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The quark-gluon plasma is the phase of matter of quantum chromodynamics at extremely high temperature. At high temperature quarks are not confined to hadron bound states but propagate freely together with the gluons, forming a “quark-gluon soup”. Since this is analogous to an ordinary plasma which is a phase where electrons and protons are no longer bound to atoms but propagate freely, one speaks of quark-gluon plasma.
Schematic phase diagram of QCD. The vertical axis indicates temperature $T$, the horizontal axis indicates baryon density. At low enough temperature quarks and gluons only appear as hadron bound states (confinement). But above a critical temperature these hadron bound states break apart (deconfinement) and quarks and gluons may exist freely. This phase of QCD is the quark-gluon plasma.
graphics grabbed from Blaizot 03.
Despite the deconfinement beyond temperature $T_c$, the quark-gluon plasma at temperature $\sim 4-5 T_c$ as produced in experiment (Adams et al. 05, Adcox et al. 05) is apparently strongly coupled, meaning that its properties are non-perturbative effects requiring discussion of QCD as a non-perturbative field theory. With an exact such theory largely missing, much of the theoretical discussion of the quark-gluon plasma involves lattice QCD computer simulation. Indication for strong coupling of the QG-plasma comes from the nature of the elliptic flow seen both in experiment as well as in these computer simulations, which shows hydrodynamic behaviour with extremely small shear viscosity (e.g. Shuryak 01, Chakraborty 12).
It has been proposed (Policastro-Son-Starinets 01) that, therefore, an analytic approach to a description of the quark-gluon plasma (i.e. not just via lattice QCD computer experiment) might be given by approximate AdS-CFT duality (see e.g. Biagazzi-Cotrone 12). The difficulty with this approach is that for QCD (as opposed to N=4 D=4 SYM) AdS-CFT duality applies only to some approximation.
At yet higher energies, the quark-gluon plasma is eventually supposed to be weakly coupled again, due to asymptotic freedom (e.g. Blaizot 03)
In the standard model of cosmology a quark gluon plasma filled the universe about $10^{-6}$ comoving seconds after the Big Bang. Decrease of temperature then led to the quark-gluon plasma condensing out to form hadrons and in particular baryons and hence in particular nucleons (protons and neutrons) and eventually atomic nuclei (cosmic nucleosynthesis?).
graphics grabbed from Haseeb 09
See the references below.
Stanislaw Mrowczynski, Quark-Gluon Plasma, Acta Phys.Polon.B29:3711, 1998 (arXiv:nucl-th/9905005)
Mahnaz Q. Haseeb, Introduction to Quark Gluon Plasma, 2009 (pdf)
Roman Pasechnik, Michal Šumbera, Phenomenological Review on Quark-Gluon Plasma: Concepts vs. Observations, Universe 2017, 3(1), 7 (arXiv:1611.01533)
Jean-Paul Blaizot, Edmond Iancu, Anton Rebhan, Thermodynamics of the high temperature quark gluon plasma, Quark–Gluon Plasma 3, pp. 60-122 (2004) (arXiv:hep-ph/0303185, spire:615570)
Jean-Paul Blaizot, around p. 17 of Thermodynamics of the high temperature Quark-Gluon Plasma, AIP Conf. Proc. 739, 63-96 (2004) (doi:10.1063/1.1843592)
See also
Discussion of non-perturbative effects in QCD:
Edward Shuryak, Nonperturbative QCD and Quark-Gluon Plasma, lectures at Trieste, 2001 (pdf)
Purnendu Chakraborty, Non-perturbative aspects of quark gluon plasma above deconfinement temperature, Proceedings of the DAE Symp. on Nucl. Phys. 57 (2012) (pdf)
Further discussion in relation to instantons in QCD includes
Realization of the quark-gluon plasma at the RHIC experiment has tentatively been claimed in
John Adams, et al. Experimental and theoretical challenges in the search for the quark–gluon plasma: The STAR Collaboration’s critical assessment of the evidence from RHIC collisions. Nuclear Physics A 757.1-2 (2005): 102-183.
K. Adcox, et al., Formation of dense partonic matter in relativistic nucleus–nucleus collisions at RHIC: experimental evaluation by the PHENIX collaboration Nuclear Physics A 757.1-2 (2005): 184-283.
Discussion of the quark gluon-plasma in cosmology as the phase of matter shortly after the big bang:
Edward Witten, Cosmic Separation Of Phases, Phys. Rev. D30, 272 (1984) (doi:10.1103/PhysRevD.30.272)
Dominik J. Schwarz, The first second of the Universe, Annalen Phys.12:220-270, 2003 (arXiv:astro-ph/0303574)
K. Sakthi Murugesan, G. Janhavi, and P. R. Subramanian, Can the phase transition from quark-gluon plasma to hadron-resonance gas affect primordial nucleosynthesis?, Phys. Rev. D 41, 2384 (doi:10.1103/PhysRevD.41.2384)
K. Sakthi Murugesan, G. Janhavi, and P. R. Subramanian, Importance of interactions in quark-gluon plasma: Baryon-number density contrast and primordial nucleosynthesis, Phys. Rev. D 42, 3576 (1990) (arXiv:10.1103/PhysRevD.42.3576)
Keith Olive, The Quark - hadron transition in cosmology and astrophysics, Science 251, 1194 (1991)
A.A. Coley, T. Trappenberg, The Quark-Hadron Phase Transition, QCD Lattice Calculations and Inhomogeneous Big-Bang Nucleosynthesis, Phys.Rev. D50 (1994) 4881-4885 (arXiv:astro-ph/9307031)
Hideo Suganuma, Hiroko Ichie, Hideko Monden, Shoichi Sasaki, Manabu Orito, Tadahiro Yamamoto, Toshitaka Kajino, QCD Phase Transition at high Temperature in Cosmology (arXiv:hep-ph/9608333)
Deepak Chandra, Ashok Goyal, Dynamical evolution of the Universe in the quark-hadron phase transition and possible nugget formation, Phys.Rev. D62 (2000) 063505 (arXiv:hep-ph/9903466)
N. Borghini, W. N. Cottingham, R. Vinh Mau, Possible Cosmological Implications of the Quark-Hadron Phase Transition, J.Phys.G26:771, 2000 (arXiv:hep-ph/0001284)
Joseph I Kapusta, Quark-Gluon Plasma in the Early Universe, in Phase Transitions in the Early Universe: Theory and Observations Springer, Dordrecht, 2001. 103-121 (arXiv:astro-ph/0101516)
Michael McGuigan, Wolfgang Söldner, QCD Cosmology from the Lattice Equation of State (arXiv:0810.0265, spire:798226)
The effect of the strong interactions on cosmology was considered early on [10, 11] but the nonperturbative nature of the strong interactions at low energy limited the progress of the subject.
S. M. Blinder, Evolution of Matter from a Quark-Gluon Plasma, Wolfram Demonstration Project, 2011
The liquid universe – quark-gluon plasma and the creation of matter (pdf)
Sz. Borsanyi, Z. Fodor, K. H. Kampert, S. D. Katz, T. Kawanai, T. G. Kovacs, S. W. Mages, A. Pasztor, F. Pittler, J. Redondo, A. Ringwald, K. K. Szabo, Lattice QCD for Cosmology (arXiv:1606.07494)
Description via AdS/CFT, hence “AdS/QCD” (see at string theory results applied elsewhere):
Expositions and reviews include
Pavel Kovtun, Quark-Gluon Plasma and String Theory, RHIC news (2009) (blog entry)
Makoto Natsuume, String theory and quark-gluon plasma (arXiv:hep-ph/0701201)
Steven Gubser, Using string theory to study the quark-gluon plasma: progress and perils (arXiv:0907.4808)
Francesco Biagazzi, A. Cotrone, Holography and the quark-gluon plasma, AIP Conference Proceedings 1492, 307 (2012) (doi:10.1063/1.4763537, slides pdf)
Brambilla et al., section 9.2.2 of QCD and strongly coupled gauge theories: challenges and perspectives, Eur Phys J C Part Fields. 2014; 74(10): 2981 (doi:10.1140/epjc/s10052-014-2981-5)
Jorge Casalderrey-Solana, Hong Liu, David Mateos, Krishna Rajagopal, Urs Achim Wiedemann,
Gauge/string duality, hot QCD and heavy ion collisions,
Cambridge University Press, 2014 (arXiv:1101.0618)
and specifically via “improved holographic QCD”
Holographic discussion of the shear viscosity of the quark-gluon plasma goes back to
Other original articles include:
Hovhannes R. Grigoryan, Paul M. Hohler, Mikhail A. Stephanov, Towards the Gravity Dual of Quarkonium in the Strongly Coupled QCD Plasma (arXiv:1003.1138)
Brett McInnes, Holography of the Quark Matter Triple Point (arXiv:0910.4456)
Last revised on December 4, 2018 at 10:10:15. See the history of this page for a list of all contributions to it.