Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nature of the Darwin term and ${(Z\alpha)^4 m^3/M^2}$ contribution to
  the Lamb shift for an arbitrary spin of the nucleus   The contact Darwin term is demonstrated to be of the same origin as the
spin-orbit interaction. The $(Z\alpha)^4 m^3/M^2$ correction to the Lamb shift,
generated by the Darwin term, is found for an arbitrary nonvanishing spin of
the nucleus, both half-integer and integer. There is also a contribution of the
same nature to the nuclear quadrupole moment.

10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org