Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The pygmy dipole strength, the neutron radius of ${}^{208}$Pb and the
  symmetry energy   The accurate characterization of the nuclear symmetry energy and its density
dependence is one of the outstanding open problems in nuclear physics. A
promising nuclear observable in order to constrain the density dependence of
the symmetry energy at saturation is the neutron skin thickness of medium and
heavy nuclei. Recently, a low-energy peak in the isovector dipole response of
neutron-rich nuclei has been discovered that may be correlated with the neutron
skin thickness. The existence of this correlation is currently under debate due
to our limited experimental knowledge on the microscopic structure of such a
peak. We present a detailed analysis of Skyrme Hartree-Fock (HF) plus random
phase approximation (RPA) predictions for the dipole response in several
neutron-rich nuclei and try to elucidate whether models of common use in
nuclear physics confirm or dismiss its possible connection with the neutron
skin thickness. Finally, we briefly present theoretical results for parity
violating electron scattering on ${}^{208}$Pb at the conditions of the PREx
experiment and discuss the implications for the neutron skin thickness of
${}^{208}$Pb and the slope of the symmetry energy.

37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol