Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The spin excitations of the block-antiferromagnetic
  K$_{0.8}$Fe$_{1.6}$Se$_2$   We study the spin excitations of the newly discovered block-antiferromagnetic
state in K$_{0.8}$Fe$_{1.6}$Se$_2$ using an effective spin Hamiltonian
suggested in the literature. Interestingly in addition to the usual Goldstone
mode, there exists three other "optical" spin wave branches. These spin
excitations are the analog of "optical phonons" in crystals with more than one
atom per unit cell. We compute the spin wave corrected ordering moment and the
uniform spin susceptibilities.

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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
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The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat
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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: plasm-ph
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The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex