Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Screening and plasma oscillations in an electron gas in the hydrodynamic
  approximation   A hydrodynamic theory of screening in a generic electron gas of arbitrary
dimensionality is given that encompasses all previously studied cases and
clarifies the predictions of the many-body approach. We find that
long-wavelength plasma oscillations are classical phenomena with
quantum-mechanical effects playing no explicit role. The character of the
oscillations is solely dictated by the dimensionality of the electron system
and its equation of state in the neutral limit. Materials whose excitations are
described by the Dirac dispersion law -- such as doped graphene or a Weyl
semimetal -- are no exception to this rule.

18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph