When Bubble Universes Collide: Boundary Failure, Persistent Interfaces, and the Question of Time

Companion animation (2 minutes, 1 second): start with the MP4 preview for an illustrative view of the impact region and three proposed configurations. The animation is a conceptual visualization, not a numerical simulation, a measured radiation field, or a prediction of physical wave speed. The PDF is the authoritative 39-page research preprint. This conceptual preprint examines conditional outcomes of collisions between two hypothetical bubble-universe regions, Universe A and Universe B, within a common parent spacetime P. It distinguishes a retained joined interface (G1), connected interiors (G2), and parent-facing boundary reconstruction (G3); a literal finite aperture remains a stronger, unconstructed claim. A specified Einstein-scalar reference potential and elementary analytic controls examine field-gradient energy, instability of a restricted wall-edge aperture, and reflection and transmission at an interface. The study develops conditional gravitational-wave and causal-observation questions, bidirectional vacuum-phase conversion, and a separately labeled hypothesis in which an effective spacetime description might cease to apply. The paper proposes explicit modeling and comparison requirements; it does not report a numerical collision simulation, stabilized breach, predicted gravitational-wave strain, observed collision, or demonstrated region without time. Scope and transparency: This is an independent, non-peer-reviewed conceptual preprint. Its reference calculations are limited to the stated assumptions. AI-assisted research organization, drafting, review, and figure preparation are disclosed in the manuscript; the author retains responsibility for all scientific claims and publication decisions.