Effective Angular Asymptotics and the Sharp $D^{-3}$ Horoconvex Gap Scale

Abstract: We prove first-band large-diameter asymptotics for the Dirichlet spectrum on horoconvex domains in real hyperbolic space. After Chebyshev centering, a divergent sequence compactifies to a horospherical support-envelope deficit [V] on [\mathbb S^{n-1}]. For graph domains [r<R-V(θ)], the first band satisfies [ λ{j+1}=α^2+\frac{π^2}{R^2} +\frac{2π^2}{R^3}\bigl(η_j(T_n+V)-b_0\bigr)+o(R^{-3}), \qquad j=0,1, ] where [T_n] is the nonlocal spherical operator with multiplier [ψ(\ell+α)-ψ(α)]. Consequently the horoconvex fundamental gap has the sharp [D^{-3}] polynomial scale, and the leading large-diameter constant is characterized by the compact variational formula [ 16π^2\inf{V\in\mathcal A_n} \bigl(η_1(T_n+V)-η_0(T_n+V)\bigr). ] Geodesic balls realize the polynomial scale, but an explicit admissible axial perturbation lowers the reduced leading-constant value at first order.