We adopt the Nambu-Jona-Lasinio (NJL) model to study the crust-core transition properties in neutron stars (NSs). For a given momentum cutoff and symmetry energy of saturation density in the NJL model, decreasing the slope of the symmetry energy gives rise to an increase in the crust-core transition density and transition pressure. Given the slope of the symmetry energy at saturation density, the transition density and corresponding transition pressure increase with increasing symmetry energy. The increasing trend between the fraction of the crustal moment of inertia and the slope of symmetry energy at saturation density indicates that a relatively large momentum cutoff of the NJL model is preferred. For a momentum cutoff of 500 MeV, the fraction of the crustal moment of inertia clearly increases with the slope of symmetry energy at saturation density. Thus, at the required fraction (7%) of the crustal moment of inertia, the NJL model with momentum cutoff of 500 MeV and a large slope of the symmetry energy of saturation density can give the upper limit of the mass of the Vela pulsar to be above 1.40 M .

Considering the importance of Lorentz invariance and chiral symmetry, we adopt the Nambu-Jona-Lasinio (NJL) model that ensures the nuclear matter saturation properties to study the density dependence of the symmetry energy. The negative symmetry energy at high densities that is usually dubbed the super-soft symmetry energy can be obtained from introducing a chiral isovector-vector interaction in the lagrangian, but should be ruled out by the neutron star (NS) stability in the mean-field approximation. It is found that the isovector-scalar interaction in the NJL model can play an important role in softening of the symmetry energy. We have investigated NS properties. The NS maximum mass obtained with various isovector-scalar couplings and momentum cutoffs is well above the 2M⊙, and the NS radius obtained well meets the limits extracted from recent measurements. In particular, the significant reduction of the canonical NS radius occurs with the moderate decrease of the slope of the symmetry energy, while the effect of the symmetry energy on the NS maximum mass remains insignificant as usual.

The sensitive correlations between the low-density halo structure and the high-density properties of the nuclear equation of state (EOS) are constructed in light kaonic nuclei with the relativistic mean-field theory. More specifically, the 1p 1/2 halo spreads out linearly with increasing the pressure and sound velocity square at supra-normal densities and decreasing the incompressibility at saturation density. These results suggest that the novel halo in light kaonic nuclei can serve as a sensitive indicator of the nuclear EOS of symmetric matter at supra-normal densities. The experimental production and detection of the light kaonic nuclei, yet to be available, is discussed in some details at last.

The heating effect of terahertz pulse with various frequencies and intensities on the heavy water solution is investigated using the molecular dynamics simulation. Resonant absorptions are found for both heavy water and light water, but at a different resonant frequency which is about 16 THz for heavy water and 21 THz for light water. This resonant phenomenon can be explained perfectly by the collective rotational modes that may release water molecules from hydrogen bonding. The findings not only illustrate the heating mechanism of heavy water solution under the terahertz pulse irradiation, but also demonstrate a novel difference between light water and heavy water that could have potential applications.

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As the experimental data from kaonic atoms and K − N scatterings imply that the K − -nucleon interaction is strongly attractive at saturation density, there is a possibility to form K − -nuclear bound states or kaonic nuclei. In this work, we investigate the ground-state properties of the light kaonic nuclei with the relativistic mean-field theory. It is found that the strong attraction between K − and nucleons reshapes the scalar and vector meson fields, leading to the remarkable enhancement of the nuclear density in the interior of light kaonic nuclei and the manifest shift of the single-nucleon energy spectra and magic numbers therein. As a consequence, the pseudospin symmetry is shown to be violated together with enlarged spin-orbit splittings in these kaonic nuclei.PACS numbers: 13.75.Jz, 21.10.Dr, 21.10.Pc, 21.60.Gx I. INTRODUCTIONThe pseudospin symmetry (PSS), manifested by the quasidegeneracy between single-nucleon states with quantum numbers (n, l, j = l + 1/2) and (n − 1, l + 2, j = l + 3/2), was found more than 40 years ago [1,2]. Subsequently, substantial efforts had been devoted to understanding the dynamic origin of the PSS until it was recognized that the PSS is a symmetry hidden in the equations for the small component of Dirac spinors. This might be natural and became clear later on since the relativistic mean-field (RMF) models are characteristic of the dynamical description of the spin degree of freedom and spin-orbit interactions [3][4][5][6][7][8][9]. The exact PSS is a consequence of the fact that the scalar and vector potentials are equal in size but opposite in sign, i.e., Σ(r) = S(r) + V (r) = 0, while in practice the PSS is approximate since the condition Σ(r) = 0 gives no bound state as in the RMF theory. However, the exception was found in Ref.[10] when the confining potential exists.In the Schrödinger-like equation for the small component of the Dirac spinor, the term proportional to dΣ(r)/dr is related to the breaking of the PSS, and the small magnitude of that term gives the approximate PSS. For further understanding the properties of the PSS, people have studied the PSS in a number of physical processes and phenomena including superdeformation [9], nucleonnucleon and nucleon-nucleus scatterings [11,12], single particle resonant states [13], superheavy magic structures [14], identical bands [15], and pseudospin partner bands [16,17], and so on.The PSS breaking, proportional to the radial gradient of the potential Σ(r), can vary with the isospin and charge of nuclei through the vector potential entry [6,7,[18][19][20]. In the past, the PSS breaking had been studied extensively, and some very useful tools were also developed to analyze the breaking [13,21,22]. In addition to the isospin effects on the PSS breaking, the variation of the isoscalar potentials can also become one PSS breaking source, although this variation in different normal nuclei in the nuclear chart is not significant. In this work, our attention to the PSS breaking is focused on the exotic systems, the kaonic nuclei...

It is very difficult for any nuclear model to pin down the saturation property and high-density equation of state (EOS) simultaneously because of high nonlinearity of the nuclear many-body problem. In this work, we propose, for the first time, to use the special property of light kaonic nuclei to characterize the relation between saturation property and high-density EOS. With a series of relativistic mean-field models, this special property is found to be the level inversion between orbitals 2S 1/2 and 1D 5/2 in light kaonic nuclei. This level inversion can serve as a theoretical laboratory to group the incompressibility at saturation density and the EOS at supra-normal densities simultaneously.

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