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Levi-Civita symbol. In mathematics, particularly in linear algebra, tensor analysis, and differential geometry, the Levi-Civita symbol or Levi-Civita epsilon represents a collection of numbers defined from the sign of a permutation of the natural numbers 1, 2, ..., n, for some positive integer n. It is named after the Italian mathematician and ...
The Levi-Civita connection (like any affine connection) also defines a derivative along curves, sometimes denoted by D. Given a smooth curve γ on (M, g) and a vector field V along γ its derivative is defined by. Formally, D is the pullback connection γ*∇ on the pullback bundle γ*TM. In particular, is a vector field along the curve γ itself.
The trace or tensor contraction, considered as a mapping. The map , representing scalar multiplication as a sum of outer products. The generalized Kronecker delta or multi-index Kronecker delta of order is a type tensor that is completely antisymmetric in its upper indices, and also in its lower indices. Two definitions that differ by a factor ...
This can be simplified by performing a contraction on the Levi-Civita symbols, = =, where is the Kronecker delta function (= when and = when =) and is the generalized Kronecker delta function. We can reason out this identity by recognizing that the index k {\displaystyle k} will be summed out leaving only i {\displaystyle i} and j ...
The last identity can be recognized as the defining relationship for ... is the type (4,4) generalized Kronecker delta in 4 ... is the Levi-Civita ...
where the solution to i 2 = −1 is the "imaginary unit", and δ jk is the Kronecker delta, which equals +1 if j = k and 0 otherwise. This expression is useful for "selecting" any one of the matrices numerically by substituting values of j = 1, 2, 3, in turn useful when any of the matrices (but no particular one) is to be used in algebraic ...
Einstein notation. In mathematics, especially the usage of linear algebra in mathematical physics and differential geometry, Einstein notation (also known as the Einstein summation convention or Einstein summation notation) is a notational convention that implies summation over a set of indexed terms in a formula, thus achieving brevity.
where is the Kronecker delta or identity matrix. Finite-dimensional real vector spaces with (pseudo-)metrics are classified up to signature, a coordinate-free property which is well-defined by Sylvester's law of inertia. Possible metrics on real space are indexed by signature (,).