Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hall current effects in mean-field dynamo theory   The role of the Hall term on large scale dynamo action is investigated by
means of the First Order Smoothing Approximation. It is shown that the standard
$\alpha$ coefficient is altered, and is zero when a specific double Beltrami
state is attained, in contrast to the Alfv\'enic state for MHD dynamos. The
$\beta$ coefficient is no longer positive definite, and thereby enables dynamo
action even if $\alpha$-quenching were to operate. The similarities and
differences with the (magnetic) shear-current effect are pointed out, and a
mechanism that may be potentially responsible for $\beta < 0$ is advanced. The
results are compared against previous studies, and their astrophysical
relevance is also highlighted.

12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
16
The categories of this paper are: stat
23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin