Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetization and collective excitations of a magnetic dipole fermion
  gas   The ground states and collective excitations of trapped Fermion gases
consisting of atoms with magnetic dipole moment are studied using a
time-dependent density-matrix approach. The advantages of the density-matrix
approach are that one-body and two-body observables are directly calculated
using one-body and two-body density matrices and that it has a clear relation
to the Hartree-Fock (HF) and time-dependent HF theory. The HF calculations show
the magnetization of the gases when the dipole-dipole interaction is strong. It
is shown that the tensor properties of the dipole-dipole interaction are
revealed in the excitation modes associated with spin degrees of freedom.

3
The categories of this paper are: physics
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio