Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Non-normal and Stochastic Amplification in Turbulent Dynamo: Subcritical
  Case   Our attention focuses on the stochastic dynamo equation with non-normal
operator that give an insight into the role of stochastics and non-normality in
the galactic magnetic field generation. The main point of this Letter is a
discussion of the generation of a large-scale magnetic field that cannot be
explained by traditional linear eigenvalue analysis. We present a simple
stochastic model for the thin-disk axisymmetric $\alpha \Omega $ dynamo
involving three factors: (a) the non-normality generated by differential
rotation, (b) the nonlinearity reflecting how the magnetic field affects the
turbulent dynamo coefficients, and (c) stochastic perturbations. We show that
even for \textit{subcritical case,} there are three possible mechanisms for the
generation of magnetic field. The first mechanism is a deterministic one that
describes an interplay between transient growth and nonlinear saturation of the
turbulent $\alpha -$effect and diffusivity. It turns out that the trivial state
is nonlinearity unstable to small but finite initial perturbations. The second
and third are the stochastic mechanisms that account for the interaction of
non-normal effect generated by differential rotation and random additive and
multiplicative fluctuations. In particular, we show that in \textit{subcritical
case}the average magnetic energy can grow exponentially with time due to the
multiplicative noise associated with $\alpha -$effect.

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The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: funct-an
2
The categories of this paper are: math
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The categories of this paper are: eess
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The categories of this paper are: econ
34
The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: adap-org