Substrate Rupture and Nested Domains in Geometric Response Cosmology: A Testable Extension of the Black Hole Formalism

In Geometric Response Cosmology (GRC), a black hole is a mechanical rupture of the substrate (φ → 0) whose edge grows at the speed c as a purely kinematic condition. The measured gravitational mass is a residual property of the formation event and must not be interpreted as tension generated by the edge. This work explores a structural hypothesis motivated by the self-similarity of the substrate: if the medium is scale-invariant, a local rupture could constitute the seed of a causally closed domain with its own field configuration. We do not derive this hypothesis from the effective Lagrangian of the substrate; we postulate it by mechanical analogy with the self-similarity of the medium. Its value lies in that it yields a specific falsifiable prediction: the black hole mass distribution must exhibit a statistically multimodal structure invariant with redshift, reflecting discrete rupture configurations of the substrate rather than continuous astrophysical evolution. The absence of such a structure would not invalidate the base GRC formalism (validated independently by the Radial Acceleration Relation and lensing), but would reduce the hierarchical extension to a hypothesis without empirical support. This work does not aim to provide a complete dynamical model of the hierarchy, but to establish an ontologically coherent hypothesis with the substrate-rupture formalism, susceptible of being refuted by observation.