This function computes mass and stiffness matrices for a mesh in 2D, assuming Neumann boundary conditions.

## Value

The function returns a list with the following elements

- G
The stiffness matrix with elements \((\nabla \phi_i, \nabla \phi_j)\).

- C
The mass matrix with elements \((\phi_i, \phi_j)\).

- Cd
The mass lumped matrix with diagonal elements \((\phi_i, 1)\).

- Hxx
Matrix with elements \((\partial_x \phi_i, \partial_x \phi_j)\).

- Hyy
Matrix with elements \((\partial_y \phi_i, \partial_y \phi_j)\).

- Hxy
Matrix with elements \((\partial_x \phi_i, \partial_y \phi_j)\).

- Hyx
Matrix with elements \((\partial_y \phi_i, \partial_x \phi_j)\).

## Author

David Bolin davidbolin@gmail.com