nLab
quark-gluon plasma

Context

Fields and quanta

fields and particles in particle physics

and in the standard model of particle physics:

force field gauge bosons

scalar bosons

matter field fermions (spinors, Dirac fields)

flavors of fundamental fermions in the
standard model of particle physics:
generation of fermions1st generation2nd generation3d generation
quarks (qq)
up-typeup quark (uu)charm quark (cc)top quark (tt)
down-typedown quark (dd)strange quark (ss)bottom quark (bb)
leptons
chargedelectronmuontauon
neutralelectron neutrinomuon neutrinotau neutrino
bound states:
mesonslight mesons:
pion (udu d)
ρ-meson (udu d)
ω-meson (udu d)
f1-meson
a1-meson
strange-mesons:
ϕ-meson (ss¯s \bar s),
kaon, K*-meson (usu s, dsd s)
eta-meson (uu+dd+ssu u + d d + s s)

charmed heavy mesons:
D-meson (uc u c, dcd c, scs c)
J/ψ-meson (cc¯c \bar c)
bottom heavy mesons:
B-meson (qbq b)
ϒ-meson (bb¯b \bar b)
baryonsnucleons:
proton (uud)(u u d)
neutron (udd)(u d d)

(also: antiparticles)

effective particles

hadrons (bound states of the above quarks)

solitons

in grand unified theory

minimally extended supersymmetric standard model

superpartners

bosinos:

sfermions:

dark matter candidates

Exotica

auxiliary fields

Contents

Idea

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 TT, 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.

Non-perturbative regime

Despite the deconfinement beyond temperature T cT_c, the quark-gluon plasma at temperature 45T c\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, hence by the AdS/QCD correspondence or fluid/gravity correspondence (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, see at AdS/QCD correspondence for more.

Perturbative regime

At yet higher energies, the quark-gluon plasma is eventually supposed to be weakly coupled again, due to asymptotic freedom (e.g. Blaizot 03)

Properties

Early cosmology and nucleosynthesis

In the standard model of cosmology a quark gluon plasma filled the universe about 10 610^{-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.


References

General

See also

On the rho-meson and its chiral partner a1-meson in the quark-gluon plasma:

Non-perturbative aspects

Discussion of non-perturbative effects in QCD:

Further discussion in relation to instantons in QCD includes

Experimental realization

Realization of the quark-gluon plasma at the RHIC experiment has tentatively been claimed in

Exposition and review:

In early universe cosmology

Discussion of the quark gluon-plasma in cosmology as the phase of matter shortly after the big bang:

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.

Description via geometric engineering of QCD on intersecting branes

Description via geometric engineering of QCD on intersecting branes (“holographic QCD” see also at string theory results applied elsewhere):

Expositions and reviews include

and specifically via “improved holographic QCD

Holographic discussion of the shear viscosity of the quark-gluon plasma goes back to

Other original articles include:

With emphasis on application to neutron stars:

See also: