Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Primordial Magnetic Field from Domain Walls   In this paper we discuss once more the zero mode contribution to the vacuum
energy density. We show that a careful treatment of the zero modes leads to the
conclusion that domain walls may be ferromagnetic, and could generate a
magnetic field of cosmological interest.

3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
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The categories of this paper are: stat
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an