Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pygmy resonances and symmetry energy   I present a brief summary of the first three decades of studies of pygmy
resonances in nuclei and their relation to the symmetry energy of nuclear
matter. I discuss the first experiments and theories dedicated to study the
electromagnetic response in halo nuclei and how a low energy peak was initially
identified as a candidate for the pygmy resonance. This is followed by the
description of a collective state in medium heavy and heavy nuclei which was
definitely identified as a pygmy resonance. The role of the slope parameter of
the symmetry energy in determining the properties of neutron stars is stressed.
The theoretical and experimental information collected on pygmy resonances,
neutron skins, and the numerous correlations found with the slope parameter is
briefly reviewed.

13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex