Layer solutions for the fractional Laplacian on hyperbolic space: existence, uniqueness and qualitative properties

We investigate the equation $$(-{\mathrm{\Delta }}_{{\mathbb{H}}^n}{)}^{\gamma }w=f(w)in{\mathbb{H}}^n,$$ where $(-{\mathrm{\Delta }}_{{\mathbb{H}}^n}{)}^{\gamma }$ corresponds to the fractional Laplacian on hyperbolic space for $\gamma \in (0,1)$ and $f$ is a smooth nonlinearity that typically comes from a double well potential. We prove the existence of heteroclinic connections in the following sense; a so-called layer solution is a smooth solution of the previous equation converging to $\pm 1$atanypointofthetwohemispheres$S_\pm \subset \partial_\infty \mathbb H^n$ and which is strictly increasing with respect to the signed distance to a totally geodesic hyperplane $\mathrm{\Pi }\mathrm{.}$ We prove that under additional conditions on the nonlinearity uniqueness holds up to isometry. Then we provide several symmetry results and qualitative properties of the layer solutions. Finally, we consider the multilayer case, at least when $\gamma$ is close to one.