1,370 research outputs found
Statistical Mechanics and Black Hole Thermodynamics
Black holes are thermodynamic objects, but despite recent progress, the
ultimate statistical mechanical origin of black hole temperature and entropy
remains mysterious. Here I summarize an approach in which the entropy is viewed
as arising from ``would-be pure gauge'' degrees of freedom that become
dynamical at the horizon. For the (2+1)-dimensional black hole, these degrees
of freedom can be counted, and yield the correct Bekenstein-Hawking entropy;
the corresponding problem in 3+1 dimensions remains open.Comment: 5 pages, LaTeX, uses espcrc2.sty; talk given at the Second Meeting on
Constrained Dynamics and Quantum Gravity, Santa Margherita Ligure, Italy,
September 199
Reflecting on the Past
150 years of Augustana storieshttps://digitalcommons.augustana.edu/ahsreflecting/1000/thumbnail.jp
Reflecting on the Past
150 years of Augustana storieshttps://digitalcommons.augustana.edu/ahsreflecting/1000/thumbnail.jp
Extremal black holes as exact string solutions
We show that the leading order solution describing an extremal electrically
charged black hole in string theory is, in fact, an exact solution to all
orders in \a' when interpreted in a Kaluza-Klein fashion. This follows from
the observation that it can be obtained via dimensional reduction from a five
dimensional background which is proved to be an exact string solution.Comment: 13 pages, harvmac, Imperial/TP/93-94/51, UCSBTH-94-24 (references
added
Spatial methods for event reconstruction in CLEAN
In CLEAN (Cryogenic Low Energy Astrophysics with Noble gases), a proposed
neutrino and dark matter detector, background discrimination is possible if one
can determine the location of an ionizing radiation event with high accuracy.
We simulate ionizing radiation events that produce multiple scintillation
photons within a spherical detection volume filled with liquid neon. We
estimate the radial location of a particular ionizing radiation event based on
the observed count data corresponding to that event. The count data are
collected by detectors mounted at the spherical boundary of the detection
volume. We neglect absorption, but account for Rayleigh scattering. To account
for wavelength-shifting of the scintillation light, we assume that photons are
absorbed and re-emitted at the detectors. Here, we develop spatial Maximum
Likelihood methods for event reconstruction, and study their performance in
computer simulation experiments. We also study a method based on the centroid
of the observed count data. We calibrate our estimates based on training data
Melvin solution in string theory
We identify a string theory counterpart of the dilatonic Melvin D=4
background describing a "magnetic flux tube" in low-energy field theory limit.
The corresponding D=5 bosonic string model containing extra compact
Kaluza-Klein dimension is a direct product of the D=2 Minkowski space and a D=3
conformal sigma model. The latter is a singular limit of the [SL(2,R) x R]/R
gauged WZW theory. This implies, in particular, that the dilatonic Melvin
background is an exact string solution to all orders in \a'. Moreover, the D=3
model is formally related by an abelian duality to a flat space with a
non-trivial topology. The conformal field theory for the Melvin solution is
exactly solvable (and for special values of magnetic field parameter is
equivalent to CFT for a orbifold of 2-plane times a circle) and should
exhibit tachyonic instabilities.Comment: 12 pages, harvmac (substantial revision, especially of the part
discussing the structure of the corresponding conformal theory
General class of BPS saturated dyonic black holes as exact superstring solutions
We show that a four-parameter generating solution for a general class of
four-dimensional, spherically-symmetric, static, dyonic BPS saturated solutions
of leading-order effective equations of toroidally compactified heterotic or
type II superstring theory are exact string solutions. The corresponding
ten-dimensional background defines a conformal sigma-model which is a
particular case of a `chiral null model' with curved `transverse' part. The
exact conformal invariance is a consequence of the chiral null structure of the
`electric' part of the model and the N=4 world-sheet supersymmetry of its
transverse `magnetic' part. The sigma-model action has a remarkable covariance
under both target space and the electromagnetic -duality transformations,
and it illustrates the relation between string-string duality in six dimensions
and -duality in four dimensions. In general, there exists a large class of
exact six-dimensional superstring solutions described by chiral null models
with four-dimensional transverse parts represented by N=4 supersymmetric
sigma-models with metrics conformal to hyper-Kahler ones.Comment: 14 pages, latex. Version to appear in Physics Letters
Bulk versus boundary quantum states
An explicit holographic correspondence between bulk and boundary
quantum states is found in the form of a one to one mapping between scalar
field creation/annihilation operators. The mapping requires the introduction of
arbitrary energy scales and exhibits an ultraviolet-infrared duality: a small
regulating mass in the boundary theory corresponds to a large momentum cutoff
in the bulk. In the massless (conformal) limit of the boundary theory the
mapping covers the whole field spectrum of both theories. The mapping strongly
depends on the discretization of the field spectrum of compactified space
in Poincare coordinates.Comment: Minor changes in the text. Typos correction. References added.
Version to appear in Phys. Lett.
Solitonic Strings and BPS Saturated Dyonic Black Holes
We consider a six-dimensional solitonic string solution described by a
conformal chiral null model with non-trivial superconformal transverse
part. It can be interpreted as a five-dimensional dyonic solitonic string wound
around a compact fifth dimension. The conformal model is regular with the
short-distance (`throat') region equivalent to a WZW theory. At distances
larger than the compactification scale the solitonic string reduces to a dyonic
static spherically-symmetric black hole of toroidally compactified heterotic
string. The new four-dimensional solution is parameterised by five charges,
saturates the Bogomol'nyi bound and has nontrivial dilaton-axion field and
moduli fields of two-torus. When acted by combined T- and S-duality
transformations it serves as a generating solution for all the static
spherically-symmetric BPS-saturated configurations of the low-energy heterotic
string theory compactified on six-torus. Solutions with regular horizons have
the global space-time structure of extreme Reissner-Nordstrom black holes with
the non-zero thermodynamic entropy which depends only on conserved (quantised)
charge vectors. The independence of the thermodynamic entropy on moduli and
axion-dilaton couplings strongly suggests that it should have a microscopic
interpretation as counting degeneracy of underlying string configurations. This
interpretation is supported by arguments based on the corresponding
six-dimensional conformal field theory. The expression for the level of the WZW
theory describing the throat region implies a renormalisation of the string
tension by a product of magnetic charges, thus relating the entropy and the
number of oscillations of the solitonic string in compact directions.Comment: 27 Pages, uses RevTeX (solution for the axion field corrected,
erratum to appear in Phys. Rev. D
QCD/String holographic mapping and high energy scattering amplitudes
We find a one to one mapping between low energy string dilaton states in AdS
bulk and high energy glueball states on the corresponding boundary. This
holographic mapping leads to a relation between bulk and boundary scattering
amplitudes. From this relation and the dilaton action we find the appropriate
momentum scaling for high energy QCD amplitudes at fixed angles.Comment: Minor changes in text. Version accepted for publication in PL
- âŠ