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Lindsay N. Childs
Hopf Galois Structures on Degree p2 Cyclic Extensions of Local Fields
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Published: |
December 5, 1996 |
Keywords: |
Galois module, Hopf Galois extension, associated order, wildly ramified, Hopf order |
Subject: |
11S15, 11R33, 16W30 |
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Abstract
Let L be a Galois extension of K, finite field extensions of
Qp, p odd, with Galois group cyclic of order p2. There are p
distinct K-Hopf algebras Ad, d = 0,...,p-1, which act on L
and make L into a Hopf Galois extension of K. We describe these
actions. Let R be the valuation ring of K. We describe a collection
of R-Hopf orders Ev in Ad, and find criteria on Ev for Ev to
be the associated order in Ad of the valuation ring S of some L.
We find criteria on an extension L/K for S to be Ev-Hopf Galois
over R for some Ev, and show that if S is Ev-Hopf Galois over
R for some Ev, then the associated order Ad of S in Ad
is Hopf, and hence S is Ad-free, for all d. Finally we
parametrize the extensions L/K whose ramification numbers are congruent to
-1 mod p2 and determine the density of the parameters of those
L/K for which the associated order of S in KG is Hopf.
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Author information
Department of Mathematics and Statistics, University at Albany, Albany, NY 12222
http://math.albany.edu:8000/~lc802/
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