Collisions in piecewise flat gravity in 3+1 dimensions

We consider the (3+1)-dimensional locally finite gravity model proposed by ’t Hooft (2008 Found. Phys. 38 733–57). In particular we revisit the problem of resolving collisions of string defects. We provide a new geometric description of the configurations of strings using piecewise flat manifolds and use it to resolve a more general class of collisions. We argue that beyond certain bounds for the deficiency/surplus angles no resolutions may be found that satisfy the imposed causality conditions.