indicates that expr is in pseudo index-free notation.
  • Pseudo index-free terms cannot be used in computations, but can be given as arguments to certain functions, such as AllContractions and ConstructDDIs.
  • The syntax for pseudo index-free notation is only giving the heads of the tensors, and not the brackets with indices. Thus RicciCD[a, b] becomes IndexFree[RicciCD], and CD[a]@RicciCD[b, c] becomes IndexFree[CD@RicciCD].
  • Pseudo index-free notation does not capture information about index contractions.
  • IndexFree threads over lists.