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In mathematics and theoretical physics, a pseudo-Euclidean space is a finite-dimensional together with a non-degenerate indefinite quadratic form . Such a quadratic form can, given a suitable choice of basis , be applied to a vector , giving (with ) : which is called the ''magnitude'' of the vector . For true Euclidean spaces, , implying that the quadratic form is positive-definite rather than indefinite. Otherwise is an isotropic quadratic form. Note that if and , then , so that is a null vector. In a pseudo-Euclidean space, unlike in a Euclidean space, there exist vectors with negative magnitude. As with the term ''Euclidean space'', ''pseudo-Euclidean space'' may refer to either an affine space or a vector space (see point–vector distinction) over real numbers. == Geometry == The geometry of a pseudo-Euclidean space is consistent in spite of a breakdown of the some properties of Euclidean space; most notably that it is not a metric space as explained below. Though, its affine structure provides that concepts of line, plane and, generally, of an affine subspace (flat), can be used without modifications, as well as line segments. 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「Pseudo-Euclidean space」の詳細全文を読む スポンサード リンク
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