7 research outputs found
Reduction without reduction: Adding KK-monopoles to five dimensional stationary axisymmetric solutions
We present a general method to add KK-monopole charge to any asymptotically
flat stationary axisymmetric solution of five dimensional General Relativity.
The technique exploits the underlying SL(3,R) invariance of the system by
identifying a particular element of the symmetry group which changes the
asymptotic boundary condition and adds KK-monopole charge. Furthermore, we
develop a set of technical tools which allow us to apply the SL(3,R)
transformations to solutions produced by the Inverse Scattering method. As an
example of our methods, we construct the exact solution describing a static
black ring carrying KK-monopole charge.Comment: 36 pages, 3 figures, LaTeX, minor typos fixe
Fractional Brane State in the Early Universe
In the early Universe matter was crushed to high densities, in a manner
similar to that encountered in gravitational collapse to black holes. String
theory suggests that the large entropy of black holes can be understood in
terms of fractional branes and antibranes. We assume a similar physics for the
matter in the early Universe, taking a toroidal compactification and letting
branes wrap around the cycles of the torus. We find an equation of state
p_i=w_i rho, for which the dynamics can be solved analytically. For black
holes, fractionation can lead to non-local quantum gravity effects across
length scales of order the horizon radius; similar effects in the early
Universe might change our understanding of Cosmology in basic ways.Comment: 40 pages, 18 figures, references adde
The quantum structure of black holes
We give an elementary review of black holes in string theory. We discuss
black hole entropy from string microstates and Hawking radiation from these
states. We then review the structure of 2-charge microstates, and explore how
`fractionation' can lead to quantum effects over macroscopic length scales of
order the horizon radius.Comment: Review article, 58 pages, 2 figures; references added, note about
topics covere
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
Massless black holes and black rings as effective geometries of the D1-D5 system
We compute correlation functions in the AdS/CFT correspondence to study the
emergence of effective spacetime geometries describing complex underlying
microstates. The basic argument is that almost all microstates of fixed charges
lie close to certain "typical" configurations. These give a universal response
to generic probes, which is captured by an emergent geometry. The details of
the microstates can only be observed by atypical probes. We compute two point
functions in typical ground states of the Ramond sector of the D1-D5 CFT, and
compare with bulk two-point functions computed in asymptotically AdS_3
geometries. For large central charge (which leads to a good semiclassical
limit), and sufficiently small time separation, a typical Ramond ground state
of vanishing R-charge has the M=0 BTZ black hole as its effective description.
At large time separation this effective description breaks down. The CFT
correlators we compute take over, and give a response whose details depend on
the microstate. We also discuss typical states with nonzero R-charge, and argue
that the effective geometry should be a singular black ring. Our results
support the argument that a black hole geometry should be understood as an
effective coarse-grained description that accurately describes the results of
certain typical measurements, but breaks down in general.Comment: 47 pages, 4 figures. v2: references added. v3: minor corrections to
Appendix A, references adde
Black Holes as Effective Geometries
Gravitational entropy arises in string theory via coarse graining over an
underlying space of microstates. In this review we would like to address the
question of how the classical black hole geometry itself arises as an effective
or approximate description of a pure state, in a closed string theory, which
semiclassical observers are unable to distinguish from the "naive" geometry. In
cases with enough supersymmetry it has been possible to explicitly construct
these microstates in spacetime, and understand how coarse-graining of
non-singular, horizon-free objects can lead to an effective description as an
extremal black hole. We discuss how these results arise for examples in Type II
string theory on AdS_5 x S^5 and on AdS_3 x S^3 x T^4 that preserve 16 and 8
supercharges respectively. For such a picture of black holes as effective
geometries to extend to cases with finite horizon area the scale of quantum
effects in gravity would have to extend well beyond the vicinity of the
singularities in the effective theory. By studying examples in M-theory on
AdS_3 x S^2 x CY that preserve 4 supersymmetries we show how this can happen.Comment: Review based on lectures of JdB at CERN RTN Winter School and of VB
at PIMS Summer School. 68 pages. Added reference