APM346-2018S > APM346--Lectures

Unbounded Terms

(1/1)

Why do we drop unbounded terms from solutions to PDE's? Specifically, in section 6.2, Laplace equation in half-strip:

$$Y''= \lambda Y$$

yields solution

$$Y=Ae^{-\sqrt{\lambda}y}+Be^{\sqrt{\lambda}y}$$

And then the second term is dropped because it is unbounded

Victor Ivrii:
We are looking for a bounded solution. You may consider this as "boundary condition at infinity"