Study On The Coexistence Of Pp,nn And Np Pairings In Nuclear Matter

The pair correlation is closely related to the deformation of the nucleus,the mo-ment of inertia,the structure of the halo nucleus,and the mass discrepancy between odd and even nuclei.In Astronomical Nuclear Physics,pair correlation is essential for un-derstanding the physics-related processes of neutron stars,including cooling,periodic jumps,r-mode instability,and gravitational wave radiation.Because of the degree of freedom of isospin,there are neutron-neutron,proton-proton,and neutron-proton cor-relations between nucleons.The current research on nucleon-pair correlation considers single pairs only.However,whether they can coexist and the impact of coexistence is a very significant question.In addition,the neutron pairings of the spin-triplet state in a strong magnetic field are a similar physical system.Exploring whether Cooper pairs of three spin orientations can coexist and what effect the pairings will have on spin polar-ization can help us understand the source of the magnetic field in magnetized neutron stars.We adopt the density-dependent effective point interaction potential to describe the three cooper pairs in asymmetric nuclear matter,and use the BCS energy gap equations to calculate their energy gaps and pairing probabilities near the Fermi surface in different environments and conditions.In the previous theoretical calculations,the energy gaps of np pairs in finite nuclei and nuclear matter are not the same.Due to the complexity of the many-body problem,The effective pairing force of the nucleon pair is not yet clear,so we artificially adjust the pairing force strength of the np pair to obtain a qualitative conclusion.At the same time,to understand the influence of the existence of nn and pp on np pairs,we also considered the case of single pairs and compared the calculation results of the same physical quantity under the same conditions.The results show that these three cooper pairs can coexist in asymmetric nuclear matter.The np pair needs to have greater pairing force strength than nn and pp pairs to exist.When its pairing force strength is much greater,The existence of nn and pp pairs is beneficial for it,but if its pairing force strength approaches that of nn and pp pairs,the np pair will be suppressed by them.We used a similar method to deal with pure neutron matter in a strong magnetic field.The results show that since there is no advantage in the pairing force strength,n?n?cannot exist in pure neutron matter,and the neutrons with upward and downward spins pair separately.The energy gap of the n?n? pair is positively related to the magnetic field strength,and the energy gap of the n?n? pair is negatively related to the magnetic field strength.When the magnetic field increases to a particular strength,neutrons with downward spins no longer exist.Superfluidity promotes neutron polarization.Although to a certain extent,the neutron cooper pairs behave like a boson,they will not condense all on the state of n?n? under the action of a small magnetic field,arranged regularly and superimposed to form a significant magnetic moment,thereby generating a large induced magnetic field.Therefore,the neutron polarization in the superfluid state is not the main source of the neutron star's magnetic field.