Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Vacuum pressures and energy in a strong magnetic field   We study vacuum in a strong magnetic field. It shows a nonlinear response, as
a ferromagnetic medium. Anisotropic pressures arise, and a negative pressure is
exerted in the direction perpendicular to the field. The analogy of this effect
with the Casimir effect is analyzed. The vacuum transverse pressure is found to
be of the same order of the statistical pressure for $B\sim10^{15}G$ and
$N\sim10^{33}electrons/cm^{3}$. Vacuum interaction with the field is studied
also for $B\sim10^{16}G$ and larger, including the electron anomalous magnetic
moment. We estimate quark contribution to vacuum behavior.

2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th