Source: /cirosantilli/cauchy-boundary-condition

= Cauchy boundary condition

Sets both a <Dirichlet boundary condition> and a <Neumann boundary condition> for a single part of the boundary.

Can be used for <hyperbolic partial differential equations>.

We understand intuitively that this imposes stricter requirements on solutions, which makes it easier to guarantee uniqueness, but also harder to have existence. TODO intuitively why hyperbolic need this extra level of restriction.