18,468 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
Quasinormal modes in Schwarschild black holes due to arbitrary spin fields
The Newman-Penrose formalism is used to deal with the massless scalar,
neutrino, electromagnetic, gravitino and gravitational quasinormal modes (QNMs)
in Schwarzschild black holes in a united form. The quasinormal mode frequencies
evaluated by using the 3rd-order WKB potential approximation show that the
boson perturbations and the fermion perturbations behave in a contrary way for
the variation of the oscillation frequencies with spin, while this is no longer
true for the damping's, which variate with in a same way both for boson and
fermion perturbations.Comment: 11 pages, 3 figure
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