Download e-book for kindle: Local fields and their extensions by I. B. Fesenko and S. V. Vostokov

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By I. B. Fesenko and S. V. Vostokov

ISBN-10: 082183259X

ISBN-13: 9780821832592

This ebook is dedicated to the examine of entire discrete valuation fields with ideal residue fields. One precise function is the absence of cohomology; even supposing such a lot experts could locate it tricky to conceive of significant discussions during this quarter with out the appliance of cohomology teams, the authors think that many difficulties could be offered extra rationally while in accordance with extra average, particular structures. additionally, a cohomology-free therapy looks prime when you are first encountering this topic. the most prerequisite is a typical graduate direction in algebra, and familiarity with $p$-adic fields is additionally worthwhile heritage.

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Example text

The ring of integers coincides with W (K ) and F0 is implies complete. The maximal ideal of W (K ) is VW (K ) and the residue field is isomorphic to K . 1), we complete the n>0 proof. Remark. 3) can be generalized to ramified Witt vectors by replacing p with (see [ Dr2 ], [ Haz4 ]). Exercises. 1. 2. 3. 4. 5. 6. 7. 2)) be defined for a ring with p = 6 0? Show that V and F are injective in W (K ) if K is a field of characteristic p . Show that F is an automorphism of W (K ) if K is a perfect field of characteristic p .

Complete) discrete valuation field and let L0 =F be the maximal unramified subextension in L=F . Then L = L0 ( ) and OL = OL0 [ ] with a prime element in L satisfying the equation X e ; 0 = 0 for some prime element 0 in L0 , where e = e(LjF ) . (2) Let L0 =F be a finite unramified extension, L = L0 ( ) with e = 2 L0 . Let p - e if p = char(F ) > 0. Then L=F is separable tamely ramified. Proof. 4) shows that L=L0 is totally ramified.

We get c. 6) shows L = M ( 1 ), and g1 (X ) 2 M [X ] is irreducible over Fb = M that w1 is the unique extension to L of w1 jM ; there are k distinct discrete valuations on M which extend v . Example. Let E = F (X ). Recall that the discrete valuations on E which are trivial on F are in one-to-one correspondence with irreducible monic polynomials p (X ) over F : p (X ) ! vp (X ) , v ! 2) Ch. I). If an is the leading coefficient of f (X ), then Y f (X ) = an pv (X )v(f (X )) : v6=v1 Let F1 be an extension of F .

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Local fields and their extensions by I. B. Fesenko and S. V. Vostokov


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