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Authors
Affiliations
1 Institut De Mathematiques De Jussieu, UMR 9994, Case 247 Universite Pierre Et Marie Curie 4, Place Jussieu 75005-Paris, FR
Source
Journal of the Ramanujan Mathematical Society, Vol 12, No 2 (1997), Pagination: 147-160
Abstract
Let Q denote the algebraic closure of Q in C, and Z denote its ring of integers. At the 1993 Luminy workshop on Grothendieck's theory of Dessins d'Enfants, Joseph Oesterle, wanting to know more about reduction of these Dessins modulo maximal ideals of Z, asked the following question: Let E be a finite extension of Q (T) unramified outside { 0,l,∞} ; is the normalisation of P1√z in E finite overP1√z? In an unpublished letter of April 17th, 1993, Y.Ihara answered this question in the affirmative, even without assuming the ramification hypothesis.