The double dot product of two matrices $A : B$ can be defined as either:
- $A : B = Tr(AB^T) = A_{ij}B_{ij}$
- $A : B = Tr(AB) = A_{ij}B_{ji}$.
I've seen the first convention called Frobenius or Holzapfel and the second one called Reddy.
Do these conventions have widely accepted names ?