Sorry for the unclear expression. I meant that I substituted \phi into this equation.
\begin{aligned}
\forall \boldsymbol{\zeta}_h \in \Sigma_h, & \left(D_{D G}(v ; g), \boldsymbol{\zeta}_h\right)_{\Omega} \\
= & -\left(v, \nabla_h \cdot \boldsymbol{\zeta}_h\right)_{\Omega}+\left\langle\{\{v\}\}+\boldsymbol{C}_{12} \cdot[[v]],\left[\left[\boldsymbol{\zeta}_h\right]\right]\right\rangle_{\Gamma^o} \\
& \quad+\left\langle g, \boldsymbol{\zeta}_h \cdot \boldsymbol{n}\right\rangle_{\Gamma^D} .
\end{aligned}
That is, substituting v with \phi , with g as the Dirichlet boundary condition, and solving D_{DG} through the Riesz representation.
The reason for doing this is that I am unable to directly substitute the trial function and test function to solve.
Additionally, I’m also curious about how to convert the Lambda functions obtained from ’ Accessing the basis function of a Finite Element ’ into the regular FEniCS functions we usually use.