  The order horismos induces the Zeeman $Z$ topology, which is coarser than the
Fine Zeeman Topology $F$. The causal curves in a spacetime under $Z$ are
piecewise null. $F$ is considered to be the most physical topology in a
spacetime manifold $M$, as the group of homeomorphisms of $M$ is isomorphic to
the group of homothetic transformations of $M$. $Z$ was used in the Ambient
Boundary-Ambient Space cosmological model, in order to show that there is no
possibility of formation of spacetime singularities. In this article we
question this result, by reviewing the corresponding articles, and we propose
new questions towards the improvement of this model.
