Mixed Poisson: inconsistency in the description of function spaces Q&V

[pa-beaufort]

Thank you for collecting such a rich tutorial about dolfinx etcie.

While reading the section related to the mixed Poisson problem, the following seems inconsistent

By reversing the description, it becomes consistent with the implementation:

• $p \in Q$ is defined in the 1st order BDM space
• $u \in V$ as the 0th degree DG space