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In mathematics, the de Franchis theorem is one of a number of closely related statements applying to compact Riemann surfaces, or, more generally, algebraic curves, ''X'' and ''Y'', in the case of genus ''g'' > 1. The simplest is that the automorphism group of ''X'' is finite (see though Hurwitz's automorphisms theorem). More generally, *the set of non-constant morphisms from ''X'' to ''Y'' is finite; *fixing ''X'', for all but a finite number of such ''Y'', there is no non-constant morphism from ''X'' to ''Y''. These results are named for Michele De Franchis (1875–1946). It is sometimes referenced as the De Franchis-Severi theorem. It was used in an important way by Gerd Faltings to prove the Mordell conjecture. ==See also== *Castelnuovo–de Franchis theorem 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「De Franchis theorem」の詳細全文を読む スポンサード リンク
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