8,768 research outputs found
Neutrino and anti-neutrino transport in accretion disks
We numerically solve the one dimensional Boltzmann equation of the neutrino
and anti-neutrino transport in accretion disks and obtain the fully energy
dependent and direction dependent neutrino and anti-neutrino emitting spectra,
under condition that the distribution of the mass density,temperature and
chemical components are given. Then, we apply the resulting neutrino and
anti-neutrino emitting spectra to calculate the corresponding annihilation rate
of neutrino pairs above the neutrino dominated accretion disk and find that the
released energy resulting from the annihilation of neutrino pairs can not
provide sufficient energy for the most energetic short gamma ray bursts whose
isotropic luminosity can be as high as ergs/s unless the high
temperature zone where the temperature is beyond 10 MeV can stretch over 200 km
in the disk. We also compare the resulting luminosity of neutrinos and
anti-neutrinos with the results from the two commonly used approximate
treatment of the neutrino and anti-neutrino luminosity: the Fermi-Dirac black
body limit and a simplified model of neutrino transport, i.e., the gray body
model, and find that both of them overestimate the neutrino/anti-neutrino
luminosity and their annihilation rate greatly. Additionally, as did in Sawyer
(2003), we also check the validity of the two stream approximation, and find
that it is a good approximation to high accuracy.Comment: Phys. Rev. D in press, 15 preprint papers, 5 figure
Detecting fractional Josephson effect through phase slip
Fractional Josephson effect is a unique character of Majorana Fermions in
topological superconductor system. This effect is very difficult to detect
experimentally because of the disturbance of quasiparticle poisoning and
unwanted couplings in the superconductor. Here, we propose a scheme to probe
fractional DC Josephson effect of semiconductor nanowire-based topological
Josephson junction through 4{\pi} phase slip. By exploiting a topological RF
SQUID system we find that the dominant contribution for Josephson coupling
comes from the interaction of Majorana Fermions, resulting the resonant
tunneling with 4{\pi} phase slip. Our calculations with experimentally
reachable parameters show that the time scale for detecting the phase slip is
two orders of magnitude shorter than the poisoning time of nonequilibrium
quasiparticles. Additionally, with a reasonable nanowire length the 4{\pi}
phase slip could overwhelm the topological trivial 2{\pi} phase slip. Our work
is meaningful for exploring the effect of modest quantum fluctuations of the
phase of the superconductor on the topological system, and provide a new method
for quantum information processing.Comment: 5 pages, 3 figure
Detecting fractional Josephson effect through phase slip
Fractional Josephson effect is a unique character of Majorana Fermions in
topological superconductor system. This effect is very difficult to detect
experimentally because of the disturbance of quasiparticle poisoning and
unwanted couplings in the superconductor. Here, we propose a scheme to probe
fractional DC Josephson effect of semiconductor nanowire-based topological
Josephson junction through 4{\pi} phase slip. By exploiting a topological RF
SQUID system we find that the dominant contribution for Josephson coupling
comes from the interaction of Majorana Fermions, resulting the resonant
tunneling with 4{\pi} phase slip. Our calculations with experimentally
reachable parameters show that the time scale for detecting the phase slip is
two orders of magnitude shorter than the poisoning time of nonequilibrium
quasiparticles. Additionally, with a reasonable nanowire length the 4{\pi}
phase slip could overwhelm the topological trivial 2{\pi} phase slip. Our work
is meaningful for exploring the effect of modest quantum fluctuations of the
phase of the superconductor on the topological system, and provide a new method
for quantum information processing.Comment: 5 pages, 3 figure
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