Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An example of a Fra\"iss\'e class without a Kat\v{e}tov functor   We disprove a conjecture from [W. Kubi\'s, D. Ma\v{s}ulovi\'c, Kat\v{e}tov
functors, preprint, http://arxiv.org/abs/1412.1850] by showing the existence of
a Fra\"iss\'e class $\mathcal{C}$ which does not admit a Kat\v{e}tov functor.
On the other hand, we show that the automorphism group of the Fra\"iss\'e limit
of $\mathcal{C}$ is universal, as it happens in the presence of a Kat\v{e}tov
functor.

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The categories of this paper are: mtrl-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: stat
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The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys
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The categories of this paper are: astro-ph
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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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: solv-int
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The categories of this paper are: alg-geom
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The categories of this paper are: eess
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph