Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Note on the Secrecy Capacity of the Multi-antenna Wiretap Channel   Recently, the secrecy capacity of the multi-antenna wiretap channel was
characterized by Khisti and Wornell [1] using a Sato-like argument. This note
presents an alternative characterization using a channel enhancement argument.
This characterization relies on an extremal entropy inequality recently proved
in the context of multi-antenna broadcast channels, and is directly built on
the physical intuition regarding to the optimal transmission strategy in this
communication scenario.

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The categories of this paper are: q-bio
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The categories of this paper are: quant-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: math-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: acc-phys
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The categories of this paper are: stat
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The categories of this paper are: chem-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc