Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Existence of weak solutions to a dynamic model for smectic-A liquid
  crystals under undulations   A nonlinear model due to Soddemann et al. [37] and Stewart [38] describing
incompressible smectic-A liquid crystals under flow is studied. In comparison
to previously considered models, this particular model takes into account
possible undulations of the layers away from equilibrium, which has been
observed in experiments. The emerging decoupling of the director and the layer
normal is incorporated by an additional evolution equation for the director.
Global existence of weak solutions to this model is proved via a Galerkin
approximation with eigenfunctions of the associated linear differential
operators in the three-dimensional case.

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The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
1
The categories of this paper are: cs
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
9
The categories of this paper are: nlin
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg