Editing Quintessence (physics) (section)

== Specific models ==
Some special cases of quintessence are [[phantom dark energy]], in which ''w''<sub>''q''</sub>&nbsp;<&nbsp;&minus;1,<ref name="Caldwell2002">{{cite journal
| last1=Caldwell |first1=R. R.
| title=A phantom menace? Cosmological consequences of a dark energy component with super-negative equation of state
| journal=[[Physics Letters B]]
| date=2002
| volume=545
|issue=1–2
| pages=23–29
| doi=10.1016/S0370-2693(02)02589-3
|bibcode=2002PhLB..545...23C
|arxiv = astro-ph/9908168 |s2cid=9820570
}}</ref> and k-essence (short for kinetic quintessence), which has a non-standard form of [[kinetic energy]]. If this type of energy were to exist, it would cause a [[big rip]]<ref name="Antoniou2016">{{cite journal
| last1=Antoniou |first1=Ioannis |last2=Perivolaropoulos |first2=Leandros
| title= Geodesics of McVittie Spacetime with a Phantom Cosmological Background
| journal=[[Phys. Rev. D]]
| volume= 93
| issue= 12
| pages= 123520
| year= 2016
| doi= 10.1103/PhysRevD.93.123520
| arxiv =1603.02569  | bibcode= 2016PhRvD..93l3520A
|s2cid=18017360 }}</ref> in the universe due to the growing energy density of dark energy, which would cause the expansion of the universe to increase at a faster-than-exponential rate.

===Holographic dark energy===
Holographic dark energy models, compared with cosmological constant models, imply a high [[degeneracy (mathematics)|degeneracy]].{{clarify|date=August 2016}}<ref>{{Cite journal|arxiv=1502.01156 |year=2015|title=Holographic Dark Energy with Cosmological Constant|journal=Journal of Cosmology and Astroparticle Physics|volume=2015|issue=8|pages=012|last1=Hu|first1=Yazhou|last2=Li|first2=Miao|last3=Li|first3=Nan|last4=Zhang|first4=Zhenhui|doi=10.1088/1475-7516/2015/08/012|bibcode=2015JCAP...08..012H|s2cid=118732915}}</ref> It has been suggested that dark energy might originate from [[quantum fluctuations]] of [[spacetime]], and is limited by the event horizon of the universe.<ref>{{cite journal |author=Gao |first=Shan |year=2013 |title=Explaining Holographic Dark Energy |url=http://philsci-archive.pitt.edu/10036/ |journal=Galaxies |volume=1 |issue=3 |pages=180–191 |bibcode=2013Galax...1..180G |doi=10.3390/galaxies1030180 |doi-access=free}}</ref>

Studies with quintessence dark energy found that it dominates gravitational collapse in a spacetime simulation, based on the holographic thermalization. These results show that the smaller the state parameter of quintessence is, the harder it is for the plasma to thermalize.<ref>{{cite journal|doi=10.1103/PhysRevD.91.046005|title=Holographic thermalization and gravitational collapse in the spacetime dominated by quintessence dark energy |journal=Physical Review D |volume=91 |issue=4 |pages=046005 |year=2015|arxiv = 1408.6632 |bibcode = 2015PhRvD..91d6005Z |last1=Zeng |first1=Xiao-Xiong |last2=Chen |first2=De-You |last3=Li |first3=Li-Fang |s2cid=119107827 }}</ref>