Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userIsovector potential of $Sigma$ in nuclei and neutron star matter
175
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We determine the coupling constants of $Sigma$ hyperon with mesons in relativistic mean field (RMF) models using $Sigma^-$ atomic shift data and examine the effects of $Sigma$ on the neutron star maximum mass. We find that we need to reduce the vector-isovector meson coupling with $Sigma$ ($g_{rhoSigma}$) from the value constrained by the SU(3)v symmetry in order to explain the $Sigma^-$ atomic shifts for light symmetric and heavy asymmetric nuclei simultaneously. With the atomic shift fit value of $g_{rhoSigma}$, $Sigma^-$ can emerge in neutron star matter overcoming the repulsive isoscalar potential for $Sigma$ hyperons. Admixture of $Sigma^-$ in neutron stars is found to reduce the neutron star maximum mass slightly.
rate research
Read More
We propose a particle number conserving formalism for the treatment of isovector-isoscalar pairing in nuclei with $N>Z$. The ground state of the pairing Hamiltonian is described by a quartet condensate to which is appended a pair condensate formed by the neutrons in excess. The quartets are built by two isovector pairs coupled to the total isospin $T=0$ and two collective isoscalar proton-neutron pairs. To probe this ansatz for the ground state we performed calculations for $N>Z$ nuclei with the valence nucleons moving above the cores $^{16}$O, $^{40}$Ca and $^{100}$Sn. The calculations are done with two pairing interactions, one state-independent and the other of zero range, which are supposed to scatter pairs in time-revered orbits. It is proven that the ground state correlation energies calculated within this approach are very close to the exact results provided by the diagonalization of the pairing Hamiltonian. Based on this formalism we have shown that moving away of N=Z line, both the isoscalar and the isovector proton-neutron pairing correlations remain significant and that they cannot be treated accurately by models based on a proton-neutron pair condensate.
We study the effects of isovector-scalar meson $delta$ on the equation of state (EOS) of neutron star matter in strong magnetic fields. The EOS of neutron-star matter and nucleon effective masses are calculated in the framework of Lagrangian field theory, which is solved within the mean-field approximation. From the numerical results one can find that the $delta$-field leads to a remarkable splitting of proton and neutron effective masses. The strength of $delta$-field decreases with the increasing of the magnetic field and is little at ultrastrong field. The proton effective mass is highly influenced by magnetic fields, while the effect of magnetic fields on the neutron effective mass is negligible. The EOS turns out to be stiffer at $B < 10^{15}$G but becomes softer at stronger magnetic field after including the $delta$-field. The AMM terms can affect the system merely at ultrastrong magnetic field($B > 10^{19}$G). In the range of $10^{15}$ G -- $10^{18}$ G the properties of neutron-star matter are found to be similar with those without magnetic fields.
Neutron-proton (np-) pairing is expected to play an important role in the N Z nuclei. In general, it can have isovector and isoscalar character. The existence of isovector np-pairing is well established. On the contrary, it is still debated whether there is an isoscalar np-pairing. The review of the situation with these two types of pairing with special emphasis on the isoscalar one is presented. It is concluded that there are no substantial evidences for the existence of isoscalar np-pairing.
We investigate the effect of a microscopic three-body force on the proton and neutron superfluidity in the $^1S_0$ channel in $beta$-stable neutron star matter. It is found that the three-body force has only a small effect on the neutron $^1S_0$ pairing gap, but it suppresses strongly the proton $^1S_0$ superfluidity in $beta$-stable neutron star matter.
We present recent investigations on dipole and quadrupole excitations in spherical skin nuclei, particular exploring their connection to the thickness of the neutron skin. Our theoretical method relies on density functional theory, which provides us with a proper link between nuclear many-body theory of the nuclear ground state and its phenomenological description. For the calculation of the nuclear excited states we apply QPM theory. A new quadrupole mode related to pygmy quadrupole resonance (PQR) in tin isotopes is suggested.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
