Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structure theorem of square complex orthogonal design   Square COD (complex orthogonal design) with size $[n, n, k]$ is an $n \times
n$ matrix $\mathcal{O}_z$, where each entry is a complex linear combination of
$z_i$ and their conjugations $z_i^*$, $i=1,\ldots, k$, such that
$\mathcal{O}_z^H \mathcal{O}_z = (|z_1|^2 + \ldots + |z_k|^2)I_n$. Closely
following the work of Hottinen and Tirkkonen, which proved an upper bound of
$k/n$ by making a crucial observation between square COD and group
representation, we prove the structure theorem of square COD.

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The categories of this paper are: chem-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
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The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
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The categories of this paper are: gr-qc
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin
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The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: quant-ph
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The categories of this paper are: plasm-ph