Quintessence (Physics)

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Quintessence (physics)

For other forms of quintessence, see Quintessence

(disambiguation). For theories and defunct or classical

concepts named after the synonym Aether, seeAether

(disambiguation).

Inphysics, quintessence is a hypotheticalform ofdark

energy, more precisely ascalar field, postulated as an ex-

planation of the observation of anaccelerating rate of ex-

pansion of the universe, rather than due to a true cos-

mological constant. The first example of this scenario

was proposed byRatraand Peebles(1988).[1] The con-cept was expanded to more general types of time-varying

dark energy and the term quintessence was first intro-

duced in a paper by R.R.Caldwell, Rahul Dave and Paul

Steinhardt.[2] It has been proposed by some physicists to

be afifth fundamental force. Quintessence differs from

the cosmological constantexplanation of dark energy in

that it is dynamic, that is, it changes over time, unlike the

cosmological constant which always stays constant. It is

suggested that quintessence can be either attractive or re-

pulsive depending on the ratio of its kinetic and potential

energy. Specifically, it is thought that quintessence be-

came repulsive about ten billion years ago (the universeis approximately 13.8 billion years old).[3]

1 Scalar field

Quintessence is ascalar field with anequation of state

where wq, the ratio of pressurepq and density q, is given

by the potential energyV(Q)and a kinetic term:

wq =pq/q =1

2Q2 V(Q)

12Q2 + V(Q)

Hence, quintessence is dynamic, and generally has a den-

sity andwqparameter that varies with time. By contrast,

a cosmological constant is static, with a fixed energy den-

sity andwq = 1.

2 Tracker behavior

Many models of quintessence have a tracker behavior,

which according to Ratra and Peebles (1988) and Paul

Steinhardt et al. (1999) partly solves the cosmologicalconstant problem.[4] In these models, the quintessence

field has a density which closely tracks (but is less

than) the radiation density untilmatter-radiation equal-

ity, which triggers quintessence to start having character-

istics similar to dark energy, eventually dominating the

universe. This naturally sets the low scale of the dark

energy.[5] When comparing the predictedexpansion rate

of the universe as given by the tracker solutions with cos-

mological data, a main feature of tracker solutions is that

one needs four parameters to properly describe the be-

havior of theirequation of state,[6][7] whereas it has been

shown that at most a two-parameter model can optimally

be constrained by mid-term future data (horizon 2015-2020).[8]

3 Specific models

Some special cases of quintessence arephantom energy,

in which wq < 1,[9] and k-essence (short for kinetic

quintessence), which has a non-standard form ofkinetic

energy. If this type of energy were to exist, it would cause

abig ripin the universe due to the growing energy den-

sity of dark energy which would cause the expansion of

the universe to increase at a faster-than-exponential rate.

3.1 Holographic Dark Energy

Holographic Dark Energy models compared to Cosmo-

logical Constant models, imply a highdegeneracy.[10] It

has been suggested that dark energy might originate from

quantum fluctuationsofspacetime, and are limited by the

event horizon of the universe.[11]

Studies with quintessence dark energy found that it dom-

inates gravitational collapse in a spacetime simulation,

based on theholographic thermalization. These results

show that the smaller the state parameter of quintessence

is, the harder it is for the plasma to thermalize.[12]

4 Quintom scenario

In 2004, when scientists fit the evolution of dark energy

with the cosmological data, they found that the equation

of state had possibly crossed the cosmological constant

boundary(w = 1) from above to below. A provenno-

go theorem indicates this situation, called theQuintomscenario, requires at least two degrees of freedomfor dark

energy models.[13]

1
https://en.wikipedia.org/wiki/Quintom_scenariohttps://en.wikipedia.org/wiki/Quintom_scenariohttps://en.wikipedia.org/wiki/No-go_theoremhttps://en.wikipedia.org/wiki/No-go_theoremhttps://en.wikipedia.org/wiki/Cosmological_constant_boundaryhttps://en.wikipedia.org/wiki/Cosmological_constant_boundaryhttps://en.wikipedia.org/wiki/Holographic_thermalizationhttps://en.wikipedia.org/wiki/Spacetimehttps://en.wikipedia.org/wiki/Quantum_fluctuationshttps://en.wikipedia.org/wiki/Degeneracy_(mathematics)https://en.wikipedia.org/wiki/Big_riphttps://en.wikipedia.org/wiki/Kinetic_energyhttps://en.wikipedia.org/wiki/Kinetic_energyhttps://en.wikipedia.org/wiki/Kinetic_quintessencehttps://en.wikipedia.org/wiki/Kinetic_quintessencehttps://en.wikipedia.org/wiki/K-essencehttps://en.wikipedia.org/wiki/Phantom_energyhttps://en.wikipedia.org/wiki/Equation_of_state_(cosmology)https://en.wikipedia.org/wiki/Metric_expansion_of_spacehttps://en.wikipedia.org/wiki/Energy_scalehttps://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang#Matter_dominationhttps://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang#Matter_dominationhttps://en.wikipedia.org/wiki/Cosmological_constant#Cosmological_constant_problemhttps://en.wikipedia.org/wiki/Cosmological_constant#Cosmological_constant_problemhttps://en.wikipedia.org/wiki/Paul_Steinhardthttps://en.wikipedia.org/wiki/Paul_Steinhardthttps://en.wikipedia.org/wiki/Equation_of_State_(Cosmology)https://en.wikipedia.org/wiki/Scalar_fieldhttps://en.wikipedia.org/wiki/Cosmological_constanthttps://en.wikipedia.org/wiki/Fifth_forcehttps://en.wikipedia.org/wiki/Paul_Steinhardthttps://en.wikipedia.org/wiki/Paul_Steinhardthttps://en.wikipedia.org/wiki/Jim_Peebleshttps://en.wikipedia.org/wiki/Bharat_Ratrahttps://en.wikipedia.org/wiki/Accelerating_universehttps://en.wikipedia.org/wiki/Accelerating_universehttps://en.wikipedia.org/wiki/Scalar_fieldhttps://en.wikipedia.org/wiki/Dark_energyhttps://en.wikipedia.org/wiki/Dark_energyhttps://en.wikipedia.org/wiki/Hypothesishttps://en.wikipedia.org/wiki/Physicshttps://en.wikipedia.org/wiki/Aether_(disambiguation)https://en.wikipedia.org/wiki/Aether_(disambiguation)https://en.wikipedia.org/wiki/Quintessence_(disambiguation)https://en.wikipedia.org/wiki/Quintessence_(disambiguation)


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2 8 EXTERNAL LINKS

5 Terminology

The name comes from the classical elementsin ancient

Greece. Theaether, a pure fifth element (quinta essen-

tia in Latin), was thought to fill the universe beyond Earth.

Similarly, modern quintessence would be the fifth known

contribution to the overall mass-energy content of the

universe. (The other four in the modern interpretation,

different from the ancient ideas, are: baryonic matter;

radiation photons and the highly relativisticneutrinos,

which may be considered hot dark matter; cold dark

matter; and the term due to spatial curvature loosely,

gravitational self-energy.)

6 See also

Dark-energy-dominated era

7 References

[1] Ratra, P.; Peebles, L. (1988). Cosmo-

logical consequences of a rolling homoge-

neous scalar field. Physical Review D 37

(12): 3406. Bibcode:1988PhRvD..37.3406R.

doi:10.1103/PhysRevD.37.3406.

[2] Caldwell, R.R.; Dave, R.; Steinhardt, P.J. (1998).

Cosmological Imprint of an Energy Component with

General Equation-of-State. Phys.Rev.Lett. 80 (8): 1582

1585.doi:10.1103/PhysRevLett.80.1582.

[3] Christopher Wanjek; Quintessence, accelerating

the Universe?"; http://www.astronomytoday.com/

cosmology/quintessence.html

[4] Zlatev, I.; Wang, L.; Steinhardt, P. (1999).

Quintessence, Cosmic Coincidence, and

the Cosmological Constant. Physical Re-

view Letters 82 (5): 896899. arXiv:astro-

ph/9807002. Bibcode:1999PhRvL..82..896Z.

doi:10.1103/PhysRevLett.82.896.

[5] Steinhardt, P.; Wang, L.; Zlatev, I. (1999).

Cosmological tracking solutions. PhysicalReview D 59 (12): 123504. arXiv:astro-

ph/9812313. Bibcode:1999PhRvD..59l3504S.

doi:10.1103/PhysRevD.59.123504.

[6] Linden, Sebastian; Virey, Jean-Marc (2008). Test

of the Chevallier-Polarski-Linder parametriza-

tion for rapid dark energy equation of state tran-

sitions. Physical Review D 78 (2): 023526.

arXiv:0804.0389. Bibcode:2008PhRvD..78b3526L.

doi:10.1103/PhysRevD.78.023526.

[7] Ferramacho, L.; Blanchard, A.; Zolnierowsky, Y.;

Riazuelo, A. (2010). Constraints on dark energy

evolution. A&A 514: A20. arXiv:0909.1703.Bibcode:2010A&A...514A..20F. doi:10.1051/0004-

6361/200913271.

[8] Linder, Eric V.; Huterer, Dragan (2005). How

many cosmological parameters. Physical

Review D 72 (4): 043509. arXiv:astro-

ph/0505330. Bibcode:2005PhRvD..72d3509L.

doi:10.1103/PhysRevD.72.043509.

[9] Caldwell, R. R. (2002). A phantom menace? Cos-

mological consequences of a dark energy component

with super-negative equation of state. Physics Let-

ters B 545 (1-2): 2329. arXiv:astro-ph/9908168.

Bibcode:2002PhLB..545...23C. doi:10.1016/S0370-

2693(02)02589-3.

[10] Yazhou Hu, Miao Li, Nan Li, Zhenhui Zhang (2015).

Holographic Dark Energy with Cosmological Constant.

[11] Shan Gao (2013). Explaining Holographic

Dark Energy. Bibcode:2013Galax...1..180G.

doi:10.3390/galaxies1030180.

[12] Xiao-Xiong Zeng, De-You Chen, Li-Fang

Li (2014). Holographic thermalization andgravitational collapse in the spacetime dom-

inated by quintessence dark energy (PDF).

arXiv:1408.6632. Bibcode:2015PhRvD..91d6005Z.

doi:10.1103/PhysRevD.91.046005.

[13] Hu, Wayne (2005). Crossing the phantom di-

vide: Dark energy internal degrees of freedom.

Physical Review D 71 (4): 047301. arXiv:astro-

ph/0410680. Bibcode:2005PhRvD..71d7301H.

doi:10.1103/PhysRevD.71.047301.

7.1 Further reading

Ostriker JP; Steinhardt P (January 2001). The

Quintessential Universe. Scientific American 284

(1): 4653. doi:10.1038/scientificamerican0101-

46.

Lawrence M. Krauss (2000). Quintessence: The

Search for Missing Mass in the Universe. Basic

Books.ISBN 978-0465037414.

8 External links
https://en.wikipedia.org/wiki/Special:BookSources/978-0465037414https://en.wikipedia.org/wiki/International_Standard_Book_Numberhttps://en.wikipedia.org/wiki/Quintessence:_The_Search_for_Missing_Mass_in_the_Universehttps://en.wikipedia.org/wiki/Quintessence:_The_Search_for_Missing_Mass_in_the_Universehttps://en.wikipedia.org/wiki/Lawrence_M._Krausshttps://dx.doi.org/10.1038%252Fscientificamerican0101-46https://dx.doi.org/10.1038%252Fscientificamerican0101-46https://en.wikipedia.org/wiki/Digital_object_identifierhttps://dx.doi.org/10.1103%252FPhysRevD.71.047301https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/2005PhRvD..71d7301Hhttps://en.wikipedia.org/wiki/Bibcodehttps://arxiv.org/abs/astro-ph/0410680https://arxiv.org/abs/astro-ph/0410680https://en.wikipedia.org/wiki/ArXivhttps://en.wikipedia.org/wiki/Physical_Review_Dhttps://dx.doi.org/10.1103%252FPhysRevD.91.046005https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/2015PhRvD..91d6005Zhttps://en.wikipedia.org/wiki/Bibcodehttps://arxiv.org/abs/1408.6632https://en.wikipedia.org/wiki/ArXivhttp://arxiv.org/pdf/1408.6632.pdfhttp://arxiv.org/pdf/1408.6632.pdfhttp://arxiv.org/pdf/1408.6632.pdfhttps://dx.doi.org/10.3390%252Fgalaxies1030180https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/2013Galax...1..180Ghttps://en.wikipedia.org/wiki/Bibcodehttp://philsci-archive.pitt.edu/10036/http://philsci-archive.pitt.edu/10036/http://arxiv.org/abs/1502.01156https://dx.doi.org/10.1016%252FS0370-2693%252802%252902589-3https://dx.doi.org/10.1016%252FS0370-2693%252802%252902589-3https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/2002PhLB..545...23Chttps://en.wikipedia.org/wiki/Bibcodehttps://arxiv.org/abs/astro-ph/9908168https://en.wikipedia.org/wiki/ArXivhttps://en.wikipedia.org/wiki/Physics_Letters_Bhttps://en.wikipedia.org/wiki/Physics_Letters_Bhttps://dx.doi.org/10.1103%252FPhysRevD.72.043509https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/2005PhRvD..72d3509Lhttps://en.wikipedia.org/wiki/Bibcodehttps://arxiv.org/abs/astro-ph/0505330https://arxiv.org/abs/astro-ph/0505330https://en.wikipedia.org/wiki/ArXivhttps://en.wikipedia.org/wiki/Physical_Review_Dhttps://en.wikipedia.org/wiki/Physical_Review_Dhttps://dx.doi.org/10.1051%252F0004-6361%252F200913271https://dx.doi.org/10.1051%252F0004-6361%252F200913271https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/2010A&A...514A..20Fhttps://en.wikipedia.org/wiki/Bibcodehttps://arxiv.org/abs/0909.1703https://en.wikipedia.org/wiki/ArXivhttps://en.wikipedia.org/wiki/Astronomy_&_Astrophysicshttps://dx.doi.org/10.1103%252FPhysRevD.78.023526https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/2008PhRvD..78b3526Lhttps://en.wikipedia.org/wiki/Bibcodehttps://arxiv.org/abs/0804.0389https://en.wikipedia.org/wiki/ArXivhttps://en.wikipedia.org/wiki/Physical_Review_Dhttps://dx.doi.org/10.1103%252FPhysRevD.59.123504https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/1999PhRvD..59l3504Shttps://en.wikipedia.org/wiki/Bibcodehttps://arxiv.org/abs/astro-ph/9812313https://arxiv.org/abs/astro-ph/9812313https://en.wikipedia.org/wiki/ArXivhttps://en.wikipedia.org/wiki/Physical_Review_Dhttps://en.wikipedia.org/wiki/Physical_Review_Dhttps://dx.doi.org/10.1103%252FPhysRevLett.82.896https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/1999PhRvL..82..896Zhttps://en.wikipedia.org/wiki/Bibcodehttps://arxiv.org/abs/astro-ph/9807002https://arxiv.org/abs/astro-ph/9807002https://en.wikipedia.org/wiki/ArXivhttps://en.wikipedia.org/wiki/Physical_Review_Lettershttps://en.wikipedia.org/wiki/Physical_Review_Lettershttp://www.astronomytoday.com/cosmology/quintessence.htmlhttp://www.astronomytoday.com/cosmology/quintessence.htmlhttps://dx.doi.org/10.1103%252FPhysRevLett.80.1582https://en.wikipedia.org/wiki/Digital_object_identifierhttp://journals.aps.org/prl/abstract/10.1103/PhysRevLett.80.1582http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.80.1582https://dx.doi.org/10.1103%252FPhysRevD.37.3406https://en.wikipedia.org/wiki/Digital_object_identifierhttp://adsabs.harvard.edu/abs/1988PhRvD..37.3406Rhttps://en.wikipedia.org/wiki/Bibcodehttps://en.wikipedia.org/wiki/Physical_Review_Dhttps://en.wikipedia.org/wiki/Dark-energy-dominated_erahttps://en.wikipedia.org/wiki/Self-energyhttps://en.wikipedia.org/wiki/Gravitationhttps://en.wikipedia.org/wiki/Cold_dark_matterhttps://en.wikipedia.org/wiki/Cold_dark_matterhttps://en.wikipedia.org/wiki/Hot_dark_matterhttps://en.wikipedia.org/wiki/Neutrinoshttps://en.wikipedia.org/wiki/Baryonhttps://en.wikipedia.org/wiki/Aether_(classical_element)https://en.wikipedia.org/wiki/Classical_element#Classical_elements_in_Greece


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