High density QCD and Compact stars

点击翻译按钮获取中文摘要

(1)Properties of the mixed phases in the first order phase transition in hadronic matter. There have been discussed various types of phase transitions, such as liquid-gas transition, kaon condensation and quark deconfinement transition, in nucloear matter as "new form of matter", and. almost all of them are of first order. Thus we must consider the first order phase transitions with multi components in hadronic matter, where the usual Maxwell construction is not accurate to get the thermodynamically well-defined equation of state (EOS). The Gibbs conditions are basic requirement for phase equilibrium. Then the structured mixed phases appears, where not only baryon number density but also charge density are nonuniform. We have studied three phase transitions mentioned above and tried to figure out the outstanding properties of the mixed phase. Based on the idea of the density functional theory we numerically determined the density profiles exactly fulfill the Gibbs conditions. In partic … More ular we have emphasized the important role of the charge screening for the Coulomb potential, which may gives rise to the mechanical instability of the geometrical structures in the mixed phase. In the extreme case the EOS given by the Maxwell construction is effectively recovered. These results affect the elementary processes inside compact stars as well as the bulk properties of compact stars.. Recently we have published a review paper concerning these works. (2)Magnetism of quark matter. We have investigated the magnetic properties of quark matter as a microscopic origin of the magnetic field observed in compact stars, based on QCD, which was stimulated by the recent discoveries of magnetars with superstrong magnetic field. As one of the important works we published a review paper in the book "Dark Matter", where we presented a basic idea about ferromagnetism in quark matter, and then discussed the coexistence of ferromagnetism with color superconductivity and production of density wave in relation to restoration of chiral symmetry. We further studied magnetism in quark matter by the use of Fermi liquid theory. We evaluated susceptibility with q-q interaction, where exchanged gluons are screened by particle-hole excitations. IR behavior of the gluon propagator is improved by the screening effect, but transverse gluons receives no static screening. We examined the screening effect on the susceptibility. We are now preparing a paper. In the ferromagnetic phase rotation symmetry is spontaneously broken, and thereby spin wave is appeared as a low energy excitation mode. We are now studying spin wave by the spiral approach. This subject is theoretically interesting, and moreover important for the temperature dependence of magnetization and specific heat. A possibility of spin density wave has been studied in relation to restoration of chiral symmetry. By considering the pseudoscalar order parameter besides the usual scalar one we presented another scenario for symmetry restoration. Less