Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ground-state energy of a high-density electron gas in a strong magnetic
  field   The high-density electron gas in a strong magnetic field B and at zero
temperature is investigated. The quantum strong-field limit is considered in
which only the lowest Landau level is occupied. It is shown that the
perturbation series of the ground-state energy can be represented in analogy to
the Gell-Mann Brueckner expression of the ground-state energy of the field-free
electron gas. The role of the expansion parameter is taken by $r_B= (2/3 \pi^2)
(B/m^2) (\hbar r_S/e)^3$ instead of the field-free Gell-Mann Brueckner
parameter r_s.

2
The categories of this paper are: math
19
The categories of this paper are: eess
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th