Piola transformation
The Piola transformation maps vectors between Eulerian and Lagrangian coordinates in continuum mechanics. It is named after Gabrio Piola.
Definition
Let with an affine transformation. Let with a domain with Lipschitz boundary. The mapping
is called Piola transformation. The usual definition takes the absolute value of the determinant, although some authors make it just the determinant.{{Cite journal |arxiv = 1205.3085|doi = 10.1137/08073901X|title = Efficient Assembly of and Conforming Finite Elements|journal = SIAM Journal on Scientific Computing|volume = 31|issue = 6|pages = 4130–4151|year = 2010|last1 = Rognes|first1 = Marie E.|author1-link= Marie Rognes |last2 = Kirby|first2 = Robert C.|last3 = Logg|first3 = Anders}}
Note: for a more general definition in the context of tensors and elasticity, as well as a proof of the property that the Piola transform conserves the flux of tensor fields across boundaries, see Ciarlet's book.{{cite book|title=Three-dimensional elasticity|last=Ciarlet|first=P. G.|publisher=Elsevier Science|year=1994|isbn=9780444817761|volume=1}}