688 research outputs found
QCD phase transition in rotaing neutron star, Neutrino beaming and Gamma-ray bursters
We have studied the emission of neutrinos from a rotating hybrid star. We
find that the emission is predominantly confined to a very small angle,
provided the core of the star is in a mixed phase of quarks and hadrons and the
size of such a mixed phase is small. Annihilation of neutrinos to produce gamma
rays has been discussed. The estimated duration of the burst is found to be
within the observational range.Comment: Modified manuscript with 9 pages including 3 ps figures, Accepted for
publication in Phys. Lett.
Neutrino Emissivity of Dense Stars
The neutrino emissivity of compact stars is investigated in this work. We
consider stars consisting of nuclear as well as quark matter for this purpose.
Different models are used to calculate the composition of nuclear and quark
matter and the neutrino emissivity. Depending on the model under consideration,
the neutrino emissivity of nuclear as well as quark matter varies over a wide
range. We find that for nuclear matter, the direct URCA processes are allowed
for most of the relativistic models without and with strange baryons, whereas
for the nonrelativistic models this shows a strong dependence on the type of
nuclear interaction employed. When the direct URCA processes are allowed, the
neutrino emissivity of hadronic matter is larger than that of the quark matter
by several orders of magnitude. We also find that the neutrino emissivity
departs from behavior when the temperature is larger than the difference
in the Fermi momenta of the particles, participating in the neutrino-producing
reactions.Comment: Latex file. 5 figures available on request. accepted in Int. J. Mod.
Phys.
Shear viscosity due to the Landau damping from quark-pion interaction
We have calculated the shear viscosity coefficient of the strongly
interacting matter in the relaxation time approximation, where a quasi particle
description of quarks with its dynamical mass is considered from NJL model. Due
to the thermodynamic scattering of quarks with pseudo scalar type condensate
(i.e. pion), a non zero Landau damping will be acquired by the propagating
quarks. This Landau damping may be obtained from the Landau cut contribution of
the in-medium self-energy of quark-pion loop, which is evaluated in the
framework of real-time thermal field theory
On the Limitations of Neutrino Emissivity Formula of Iwamoto
The neutrino emissivity from two and three flavour quark matter is
numerically calculated and compared with Iwamoto's formula. We find that the
calculated emissivity is smaller than Iwamoto's result by orders of magnitude
when is comparable with the temperature. We
attribute it to the severe restriction imposed by momentum conservation on the
phase space integral. We obtain an alternate formula for the neutrino
emissivity which is valid when the quarks and electrons are degenerate and
is large compared to the temperature.Comment: Latex Version 2.09, 15 pages, 5 postscript figures available upon
request, preprint No. IP/BBSR/93-6
- …