Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Itinerant Ferromagnetism in ultracold Fermi gases   Itinerant ferromagnetism in cold Fermi gases with repulsive interactions is
studied applying the Jastrow-Slater approximation generalized to finite
polarization and temperature. For two components at zero temperature a second
order transition is found at $ak_F\simeq0.90$ compatible with QMC.
Thermodynamic functions and observables such as the compressibility and spin
susceptibility and the resulting fluctuations in number and spin are
calculated. For trapped gases the resulting cloud radii and kinetic energies
are calculated and compared to recent experiments. Spin polarized systems are
recommended for effective separation of large ferromagnetic domains. Collective
modes are predicted and tri-critical points are calculated for multi-component
systems.

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The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ