Searcharxiv⌕ Search

arXiv subjects

Masayuki Matsuzaki

Publications and source records attributed to Masayuki Matsuzaki.

52 records · Page 3Linked to original sources
arXiv2003

Possibility of ΛΛpairing and its dependence on background density in relativistic Hartree-Bogoliubov model

We calculate a ΛΛpairing gap in binary mixed matter of nucleons and Λhyperons within the relativistic Hartree-Bogoliubov model. Lambda hyperons to be paired up are immersed in background nucleons in a normal state. The gap is calculated with a one-boson-exchange interaction obtained from a relativistic Lagrangian. It is found that at background density ρ_{N}=2.5ρ_{0} the ΛΛpairing gap is very small, and that denser background makes it rapidly suppressed. This result suggests a mechanism, specific to mixed matter dealt with relativistic models, of its dependence on the nucleon density. An effect of weaker ΛΛattraction on the gap is also examined in connection with revised information of the ΛΛinteraction.

nucl-th↗
arXiv2002

Wobbling Motion in Atomic Nuclei with Positive-Gamma Shapes

The three moments of inertia associated with the wobbling mode built on the superdeformed states in 163Lu are investigated by means of the cranked shell model plus random phase approximation to the configuration with an aligned quasiparticle. The result indicates that it is crucial to take into account the direct contribution to the moments of inertia from the aligned quasiparticle so as to realize J_x > J_y in positive-gamma shapes. Quenching of the pairing gap cooperates with the alignment effect. The peculiarity of the recently observed 163Lu data is discussed by calculating not only the electromagnetic properties but also the excitation spectra.

nucl-th↗
arXiv2001

Relativistic Hartree-Bogoliubov Calculation of Specific Heat of the Inner Crust of Neutron Stars

We calculate the specific heat of the inner crust of neutron stars within a local-density approximation to an improved relativistic Hartree-Bogoliubov theory. Non-uniformness of the system enhances the specific heat in particular at low temperatures. The degree of enhancement is similar to that in the spherical phase of Elgarøy et al. We examine a schematic interpolation between the results of Broglia et al. adopting the Gogny force and ours based on the Lagrangian of the relativistic mean field model.

nucl-th↗
arXiv2000

Relativistic mean field description for the shears band mechanism in $^{84}$Rb

For the first time, the Relativistic Mean Field (RMF) model is applied to the shears band recently observed in $_{37}^{84}$Rb. Signals of the appearance of the shears mechanism, such as smooth decreases of the shears angle and of the $B$(M1)/$B$(E2) ratio with keeping the nearly constant tilt angle, are well reproduced. Thus it is shown that the microscopic RMF model can nicely describe the shears band in this nucleus.

nucl-th↗
arXiv2000

Phenomenological construction of a relativistic nucleon-nucleon interaction for the superfluid gap equation in finite density systems

We construct phenomenologically a relativistic particle-particle channel interaction which suits the gap equation for nuclear matter. This is done by introducing a density-independent momentum-cutoff parameter to the relativistic mean field (Hartree and Hartree-Fock) models so as to reproduce the pairing properties obtained by the Bonn-B potential and not to change the saturation property. The interaction so obtained can be used for the Relativistic Hartree-Bogoliubov calculation, but some reservation is necessary for the Relativistic Hartree-Fock-Bogoliubov calculation.

nucl-th↗
arXiv2000

Spatial structure of quark Cooper pairs in a color superconductor

Spatial structure of Cooper pairs with quantum numbers color 3^*, I=J=L=S=0 in ud 2 flavor quark matter is studied by solving the gap equation and calculating the coherence length in full momentum range without the weak coupling approximation. Although the gap at the Fermi surface and the coherence length depend on density weakly, the shape of the r-space pair wave function varies strongly with density. This result indicates that quark Cooper pairs become more bosonic at higher densities.

hep-ph↗
arXiv1999

Effect of Vector Meson Mass Decrease on Superfluidity in Nuclear Matter

$^1S_0$ pairing in nuclear matter is investigated by taking the hadron mass decrease into account via the ``In-Medium Bonn potential'' which was recently proposed by Rapp et al. The resulting gap is significantly reduced in comparison with the one obtained with the original Bonn-B potential and we ascertain that the meson mass decrease is mainly responsible for this reduction.

nucl-th↗
arXiv1998

Effects of Meson Mass Decrease on Superfluidity in Nuclear Matter

We calculate the $^1S_0$ pairing gap in nuclear matter by adopting the "in-medium Bonn potential" proposed by Rapp et al. [e-print nucl-th/9706006], which takes into account the in-medium meson mass decrease, as the particle-particle interaction in the gap equation. The resulting gap is significantly reduced in comparison with the one obtained by adopting the original Bonn potential.

nucl-th↗
arXiv1998

Dirac Sea Effects on Superfluidity in Nuclear Matter

We study two kinds of Dirac sea effects on the $^1S_0$ pairing gap in nuclear matter based on the relativistic Hartree approximation to quantum hadrodynamics and the Gor'kov formalism. We show that the vacuum fluctuation effect on the nucleon effective mass is more important than the direct coupling between the Fermi sea and the Dirac sea due to the pairing interaction. The effects of the high-momentum cutoff are also discussed.

nucl-th↗
arXiv1997

Relativistic Mean Field Description of Nuclear Collective Rotation -The Superdeformed Rotational Bands in the A$\sim$60 Mass Region-

Relativistic Mean Field Theory is applied to the description of rotating nuclei. Since the previous formulation of Munich group was based on a special relativistic transformation property of the spinor fields, we reformulate in a fully covariant manner using tetrad formalism. The numerical calculations are performed for 3 zinc isotopes, including the newly discovered superdeformed band in $^{62}$Zn which is the first experimental observation in this mass region.

nucl-th↗
arXiv1994

Nuclear Wobbling Motion and Electromagnetic Transitions

The nuclear wobbling motion is studied from a microscopic viewpoint. It is shown that the expressions not only of the excitation energy but also of the electromagnetic transition rate in the microscopic RPA framework can be cast into the corresponding forms of the macroscopic rotor model. Criteria to identify the rotational band associated with the wobbling motion are given, based on which examples of realistic calculations are investigated and some theoretical predictions are presented.

nucl-th↗
arXiv1994

Two-dimensional SU(N) Gauge Theory on the Light Cone

Two-dimensional SU($N$) gauge theory is accurately analyzed with the light-front Tamm-Dancoff approximation, both numerically and analytically. The light-front Einstein-Schrödinger equation for mesonic mass reduces to the 't Hooft equation in the large $N$ limit, $g^2N$ fixed, where $g$ is the coupling constant. Hadronic masses are numerically obtained in the region of $m^2 \ll g^2N$, where $m$ is the bare quark (q) mass. The lightest mesonic and baryonic states are almost in valence. The second lightest mesonic state is highly relativistic in the sense that it has a large 4-body ($ {\rm qq} \bar{\rm q} \bar{\rm q} $) component in addition to the valence (${\rm q} \bar{\rm q}$) one. In the strong coupling limit our results are consistent with the prediction of the bosonization for ratios of the lightest and second lightest mesonic masses to the lightest baryonic one. Analytic solutions to the lightest hadronic masses are obtained, with a reasonable approximation, as $\sqrt{2Cm}(1-1/N^2)^{1/4}$ in the mesonic case and $\sqrt{CmN(N-1)}(1-1/N^2)^{1/4}$ in the baryonic case, where $C=(g^2Nπ/6)^{1/2}$. The solutions well reproduce the numerical ones. The $N$- and $m$-dependences of the hadronic masses are explicitly shown by the analytical solutions.

hep-th↗