Error on UFL Exception

Question

Hi
I tried it, but no improvement

y*div(p2)*dx

Error on UFL Exception: Trying to integrate expression of rank 1 with free indices ().

I clearly edit my question in main page seeing below

Answer 1

Hi, if you run

X.element().value_rank()

somewhere before the code crashes, you'll see that the rank is 2 and consequently
the terms in your form are vectors and not scalars as they should be. The problem lies in your definition of X. It should be

X = FunctionSpace(mesh, "RT", 2)

This gives you vectors already. There are no scalar RT elements.

Comments

Can you see Error on Interpolate and projection discussion about RT is a vector-element.
In my case, taking inner product after it should be scalar term, but her combination of vector.

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Hi, I saw that discussion and the comments there are the same as I gave you here.
If X is FunctionSpace(..., "RT", ...) and u is a function in X, then div(u) is scalar and grad(u) is a tensor of order 2. On the other hand, If X is VectorFunctionSpace(..., "RT", ...) and u is a function in X, then div(u) is vector and grad(u) is a tensor of order 3. You should keep this in mind when projecting, interpolating and writing the variational form.

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Hi, This concept more fine to me, but space is not problem.
Problem occur inner product, while taking div(p) in RT space, then it should be a scalar. After, that inner product with another one scalar in test function, it doesn't work in FEniCS.

See inner product