They are caused by beamdumps like the ones in Cern. Once the energy of the first beam is absorbed in a stack of graphite there is only one beam left that has a dragging effect on the surrounding quantumfield. Dumping the second beam collapses that rotating quantumfield. That very fast collapsing process causes very often, but not always, the forming of a new time line. This means that only circular accelerators can cause this,not linear ones.