The Study Of Dynamics Of Strange Quark Matter And Properties Of Strange Stars

Ever since the hypothesis under which strange quark matter is the absolute ground state of the strong interaction was assumed by Witten in 1984, strange quark matter is believed to exist, and the structure and properties of strange star have been widely studied. One important problem of these studies is how to distinguish strange star from neutron star. Since the 1970's, gravitational wave instability has been believed to set the exact spinning limit to compact star. And when r-mode instability was discovered in 1998, it was suddenly paid great attention because it turned out to be very important in many aspects such as the distinction of neutron star from strange star, the explanation of pulsar data and the gravitational wave emission.The r-mode instability is the base of this thesis, and it is reviewed as the following: Firstly, we demonstrate the mechanism of r-mode instability-the CFS mechanism, and find that the instability happens only when the gravitational wave driving effect is larger than the viscosity damping effect to the mode. Secondly, we deduce the lowest and the second order perturbation equations of r-mode using the small angular-velocity expansion method, and give the lowest and the second order r-mode. Thirdly, we get the energy , the gravitational wave driving timescale and the shear viscosity damping timescale of r-mode in the lowest order, but since the bulk viscosity coupling to the lowest r-mode vanishes, the bulk viscosity damping timescale has to be calculated to the second order. At last, we analysis the r-mode instability window and pointed that the l = m = 2 r-mode is the most important one.The r-mode instability of compact star is firmly related to the viscosity of the star, and to study the viscosity we have to study the equation of state of the star first. We review the equation of state and the mass radius relation ofcompact star. Especially, we calculate the equation of state of strange quark matter both under the simple bag model and under the bag model including the medium effect, and find that the medium effect have small influence to the equation of state and the mass radius relation of strange star. We also study the viscosity properties of strange star, and find that despite its small influence to the equation of state, the medium effect has great influence on bulk viscosity and it can increase the bulk viscosity as large as two orders.Based on the r-mode instability and the bulk viscosity of strange quark matter, we calculate the r-mode instability window and study the spin evolution behavior of strange star. Our result is that the medium effect can decrease the lowest critical rotating period from 2.5~3ms to 1.78ms, this can give a better explanation to the two most fastest pulsar data and also can explain the clustering of spin data of the pulsars in Low Mass X-ray Binaries.