Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Tukey types of ultrafilters   We investigate the structure of the Tukey types of ultrafilters on countable
sets partially ordered by reverse inclusion. A canonization of cofinal maps
from a p-point into another ultrafilter is obtained. This is used in particular
to study the Tukey types of p-points and selective ultrafilters. Results fall
into three main categories: comparison to a basis element for selective
ultrafilters, embeddings of chains and antichains into the Tukey types, and
Tukey types generated by block-basic ultrafilters on FIN.

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The categories of this paper are: cond-mat
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The categories of this paper are: q-alg
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: astro-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: physics
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The categories of this paper are: hep-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio