Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mean-field equations for weakly nonlinear two-scale perturbations of
  forced hydromagnetic convection in a rotating layer   We consider stability of regimes of hydromagnetic thermal convection in a
rotating horizontal layer with free electrically conducting boundaries, to
perturbations involving large spatial and temporal scales. Equations governing
the evolution of weakly nonlinear mean perturbations are derived under the
assumption that the alpha-effect is insignificant in the leading order (e.g.,
due to a symmetry of the system). The mean-field equations generalise the
standard equations of hydromagnetic convection: New terms emerge -- a
second-order linear operator representing the combined eddy diffusivity, and
quadratic terms associated with the eddy advection. If the perturbed CHM regime
is non-steady and insignificance of the alpha-effect in the system does not
rely on the presence of a spatial symmetry, the combined eddy diffusivity
operator also involves a non-local pseudodifferential operator. If the
perturbed CHM state is almost symmetric, alpha-effect terms appear in the
mean-field equations as well. Near a point of a symmetry-breaking bifurcation,
cubic nonlinearity emerges in the equations. All the new terms are in general
anisotropic. A method for evaluation of their coefficients is presented; it
requires solution of a significantly smaller number of auxiliary problems than
in a straightforward approach.

19
The categories of this paper are: eess
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an