Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hamiltonian reduction for the magnetic dynamics in antiferromagnetic
  crystals   The nonlinear spin dynamics in antiferromagnetic crystals is studied for the
magnetic structures similar to that of hematite. For the case when only two
magnetization vectors are non-zero and the Hamiltonian has an axial symmetry, a
reduction to a Hamiltonian system with one degree of freedom is performed,
based on the corresponding conservation law. The analysis of the phase
portraits of this system provides tractable analytical and geometric
descriptions of the regimes of nonlinear spin dynamics in the crystal.

23
The categories of this paper are: solv-int
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
21
The categories of this paper are: adap-org