As an example from the nuclear many-body problem, we have Schroedinger's equation as a differential equation
\hat{H}\Psi(\boldsymbol{r}_1,..,\boldsymbol{r}_A,\alpha_1,..,\alpha_A)=E\Psi(\boldsymbol{r}_1,..,\boldsymbol{r}_A,\alpha_1,..,\alpha_A)where
\boldsymbol{r}_1,..,\boldsymbol{r}_A,are the coordinates and
\alpha_1,..,\alpha_A,are sets of relevant quantum numbers such as spin and isospin for a system of A nucleons ( A=N+Z , N being the number of neutrons and Z the number of protons).