Comments on the nuclear symmetry energy

Abstract

According to standard textbooks, the nuclear symmetry energy originates from the kinetic energy and the interaction itself. We argue that this view requires certain modifications and propose a different scenario. We ascribe the physical origin of the kinetic term to the discreteness of fermionic levels of, in principle arbitrary binary fermionic systems, and relate its mean value directly to the average level density. Physically it connects this part also to the isoscalar interaction which, at least in self-bound systems like atomic nuclei, decides upon the spatial dimensions of the system. For the general case of binary fermionic systems possible external confining potentials as well as specific boundary conditions will contribute to this part. The reliability of this concept is verified using self-consistent Skyrme–Hartree–Fock calculations.