34 research outputs found
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
Almost-BPS Solutions in Multi-Center Taub-NUT
Microstates of multiple collinear black holes embedded in a non-collinear two-center Taub-NUT spacetime are sought in 4 dimensions. A set of coupled partial differential equations are obtained and solved for almost-BPS states, where some supersymmetry is preserved in the context of N = 2 supergravity in 4 dimensions. The regularity of solutions is carefully considered, and we ensure that no CTC (closed time-like curves) are present. The larger framework is that of 11-dimensional N = 2 supergravity, and the current theory is obtained by compactifying it down to 4 dimensions. This work is a generalization (to three non-collinear centers) of a previous paper by Bena et al
Supergravity Solutions from Floating Branes
We solve the equations of motion of five-dimensional ungauged supergravity
coupled to three U(1) gauge fields using a floating-brane Ansatz in which the
electric potentials are directly related to the gravitational warp factors. We
find a new class of non-BPS solutions, that can be obtained linearly starting
from an Euclidean four-dimensional Einstein-Maxwell base. This class - the
largest known so far - reduces to the BPS and almost-BPS solutions in certain
limits. We solve the equations explicitly when the base space is given by the
Israel-Wilson metric, and obtain solutions describing non-BPS D6 and anti-D6
branes kept in equilibrium by flux. We also examine the action of spectral flow
on solutions with an Israel-Wilson base and show that it relates these
solutions to almost-BPS solutions with a Gibbons-Hawking base.Comment: 24 pages, 1 figur
Radiation from the non-extremal fuzzball
The fuzzball proposal says that the information of the black hole state is
distributed throughout the interior of the horizon in a `quantum fuzz'. There
are special microstates where in the dual CFT we have `many excitations in the
same state'; these are described by regular classical geometries without
horizons. Jejjala et.al constructed non-extremal regular geometries of this
type. Cardoso et. al then found that these geometries had a classical
instability. In this paper we show that the energy radiated through the
unstable modes is exactly the Hawking radiation for these microstates. We do
this by (i) starting with the semiclassical Hawking radiation rate (ii) using
it to find the emission vertex in the CFT (iii) replacing the Boltzman
distributions of the generic CFT state with the ones describing the microstate
of interest (iv) observing that the emission now reproduces the classical
instability. Because the CFT has `many excitations in the same state' we get
the physics of a Bose-Einstein condensate rather than a thermal gas, and the
usually slow Hawking emission increases, by Bose enhancement, to a classically
radiated field. This system therefore provides a complete gravity description
of information-carrying radiation from a special microstate of the nonextremal
hole.Comment: corrected typo
Imaginary Soaring Branes: A Hidden Feature of Non-Extremal Solutions
A key property of many BPS solutions of supergravity is the fact that certain
probe branes placed in these solutions feel no force, essentially because
electric repulsion and gravitational attraction balance one another. In this
letter we show that the existence of brane probes that feel no force is also a
property of many non-supersymmetric, non-extremal solutions of supergravity.
This observation requires a new class of brane probes that move with constant
velocity along one or several internal directions of the solution but the
zero-force condition that makes the branes "float along" at constant speed, or
soar, requires the velocity to be purely imaginary. While these probes are not
physical, their no-force condition implies the existence of hidden relations
between the warp factors and electric potentials of non-extremal solutions in
certain duality frames, and this provides insight into the structure of such
solutions and can greatly simplify the search for them.Comment: 14 pages LeTe
Holographic Coulomb Branch Flows with N=1 Supersymmetry
We obtain a large, new class of N=1 supersymmetric holographic flow
backgrounds with U(1)^3 symmetry. These solutions correspond to flows toward
the Coulomb branch of the non-trivial N=1 supersymmetric fixed point. The
massless (complex) chiral fields are allowed to develop vevs that are
independent of their two phase angles, and this corresponds to allowing the
brane to spread with arbitrary, U(1)^2 invariant, radial distributions in each
of these directions. Our solutions are "almost Calabi-Yau:" The metric is
hermitian with respect to an integrable complex structure, but is not Kahler.
The "modulus squared" of the holomorphic (3,0)-form is the volume form, and the
complete solution is characterized by a function that must satisfy a single
partial differential equation that is closely related to the Calabi-Yau
condition. The deformation from a standard Calabi-Yau background is driven by a
non-trivial, non-normalizable 3-form flux dual to a fermion mass that reduces
the supersymmetry to N=1. This flux also induces dielectric polarization of the
D3-branes into D5-branes.Comment: 22 pages; harvmac. Typos corrected;small improvements in presentatio
Supersymmetric Charged Clouds in AdS_5
We consider supersymmetric holographic flows that involve background gauge
fields dual to chemical potentials in the boundary field theory. We use a
consistent truncation of gauged N=8 supergravity in five dimensions and we give
a complete analysis of the supersymmetry conditions for a large family of
flows. We examine how the well-known supersymmetric flow between two fixed
points is modified by the presence of the chemical potentials and this yields a
new, completely smooth, solution that interpolates between two global AdS
spaces of different radii and with different values of the chemical potential.
We also examine some black-hole-like singular flows and a new
non-supersymmetric black hole solution. We comment on the interpretation of our
new solutions in terms of giant gravitons and discuss the implications of our
work for finding black-hole solutions in AdS geometries.Comment: 31 pages, 6 figures; minor corrections, updated reference
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
The information paradox: A pedagogical introduction
The black hole information paradox is a very poorly understood problem. It is
often believed that Hawking's argument is not precisely formulated, and a more
careful accounting of naturally occurring quantum corrections will allow the
radiation process to become unitary. We show that such is not the case, by
proving that small corrections to the leading order Hawking computation cannot
remove the entanglement between the radiation and the hole. We formulate
Hawking's argument as a `theorem': assuming `traditional' physics at the
horizon and usual assumptions of locality we will be forced into mixed states
or remnants. We also argue that one cannot explain away the problem by invoking
AdS/CFT duality. We conclude with recent results on the quantum physics of
black holes which show the the interior of black holes have a `fuzzball'
structure. This nontrivial structure of microstates resolves the information
paradox, and gives a qualitative picture of how classical intuition can break
down in black hole physics.Comment: 38 pages, 7 figures, Latex (Expanded form of lectures given at CERN
for the RTN Winter School, Feb 09), typo correcte