8,208 research outputs found
Superconducting Hair on Charged Black String Background
Behaviour of Dirac fermions in the background of a charged black string
penetrated by an Abelian Higgs vortex is elaborated. One finds the evidence
that the system under consideration can support fermion fields acting like a
superconducting cosmic string in the sence that a nontrivial Dirac fermion
field can be carried by the system in question. The case of nonextremal and
extremal black string vortex systems were considered. The influence of electric
and Higgs charge, the winding number and the fermion mass on the fermion
localization near the black string event horizon was studied. It turned out
that the extreme charged black string expelled fermion fields more violently
comparing to the nonextremal one.Comment: RevTex, 16 pages, 12 figures, to be published in Phys.REvD1
On the CFT duals for near-extremal black holes
We consider Kerr-Newman-AdS-dS black holes near extremality and work out the
near-horizon geometry of these near-extremal black holes. We identify the exact
U(1)_L x U(1)_R isometries of the near-horizon geometry and provide boundary
conditions enhancing them to a pair of commuting Virasoro algebras. The
conserved charges of the corresponding asymptotic symmetries are found to be
well defined and non-vanishing and to yield central charges c_L\neq0 and c_R=0.
The Cardy formula subsequently reproduces the Bekenstein-Hawking entropy of the
black hole. This suggests that the near-extremal Kerr-Newman-AdS-dS black hole
is holographically dual to a non-chiral two-dimensional conformal field theory.Comment: 11 page
The Anti-Coincidence Detector for the GLAST Large Area Telescope
This paper describes the design, fabrication and testing of the
Anti-Coincidence Detector (ACD) for the Gamma-ray Large Area Space Telescope
(GLAST) Large Area Telescope (LAT). The ACD is LAT first-level defense against
the charged cosmic ray background that outnumbers the gamma rays by 3-5 orders
of magnitude. The ACD covers the top and 4 sides of the LAT tracking detector,
requiring a total active area of ~8.3 square meters. The ACD detector utilizes
plastic scintillator tiles with wave-length shifting fiber readout. In order to
suppress self-veto by shower particles at high gamma-ray energies, the ACD is
segmented into 89 tiles of different sizes. The overall ACD efficiency for
detection of singly charged relativistic particles entering the tracking
detector from the top or sides of the LAT exceeds the required 0.9997.Comment: 33 pages, 19 figure
A near-NHEK/CFT correspondence
We consider excitations around the recently introduced near-NHEK metric
describing the near-horizon geometry of the near-extremal four-dimensional Kerr
black hole. This geometry has a U(1)_L x U(1)_R isometry group which can be
enhanced to a pair of commuting Virasoro algebras. We present boundary
conditions for which the conserved charges of the corresponding asymptotic
symmetries are well defined and non-vanishing and find the central charges
c_L=12J/hbar and c_R=0 where J is the angular momentum of the black hole.
Applying the Cardy formula reproduces the Bekenstein-Hawking entropy of the
black hole. This suggests that the near-extremal Kerr black hole is
holographically dual to a non-chiral two-dimensional conformal field theory.Comment: 11 pages, v2: references updated, adde
Inverse hyperbolic problems and optical black holes
In this paper we give a more geometrical formulation of the main theorem in
[E1] on the inverse problem for the second order hyperbolic equation of general
form with coefficients independent of the time variable. We apply this theorem
to the inverse problem for the equation of the propagation of light in a moving
medium (the Gordon equation). Then we study the existence of black and white
holes for the general hyperbolic and for the Gordon equation and we discuss the
impact of this phenomenon on the inverse problems
High-Energy Neutrinos from Photomeson Processes in Blazars
An important radiation field for photomeson neutrino production in blazars is
shown to be the radiation field external to the jet. Assuming that protons are
accelerated with the same power as electrons and injected with a -2 number
spectrum, we predict that km^2 neutrino telescopes will detect about
1-to-several neutrinos per year from flat spectrum radio quasars (FSRQs) such
as 3C 279. The escaping high-energy neutron and photon beams transport inner
jet energy far from the black-hole engine, and could power synchrotron X-ray
jets and FR II hot spots and lobes.Comment: revised paper (minor revisions), accepted for publication in PR
The last Gift of BeppoSAX: PDS Observations of the two Blazars 1ES 0507-040 and PKS 1229-021
Towards the end of the BeppoSAX mission, the only operated Narrow Field
Instrument was the PDS, which covers the energy range 13-300 keV. Two blazars,
1ES 0507-040 (z=0.304) and PKS 1229-021 (z= 1.045), suitably located in the sky
for BeppoSAX pointing, were observed for about 2 days each in Spring 2002 with
the PDS and detected up to 50 keV. 1ES0507-040 had been already observed by the
BeppoSAX NFIs at an earlier epoch for a much shorter time. We have re-analysed
those data as well, and identified a possible contamination problem in the PDS
spectrum. We present our recent PDS data on both sources, combined with the
previous BeppoSAX data and with non-simultaneous observations at other
frequencies. The derived Spectral Energy Distributions allow us to discuss the
origin of the high energy component.Comment: 4 pages, 6 figures, poster presented at the symposium: The Restless
High-Energy Universe, Amsterdam, May 200
High energy gamma ray results from the second small astronomy satellite
A high energy (35 MeV) gamma ray telescope employing a thirty-two level magnetic core spark chamber system was flown on SAS 2. The high energy galactic gamma radiation is observed to dominate over the general diffuse radiation along the entire galactic plane, and when examined in detail, the longitudinal and latitudinal distribution seem generally correlated with galactic structural features, particularly with arm segments. The general high energy gamma radiation from the galactic plane, explained on the basis of its angular distribution and magnitude, probably results primarily from cosmic ray interactions with interstellar matter
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