Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Updated constraint on a primordial magnetic field during big bang
  nucleosynthesis and a formulation of field effects   A new upper limit on the amplitude of primordial magnetic field (PMF) is
derived by a comparison between a calculation of elemental abundances in big
bang nucleosynthesis (BBN) model and the latest observational constraints on
the abundances. Updated nuclear reaction rates are adopted in the calculation.
Effects of PMF on the abundances are consistently taken into account in the
numerical calculation with the precise formulation of changes in physical
variables. We find that abundances of 3He and 6Li increase while that of 7Li
decreases when the PMF amplitude increases, in the case of the baryon-to-photon
ratio determined from the measurement of cosmic microwave background radiation.
We derive a constraint on the present amplitude of PMF, i.e., B(0)<1.5 micro G
[corresponding to the amplitude less than 2.0x10^{11} G at BBN temperature of
T=10^9 K] based on the rigorous calculation.

31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th