604 research outputs found
Jet-cloud/star interaction as an interpretation of neutrino outburst from the blazar TXS 0506+056
Recently, a high-energy neutrino event IceCube-170922A in the spatial and
temporal coincidence with the flaring gamma-ray blazar TXS 0506+056 was
reported. A neutrino outburst between September 2014 and March 2015 was
discovered in the same direction by a further investigation of years of
IceCube data, while the blazar is in a quiescent state during the outburst with
a gamma-ray flux only about one-fifth of the neutrino flux. In this letter, we
propose the neutrino outburst originates from the interaction between a
relativistic jet and a dense gas cloud which may be formed via the tidally
disrupted envelope of a red giant being blown by the impact of the jet.
Gamma-ray photons and electron/positron pairs that are produced correspondingly
will induce electromagnetic cascades. Comptonization of the cascade emission
inside the cloud forms an X-ray photon field with Wien distribution. GeV flux
is suppressed due to the absorption by the Comptonized photon field and, as a
result, a hard spectrum above 10 GeV is formed. The gamma-ray spectrum
predicted in our model is consistent with the Fermi-LAT data of TXS 0506+056.Comment: 6 pages, 3 figure
IceCube Non-detection of GRBs: Constraints on the Fireball Properties
The increasingly deep limit on the neutrino emission from gamma-ray bursts
(GRBs) with IceCube observations has reached the level that could put useful
constraints on the fireball properties. We first present a revised analytic
calculation of the neutrino flux, which predicts a flux an order of magnitude
lower than that obtained by the IceCube collaboration. For benchmark model
parameters (e.g. the bulk Lorentz factor is \Gamma=10^{2.5}, the observed
variability time for long GRBs is t_v=0.01 s and the ratio between the energy
in accelerated protons and in radiation is \eta_p=10 for every burst) in the
standard internal shock scenario, the predicted neutrino flux from 215 bursts
during the period of the 40-string and 59-string configurations is found to be
a factor of ~3 below the IceCube sensitivity. However, if we accept the
recently found inherent relation between the bulk Lorentz factor and burst
energy, the expected neutrino flux increases significantly and the spectral
peak shifts to lower energy. In this case, the non-detection then implies that
the baryon loading ratio should be \eta_p<10 if the variability time of long
GRBs is fixed to t_v=0.01 s. Instead, if we relax the standard internal shock
scenario but keep to assume \eta_p=10, the non-detection constrains the
dissipation radius to be R>4x10^{12} cm assuming the same dissipation radius
for every burst and benchmark parameters for fireballs. We also calculate the
diffuse neutrino flux from GRBs for different luminosity functions existing in
the literature. The expected flux exceeds the current IceCube limit for some
luminosity functions, and thus the non-detection constrains \eta_p<10 in such
cases when the variability time of long GRBs is fixed to t_v=0.01 s.Comment: Accepted by ApJ, 14 pages, 5 figures, typos corrected, scheduled for
the June 10, 2012, v752 - 1 issu
Fractional quantum Hall effect at : Ground states, non-Abelian quasiholes, and edge modes in a microscopic model
We present a comprehensive numerical study of a microscopic model of the
fractional quantum Hall system at filling fraction , based on the
disc geometry. Our model includes Coulomb interaction and a semi-realistic
confining potential. We also mix in some three-body interaction in some cases
to help elucidate the physics. We obtain a phase diagram, discuss the
conditions under which the ground state can be described by the Moore-Read
state, and study its competition with neighboring stripe phases. We also study
quasihole excitations and edge excitations in the Moore-Read--like state. From
the evolution of edge spectrum, we obtain the velocities of the charge and
neutral edge modes, which turn out to be very different. This separation of
velocities is a source of decoherence for a non-Abelian quasihole/quasiparticle
(with charge ) when propagating at the edge; using numbers obtained
from a specific set of parameters we estimate the decoherence length to be
around four microns. This sets an upper bound for the separation of the two
point contacts in a double point contact interferometer, designed to detect the
non-Abelian nature of such quasiparticles. We also find a state that is a
potential candidate for the recently proposed anti-Pfaffian state. We find the
speculated anti-Pfaffian state is favored in weak confinement (smooth edge)
while the Moore-Read Pfaffian state is favored in strong confinement (sharp
edge).Comment: 15 pages, 9 figures; Estimate of e/4 quasiparticle/hole coherence
length when propagating along the edge modified in response to a recent
revision of Ref. 25, and minor changes elsewher
Biorthogonal dynamical quantum phase transitions in non-Hermitian systems
By using biorthogonal bases, we construct a complete framework for
biorthogonal dynamical quantum phase transitions in non-Hermitian systems. With
the help of associated state which is overlooked previously, we define the
automatically normalized biorthogonal Loschmidt echo. This approach is capable
of handling arbitrary non-Hermitian systems with complex eigenvalues, which
naturally eliminates the negative value of Loschmidt rate obtained without the
biorthogonal bases. Taking the non-Hermitian Su-Schrieffer-Heeger model as a
concrete example, a peculiar change in biorthogonal dynamical topological
order parameter, which is beyond the traditional dynamical quantum phase
transitions is observed. We also find the periodicity of biorthogonal dynamical
quantum phase transitions depend on whether the two-level subsystem at the
critical momentum oscillates or reaches a steady state.Comment: 8 pages, 5 figure
Probing the tidal disruption flares of massive black holes with high-energy neutrinos
The recently discovered high-energy transient Swift J164449.3+573451 (Sw
J1644+57) is thought to arise from the tidal disruption of a passing star by a
dormant massive black hole. Modeling of the broadband emission suggests the
presence of a powerful relativistic jet, which contributes dominantly to the
observed X-ray emission. Here we suggest that protons can be accelerated to
ultra-high energies by internal shocks occurring in the jets, but their flux is
insufficient to account for the observed flux of ultra-high energy cosmic rays.
High energy protons can produce ~0.1-10 PeV neutrinos through photomeson
interactions with X-ray photons. The large X-ray fluence (7x10^-4 erg cm^-2)
and high photopion efficiency, together with the insignificant cooling of
secondary mesons, result in bright neutrino emission expected from Sw J1644+57
if the jet composition is matter-dominated. One to several neutrinos may be
detected by a Km^3-scale detector from one tidal disruption event similar to Sw
J1644+57, thereby providing a powerful probe of the composition of the jets.Comment: 5 pages, 2 figures, accepted for publication as a Rapid Communication
in Physical Review D, abstract slightly extende
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