This article presents three isometric models of the Funk disc: the Finsler upper half of the hyperboloid of two sheets model, Finsler band model, and Finsler upper hemi sphere model.
Two new models of the Finsler-Poincaré disc are also introduced.
The geodesics in each model are explicitly described.
The Busemann function and horocycles in the Funk and Hilbert disc are computed and described.
Additionally, the article proves the asymptotic harmonicity of the Funk disc. It is demonstrated that the concept of asymptotic harmonicity in Finsler manifolds depends on the measure, contrasting the Riemannian case.
Another article by Jiayin Pan and Guofang Wei provides the first example of an open manifold with positive Ricci curvature and a non-proper Busemann function at a point. This counters the well-known open question regarding the properness of Busemann functions on open manifolds with nonnegative Ricci curvature.