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In algebraic geometry, a morphism of schemes :''f'': ''X'' → ''Y'' is called radicial or universally injective, if, for every field ''K'' the induced map ''X''(''K'') → ''Y''(''K'') is injective. (EGA I, (3.5.4)) This is a generalization of the notion of a purely inseparable extension of fields (sometimes called a radicial extension, which should not be confused with a radical extension.) It suffices to check this for ''K'' algebraically closed. This is equivalent to the following condition: ''f'' is injective on the topological spaces and for every point ''x'' in ''X'', the extension of the residue fields :''k''(''f''(''x'')) ⊂ ''k''(''x'') is radicial, i.e. purely inseparable. It is also equivalent to every base change of ''f'' being injective on the underlying topological spaces. (Thus the term ''universally injective''.) Radicial morphisms are stable under composition, products and base change. If ''gf'' is radicial, so is ''f''. ==References== * , section I.3.5. * , see section V.5. 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「Radicial morphism」の詳細全文を読む スポンサード リンク
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