Editing Cosmic inflation (section)

===Early inflationary models===
[[Image:Horizonte inflacionario.svg|thumb|upright=1.4|The physical size of the [[Hubble radius]] (solid line) as a function of the linear expansion (scale factor) of the universe. During cosmological inflation, the Hubble radius is constant. The physical wavelength of a perturbation mode (dashed line) is also shown. The plot illustrates how the perturbation mode grows larger than the horizon during cosmological inflation before coming back inside the horizon, which grows rapidly during radiation domination. If cosmological inflation had never happened, and radiation domination continued back until a [[gravitational singularity]], then the mode would never have been inside the horizon in the very early universe, and no [[causality (physics)|causal]] mechanism could have ensured that the universe was homogeneous on the scale of the perturbation mode.]]
Guth proposed inflation in January 1981 to explain the nonexistence of magnetic monopoles;<ref name=SLAC>[[Stanford Linear Accelerator Center|SLAC]] seminar, "{{10^|−35}} seconds after the Big Bang", 23 January 1980. See {{harvp|Guth|1997|p=186}}</ref><ref name="guth">
{{cite journal
 |doi=10.1103/PhysRevD.23.347
 |title=Inflationary universe: A possible solution to the horizon and flatness problems
 |url=http://www.astro.rug.nl/~weygaert/tim1publication/cosmo2007/literature/inflationary.universe.guth.physrevd-1981.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.astro.rug.nl/~weygaert/tim1publication/cosmo2007/literature/inflationary.universe.guth.physrevd-1981.pdf |archive-date=2022-10-09 |url-status=live
 |year=1981
 |last1=Guth |first1=Alan H.
 |journal=[[Physical Review D]]
 |volume=23 |issue=2 |pages=347–356
 |bibcode=1981PhRvD..23..347G |doi-access=free
}}
</ref> it was Guth who coined the term "inflation".<ref name="peebles 17">{{harvp|Peebles|1993|at=ch&nbsp;17}}</ref> At the same time, Starobinsky argued that quantum corrections to gravity would replace the supposed initial singularity of the Universe with an exponentially expanding de Sitter phase.<ref>
{{cite journal
 |first=Alexei A. |last=Starobinsky
 |year=1980
 |title=A new type of isotropic cosmological models without singularity
 |journal=[[Physics Letters B]]
 |volume=91 |issue=1 |pages=99–102
 |bibcode=1980PhLB...91...99S |doi=10.1016/0370-2693(80)90670-X
}}
</ref> In October 1980, Demosthenes Kazanas suggested that exponential expansion could eliminate the [[particle horizon]] and perhaps solve the horizon problem,<ref>
{{cite journal
 |first=Demosthenes |last=Kazanas <!-- |author-link=Demosthenes Kazanas -->
 |date=October 1980
 |title=Dynamics of the universe and spontaneous symmetry breaking
 |journal=[[Astrophysical Journal]]
 |volume=241 |pages=L59–63
 |doi=10.1086/183361 |doi-access=free
 |bibcode=1980ApJ...241L..59K
}}
</ref><ref>
{{cite conference
 |first=Demosthenes |last=Kazanas <!-- |author-link=Demosthenes Kazanas -->
 |date= 2007
 |publication-date=2009
 |title=Cosmological Inflation: A Personal Perspective
 |editor1=Contopoulos, G.
 |editor2=Patsis, P.A.
 |book-title=Chaos in Astronomy: Conference 2007
 |series=Astrophysics and Space Science Proceedings Vol. 8
 |pages=485–496
 |publisher=Springer Science & Business Media
 |isbn=978-3-540-75825-9  |s2cid=14520885
 |arxiv=0803.2080  |bibcode=2009ASSP....8..485K
 |doi=10.1007/978-3-540-75826-6_49
 |url=https://books.google.com/books?id=QfipHB0XK58C&pg=PA485
}}
</ref> while [[Katsuhiko Sato (physicist)|Katsuhiko Sato]] suggested that an exponential expansion could eliminate [[Domain wall (string theory)|domain walls]] (another kind of exotic relic).<ref>
{{Cite journal
 |first=K. |last=Sato
 |year=1981
 |title=Cosmological baryon number domain structure and the first order phase transition of a vacuum
 |journal=[[Physics Letters B]]
 |volume=33  |issue=1  |pages=66–70
 |bibcode=1981PhLB...99...66S
 |doi=10.1016/0370-2693(81)90805-4
}}
</ref> In 1981, Einhorn and Sato<ref>
{{Cite journal
 |last1=Einhorn  |first1=Martin B.
 |last2=Sato     |first2=Katsuhiko 
 |year=1981
 |title=Monopole production in the very early universe, in a first-order phase transition
 |journal=[[Nuclear Physics B]]
 |volume=180  |issue=3  |pages=385–404
 |doi=10.1016/0550-3213(81)90057-2
 |bibcode=1981NuPhB.180..385E
}}
</ref> published a model similar to Guth's and showed that it would resolve the puzzle of the [[magnetic monopole]] abundance in Grand Unified Theories. Like Guth, they concluded that such a model not only required fine tuning of the cosmological constant, but also would likely lead to a much too granular universe, i.e., to large density variations resulting from bubble wall collisions.

Guth proposed that as the early universe cooled, it was trapped in a false vacuum with a high energy density, which is much like a cosmological constant. As the very early universe cooled it was trapped in a [[metastability|metastable]] state (it was supercooled), which it could only decay out of through the process of [[nucleation|bubble nucleation]] via [[quantum tunneling]]. Bubbles of [[vacuum state|true vacuum]] spontaneously form in the sea of false vacuum and rapidly begin expanding at the [[speed of light]]. Guth recognized that this model was problematic because the model did not reheat properly: when the bubbles nucleated, they did not generate radiation. Radiation could only be generated in collisions between bubble walls. But if inflation lasted long enough to solve the initial conditions problems, collisions between bubbles became exceedingly rare. In any one causal patch it is likely that only one bubble would nucleate.
{{clear}}
{{Blockquote|
... {{harvp|Kazanas|1980}} called this phase of the early Universe "de Sitter's phase". The name "inflation" was given by {{harvp|Guth|1981}}. ... Guth himself did not refer to work of Kazanas until he published a book on the subject, under the title ''The Inflationary Universe: The quest for a new theory of cosmic origin'' (1997),<ref name=guth97/> where he apologizes for not having referenced the work of Kazanas and of others, related to inflation.<ref>
{{cite book
 |last=Contopoulos |first=George
 |year=2004
 |title=Adventures in Order and Chaos: A scientific autobiography
 |volume=313 |pages=88–89
 |publisher=Springer Science & Business Media
 |isbn=9781402030406
 |url=https://books.google.com/books?id=3UXak_7yR3MC&pg=PA88
}}
</ref>
}}