We construct asymptotically flat vacuum initial data without trapped surfaces whose Einstein evolution leads to the formation of several disjoint trapped regions in finite time. The construction combines Christodoulou’s short pulse method with a surgical modification of the Brill–Lindquist manifold, replacing neighborhoods of its poles by constant-time slices of suitable dynamical spacetimes, while remaining exactly Brill–Lindquist outside. This is joint work with Dawei Shen (Columbia University).
