1,273 research outputs found
Comments on information loss and remnants
The information loss and remnant proposals for resolving the black hole
information paradox are reconsidered. It is argued that in typical cases
information loss implies energy loss, and thus can be thought of in terms of
coupling to a spectrum of ``fictitious'' remnants. This suggests proposals for
information loss that do not imply planckian energy fluctuations in the low
energy world. However, if consistency of gravity prevents energy
non-conservation, these remnants must then be considered to be real. In either
case, the catastrophe corresponding to infinite pair production remains a
potential problem. Using Reissner-Nordstrom black holes as a paradigm for a
theory of remnants, it is argued that couplings in such a theory may give
finite production despite an infinite spectrum. Evidence for this is found in
analyzing the instanton for Schwinger production; fluctuations from the
infinite number of states lead to a divergent stress tensor, spoiling the
instanton calculation. Therefore naive arguements for infinite production fail.Comment: 30 pages (harvmac l mode) UCSBTH-93-35 (minor reference and typo
corrections
The information paradox and the locality bound
Hawking's argument for information loss in black hole evaporation rests on
the assumption of independent Hilbert spaces for the interior and exterior of a
black hole. We argue that such independence cannot be established without
incorporating strong gravitational effects that undermine locality and
invalidate the use of quantum field theory in a semiclassical background
geometry. These considerations should also play a role in a deeper
understanding of horizon complementarity.Comment: 21 pages, harvmac; v2-3. minor corrections, references adde
Dynamics of Extremal Black Holes
Particle scattering and radiation by a magnetically charged, dilatonic black
hole is investigated near the extremal limit at which the mass is a constant
times the charge. Near this limit a neighborhood of the horizon of the black
hole is closely approximated by a trivial product of a two-dimensional black
hole with a sphere. This is shown to imply that the scattering of
long-wavelength particles can be described by a (previously analyzed)
two-dimensional effective field theory, and is related to the
formation/evaporation of two-dimensional black holes. The scattering proceeds
via particle capture followed by Hawking re-emission, and naively appears to
violate unitarity. However this conclusion can be altered when the effects of
backreaction are included. Particle-hole scattering is discussed in the light
of a recent analysis of the two-dimensional backreaction problem. It is argued
that the quantum mechanical possibility of scattering off of extremal black
holes implies the potential existence of additional quantum numbers - referred
to as ``quantum whiskers'' - characterizing the black hole.Comment: 31 page
Kaluza-Klein Black Holes in String Theory
Exact solutions of heterotic string theory corresponding to four-dimensional
magnetic black holes in supergravity are described. The solutions
describe the black holes in the throat limit, and consist of a tensor product
of an WZW orbifold with the linear dilaton vacuum, supersymmetrized to
world sheet SUSY. One dimension of the model is interpreted as
a compactified fifth dimension, leading to a four dimensional solution with a
Kaluza-Klein gauge field having a magnetic monopole background; this
corresponds to a solution in supergravity, since that theory is obtained
by dimensional reduction of string theory.Comment: 13p. uses Harvma
Spacetime Embedding Diagrams for Black Holes
We show that the 1+1 dimensional reduction (i.e., the radial plane) of the
Kruskal black hole can be embedded in 2+1 Minkowski spacetime and discuss how
features of this spacetime can be seen from the embedding diagram. The purpose
of this work is educational: The associated embedding diagrams may be useful
for explaining aspects of black holes to students who are familiar with special
relativity, but not general relativity.Comment: 22 pages, 21 figures, RevTex. To be submitted to the American Journal
of Physics. Experts will wish only to skim appendix A and to look at the
pictures. Suggested Maple code is now compatible with MapleV4r
Exact Models of Extremal Dyonic 4D Black Hole Solutions of Heterotic String Theory
Families of exact supersymmetric conformal field theories of
magnetically and electrically charged extremal 4D black hole solutions of
heterotic string theory are presented. They are constructed using a
supersymmetric WZW model where anomalously embedded
subgroups are gauged. Crucial cancelations of the
anomalies coming from the supersymmetric fermions, the current algebra fermions
and the gauging ensure that there is a consistency of these models at the
quantum level. Various 2D models, which may be considered as building blocks
for extremal 4D constructions, are presented. They generalise the class of 2D
models which might be obtained from gauging and coincide with known
heterotic string backgrounds. The exact conformal field theory presented by
Giddings, Polchinski and Strominger describing the angular sector of the
extremal magnetically charged black hole is a special case of this
construction. An example where the radial and angular theories are mixed
non--trivially is studied in detail, resulting in an extremal dilatonic
Taub--NUT--like dyon.Comment: 42 pages (Plain TEX), IASSNS-HEP-94/20 (Revised version has minor
corrections, references and a note added and is now identical to published
version in Phys Rev D.
Scales and hierarchies in warped compactifications and brane worlds
Warped compactifications with branes provide a new approach to the hierarchy
problem and generate a diversity of four-dimensional thresholds. We investigate
the relationships between these scales, which fall into two classes.
Geometrical scales, such as thresholds for Kaluza-Klein, excited string, and
black hole production, are generically determined soley by the spacetime
geometry. Dynamical scales, notably the scale of supersymmetry breaking and
moduli masses, depend on other details of the model. We illustrate these
relationships in a class of solutions of type IIB string theory with imaginary
self-dual fluxes. After identifying the geometrical scales and the resulting
hierarchy, we determine the gravitino and moduli masses through explicit
dimensional reduction, and estimate their value to be near the four-dimensional
Planck scale. In the process we obtain expressions for the superpotential and
Kahler potential, including the effects of warping. We identify matter living
on certain branes to be effectively sequestered from the supersymmetry breaking
fluxes: specifically, such "visible sector" fields receive no tree-level masses
from the supersymmetry breaking. However, loop corrections are expected to
generate masses, at the phenomenologically viable TeV scale.Comment: 33 pages, LaTeX. v2: reference added v3: reference added, typos
correcte
Wormholes and Supersymmetry
Revisions: reference added to: G. Gilbert, {\sl Nucl.Phys.} {\bf B328}, 159
(1989)Comment: 29 pages, jnl, McGill/92-2
A Conformal Field Theory of a Rotating Dyon
A conformal field theory representing a four-dimensional classical solution
of heterotic string theory is presented. The low-energy limit of this solution
has U(1) electric and magnetic charges, and also nontrivial axion and dilaton
fields. The low-energy metric contains mass, NUT and rotation parameters. We
demonstrate that this solution corresponds to part of an extremal limit of the
Kerr-Taub-NUT dyon solution. This limit displays interesting `remnant'
behaviour, in that asymptotically far away from the dyon the angular momentum
vanishes, but far down the infinite throat in the neighbourhood of the horizon
(described by our CFT) there is a non-zero angular velocity. A further natural
generalization of the CFT to include an additional parameter is presented, but
the full physical interpretation of its role in the resulting low energy
solution is unclear.Comment: 43 pages, Plain TEX + epsf.tex for one uuencoded figure
Black Holes with a Massive Dilaton
The modifications of dilaton black holes which result when the dilaton
acquires a mass are investigated. We derive some general constraints on the
number of horizons of the black hole and argue that if the product of the black
hole charge and the dilaton mass satisfies then the black
hole has only one horizon. We also argue that for there may exist
solutions with three horizons and we discuss the causal structure of such
solutions. We also investigate the possible structures of extremal solutions
and the related problem of two-dimensional dilaton gravity with a massive
dilaton.Comment: 36 pages with 5 figures (as uuencoded compressed tar file) (revised
version has one major change in bound on mass for extremal solution and minor
typos fixed), harvma
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