Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Matter distribution and spin-orbit force in spherical nuclei   We investigate the possibility that some nuclei show density distributions
with a depletion in the center, a semi-bubble structure, by using a
Hartree-Fock plus Bardeen-Cooper-Schrieffer approach. We separately study the
proton, neutron and matter distributions in 37 spherical nuclei mainly in the
$s - d$ shell region. We found a relation between the semi-bubble structure and
the energy splitting of spin-orbit partner single particle levels. The presence
of semi-bubble structure reduces this splitting, and we study its consequences
on the excitation spectrum of the nuclei under investigation by using a
quasi-particle random-phase-approximation approach. The excitation energies of
the low-lying $4^+$ states can be related to the presence of semi-bubble
structure in nuclei.

3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
28
The categories of this paper are: alg-geom
17
The categories of this paper are: q-fin
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The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph