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In mathematics, Fenchel's duality theorem is a result in the theory of convex functions named after Werner Fenchel. Let ''ƒ'' be a proper convex function on R''n'' and let ''g'' be a proper concave function on R''n''. Then, if regularity conditions are satisfied, : where ''ƒ'' * is the convex conjugate of ''ƒ'' (also referred to as the Fenchel–Legendre transform) and ''g'' * is the concave conjugate of ''g''. That is, : : ==Mathematical theorem== Let ''X'' and ''Y'' be Banach spaces, and be convex functions and be a bounded linear map. Then the Fenchel problems: : : satisfy weak duality, i.e. . Note that are the convex conjugates of ''f'',''g'' respectively, and is the adjoint operator. The perturbation function for this dual problem is given by . Suppose that ''f'',''g'', and ''A'' satisfy either # ''f'' and ''g'' are lower semi-continuous and where is the algebraic interior and where ''h'' is some function is the set , or # where are the points where the function is continuous. Then strong duality holds, i.e. . If then supremum is attained. 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「Fenchel's duality theorem」の詳細全文を読む スポンサード リンク
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