tensor/Ricci

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tensor[Ricci] - compute the covariant Ricci tensor

	Calling Sequence
	Ricci(ginv, Rmn)

Parameters

ginv	-	rank two tensor_type of character [1,1] representing the contravariant metric tensor; specifically, $(ginv[compts])[i,j]:=g^{ij}$
Rmn	-	rank four tensor_type of character [-1,-1,-1,-1] representing the covariant Riemann curvature tensor; specifically, $Rmn[compts][i, j, k, l] := R_*{ijkl}$

Description

•	The resultant tensor_type of this routine is the covariant Ricci tensor: a covariant rank 2 tensor that is symmetric in its indices (the component array of the result uses the Maple symmetric indexing function).

•	ginv should be indexed using the symmetric indexing function. Rmn should be indexed using the `cov_riemann` indexing function provided by the package. It is recommended that tensor[invert] and tensor[Riemann] be used to compute these quantities.

•

Simplification: This routine uses the `tensor/Ricci/simp` routine for simplification purposes. The simplification routine is applied to each component of result after it is computed. By default, `tensor/Ricci/simp` is initialized to the `tensor/simp` routine. It is recommended that the `tensor/Ricci/simp` routine be customized to suit the needs of the particular problem.

•	This function is part of the tensor package, and so can be used in the form Ricci(..) only after performing the command with(tensor) or with(tensor, Ricci). The function can always be accessed in the long form tensor[Ricci](..).

Examples

Define the coordinate variables and the covariant components of the Schwarzchild metric.

g := TABLE([compts = matrix([[1-2*m/r, 0, 0, 0], [0, -1/(1-2*m/r), 0, 0], [0, 0, -r^2, 0], [0, 0, 0, -r^2*sin(theta)^2]]), index_char = [-1, -1]])

(1)

Compute the Ricci tensor.

RICCI := TABLE([compts = matrix([[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]), index_char = [-1, -1]])

(2)

You can also view the result using the tensor package function displayGR.

	See Also
	Physics[Christoffel], Physics[D_], Physics[d_], Physics[Einstein], Physics[g_], Physics[LeviCivita], Physics[Ricci], Physics[Riemann], Physics[Weyl], tensor, tensor[displayGR], tensor[invert], tensor[Riemann], tensor[simp], tensor[tensorsGR]