Evolving warp bubble reveals instability: caustics create multivalued flow
A 2026 study allowed an Alcubierre‑like warp field to evolve rather than enforcing a fixed bubble profile; under an inertial‑motion setup, neighboring trajectories cross to form caustics, producing a multivalued velocity at some locations and destroying a smooth, single‑valued field. The result shows that simply prescribing a bubble shape is not the same as explaining how such a field forms or persists, and stabilizing it would require additional physical dynamics (e.g., a material model with a suitable equation of state). The work does not present a working warp drive, but highlights the need for concrete stabilization mechanisms beyond the initial profile.