Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thermal Versus Vacuum Magnetization in QED   The magnetized relativistic Fermi and Bose gases are studied at finite
temperature and density.In the case of the Fermi gas, the contribution to the
magnetization from the vacuum becomes dominant for high magnetic fields, when
the thermal contribution saturates.
  In the case of the charged Bose gas, the (paramagnetic) vacuum--magnetization
becomes dominant when the gas changes from a diamagnetic to a paramagnetic
behaviour. We furthermore find that the scalar--QED effective coupling constant
for a weak non--zero external magnetic field is a decreasing function of the
temperature.

28
The categories of this paper are: alg-geom
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph