# Large period limit

The large period limit of a periodic equation, say on a large torus $(\mathbf{R}/L\mathbf{Z})^d$ denotes the limit when $L \to \infty$. Formally, this limit should converge to the same equation on the non-periodic domain $\mathbf{R}^d$, though when the equation has infinite speed of propagation then the justification of this limit can be quite delicate.