ricci - Ricci Calculus
Provides a compact 'R' interface for performing tensor
calculations. This is achieved by allowing (upper and lower)
index labeling of arrays and making use of Ricci calculus
conventions to implicitly trigger contractions and diagonal
subsetting. Explicit tensor operations, such as addition,
subtraction and multiplication of tensors via the standard
operators, raising and lowering indices, taking symmetric or
antisymmetric tensor parts, as well as the Kronecker product
are available. Common tensors like the Kronecker delta, Levi
Civita epsilon, certain metric tensors, the Christoffel
symbols, the Riemann as well as Ricci tensors are provided. The
covariant derivative of tensor fields with respect to any
metric tensor can be evaluated. An effort was made to provide
the user with useful error messages.
