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](..).

$\mathrm{with}\left(\mathrm{tensor}\right)\:$

$\mathrm{coord}≔\left[t\,r\,\mathrm{\theta }\,\mathrm{\phi }\right]\:$

$\mathrm{g\_compts}≔\mathrm{array}\left(\mathrm{symmetric}\,\mathrm{sparse}\,1..4\,1..4\right)\:$

$\mathrm{g\_compts}\left[1,1\right]≔1-\frac{2m}{r}\:$$\mathrm{g\_compts}\left[2,2\right]≔-\frac{1}{\mathrm{g\_compts}\left[1,1\right]}\:$

$\mathrm{g\_compts}\left[3,3\right]≔-r^2\:$$\mathrm{g\_compts}\left[4,4\right]≔-r^2{\sin \left(\mathrm{\theta }\right)}^2\:$

$g≔\mathrm{create}\left(\left[-1\,-1\right]\,\mathrm{eval}\left(\mathrm{g\_compts}\right)\right)$

$g≔table\left(\left[\mathrm{index\_char}=\left[\mathrm{-1}\,\mathrm{-1}\right]\,\mathrm{compts}=\left[\begin{array}{cccc}1-\frac{2m}{r}& 0& 0& 0\\ 0& -\frac{1}{1-\frac{2m}{r}}& 0& 0\\ 0& 0& -r^2& 0\\ 0& 0& 0& -r^2{\sin \left(\mathrm{\theta }\right)}^2\end{array}\right]\right]\right)$

$\mathrm{ginv}≔\mathrm{invert}\left(g\,'\mathrm{detg}'\right)\:$

$\mathrm{D1g}≔\mathrm{d1metric}\left(g\,\mathrm{coord}\right)\:$$\mathrm{D2g}≔\mathrm{d2metric}\left(\mathrm{D1g}\,\mathrm{coord}\right)\:$

$\mathrm{Cf1}≔\mathrm{Christoffel1}\left(\mathrm{D1g}\right)\:$

$\mathrm{RMN}≔\mathrm{Riemann}\left(\mathrm{ginv}\,\mathrm{D2g}\,\mathrm{Cf1}\right)\:$

$\mathrm{RICCI}≔\mathrm{Ricci}\left(\mathrm{ginv}\,\mathrm{RMN}\right)$

$\mathrm{RICCI}≔table\left(\left[\mathrm{index\_char}=\left[\mathrm{-1}\,\mathrm{-1}\right]\,\mathrm{compts}=\left[\begin{array}{cccc}0& 0& 0& 0\\ 0& 0& 0& 0\\ 0& 0& 0& 0\\ 0& 0& 0& 0\end{array}\right]\right]\right)$