Let $X$ and $Y$ be two different exotic spheres. Are there metrics $g$ and $h$ on $X$ and $Y$, respectively, such that the laplacians of $(X,g)$ and $(Y,h)$ have the same spectrum?
I would be happy with any $X,Y$ that are not diffeomorphic but are homeomorphic. This is a copy of the (unanswered) question here.