A pocket universe or bubble universe, also colloquially called pocket dimension is a concept in

inflationary theory In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from seconds after the conjectured Big Bang singularit ...

, proposed by

Alan Guth Alan Harvey Guth (; born February 27, 1947) is an American theoretical physicist and cosmologist. Guth has researched elementary particle theory (and how particle theory is applicable to the early universe). He is Victor Weisskopf Professor of ...

Description

It defines a realm like the one that contains the

observable universe The observable universe is a ball-shaped region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time, because the electromagnetic radiation from these obj ...

as only one of many inflationary zones. Astrophysicist

Jean-Luc Lehners Jean-Luc may refer to: In politics: * Jean-Luc Bennahmias (born 1954), a French politician and Member of the European Parliament * Jean-Luc Dehaene (1940–2014), a Flemish politician * Jean-Luc Laurent (born 1957), a French politician * Jean-Lu ...

, of the

Princeton Princeton University is a private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth as the College of New Jersey, Princeton is the fourth-oldest institution of higher education in the United States and one of the ni ...

Center for Theoretical Science, has argued that an

inflationary Inflationism is a heterodox economic, fiscal, or monetary policy, that predicts that a substantial level of inflation is harmless, desirable or even advantageous. Similarly, inflationist economists advocate for an inflationist policy. Mainstream ec ...

universe does produce pockets. In his 2012 journal, Lehners wrote about how pocket universes can emerge as a result of

eternal inflation Eternal inflation is a hypothetical inflationary universe model, which is itself an outgrowth or extension of the Big Bang theory. According to eternal inflation, the inflationary phase of the universe's expansion lasts forever throughout most of ...

. The mechanisms of inflation within these pocket universes could function in a variety of manners, such as slow-roll inflation, undergoing cycles of cosmological evolution, or resembling of the

Galilean genesis Generically, a Galilean (; he, גלילי; grc, Γαλιλαίων; la, Galilaeos) is an inhabitant of Galilee, a region of Israel surrounding the Sea of Galilee (Kinneret). The New Testament notes that the Apostle Peter's accent gave him ...

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. But, Lehners continues, "the current leading measure proposals—namely, the global

light-cone In special and general relativity, a light cone (or "null cone") is the path that a flash of light, emanating from a single event (localized to a single point in space and a single moment in time) and traveling in all directions, would take thro ...

cutoff and its local counterpart, the causal diamond measure—as well as closely related proposals, all predict that we should live in a pocket universe that starts out with a small Hubble 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."

References

{{reflist Inflation (cosmology)