An abstract spectral approach to horospherical equidistribution

This paper introduces an abstract spectral approach to prove effective equidistribution of expanding horospheres in hyperbolic manifolds. The method, which is motivated by the approach to counting developed by (Lax-Phillips 1982), produces highly effective, explicit error terms. To exhibit the flexibility of this method we prove effective horospherical equidistribution theorems in $T^1({\mathbb{H}}^{n+1})$ and in the higher rank setting, ${\mathrm{SL}}_n(\mathbb{R})\mathrm{/}{\mathrm{SO}}_n(\mathbb{R})$.