Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Valuation Criterion for Normal Basis Generators of Hopf-Galois
  Extensions in Characteristic p   Let S/R be a finite extension of discrete valuation rings of characteristic
p>0, and suppose that the corresponding extension L/K of fields of fractions is
separable and is H-Galois for some K-Hopf algebra H. Let D_{S/R} be the
different of S/R. We show that if S/R is totally ramified and its degree n is a
power of p, then any element $\rho$ of L with $v_L(\rho)$ congruent to
$-v_L(D_{S/R})-1$ mod n generates L as an H-module. This criterion is best
possible. These results generalise to the Hopf-Galois situation recent work of
G. Elder for Galois extensions.

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The categories of this paper are: physics
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: chem-ph
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-th
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The categories of this paper are: cond-mat
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The categories of this paper are: supr-con
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The categories of this paper are: ao-sci
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The categories of this paper are: q-alg
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: astro-ph