2,567 research outputs found

### BCS-BEC crossover in nuclear matter with the relativistic Hartree-Bogoliubov theory

Based on the relativistic Hartree-Bogoliubov theory, the influence of the
pairing interaction strength on the di-neutron correlations and the crossover
from superfluidity of neutron Cooper pairs in the $^{1}S_{0}$ channel to
Bose-Einstein condensation of di-neutron pairs is systematically investigated
in the nuclear matter. The bare nucleon-nucleon interaction Bonn-B is taken in
the particle-particle channel with an effective factor to simulate the medium
effects and take into account the possible ambiguity of pairing force, and the
effective interaction PK1 is used in the particle-hole channel. If the
effective factor is larger than 1.10, a di-neutron BEC state appears in the
low-density limit, and if it is smaller than 0.85, the neutron Cooper pairs are
found totally in the weak coupling BCS region. The reference values of several
characteristic quantities which characterize the BCS-BEC crossover are obtained
respectively from the dimensionless parameter $1/(k_{\rm Fn}a)$ with $a$ the
scattering length and $k_{\rm{Fn}}$ the neutron Fermi momentum, the
zero-momentum transfer density correlation function D(0) and the effective
chemical potential $\nu_{\rm n}$.Comment: 8 pages, 4 figures, 2 tables, Accepted Thursday Jun 14, 2012 for
Physical Review

### Pairing Properties of Symmetric Nuclear Matter in Relativistic Mean Field Theory

The properties of pairing correlations in symmetric nuclear matter are
studied in the relativistic mean field (RMF) theory with the effective
interaction PK1. Considering well-known problem that the pairing gap at Fermi
surface calculated with RMF effective interactions are three times larger than
that with Gogny force, an effective factor in the particle-particle channel is
introduced. For the RMF calculation with PK1, an effective factor 0.76 give a
maximum pairing gap 3.2 MeV at Fermi momentum 0.9 fm$^{-1}$, which are
consistent with the result with Gogny force.Comment: 14 pages, 6 figures

### Deformation effect on the center-of-mass correction energy in nuclei ranging from Oxygen to Calcium

The microscopic center-of-mass (c.m.) correction energies for nuclei ranging
from Oxygen to Calcium are systematically calculated by both spherical and
axially deformed relativistic mean-field (RMF) models with the effective
interaction PK1. The microscopic c.m. correction energies strongly depend on
the isospin as well as deformation and deviate from the phenomenological ones.
The deformation effect is discussed in detail by comparing the deformed with
the spherical RMF calculation. It is found that the direct and exchange terms
of the c.m. correction energies are strongly correlated with the density
distribution of nuclei and are suppressed in the deformed case.Comment: 7 pages, 3 figures, accepted by Chin.Phys.Let

### Deformation effect on the center-of-mass correction energy in nuclei ranging from Oxygen to Calcium

The microscopic center-of-mass (c.m.) correction energies for nuclei ranging
from Oxygen to Calcium are systematically calculated by both spherical and
axially deformed relativistic mean-field (RMF) models with the effective
interaction PK1. The microscopic c.m. correction energies strongly depend on
the isospin as well as deformation and deviate from the phenomenological ones.
The deformation effect is discussed in detail by comparing the deformed with
the spherical RMF calculation. It is found that the direct and exchange terms
of the c.m. correction energies are strongly correlated with the density
distribution of nuclei and are suppressed in the deformed case.Comment: 7 pages, 3 figures, accepted by Chin.Phys.Let

### Applicability of Relativistic Point-Coupling Models to Neutron Star Physics

Comparing with a wide range of covariant energy density functional models
based on the finite-range meson-exchange representation, the relativistic
mean-field models with the zero-range contact interaction, namely the
relativistic point-coupling models, are still infrequent to be utilized in
establishing nuclear equation of state (EoS) and investigating neutron star
properties, although comprehensive applications and achievements of them in
describing many nuclear properties both in ground and exited states are mature.
In this work, the EoS of neutron star matter is established constructively in
the framework of the relativistic point-coupling models to study neutron star
physics. Taking two selected functionals DD-PC1 and PC-PK1 as examples, nuclear
symmetry energies and several neutron star properties including proton
fractions, mass-radius relations, the core-crust transition density, the
fraction of crustal moment of inertia and dimensionless tidal deformabilities
are discussed. A suppression of pressure of neutron star matter found in the
functional PC-PK1 at high densities results in the difficulty of its prediction
when approaching to the maximum mass of neutron stars. In addition, the
divergences between two selected functionals in describing neutron star
quantities mentioned above are still large, ascribing to the less constrained
behavior of these functionals at high densities. Then it is expected that the
constraints on the dense matter EoS from precise and massive modern
astronomical observations, such as the tidal-deformabilities taken from
gravitational-wave events, would be essential to improve the parameterizing of
the relativistic point-coupling models.Comment: To appear in the AIP Proceedings of the Xiamen-CUSTIPEN Workshop on
the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave
Astronomy, Jan. 3-7, Xiamen, Chin

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