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List of formulas in Riemannian geometry : ウィキペディア英語版 | List of formulas in Riemannian geometry This is a list of formulas encountered in Riemannian geometry. ==Christoffel symbols, covariant derivative==
In a smooth coordinate chart, the Christoffel symbols of the first kind are given by : and the Christoffel symbols of the second kind by : Here is the inverse matrix to the metric tensor . In other words, : and thus : is the dimension of the manifold. Christoffel symbols satisfy the symmetry relations : or, respectively, , the second of which is equivalent to the torsion-freeness of the Levi-Civita connection. The contracting relations on the Christoffel symbols are given by : and : where |''g''| is the absolute value of the determinant of the metric tensor . These are useful when dealing with divergences and Laplacians (see below). The covariant derivative of a vector field with components is given by: : this becomes : and likewise for tensors with more indices. The covariant derivative of a function (scalar) is just its usual differential: : Because the Levi-Civita connection is metric-compatible, the covariant derivatives of metrics vanish, : as well as the covariant derivatives of the metric's determinant (and volume element) : The geodesic starting at the origin with initial speed has Taylor expansion in the chart: :
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