Black hole formation from collisions of cosmic strings

We explain simple semi-classical rules to estimate the lifetime of any given highly excited quantum state of the string spectrum and apply them to identify new long-lived string states. Using analytic formulae for the string evolution after joining and interconnection, we study examples of fundamental cosmic string collisions leading to gravitational collapse. We find that the interconnection of two strings of equal and opposite maximal angular momenta and arbitrarily large mass generically leads to the formation of black holes. (Based on the works (Iengo and Russo 2006 J. High Energy Phys.JHEP02(2006)041, Iengo and Russo 2006 J. High Energy Phys.JHEP08(2006)079).)