Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Linear and non-linear theory of a parametric instability of hydrodynamic
  warps in Keplerian discs   We consider the stability of warping modes in Keplerian discs. We find them
to be parametrically unstable using two lines of attack, one based on
three-mode couplings and the other on Floquet theory. We confirm the existence
of the instability, and investigate its nonlinear development in three
dimensions, via numerical experiment. The most rapidly growing non-axisymmetric
disturbances are the most nearly axisymmetric (low m) ones. Finally, we offer a
simple, somewhat speculative model for the interaction of the parametric
instability with the warp. We apply this model to the masing disc in NGC 4258
and show that, provided the warp is not forced too strongly, parametric
instability can fix the amplitude of the warp.

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The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat