An ultraviolet cutoff dependent on the chemical potential as proposed by Casalbuoni {it et al} is used in the su(3) Nambu-Jona-Lasinio model. The model is applied to the description of stellar quark matter and compact stars. It is shown that with a n
ew cutoff parametrization it is possible to obtain stable hybrid stars with a quark core. A larger cutoff at finite densities leads to a partial chiral symmetry restoration of quark $s$ at lower densities. A direct consequence is the onset of the $s$ quark in stellar matter at lower densities and a softening of the equation of state.
We investigate the hadron-quark phase transition inside neutron stars and obtain mass-radius relations for hybrid stars. The equation of state for the quark phase using the standard NJL model is too soft leading to an unstable star and suggesting a m
odification of the NJL model by introducing a momentum cutoff dependent on the chemical potential. However, even in this approach, the instability remains. In order to remedy the instability we suggest the introduction of a vector coupling in the NJL model, which makes the EoS stiffer, reducing the instability. We conclude that the possible existence of quark matter inside the stars require high densities, leading to very compact stars.
In this work we study the Nambu-Jona-Lasinio model in the SU (2) version with repulsive vector coupling and apply it to quark stellar matter. We discuss the influence of the vector interaction on the equation of state (EoS) and study quark stars that
are composed of pure quark matter with two flavors. We show that, increasing the vector coupling, we obtain more massive stars with larger radii for the same central energy density.
The direct detection of gravitational waves will provide valuable astrophysical information about many celestial objects. Also, it will be an important test to general relativity and other theories of gravitation. The gravitational wave detector SCHE
NBERG has recently undergone its first test run. It is expected to have its first scientific run soon. In this work the data analysis system of this spherical, resonant mass detector is tested through the simulation of the detection of gravitational waves generated during the inspiralling phase of a binary system. It is shown from the simulated data that it is not necessary to have all six transducers operational in order to determine the sources direction and the waves amplitudes.
