Perturbative regimeĪt yet higher energies, the quark-gluon plasma is eventually supposed to be weakly coupled again, due to asymptotic freedom (e.g. 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. 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. It has been proposed ( Policastro-Son-Starinets 01) that, therefore, an analytic approach to a description of the quark-gluon plasma (i.e. 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. With an exact such theory largely missing, much of the theoretical discussion of the quark-gluon plasma involves lattice QCD computer simulation. 05) is apparently strongly coupled, meaning that its properties are non-perturbative effects requiring discussion of QCD as a non-perturbative field theory. Non-perturbative regimeĭespite the deconfinement beyond temperature T c T_c, the quark-gluon plasma at temperature â¼ 4 â 5 T c \sim 4-5 T_c as produced in experiment ( Adams et al. This phase of QCD is the quark-gluon plasma. But above a critical temperature these hadron bound states break apart (deconfinement) and quarks and gluons may exist freely. At low enough temperature quarks and gluons only appear as hadron bound states ( confinement). The vertical axis indicates temperature T T, the horizontal axis indicates baryon density. 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. At high temperature quarks are not confined to hadron bound states but propagate freely together with the gluons, forming a âquark-gluon soupâ. The quark-gluon plasma is the phase of matter of quantum chromodynamics at extremely high temperature. Description via geometric engineering of QCD on intersecting branes.Gravitino - field of supergravity ( Rarita-Schwinger field) Minimally extended supersymmetric standard model Hadrons ( bound states of the above quarks) Eta-meson ( u u d d s s u u d d s s)
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