Lower bounds for Maass forms on semisimple groups

Let G be an anisotropic semisimple group over a totally real number field F. Suppose that G is compact at all but one infinite place v 0. In addition, suppose that G v0 is R-almost simple, not split, and has a Cartan involution defined over F. If Y is a congruence arithmetic manifold of non-positive curvature associated to G, we prove that there exists a sequence of Laplace eigenfunctions on Y whose sup norms grow like a power of the eigenvalue.