Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic Phases of the 2D Hubbard Model at Low Doping   We study the equilibrium spin configuration of the 2D Hubbard model at low
doping, when a long-range magnetic order is still present. We use the
spin-density-wave formalism and examine the two suggested candidates for a
ground state: the planar spiral $(\pi,Q)$ and $(Q,Q)$ states. In a mean-field
theory, each of these two states is a ground state in a certain range of
parameters. We however show that both states have negative bosonic modes in a
transverse channel which implies that the spiral states are in fact unstable
(the $(Q,Q)$ state, in addition, has a negative longitudinal stiffness). We
searched for a ground state in a parameter range which on a mean-field level
favored the $(\pi,Q)$ phase, and found that the equilibrium spin configuration
is noncoplanar. These findings lead to a novel scenario of spin reorientation
upon doping in Hubbard antiferromagnets.

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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: gr-qc
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The categories of this paper are: cmp-lg
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The categories of this paper are: eess
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The categories of this paper are: adap-org
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The categories of this paper are: nlin
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn