Neutrino Interactions in Octet Baryon Matter

Neutrino processes caused by the neutral current are studied in octet baryon matter. Previous confusion about the baryonic matrix elements of the neutral current interaction is excluded, and a correct table for them improved by consideration of the proton spin problem is presented instead.Comment: 6 page

Quark description of the Nambu-Goldstone bosons in the color-flavor locked phase

We investigate the color-singlet order parameters and the quark description of the Nambu-Goldstone (NG) bosons in the color-flavor locked (CFL) phase. We put emphasis on the NG boson (phason) called ``H'' associated with the $\mathrm{U_B(1)}$ symmetry breaking. We qualitatively argue the nature of H as the second sound in the hydrodynamic regime. We articulate, based on a diquark picture, how the structural change of the condensates and the associated NG bosons occurs continuously from hadronic to CFL quark matter if the quark-hadron continuity is realized. We sharpen the qualitative difference between the flavor octet pions and the singlet phason. We propose a conjecture that superfluid H matter undergoes a crossover to a superconductor with tightly-bound diquarks, and then a crossover to superconducting matter with diquarks dissociated.Comment: 14 pages, 1 table, 1 figure and confusing statements are correcte

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.Comment: 11 pages, 1 figur

Kaonic nuclei studied based on a new framework of Antisymmetric Molecular Dynamics

We have developed a new framework of Antisymmetrized Molecular Dynamics (AMD), to adequately treat the I=0 \={K}N interaction, which is essential to study kaonic nuclei. The improved points are 1) pK$^-$/n\={K}$^0$ mixing and 2) total spin and isospin projections. These improvements enable us to investigate various kaonic nuclei (ppnK$^-$, pppK$^-$, pppnK$^-$, $^6$BeK$^-$ and $^9$BK$^-$) systematically. We have found that they are deeply bound and extremely dense with a variety of shapes.Comment: 10 pages, 5 figure

Ab initio approach to s-shell hypernuclei 3H_Lambda, 4H_Lambda, 4He_Lambda and 5He_Lambda with a Lambda N-Sigma N interaction

Variational calculations for s-shell hypernuclei are performed by explicitly including $\Sigma$ degrees of freedom. Four sets of YN interactions (SC97d(S), SC97e(S), SC97f(S) and SC89(S)) are used. The bound-state solution of $_\Lambda^5$He is obtained and a large energy expectation value of the tensor $\Lambda N-\Sigma N$ transition part is found. The internal energy of the $^4$He subsystem is strongly affected by the presence of a $\Lambda$ particle with the strong tensor $\Lambda N-\Sigma N$ transition potential.Comment: Phys. Rev. Lett. 89, 142504 (2002

Dipole resonances in light neutron-rich nuclei studied with time-dependent calculations of antisymmetrized molecular dynamics

In order to study isovector dipole response of neutron-rich nuclei, we have applied a time-dependent method of antisymmetrized molecular dynamics. The dipole resonances in Be, B and C isotopes have been investigated. In $^{10}$Be, $^{15}$B, $^{16}$C, collective modes of the vibration between a core and valence neutrons cause soft resonances at the excitation energy $E_x=10-15$ MeV below the giant dipole resonance(GDR). In $^{16}$C, we found that a remarkable peak at $E_x=14$ MeV corresponds to coherent motion of four valence neutrons against a $^{12}$C core, while the GDR arises from the core vibration in the $E_x >20$ MeV region. In $^{17}$B and $^{18}$C, the dipole strengths in the low energy region decline compared with those in $^{15}$B and $^{16}$C. We also discuss the energy weighted sum rule for the $E1$ transitions.Comment: 12 figures, submitted to Phys. Rev.

Deformations in N=14 isotones

Systematic analysis of deformations in neutron-rich N=14 isotones was done based on the method of antisymmetrized molecular dynamics. The property of the shape coexistence in $^{28}$Si, which is known to have the oblate ground state and the prolate excited states, was successfully described. The results suggest that the shape coexistence may occur also in neutron-rich N=14 nuclei as well as $^{28}$Si. It was found that the oblate neutron shapes are favored because of the spin-orbit force in most of N=14 isotones. $Q$ moments and $E2$ transition strengths in the neutron-rich nuclei were discussed in relation to the intrinsic deformations, and a possible difference between the proton and neutron deformations in $^{24}$Ne was proposed.Comment: 13 pages, 7 figures, sumitted to Phys.Rev.

Stability of the mixed phase in hybrid stars

The transition from hadronic matter to quark matter in the core of neutron stars is likely to be associated with the appearance of a mixed phase, leading to a smooth variation of the star density profile. We discuss the results of a systematic study of the properties of the mixed pase upon Coulomb and surface effects. A state of the art nonrelativistic equation of state of nuclear matter has been used for the low density phase, while quark matter has been described within the MIT bag model, including the effect of perturbative one-gluon exchange interactions. The implications for neutron star structure are discussed.Comment: Submitted to Astronomy & Astrophysic

Dilute Multi Alpha Cluster States in Nuclei

Dilute multi $\alpha$ cluster condensed states with spherical and axially deformed shapes are studied with the Gross-Pitaevskii equation and Hill-Wheeler equation, where the $\alpha$ cluster is treated as a structureless boson. Applications to self-conjugate $4N$ nuclei show that the dilute $N\alpha$ states of $^{12}$C to $^{40}$Ca with $J^\pi=0^+$ appear in the energy region from threshold up to about 20 MeV, and the critical number of $\alpha$ bosons that the dilute $N\alpha$ system can sustain as a self-bound nucleus is estimated roughly to be $N_{cr}\sim10$. We discuss the characteristics of the dilute $N\alpha$ states with emphasis on the $N$ dependence of their energies and rms radii.Comment: 44 pages, 8 figure