arXiv subjects

T. Tatsumi

Publications and source records attributed to T. Tatsumi.

31 records · Page 2Linked to original sources

arXiv2005

Magnetism and superconductivity in quark matter

Magnetic properties of quark matter and its relation to the microscopic origin of the magnetic field observed in compact stars are studied. Spontaneous spin polarization appears in high-density region due to the Fock exchange term, which may provide a scenario for the behaviors of magnetars. On the other hand, quark matter becomes unstable to form spin density wave in the moderate density region, where restoration of chiral symmetry plays an important role. Coexistence of magnetism and color superconductivity is also discussed.

hep-ph↗

arXiv2005

Chiral symmetry and density wave in quark matter

A density wave in quark matter is discussed at finite temperature, which occurs along with the chiral condensation, and is described by a dual standing wave in scalar and pseudo-scalar condensates on the chiral circle. The mechanism is quite similar to that for the spin density wave suggested by Overhauser, and entirely reflects many-body effects. It is found that the chiral condensed phase with the density wave develops at a high-density region just outside the usual chiral-transition line in phase diagram. A magnetic property of the density wave is also elucidated.

hep-ph↗

arXiv2005

Origin of magnetic field in compact stars and magnetic properties of quark matter

Microscopic origin of the magnetic field observed in compact stars is studied in quark matter. Spontaneous spin polarization appears in high-density region due to the Fock exchange term. On the other hand, quark matter becomes unstable to form spin density wave in the moderate density region, where restoration of chiral symmetry plays an important role. Coexistence of the magnetism and color superconductivity is briefly discussed.

hep-ph↗

arXiv2004

Dual chiral density wave in quark matter

Possible manifestation of a dual chiral density wave in quark matter is discussed in relation to the chiral symmetry of QCD, which is described by a dual standing wave of the scalar and pseudo-scalar densities. It is demonstrated that quark matter is unstable for forming the dual chiral density wave at moderate densities in the Nambu-Jona-Lasinio model;accordingly the critical density for restoration of chiral symmetry becomes higher than ever considered. A unique magnetic property is also pointed out in the new phase.

hep-ph↗

arXiv2003

Screening Effect in Quark-Hadron Mixed Phase

Possibility of the structured mixed phases at first order phase transitions in neutron stars is reexamined by taking into account the charge screening effect. The Maxwell construction is shown to be not conflicted with the Gibbs conditions once the Coulomb potential is properly taken into account. Taking the hadron-quark deconfinement transition as an example, we explicitly demonstrate a mechanical instability of the geometrical structure of the structured mixed phase by the charge screening effect. In this case we have effectively the picture given by the Maxwell construction.

nucl-th↗

arXiv2003

Spin Polarization and Color Superconductivity in Quark Matter

A coexistent phase of spin polarization and color superconductivity in high-density QCD is investigated using a self-consistent mean-field method at zero temperature. The axial-vector current stemming from the Fock exchange term of the one-gluon-exchange interaction has a central role to cause spin polarization. The magnitude of spin polarization is determined by the coupled Schwinger-Dyson equation with a superconducting gap function. As a significant feature the Fermi surface is deformed by the axial-vector self-energy and then rotational symmetry is spontaneously broken. The gap function is also taken to be anisotropic in accordance with the deformation. As a result of numerical calculation, it is found that spin polarization barely conflicts with color superconductivity, but almost coexists with it.

hep-ph↗

arXiv2003

Pseudoscalar Mesons in Nuclear Medium

The behavior of pseudoscalar mesons in nuclear medium is reviewed with an emphasis on the possibility of their Bose-Einstein condensation in dense matter. In particular pion condensation is reexamined in detail, stimulated by recent theoretical and observational developments.

nucl-th↗

arXiv2003

Charge Screening at First Order Phase Transitions and Hadron - Quark Mixed Phase

Possibility of structured mixed phases at first order phase transitions in neutron stars is re-examined by taking into account charge screening and surface effects. Transition from the hadron $npe$ phase to the quark phase is studied. Two possibilities, the mixed phase and two separate phases given by the double-tangent (Maxwell) construction are considered. Inhomogeneous profiles of the electric potential and their contribution to the energy are analytically calculated. The electric field configurations determine the droplet size and the geometry of structures.

nucl-th↗

arXiv2002

Hadron-quark mixed phase in neutron stars

Possibility of structured mixed phase at first order phase transitions is examined by taking into account of charge screening and surface effects. Hadron-quark phase transition in dense neutron star interiors is considered as a concrete example.

nucl-th↗

arXiv2002

Confronting Neutron Star Cooling Theories with New Observations

With the successful launch of Chandra and XMM/Newton X-ray space missions combined with the lower-energy band observations, we are in the position where careful comparison of neutron star cooling theories with observations will make it possible to distinguish among various competing theories. For instance, the latest theoretical and observational developments already exclude both nucleon and kaon direct URCA cooling. In this way we can now have realistic hope for determining various important properties, such as the composition, degree of superfluidity, the equation of state and steller radius. These developments should help us obtain better insight into the properties of dense matter.

astro-ph↗

arXiv2001

Charge Screening at First Order Phase Transitions

Possibility of structured mixed phases at first order phase transitions is examined with taking into account of charge screening and surface effects. Hadron-quark phase transition in dense neutron star interior is considered, as concrete example.

nucl-th↗

arXiv1999

The Landau-Migdal Parameters, g'_NN and g'_NΔand Pion Condensations

The Landau-Migdal parameters for nucleon-nucleon (g'_NN) and nucleon-Δ(g'_NΔ) couplings are estimated from recent experimental data on the giant Gamow-Teller state of 90Nb. The observed quenching of the GT strength by 10% provides 0.16<g'_NΔ<0.23 for g'_ΔΔ<1.0, while the excitation energy g'_NN\sim 0.59. The critical density of pion condensations is much lower than those previously discussed with the universality ansatz.

nucl-th↗

arXiv1995

On Neutrino Emission From Dense Matter Containing Meson Condensates

We consider the rate at which energy is emitted by neutrinos from the dense interior of neutron stars containing a Bose condensate of pions or kaons. The rates obtained are larger, by a factor of 2, than those found earlier, and are consistent with those found for the direct Urca processes.

nucl-th↗