Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Itinerant Ferromagnetism in an Ultracold Atom Fermi Gas   We address the possible occurrence of ultracold atom ferromagnetism by
evaluating the free energy of a spin polarized Fermi gas to second order in its
interaction parameter. We find that Hartree-Fock theory underestimates the
tendency toward ferromagnetism, predict that the ferromagnetic transition is
first order at low temperatures, and point out that the spin coherence time of
gases prepared in a ferromagnetic state is strongly enhanced as the transition
is approached. We relate our results to recent experiments.

2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
37
The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg