Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A long-wave action of spin Hamiltonians and the inverse problem of the
  calculus of variations   We suggest a method of derivation of the long-wave action of the model spin
Hamiltonians using the non-linear partial differential equations of motions of
the individual spins. According to the Vainberg's theorem the set of these
equations are (formal) potential if the symmetry analysis for the Frechet
derivatives of the system is true. The case of Heisenberg (anti)ferromagnets is
considered. It is shown the functional whose stationary points are described by
the equations coincides with the long-wave action and includes the non-trivial
topological term (Berry phase).

21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th