We study the formation and stability of regular black holes by employing a thin shell approximation to the dynamics of collapsing magnetic monopoles. The core deSitter region of the monopole is matched across the shell to a Reissner-Nordstrom exterior. We find static configurations which are nonsingular black holes and also oscillatory trajectories about these static points that share the same causal structure. In these spacetimes the shell is always hidden behind the black hole horizon. We also find shell trajectories that pass through the asymptotically flat region and model collapse of a monopole to form a regular black hole. In addition there are trajectories in which the deSitter core encompasses a deSitter horizon and hence undergoes topological inflation. However, these always yield singular black holes and never have the shell passing through the aymptotically flat region. Although the regular black hole spacetimes satisfy the strong energy condition, they avoid the singularity theorems by failing to satisfy the genericity condition on the Riemann tensor. The regular black holes undergo a change in spatial topology in accordance with a theorem of Borde’s.
Cho, Hyunji; Kastor, David; and Traschen, Jennie, "The Dynamics of Collapsing Monopoles and Regular Black Holes" (2000). Physics Department Faculty Publication Series. 1216.