Toshitaka Tatsumi

Signatures of hadron-quark mixed phase in gravitational waves

We calculate stellar oscillations, including the hadron-quark mixed phase, considering finite-size effects. We find that it is possible to distinguish whether the density discontinuity exists or not in the stars, even if one observes the gravitational waves of the fundamental mode. Additionally, the normalized eigenfrequencies of pressure modes depend strongly on the stellar mass and on the adopted equation of state. In particular, in spite of the fact that the radius of the neutron star with 1.4M{sub {center_dot}}, which is the standard mass, is almost independent of the equation of state with quark matter, the frequencies of the pressure modes depend on the adopted equation of state. Thus, via observing the many kinds of gravitational waves, it will be possible to make a restriction on the equation of state.

PION CONDENSATION BASED ON A RELATIVISTIC DESCRIPTION OF PARTICLE-HOLE AND DELTA-HOLE EXCITATIONS

The critical density of neutral pion condensation is reinvestigated based on the relativistic framework and compared with nonrelativistic results. The particle-hole and delta-hole polarizations of the pion selfenergy are calculated in the relativistic way by using a new set of Landau–Migdal parameters derived from recent experimental data. It is concluded that the use of relativistic particle-hole and delta-hole excitations for the pion selfenergy increases the critical density, but still leads to condensation for densities from two to three times the normal nuclear matter density within the random phase approximation.

Multi-antikaonic nuclei in relativistic mean-field theory

Properties of multi-antikaonic nuclei (MKN), where several numbers of K{sup -} mesons are bound, are studied in the relativistic mean-field model, combined with chiral dynamics for the kaonic part of the thermodynamic potential. The density profiles for nucleons and K{sup -} mesons, the single particle energy of the K{sup -} mesons, and binding energy of the MKN are obtained. The effects of the K-K interactions on these quantities are discussed in comparison with other meson ({sigma}, {omega}, and {rho})-exchange models. It is shown that the K-K interactions originate from two contributions: One is the contact interaction between antikaons inherent in chiral symmetry, and the other is the one generated through coupling between the K{sup -} and meson mean fields. Both effects of the K-K repulsive interactions become large on the ground state properties of the MKN as the number of the embedded K{sup -} mesons increases. A relation between the multi-antikaonic nuclei and kaon condensation in infinite and uniform matter is mentioned.

Magnetic susceptibility of quark matter within Fermi-liquid theory

Possibility of spontaneous magnetization in QCD and magnetic properties of quark matter are discussed by evaluating the magnetic susceptibility within Fermi-liquid theory. The screening effects for gluons are taken into account to figure out the specific properties of the magnetic transition in gauge theories. It is shown that the static screening effect in terms of the Debye mass does not necessarily work against the magnetic instability; it promotes the instability, depending on the coupling constant and the number of flavors.

Hot hadron-quark mixed phase including hyperons

We study the hadron-quark phase transition with the finite-size effects at finite temperature. For the hadron phase, we adopt a realistic equation of state in the framework of the Brueckner-Hartree-Fock theory including hyperons. The properties of the mixed phase are clarified by considering the finite-size effects under the Gibbs conditions. We find that the equation of state becomes softer than that at zero temperature for some density region. We also find that the equation of state gets closer to that given by the Maxwell construction. Moreover, the number of hyperons is suppressed by the presence of quarks. These are characteristic features of the hadron-quark mixed phase, and should be important for many astrophysical phenomena such as mergers of binary neutron stars.

Non-Fermi-liquid effect in magnetic susceptibility

Abstract Taking into account the anomalous self-energy for quarks due to the dynamic screening effect for the transverse gluon propagator, we study the temperature dependence of the magnetic susceptibility in detail. It is shown that there does not exist the T ln T term in the susceptibility, different from the specific heat, but an anomalous T 2 ln T term arises instead as a novel non-Fermi-liquid effect.

Spontaneous magnetization in QCD and non-Fermi-liquid effects

Abstract Magnetic properties of quark matter at finite temperature are discussed by evaluating the magnetic susceptibility. Combining the microscopic calculation of the self-energy for quarks as well as the screening effects for gluons with Fermi-liquid theory in a consistent way, we study the temperature dependence of the magnetic susceptibility. The longitudinal gluons have the static screening given by the Debye mass, and have a standard temperature dependence of O ( T 2 ) . An anomalous T 2 ln T term arises in the magnetic susceptibility as a novel non-Fermi-liquid effect due to the anomalous self-energy for quarks given by the dynamic screening for transverse gluons. We then extract the critical (Curie) temperature and present the magnetic phase diagram on the density–temperature plane.

Equation of State of Structured Matter at Finite Temperature

We investigate the properties of nuclear matter at the first-order phase transitions such as liquid-gas phase transition and hadron-quark phase transition. As a general feature of the first-order phase transitions of matter consisting of many species of charged particles, there appears a mixed phases with geometrical structures called ``pasta due to the balance of the Coulomb repulsion and the surface tension between two phases. The equation of state (EOS) of mixed phase is different from the one obtained by a bulk application of the Gibbs conditions or by the Maxwell construction due to the effects of the non-uniform structure. We show that the charge screening and strong surface tension make the EOS close to that of the Maxwell construction. The thermal effects are elucidated as well as the above finite-size effects.

General relativistic compact stars with exotic matter

We study the structures of general relativistic compact stars with exotic matter. Our study is based on axisymetric and stationary formalism including purely toroidal magnetic field. We also study the finite size effects of quark‐hadron mixed phase on the structures of magnetars. For hybrid stars, we find the characteristic distribution of magnetic field, which has a discontinuity originated in the quark‐hadron mixed phase. These distributions of magnetic field will change astrophysical phenomena, such as cooling processes.

STRUCTURE OF MULTI-ANTIKAONIC NUCLEI IN THE RELATIVISTIC MEAN-FIELD MODEL

The structure of multi-antikaonic nuclei (MKN), where several K− mesons are bound in the nucleus, is studied in the relativistic mean-field model. A kaonic part of the thermodynamic potential including kaon-nucleon interactions is derived on the basis of chiral symmetry (abbreviated as a chiral model). It is shown that nonperturbative effects from kaons in the chiral model on the properties of the MKN such as the density distributions of nucleons and K− mesons and the binding energy become important since the number of the embedded K− increases.