According to Q-FFF Theory, portals are assume to be located between two equal sized Black Holes, just like the starforming Herbig Haro system often observed in space.
The Q-FFF Rigid String Theory says: (1) There is only one CONSTRUCTIVE Topological and Resilient TRANSFORMING STRING (Axion/vacuum Dark Energy building block ), forming direct after the Black Hole Splitting Big Bang. so called Travelling TADPOLE Black Hole based Filaments, expanding the Cosmic Lyman Alpha Structure. (2) A Raspberry Entangled 12x Mirror Copy Multiverse is Postulated as base for uncertainty (ER=EPR) and Libet's FREE VETO WILL . SO We live inside an exploded BH