7,779 research outputs found
Energetic stability and magnetic properties of Mn dimers in silicon
We present an accurate first-principles study of magnetism and energetics of single Mn impurities and Mn dimers in Si. Our results, in general agreement with available experiments, show that (i) Mn atoms tend to aggregate, the formation energy of dimers being lower than the sum of the separate constituents, (ii) ferromagnetic coupling is favored between the Mn atoms constituting the dimers in p-type Si, switching to an antiferromagnetic coupling in n-type Si, (iii) Mn atoms show donors (acceptor) properties in p-type (n-type) Si, therefore they tend to compensate doping, while dimers being neutral or acceptors allow for Si to be doped p-type. (C) 2004 American Institute of Physics
Searching for tau neutrinos with Cherenkov telescopes
Cherenkov telescopes have the capability of detecting high energy tau
neutrinos in the energy range of 1--1000 PeV by searching for very inclined
showers. If a tau lepton, produced by a tau neutrino, escapes from the Earth or
a mountain, it will decay and initiate a shower in the air which can be
detected by an air shower fluorescence or Cherenkov telescope. In this paper,
we present detailed Monte Carlo simulations of corresponding event rates for
the VERITAS and two proposed Cherenkov Telescope Array sites: Meteor Crater and
Yavapai Ranch, which use representative AGN neutrino flux models and take into
account topographic conditions of the detector sites. The calculated neutrino
sensitivities depend on the observation time and the shape of the energy
spectrum, but in some cases are comparable or even better than corresponding
neutrino sensitivities of the IceCube detector. For VERITAS and the considered
Cherenkov Telescope Array sites the expected neutrino sensitivities are up to
factor 3 higher than for the MAGIC site because of the presence of surrounding
mountains.Comment: arXiv admin note: text overlap with arXiv:1308.019
Relation between phase and dwell times for quantum tunneling of a relativistically propagating particle
The general and explicit relation between the phase time and the dwell time
for quantum tunneling of a relativistically propagating particle is
investigated and quantified. In analogy with previously obtained
non-relativistic results, it is shown that the group delay can be described in
terms of the dwell time and a self-interference delay. Lessons concerning the
phenomenology of the relativistic tunneling are drawn
- …