Going through a proof of uniqueness for stokes flow for a fluids class I'm taking. Part of it involves replacing the strain tensor (e) with the stress tensor (a), ie going from
aij = -p*dij + 2u*eij
dij = 1 if i=j, 0 otherwise.
The Attempt at a Solution
I can see you simply substitute for 2u*eij to the integral as follows,
int(eij*(eij*(p*dij + aij))dV
but why does eij*p*dij = 0 ????????