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Ramification of Some Automorphisms of Local Fields

✍ Scribed by F Laubie; M Saı̈ne

Publisher
Elsevier Science
Year
1998
Tongue
English
Weight
217 KB
Volume
72
Category
Article
ISSN
0022-314X

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✦ Synopsis

Let k be a perfect field of characteristic p and let # # Aut(k((t))). Define the ramification numbers of # by i m =v t (# p m (t)&t)&1. We give a characterization of the sequences (i m ) which are the sequences of ramification numbers of infinite order automorphisms of formal power series fields over finite fields. Then, given a perfect field k, we give sufficient conditions on (i m ) to be the sequence of ramification numbers of an autormorphism # # Aut k (k((t))) and we investigate these sequences (i m ) in the case where there exists _ # Aut k (k((t))) such that _#=#_ with _{# & for all & # Z p .

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