The Quark-Gluon Plasma in the AdS/CFT Correspondence and Thermal Perturbative QCD

In this dissertation, I present my research on different aspects of the quark-gluon plasma (QGP) by using the AdS/CFT correspondence, and thermal perturbative QCD approaches. The effects of external magnetic field on the thermalization of the QGP (dual to black hole formation in AdS space), and the critical temperature of the confinement-deconfinement phase transition of the QGP (dual to Hawking-Page phase transition in AdS space) will be studied. The violation of the KSS viscosity bound in anisotropic QGP or anisotropic black hole geometries in AdS space will be shown. Moreover, using the holographic RG fow and Schwinger-Keldysh formalisms in the AdS/CFT correspondence, as well as thermal perturbative QCD, the electromagnetic probes of the QGP will be investigated by taking into account the effects of external magnetic field, velocity gradient correction, and axial anomaly. The hard probes of the strongly magnetized QGP, such as jet quenching and energy loss of a heavy quark, will also be investigated by using thermal perturbative QCD, and string theory in AdS space. Finally, different aspects of N = 4 super Yang-Mills theory on the Coulomb branch will be explored by using its string theory dual, and will be shown to have most of the properties expected from pure Yang-Mills theory at strong coupling. In addition, a new holographic mechanism for hadronization or particle production from the QGP will be proposed, and shown to be equivalent to the well-known Cooper-Frye formula in the hydrodynamic or low frequency limit.