Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Limits on possible magnetic fields at nucleosynthesis time   In this paper we discuss limits on magnetic fields that could have been
present at nucleosynthesis time. We considered several effects that could be
relevant modifing light elements relic abundances. They include: changes in
reaction rates, mass shifts due to strong and electromagnetic interactions,
variation of the expansion rate of the Universe due to both the magnetic field
energy density and the increasing of the electrons density in overcritical
magnetic fields.
  We find that the latter is the main effect. It was not taken into account in
previous calculations. The allowed field intensity at the end of
nucleosynthesis ($T =1\times 10^9\;^o{\rm K}$) is $B \le 3\times 10^{10}$
Gauss.

16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
3
The categories of this paper are: physics
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an