Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extragalactic magnetic fields unlikely generated at the electroweak
  phase transition   In this letter we show that magnetic fields generated at the electroweak
phase transition are most likely too weak to explain the void magnetic fields
apparently observed today unless they have considerable helicity. We show that,
in the simplest estimates, the helicity naturally produced in conjunction with
the baryon asymmetry is too small to explain observations, which require a
helicity fraction at least of order $10^{-14}-10^{-10}$ depending on the void
fields constraint used. Therefore new mechanisms to generate primordial
helicity are required if magnetic fields generated during the electroweak phase
transition should explain the extragalactic fields.

26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
35
The categories of this paper are: mtrl-th