6,694 research outputs found
NS5-branes on an ellipsis and novel marginal deformations with parafermions
We consider NS5-branes distributed along the circumference of an ellipsis and
explicitly construct the corresponding gravitational background. This provides
a continuous line of deformations between the limiting cases, considered
before, in which the ellipsis degenerates into a circle or into a bar. We show
that a slight deformation of the background corresponding to a circle
distribution into an ellipsoidal one is described by a novel non-factorizable
marginal perturbation of bilinears of dressed parafermions. The latter are
naturally defined for the circle case since, as it was shown in the past, the
background corresponds to an orbifold of the exact conformal field theory coset
model SU(2)/U(1) times SL(2,R)/U(1). We explore the possibility to define
parafermionic objects at generic points of the ellipsoidal families of
backgrounds away from the circle point. We also discuss a new limiting case in
which the ellipsis degenerates into two infinitely stretched parallel bars and
show that the background is related to the Eguchi-Hanson metric, via T-duality.Comment: 24 page
Interior of Distorted Black Holes
We study the interior of distorted static axisymmetric black holes. We obtain
a general interior solution and study its asymptotics both near the horizon and
singularity. As a special example, we apply the obtained results to the case of
the so-called `caged' black holes.Comment: 12 pages, 16 figure
Inverse Square Law of Gravitation in (2+1)-Dimensional Space-Time as a Consequence of Casimir Energy
The gravitational effect of vacuum polarization in space exterior to a
particle in (2+1)-dimensional Einstein theory is investigated. In the weak
field limit this gravitational field corresponds to an inverse square law of
gravitational attraction, even though the gravitational mass of the quantum
vacuum is negative. The paradox is resolved by considering a particle of finite
extension and taking into account the vacuum polarization in its interior.Comment: 10 pages, LaTeX, Report: UPR-0540-T, To appear in Physica Script
Relative abundances of elements (20 or = Z or = 28) at energies up to 70 GeV/amu using relativistic rise in ion chambers
The results of a new balloon borne cosmic ray detector flown from Palestine, TX in Sept., 1982 are discussed. The exposure of 62 square meter-ster-hr is sufficient to prove the concept of using gas ionization chambers as energy measuring devices in the relativistic rise region. The abundances, relative Fe-26, of the pure secondaries Cr-22 and Ti-24, the pure primary Ni26, and the mixed primary and secondary Ca-20 between 6 and 70GeV/amu were measured
A Comment on Junction and Energy Conditions in Thin Shells
This comment contains a suggestion for a slight modification of Israel's
covariant formulation of junction conditions between two spacetimes, placing
both sides on equal footing with normals having uniquely defined orientations.
The signs of mass energy densities in thin shells at the junction depend not
only on the orientations of the normals and it is useful therefore to discuss
the sign separately. Calculations gain in clarity by not choosing the
orientations in advance. Simple examples illustrate our point and complete
previous classifications of spherical thin shells in spherically symmetric
spacetimes relevant to cosmology.Comment: (Tex file + PS file with a figure) Tex errors were correcte
Maintaining a Wormhole with a Scalar Field
It is well known that it takes matter that violates the averaged weak energy
condition to hold the throat of a wormhole open. The production of such
``exotic'' matter is usually discussed within the context of quantum field
theory. In this paper I show that it is possible to produce the exotic matter
required to hold a wormhole open classically. This is accomplished by coupling
a scalar field to matter that satisfies the weak energy condition. The
energy-momentum tensor of the scalar field and the matter separately satisfy
the weak energy condition, but there exists an interaction energy-momentum
tensor that does not. It is this interaction energy-momentum tensor that allows
the wormhole to be maintained.Comment: 12 pages, LaTe
The partition function of the supersymmetric two-dimensional black hole and little string theory
We compute the partition function of the supersymmetric two-dimensional
Euclidean black hole geometry described by the SL(2,R)/U(1) superconformal
field theory. We decompose the result in terms of characters of the N=2
superconformal symmetry. We point out puzzling sectors of states besides
finding expected discrete and continuous contributions to the partition
function. By adding an N=2 minimal model factor of the correct central charge
and projecting on integral N=2 charges we compute the partition function of the
background dual to little string theory in a double scaling limit. We show the
precise correspondence between this theory and the background for NS5-branes on
a circle, due to an exact description of the background as a null gauging of
SL(2,R) x SU(2). Finally, we discuss the interplay between GSO projection and
target space geometry.Comment: JHEP class, 35 pages, no figures; v2: minor changes, typos corrected,
published versio
Linking the X-ray timing and spectral properties of the glitching AXP 1RXS J170849-400910
Previous studies of the X-ray flux and spectral properties of 1RXS
J170849-400910 showed hints of a possible correlation with the spin glitches
that occurred in 1999 and 2001. However, due to the sparseness of spectral
measurements and the paucity of detected glitches no firm conclusion could be
drawn. We retrieved and analysed archival XTE pointings of 1RXS J170849-400910
covering the time interval between January 2003 and June 2006 and carried out a
detailed timing analysis by means of phase fitting techniques. We detected two
relatively large glitches Delta nu / nu of 1.2 and 2.1 10^-6 occurred in
January and June 2005. Interestingly, the occurrence times of these glitches
are in agreement with the predictions made in our previous studies. This
finding strongly suggests a connection between the flux, spectral and timing
properties of 1RXS J170849-400910.Comment: Submitted to A&A, 4 pages; results presented at the INT meeting "The
Neutron Star Crust and Surface: Observations and Models" on June 27; referee
comments adde
D-branes in Lorentzian AdS(3)
We study the exact construction of D-branes in Lorentzian AdS(3). We start by
defining a family of conformal field theories that gives a natural Euclidean
version of the SL(2,R) CFT and does not correspond to H(3)+, the analytic
continuation of AdS(3). We argue that one can recuperate the exact CFT results
of Lorentzian AdS(3), upon an analytic continuation in the moduli space of
these conformal field theories. Then we construct exact boundary states for
various symmetric and symmetry-breaking D-branes in AdS(3).Comment: JHEP style;21 pages, no figures; v2:some corrections, comments and
references adde
Hydrogen thermal conductivity at temperatures from 2000 to 4000 deg F Final report
Hydrogen thermal conductivity at temperatures from 2000 to 4600 deg
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