Point-free locale formulation of the causal completion

Relate the point-free causal boundary construction based on locales to the round-ideal completion of continuous posets, thereby extending the continuous-poset development from Scott-open frames on points to a locale-theoretic setting.

Background

The paper’s development is naturally expressed through the frame of Scott-open sets associated with a continuous poset. It suggests extending the theory one level of abstraction by working directly with locales rather than with points.

The proposed comparison concerns the point-free causal boundary introduced by van der Schaaf and the round-ideal completion developed in the paper. Establishing this relationship would clarify how the order-theoretic completion behaves in a point-free causal framework.

References

Since the entire development is naturally phrased in terms of the frame of Scott-open sets, it would be interesting to carry it out one level of abstraction further, directly on locales rather than on points, in the spirit of the point-free causal boundary recently proposed by van der Schaaf ; relating that construction to the round-ideal completion of Prop.\ \ref{roundidealprop} is left for future work.

Spacetimes via Continuous posets: Old foundations and new developments  (2608.19502 - Minguzzi, 19 Aug 2026) in Section Conclusions