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In differential geometry, the four-gradient is the four-vector analogue of the gradient from Gibbs-Heaviside vector calculus. ==Definition== The covariant components compactly written in index notation are:〔The Cambridge Handbook of Physics Formulas, G. Woan, Cambridge University Press, 2010, ISBN 978-0-521-57507-2〕 : implies the ''partial differentiation'' with respect to . This is not the same as a semi-colon, used for the covariant derivative. The contravariant components are:〔The Cambridge Handbook of Physics Formulas, G. Woan, Cambridge University Press, 2010, ISBN 978-0-521-57507-2〕 : where ''gαβ'' is the metric tensor, which here has been chosen for flat spacetime with the metric signature (+,−,−,−). Alternative symbols to are and ''D''. 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「Four-gradient」の詳細全文を読む スポンサード リンク
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