Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Planar QED at finite temperature and density: Hall conductivity, Berry's
  phases and minimal conductivity of graphene   We study 1-loop effects for massless Dirac fields in two spatial dimensions,
coupled to homogeneous electromagnetic backgrounds, both at zero and at finite
temperature and density. In the case of a purely magnetic field, we analyze the
relationship between the invariance of the theory under large gauge
transformations, the appearance of Chern-Simons terms and of different Berry's
phases. In the case of a purely electric background field, we show that the
effective Lagrangian is independent of the chemical potential and of the
temperature. More interesting: we show that the minimal conductivity, as
predicted by the quantum field theory, is the right multiple of the
conductivity quantum and is, thus, consistent with the value measured for
graphene, with no extra factor of pi in the denominator.

1
The categories of this paper are: cs
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph