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In mathematics, the Grothendieck inequality states that there is a universal constant ''k'' with the following property. If ''a''''i'',''j'' is an ''n'' by ''n'' (real or complex) matrix with : for all (real or complex) numbers ''s''''i'', ''t''''j'' of absolute value at most 1, then :, for all vectors ''S''''i'', ''T''''j'' in the unit ball ''B''(''H'') of a (real or complex) Hilbert space ''H''. The smallest constant ''k'' which satisfies this property for all ''n'' by ''n'' matrices is called a Grothendieck constant and denoted ''k''(''n''). In fact there are two Grothendieck constants ''k''R(''n'') and ''k''C(''n'') for each ''n'' depending on whether one works with real or complex numbers, respectively.〔.〕 The Grothendieck inequality and Grothendieck constants are named after Alexander Grothendieck, who proved the inequality and the existence of the constants in a paper published in 1953.〔 ==Bounds on the constants== The sequences ''k''R(''n'') and ''k''C(''n'') are easily seen to be increasing, and Grothendieck's result states that they are bounded, so they have limits. With ''k''R defined to be sup''n'' ''k''R(''n'') then Grothendieck proved that: . improved the result by proving: 1.67696... ≤ ''k''R ≤ 1.7822139781...=, conjecturing that the upper bound is tight. However, this conjecture was disproved by . 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「Grothendieck inequality」の詳細全文を読む スポンサード リンク
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