravitational fields with both nonzero and zero cosmological constants are reduced for gravitational fields outside of the field sources. Then new classes of exact solutions of the nondegenerate Petrov II type are derived under the additional requirement that a single-parameter group of isometric motions exist. © 1996 Plenum Publishing Corporation
AdS pp-waves
We obtain the pp-waves of D=5 and D=4 gauged supergravities supported by
and gauge field strengths respectively. We show that
generically these solutions preserve 1/4 of the supersymmetry, but
supernumerary supersymmetry can arise for appropriately constrained harmonic
functions associated with the pp-waves. In particular it implies that the
solutions are independent of the light-cone coordinate . We also obtain
the pp-waves in the Freedman-Schwarz model.Comment: Latex, 19 pages, minor changes, to appear in JHE
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