1,703 research outputs found
Uniqueness of the electrostatic solution in Schwarzschild space
In this Brief Report we give the proof that the solution of any static test
charge distribution in Schwarzschild space is unique. In order to give the
proof we derive the first Green's identity written with p-forms on (pseudo)
Riemannian manifolds. Moreover, the proof of uniqueness can be shown for either
any purely electric or purely magnetic field configuration. The spacetime
geometry is not crucial for the proof.Comment: 3 pages, no figures, uses revtex4 style file
MAGIC and the Search for Signatures of Supersymmetric Dark Matter
The 17m Imaging Air shower Cherenkov Telescope MAGIC (Roque de los Muchachos
Observatory, La Palma, Canary Islands) has recently entered its commissioning
phase. One of the main goals of the MAGIC telescope project is to provide an
unprecedented sensitivity for the detection of gamma rays with energies as low
as 30 GeV. A dedicated search for the gamma rays expected to be produced by
WIMP annihilations is a prime object of the MAGIC physics program. We consider
annihilating supersymmetric dark matter in M 87 and discuss a possible
observation strategy. New calculations concerning the extragalactic gamma ray
and neutrino backgrounds owing to cosmological neutralino annihilation are also
briefly discussed.Comment: To be published in the proceedings of the "6th UCLA Symposium on
Sources and Detection of Dark Matter and Dark Energy in the Universe", Marina
del Rey, 200
Atomic defects and dopants in ternary Z-phase transition-metal nitrides CrMN with M=V, Nb, Ta investigated with density functional theory
A density functional theory study of atomic defects and dopants in ternary
Z-phase transition-metal nitrides CrMN with M=V, Nb, or Ta is presented.
Various defect formation energies of native point defects and of substitutional
atoms of other metal elements which are abundant in the steel as well, are
evaluated. The dependence thereof on the thermodynamic environment, i.e. the
chemical conditions of a growing Z-phase precipitate, is studied and different
growth scenarios are compared. The results obtained may help to relate results
of experimental atomic-scale analysis, by atom probe tomography or transmission
electron microscopy, to the theoretical modeling of the formation process of
the Z phase from binary transition metal nitrides
Gamma-rays from pulsar wind nebulae in starburst galaxies
Recently, gamma-ray emission at TeV energies has been detected from the
starburst galaxies NGC253 (Acero et al., 2009) and M82 (Acciari et al., 2009.
It has been claimed that pion production due to cosmic rays accelerated in
supernova remnants interacting with the interstellar gas is responsible for the
observed gamma rays. Here, we show that the gamma-ray pulsar wind nebulae left
behind by the supernovae contribute to the TeV luminosity in a major way. A
single pulsar wind nebula produces about ten times the total luminosity of the
Sun at energies above 1 TeV during a lifetime of 10^5 years. A large number of
3x10^4 pulsar wind nebulae expected in a typical starburst galaxy at a distance
of 4 Mpc can readily produce the observed TeV gamma rays.Comment: 5 pages, 2 figures, accepted for publication in Astropart. Phy
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