37 research outputs found
Virtual Black Holes
One would expect spacetime to have a foam-like structure on the Planck scale
with a very high topology. If spacetime is simply connected (which is assumed
in this paper), the non-trivial homology occurs in dimension two, and spacetime
can be regarded as being essentially the topological sum of and
bubbles. Comparison with the instantons for pair creation of black holes
shows that the bubbles can be interpreted as closed loops of
virtual black holes. It is shown that scattering in such topological
fluctuations leads to loss of quantum coherence, or in other words, to a
superscattering matrix that does not factorise into an matrix and its
adjoint. This loss of quantum coherence is very small at low energies for
everything except scalar fields, leading to the prediction that we may never
observe the Higgs particle. Another possible observational consequence may be
that the angle of QCD is zero without having to invoke the
problematical existence of a light axion. The picture of virtual black holes
given here also suggests that macroscopic black holes will evaporate down to
the Planck size and then disappear in the sea of virtual black holes.Comment: 24p, LaTeX, 3 postscript figures included with epsf sent in a
seperate uuencoded fil
Gauge Theory Description of D-brane Black Holes: Emergence of the Effective SCFT and Hawking Radiation
We study the hypermultiplet moduli space of an N=4, U(Q_1)xU(Q_5) gauge
theory in 1+1 dimensions to extract the effective SCFT description of near
extremal 5-dimensional black holes modelled by a collection of D1- and
D5-branes. On the moduli space, excitations with fractional momenta arise due
to a residual discrete gauge invariance. It is argued that, in the infra-red,
the lowest energy excitations are described by an effective c=6, N=4 SCFT on
T^4, also valid in the large black hole regime. The ``effective string
tension'' is obtained using T-duality covariance. While at the microscopic
level, minimal scalars do not couple to (1,5) strings, in the effective theory
a coupling is induced by (1,1) and (5,5) strings, leading to Hawking radiation.
These considerations imply that, at least for such black holes, the calculation
of the Hawking decay rate for minimal scalars has a sound foundation in string
theory and statistical mechanics and, hence, there is no information loss.Comment: 24 pages, LaTeX, very minor changes, to appear in Nucl. Phys.
Duality between Electric and Magnetic Black Holes
A number of attempts have recently been made to extend the conjectured
duality of Yang Mills theory to gravity. Central to these speculations has been
the belief that electrically and magnetically charged black holes, the solitons
of quantum gravity, have identical quantum properties. This is not obvious,
because although duality is a symmetry of the classical equations of motion, it
changes the sign of the Maxwell action. Nevertheless, we show that the chemical
potential and charge projection that one has to introduce for electric but not
magnetic black holes exactly compensate for the difference in action in the
semi-classical approximation. In particular, we show that the pair production
of electric black holes is not a runaway process, as one might think if one
just went by the action of the relevant instanton. We also comment on the
definition of the entropy in cosmological situations, and show that we need to
be more careful when defining the entropy than we are in an asymptotically-flat
case.Comment: 23 pages, revtex, no figures. Major revision: two sections on the
electric Ernst solution adde
Gravity Dual of Gauge Theory on S^2 x S^1 x R
We (numerically) construct new static, asymptotically AdS solutions where the
conformal infinity is the product of time and S^2 x S^1. There always exist a
family of solutions in which the S^1 is not contractible and, for small S^1,
there are two additional families of solutions in which the S^1 smoothly
pinches off. This shows that (when fermions are antiperiodic around the S^1)
there is a quantum phase transition in the gauge theory as one decreases the
radius of the S^1 relative to the S^2. We also compare the masses of our
solutions and argue that the one with lowest mass should minimize the energy
among all solutions with conformal boundary S^2 x S^1 x R. This provides a new
positive energy conjecture for asymptotically locally AdS metrics. A simple
analytic continuation produces AdS black holes with topology S^2 x S^1.Comment: 17 pages, 4 figures, v2: minor changes, added reference
An approach to F-theory
We consider BPS configurations in theories with two timelike directions from
the perspective of the supersymmetry algebra. We show that whereas a BPS state
in a theory with one timelike variable must have positive energy, in a theory
with two times any BPS state must have positive angular momentum in the
timelike plane, in that , where and are the
two timelike directions. We consider some generic BPS solutions of theories
with two timelike directions, and then specialise to the study of the (10,2)
dimensional superalgebra for which the spinor operators generate 2-forms and
6-forms. We argue that the BPS configurations of this algebra relate to
F-theory in the same way that the BPS configurations of the eleven dimensional
supersymmetry algebra relate to M-theory. We show that the twelve dimensional
theory is one of fundamental 3-branes and 7-branes, along with their dual
partners. We then formulate the new intersection rules for these objects. Upon
reduction of this system we find the algebraic description of the IIB-branes
and the M-branes. Given these correspondences we may begin an algebraic study
of F-theory.Comment: 20 pages, no figures, late
Thermodynamics of charged and rotating black strings
We study thermodynamics of cylindrically symmetric black holes. Uncharged as
well as charged and rotating objects have been discussed. We derive surface
gravity and hence the Hawking temperature and entropy for all these cases. We
correct some results in the literature and present new ones. It is seen that
thermodynamically these black configurations behave differently from
spherically symmetric objects
A Generalized Representation Formula for Systems of Tensor Wave Equations
In this paper, we generalize the Kirchhoff-Sobolev parametrix of Klainerman
and Rodnianski to systems of tensor wave equations with additional first-order
terms. We also present a different derivation, which better highlights that
such representation formulas are supported entirely on past null cones. This
generalization is a key component for extending Klainerman and Rodnianski's
breakdown criterion result for Einstein-vacuum spacetimes to Einstein-Maxwell
and Einstein-Yang-Mills spacetimes.Comment: 29 page
Tachyon Condensation and Black Strings
We show that under certain conditions, closed string tachyon condensation
produces a topology changing transition from black strings to Kaluza-Klein
"bubbles of nothing." This can occur when the curvature at the horizon is much
smaller than the string scale, so the black string is far from the
correspondence point when it would make a transition to an excited fundamental
string. This provides a dramatic new endpoint to Hawking evaporation. A similar
transition occurs for black p-branes, and can be viewed as a nonextremal
version of a geometric transition. Applications to AdS black holes and the AdS
soliton are also discussed.Comment: 23 pages, 1 figure, v2: references adde
Solitons in Five Dimensional Minimal Supergravity: Local Charge, Exotic Ergoregions, and Violations of the BPS Bound
We describe a number of striking features of a class of smooth solitons in
gauged and ungauged minimal supergravity in five dimensions. The solitons are
globally asymptotically flat or asymptotically AdS without any Kaluza-Klein
directions but contain a minimal sphere formed when a cycle pinches off in the
interior of the spacetime. The solutions carry a local magnetic charge and many
have rather unusual ergosurfaces. Perhaps most strikingly, many of the solitons
have more electric charge or, in the asymptotically AdS case, more electric
charge and angular momentum than is allowed by the usual BPS bound. We comment
on, but do not resolve, the new puzzle this raises for AdS/CFT.Comment: 60 pages, 12 figures, 3 table
Lodged in the throat: Internal infinities and AdS/CFT
In the context of AdS3/CFT2, we address spacetimes with a certain sort of
internal infinity as typified by the extreme BTZ black hole. The internal
infinity is a null circle lying at the end of the black hole's infinite throat.
We argue that such spacetimes may be described by a product CFT of the form
CFT-L * CFT-R, where CFT-R is associated with the asymptotically AdS boundary
while CFT-L is associated with the null circle. Our particular calculations
analyze the CFT dual of the extreme BTZ black hole in a linear toy model of
AdS3/CFT2. Since the BTZ black hole is a quotient of AdS3, the dual CFT state
is a corresponding quotient of the CFT vacuum state. This state turns out to
live in the aforementioned product CFT. We discuss this result in the context
of general issues of AdS/CFT duality and entanglement entropy.Comment: 11 pages, 2 figures; v2 - some typos corrected, minor revision