Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: DNS of the kappa-mechanism   We present a purely-radiative hydrodynamic model of the kappa-mechanism that
sustains radial oscillations in Cepheid variables. We determine the physical
conditions favourable for the kappa-mechanism to occur by the means of a
configurable hollow in the radiative conductivity profile. By starting from
these most favourable conditions, we complete nonlinear direct numerical
simulations (DNS) and compare them with the results given by a linear-stability
analysis of radial modes. We find that well-defined instability strips are
generated by changing the location and shape of the conductivity hollow. For a
given position in the layer, the hollow amplitude and width stand out as the
key parameters governing the appearance of unstable modes driven by the
kappa-mechanism. The DNS confirm both the growth rates and structures of the
linearly-unstable modes. The nonlinear saturation that arises is produced by
intricate couplings between the excited fundamental mode and higher damped
overtones. These couplings are measured by projecting the DNS fields onto an
acoustic subspace built from regular and adjoint eigenvectors and a 2:1
resonance is found to be responsible for the saturation of the kappa-mechanism
instability.

22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics