Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the closure of the diagonal of a $T_1$-space   Let X be a topological space. The closure of \Delta = {(x, x) : x \in X} in X
\times X is a symmetric relation on X. We characterise those equivalence
relations on an infinite set that arise as the closure of the diagonal with
respect to a T_1-topology.

5
The categories of this paper are: gr-qc
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: q-alg
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph