5,914 research outputs found
Doppler effect of gamma-ray bursts in the fireball framework
The influence of the Doppler effect in the fireball framework on the spectrum
of gamma-ray bursts is investigated. The study shows that the shape of the
expected spectrum of an expanding fireball remains almost the same as that of
the corresponding rest frame spectrum for constant radiations of the
bremsstrahlung, Comptonized, and synchrotron mechanisms as well as for that of
the GRB model. The peak flux spectrum and the peak frequency are obviously
correlated. When the value of the Lorentz factor becomes 10 times larger, the
flux of fireballs would be several orders of magnitude larger. The expansion
speed of fireballs is a fundamental factor of the enhancement of the flux of
gamma-ray bursts.Comment: 19 pages, 13 figure
Superfluidity and effective mass of magnetoexcitons in topological insulator bilayers: Effect of inter-Landau-level Coulomb interaction
The effective mass and superfluidity-normal phase transition temperature of
magnetoexcitons in topological insulator bilayers are theoretically
investigated. The intra-Landau-level Coulomb interaction is treated
perturbatively, from which the effective magnetoexciton mass is analytically
discussed. The inclusion of inter-Landau-level Coulomb interaction by more
exact numerical diagonalization of the Hamiltonian brings out important
modifications to magnetoexciton properties, which are specially characterized
by prominent reduction in the magnetoexciton effective mass and promotion in
the superfluidity-normal phase transition temperature at a wide range of
external parameters.Comment: 5.6 EPL pages, 4 figure
Dependence of Temporal Properties on Energy in Long-Lag, Wide-Pulse Gamma-Ray Bursts
We employed a sample compiled by Norris et al. (2005, ApJ, 625, 324) to study
the dependence of the pulse temporal properties on energy in long-lag,
wide-pulse gamma-ray bursts. Our analysis shows that the pulse peak time, rise
time scale and decay time scale are power law functions of energy, which is a
preliminary report on the relationships between the three quantities and
energy. The power law indexes associated with the pulse width, rise time scale
and decay time scale are correlated and the correlation between the indexes
associated with the pulse width and the decay time scale is more obvious. In
addition, we have found that the pulse peak lag is strongly correlated with the
CCF lag, but the centroid lag is less correlated with the peak lag and CCF lag.
Based on these results and some previous investigations, we tend to believe
that all energy-dependent pulse temporal properties may come from the joint
contribution of both the hydrodynamic processes of the outflows and the
curvature effect, where the energy-dependent spectral lag may be mainly
dominated by the dynamic process and the energy-dependent pulse width may be
mainly determined by the curvature effect.Comment: 20 pages, 7 figures, added references, matched to published version,
accepted for publication in PAS
Probing crossover from analogous weak antilocalization to localization by an Aharonov-Bohm interferometer on topological insulator surface
We propose a scanning tunneling microscopy Aharonov-Bohm (AB) interferometer
on the surface of a topological insulator (TI) to probe the crossover from
analogous weak antilocalization (WAL) to weak localization (WL) phenomenon via
the AB oscillations in spin-resolved local density of states (LDOS). Based on
our analytical and numerical results, we show that with increasing the energy
gap of TI surface states, the = periodic AB oscillations in
spin-resolved LDOS gradually transit into the periodic oscillations.Comment: 4.2 APL pages, 2 figure
Fractional quantum Hall effect of topological surface states under a strong tilted magnetic field
The fractional quantum Hall effect (FQHE) of topological surface-state
particles under a tilted strong magnetic field is theoretically studied by
using the exact diagonalization method. The Haldane's pseudopotentials for the
Coulomb interaction are analytically obtained. The results show that by
increasing the in-plane component of the tilted magnetic field, the FQHE state
at =0 Landau level (LL) becomes more stable, while the stabilities of
= LLs become weaker. Moreover, we find that the excitation gaps of the
FQHE states increase as the tilt angle is increased.Comment: 4.2 pages, 4 figure
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