Apocket universe orbubble universe, also calledpocket dimension, is a concept ininflationary theory, proposed byAlan Guth.
It defines a realm like the one that contains theobservable universe as only one of many inflationary zones.[1][2]
AstrophysicistJean-Luc Lehners, of thePrinceton Center for Theoretical Science, has argued that aninflationary universe does produce pockets. In his 2012 journal, Lehners wrote about how pocket universes can emerge as a result ofeternal inflation. The mechanisms of inflation within these pocket universes could function in a variety of manners, such asslow-roll inflation, undergoing cycles ofcosmological evolution, or resembling of theGalilean genesis or other'emergent' universe scenarios. Lehners goes on to discuss which one of these types of universes we live in, and how that is dependent on the measurement of the regulation of infinities inherent in eternal inflation.[3]
But, Lehners continues, "the current leading measure proposals—namely, the globallight-cone cutoff and its local counterpart, thecausal diamond measure—as well as closely related proposals, all predict that we should live in a pocket universe that starts out with a smallHubble rate, thus favoring emergent and cyclic models." Lehners adds, "Pocket universes which undergo cycles are further preferred, because they produce habitable conditions repeatedly inside each pocket."
Pocket dimensions are used as a plot device in myriad media. In theSCP Foundation series of collaborative writing, SCP-106, otherwise known as "The Old Man," dwells in a pocket dimension into which it lures its victims.