Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Poisson-Bracket Approach to the Dynamics of Nematic Liquid Crystals. The
  Role of Spin Angular Momentum   Nematic liquid crystals are well modeled as a fluid of rigid rods. Starting
from this model, we use a Poisson-bracket formalism to derive the equations
governing the dynamics of nematic liquid crystals. We treat the spin angular
momentum density arising from the rotation of constituent molecules about their
centers of mass as an independent field and derive equations for it, the mass
density, the momentum density, and the nematic director. Our equations reduce
to the original Leslie-Ericksen equations, including the inertial director term
that is neglected in the hydrodynamic limit, only when the moment of inertia
for angular momentum parallel to the director vanishes and when a dissipative
coefficient favoring locking of the angular frequencies of director rotation
and spin angular momentum diverges. Our equations reduce to the equations of
nematohydrodynamics in the hydrodynamic limit but with dissipative coefficients
that depend on the coefficient that must diverge to produce the Leslie-Ericksen
equations.

16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
13
The categories of this paper are: quant-ph