Unsupported operand type(s) for ** : 'SumOfIntegrals' and 'int'

Hello, I want to differentiate an integral with a certain power :


My idea of code is the following :

T = theta* stress(Sym(Grad(u))) *dx

LF = LinearForm(pwc)
gfpwc= pwc.TestFunction()
# gfRho = theta :
LF +=  (T**p).Diff(gfRho, gfpwc)

The problem is that I can’t differentiate an Integral to a certain power. I can for the integrale alone, but not with the power.
I have the following error :

Do you have any clue for my question ?

Thank you :slight_smile: