Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Twisted covers and specializations   The central topic is this question: is a given $k$-\'etale algebra
$\prod_lE_l/k$ the specialization of a given $k$-cover $f:X\rightarrow B$ at
some point $t_0\in B(k)$? Our main tool is a {\it twisting lemma} that reduces
the problem to finding $k$-rational points on a certain $k$-variety. Previous
forms of this twisting lemma are generalized and unified. New applications are
given: a Grunwald form of Hilbert's irreducibility theorem over number fields,
a non-Galois variant of the Tchebotarev theorem for function fields over finite
fields, some general specialization properties of covers over PAC or ample
fields.

6
The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ