Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On a variational formulation of the weakly nonlinear magnetic
  Rayleigh--Taylor instability   The magnetic-Rayleigh--Taylor (MRT) instability is a ubiquitous phenomenon
that occurs in magnetically-driven Z-pinch implosions. It is important to
understand this instability since it can decrease the performance of such
implosions. In this work, I present a theoretical model for the weakly
nonlinear MRT instability. I obtain such model by asymptotically expanding an
action principle, whose Lagrangian leads to the fully nonlinear MRT equations.
After introducing a suitable choice of coordinates, I show that the theory can
be cast as a Hamiltonian system, whose Hamiltonian is calculated up to sixth
order in a perturbation parameter. The resulting theory captures the harmonic
generation of MRT modes. In particular, it is shown that the saturation
amplitude of the linear MRT instability grows as the stabilization effect of
the magnetic-field tension increases. Overall, the theory provides an intuitive
interpretation of the weakly nonlinear MRT instability and provides a
systematic approach for studying this instability in more complex settings.

29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an