A theorem of Roe and Strichartz for Riemannian symmetric spaces of noncompact type

Abstract

Generalizing a result of Roe \cite{Roe} Strichartz proved in \cite{Str} that if a doubly-infinite sequence $\{f_k\}$ of functions on ${\mathbb{R}}^n$ satisfies $f_{k+1}=\Delta f_k$ and $|f_k(x)|\le M$ for all $k=0,\pm 1,\pm 2,...$ and $x\in {\mathbb{R}}^n$, then $\Delta f_0(x)=-f_0$. Strichartz also showed that the result fails for hyperbolic 3-space. This negative result can be indeed extended to any Riemannian symmetric space of noncompact type. Taking this into account we shall prove that for all Riemannian symmetric spaces of noncompact type the theorem actually holds true when uniform boundedness is modified suitably.