| E. Bombieri, A.J. van der Poorten and J. D. Vaaler. Effective Measures of Irrationality for Cubic Extensions of Number Fields, Ann Scuola Norm. Sup. Pisa Cl. Sci. (to appear). |
.... ; ff N Gamma1 ] for the homogeneous coordinates of a generic element in P N Gamma1 (k v ) We let the quotient map OE : k N v Gamma f0g Gamma P N Gamma1 (k v ) be OE(ff 0 ; ff 1 ; Delta Delta Delta ; ff N Gamma1 ) ff 0 ; ff 1 ; Delta Delta Delta ; ff N Gamma1 ] As in [1], 5] and [9] one can define a projective metric on P N Gamma1 (k v ) as follows. If ff and fi belong to P N Gamma1 (k v ) then we define Delta v (ff; fi) kff fik v kffk v kfik v (1.3) and ffi v (ff; fi) jff fij v jffj v jfij v where is the wedge product. It follows from ....
....Y v jfij v ; 1.8) where the product is over all places v of k. In view of the product formula, the height function is well defined on P N Gamma1 (k) To illustrate a basic Diophantine inequality in this setting, we state the following projective form of Dirichlet s Theorem (e.g. Theorem 1 of [1] or Theorem 1 of [5] Dirichlet s Theorem. Let ff belong to P N Gamma1 (k v ) belong to k v and assume that 1 j j v . Then there exists fi in P N Gamma1 (k) such that (i) H(fi) c k (N)j j N Gamma1 v , ii) ffi v (ff; fi) c k (N)fj j v H(fi)g Gamma1 , where c k (N) ....
E. Bombieri, A.J. van der Poorten and J. D. Vaaler. Effective Measures of Irrationality for Cubic Extensions of Number Fields, Ann Scuola Norm. Sup. Pisa Cl. Sci. (to appear).
....a point fi in k such that the height of fi is bounded by a suitable parameter and jff Gamma fij v is relatively small. And for special numbers ff it is a basic problem of Diophantine approximation to show that jff Gamma fij v cannot be too small if the height of fi is bounded. In a recent paper [2] such problems were reformulated in projective space over k v by replacing the Omega Gammae metric determined by j j v with a projective metric ffi v . Our purpose here is to give a proof of the projective form of Dirichlet s Theorem and to prove a useful inequality for the projective metric. We ....
....purpose here is to give a proof of the projective form of Dirichlet s Theorem and to prove a useful inequality for the projective metric. We also discuss some open problems suggested by these results. At each place v of k we use two absolute values j j v and k k v which are determined as in [1] [2], or [3] Thus we have jxj v = kxk dv=d v for all x in k v , where d = k : Q] and d v = k v : Q v ] These absolute values have unique extensions to Omega v , the completion of an algebraic closure of k v . We extend j j v to a norm on finite dimensional vector spaces over Omega v as ....
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E. Bombieri, A.J. van der Poorten, and J.D. Vaaler, Effective measures of irrationality for cubic extensions of number fields, Ann. Scuola Norm. Sup. Pisa Cl. Sci. 23 (1996), 211--248.
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