2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/184953When two point particles, coupled to three dimensional gravity with a negative cosmological constant, approach each other with a sufficiently large center of mass energy, then a BTZ black hole is created. An explicit solution to the Einstein equations is presented, describing the collapse of two massless particles into a non-rotating black hole. Some general arguments imply that massive particles can be used as well, and the creation of a rotating black hole is also possible.LaTeX2e, 33 pages, 8 EPS figures, final version for publication, some minor changesGeneral Relativity and Quantum Cosmologytext