Hal Jordan has the power to access to wormholes in space using the power ring by rapidly cutting time and distance. The Guardians created a famous wormhole wormhole to Oa and it was only accessible using a Power ring. If you are an experienced ring wielder you can actually navigate Black holes. The power ring cannot generate a Boom Tube as it needs a Mother Box and a sample of the highly unstable X-Element and there is no plausible form of duplicating either of them using the power ring.
