384 research outputs found
Multi-Centered Black Hole Flows
We describe the systematical construction of the first order formalism for
multi-centered black holes with flat three dimensional base-space, within the
so-called model of N=2, D=4 ungauged Maxwell-Einstein supergravity. The
three possible flow classes (BPS, composite non-BPS and almost-BPS) are
analyzed in detail, and various solutions, such as single-centered (static or
under-rotating) and all known multi-centered black holes, are recovered in this
unified framework. We also consider the possibility of obtaining new solutions.
The almost-BPS class is proved to split into two general sub-classes,
corresponding to a positive or negative value of the duality-invariant
polynomial for the total charge; the well known almost BPS system is shown to
be a particular solution of the second sub-class.Comment: 17 pages,no figure
Duality covariant non-BPS first order systems
We study extremal black hole solutions to four dimensional N=2 supergravity
based on a cubic symmetric scalar manifold. Using the coset construction
available for these models, we define the first order flow equations implied by
the corresponding nilpotency conditions on the three-dimensional scalar momenta
for the composite non-BPS class of multi-centre black holes. As an application,
we directly solve these equations for the single-centre subclass, and write the
general solution in a manifestly duality covariant form. This includes all
single-centre under-rotating non-BPS solutions, as well as their
non-interacting multi-centre generalisations.Comment: 31 pages, v2: Discussion of the quadratic constraint clarified,
references added, typos corrected, published versio
String Theory, Unification and Quantum Gravity
An overview is given of the way in which the unification program of particle
physics has evolved into the proposal of superstring theory as a prime
candidate for unifying quantum gravity with the other forces and particles of
nature. A key concern with quantum gravity has been the problem of ultraviolet
divergences, which is naturally solved in string theory by replacing particles
with spatially extended states as the fundamental excitations. String theory
turns out, however, to contain many more extended-object states than just
strings. Combining all this into an integrated picture, called M-theory,
requires recognition of the r\^ole played by a web of nonperturbative duality
symmetries suggested by the nonlinear structures of the field-theoretic
supergravity limits of string theory.Comment: 29 pages, 13 figures, 3 tables; Lectures given at the 6th Aegean
Summer School "Quantum Gravity and Quantum Cosmology", Chora, Naxos Island,
Greece, 12-17 September 201
New instability of non-extremal black holes: spitting out supertubes
We search for stable bound states of non-extremal rotating three-charge black
holes in five dimensions (Cvetic-Youm black holes) and supertubes. We do this
by studying the potential of supertube probes in the non-extremal black hole
background and find that generically the marginally bound state of the
supersymmetric limit becomes metastable and disappears with non-extremality
(higher temperature). However near extremality there is a range of parameters
allowing for stable bound states, which have lower energy than the
supertube-black hole merger. Angular momentum is crucial for this effect. We
use this setup in the D1-D5 decoupling limit to map a thermodynamic instability
of the CFT (a new phase which is entropically dominant over the black hole
phase) to a tunneling instability of the black hole towards the supertube-black
hole bound state. This generalizes the results of ArXiv:1108.0411 [hep-th],
which mapped an entropy enigma in the bulk to the dual CFT in a supersymmetric
setup.Comment: 28 pages + appendix, 15 figures, v2: References added, typos
corrected. Version published in JHE
Octonionic black holes
Using algebraic tools inspired by the study of nilpotent orbits in simple Lie
algebras, we obtain a large class of solutions describing interacting non-BPS
black holes in N=8 supergravity, which depend on 44 harmonic functions. For
this purpose, we consider a truncation E6(6) / Sp(8,R) of the non-linear sigma
model describing stationary solutions of the theory, which permits a reduction
of algebraic computations to the multiplication of 27 by 27 matrices. The lift
to N=8 supergravity is then carried out without loss of information by using a
pertinent representation of the moduli parametrizing E7(7) / SU(8) in terms of
complex valued Hermitian matrices over the split octonions, which generalise
the projective coordinates of exceptional special Kaehler manifolds. We extract
the electromagnetic charges, mass and angular momenta of the solutions, and
exhibit the duality invariance of the black holes distance separations. We
discuss in particular a new type of interaction which appears when interacting
non-BPS black holes are not aligned. Finally we will explain the possible
generalisations toward the description of the most general stationary black
hole solutions of N=8 supergravity.Comment: 90 pages, Corrected version for publication in JHE
First-order flows and stabilisation equations for non-BPS extremal black holes
We derive a generalised form of flow equations for extremal static and
rotating non-BPS black holes in four-dimensional ungauged N = 2 supergravity
coupled to vector multiplets. For particular charge vectors, we give
stabilisation equations for the scalars, analogous to the BPS case, describing
full known solutions. Based on this, we propose a generic ansatz for the
stabilisation equations, which surprisingly includes ratios of harmonic
functions.Comment: 27 pages; v2: presentation improved and references added as in the
published versio
A General Black String and its Microscopics
Using G2(2) dualities we construct the most general black string solution of
minimal five-dimensional ungauged supergravity. The black string has five
independent parameters, namely, the magnetic one-brane charge, smeared electric
zero-brane charge, boost along the string direction, energy above the BPS
bound, and rotation in the transverse space. In one extremal limit it reduces
to the three parameter supersymmetric string of five-dimensional minimal
supergravity; in another extremal limit it reduces to the three parameter
non-supersymmetric extremal string of five-dimensional minimal supergravity. It
also admits an extremal limit when it has maximal rotation in the
four-dimensional transverse space. The decoupling limit of our general black
string is a BTZ black hole times a two sphere. The macroscopic entropy of the
string is reproduced by the Maldacena-Strominger-Witten CFT in appropriate
ranges of the parameters. When the pressureless condition is imposed, our
string describes the infinite radius limit of the most general class of black
rings of minimal supergravity. We discuss implications our solution has for
extremal and non-extremal black rings of minimal supergravity.Comment: 35 pages; 3 figures; v2 section 4.1.1 rewritten + minor changes + ref
adde
Subtracted Geometry From Harrison Transformations
We consider the rotating non-extremal black hole of N=2 D=4 STU supergravity
carrying three magnetic charges and one electric charge. We show that its
subtracted geometry is obtained by applying a specific SO(4,4) Harrison
transformation on the black hole. As previously noted, the resulting subtracted
geometry is a solution of the N=2 S=T=U supergravity.Comment: 11 pages main text; total 24 pages; Latex file; v2 typos corrected +
ref added; v3 results significantly strengthened, changes in section 3.1 and
appendix C, version to appear in JHE
Non-extremal Black Hole Microstates: Fuzzballs of Fire or Fuzzballs of Fuzz ?
We construct the first family of microstate geometries of near-extremal black
holes, by placing metastable supertubes inside certain scaling supersymmetric
smooth microstate geometries. These fuzzballs differ from the classical black
hole solution macroscopically at the horizon scale, and for certain probes the
fluctuations between various fuzzballs will be visible as thermal noise far
away from the horizon. We discuss whether these fuzzballs appear to infalling
observers as fuzzballs of fuzz or as fuzzballs of fire. The existence of these
solutions suggests that the singularity of non-extremal black holes is resolved
all the way to the outer horizon and this "backwards in time" singularity
resolution can shed light on the resolution of spacelike cosmological
singularities.Comment: 34 pages, 10 figure
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
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