Quarks and Compact Stars (QCS)
Oct. 20-22, 2014, KIAA at Peking University, Beijing - P. R. China


Invited Talk

A possibility of quark spin polarized phase in high density quark matter

Yasuhiko Tsue

Kochi University

Abstract: One of recent interests in the physics governed by the quantum chromodynamics (QCD) may be to study the possibility of various phases under extreme conditions such as high temperature, high density, strong field and so on, such as, in the core of neutron stars. Especially, in the region of high baryon density and low temperature, it is expected that the color superconducting phase is realized in quark matter. However, another possibility with respect to the realized phase is investigated here in the region of high baryon density and zero temperature. Namely, it is indicated that the quark spin polarization for each flavor may occur by the use of the Nambu-Jona-Lasinio (NJL) model with tensor-type four-point interaction. In the two-flavor case, it is believed that the two-flavor color superconducting (2SC) phase is realized at high density quark matter. However, it is here shown that each quark spin for $u$- and $d$-quark may be aligned which leads to each quark spin polarized (SP) phase in the region of rather higher density. The behavior of phase transition from 2SC to SP phase is discussed numerically. Further, in the three-flavor case, much study indicates that the color-flavor locked (CFL) phase may be realized. Usually, it is expected that the phase transition from 2SC to CFL phase occurs as the quark number density is increasing. Even in this situation, in the region of high baryon density, the quark spin polarization for each quark flavor, $u$-, $d$- and $s$-quark, may be occur. It is really shown that the each quark spin polarized phase is realized in the high baryon density by using the NJL model with tensor-type four-point interaction. Also, the behavior of phase transition from CFL to SP phase is investigated within the perturbative approach.