Heavy ion collision experiments recreating the quark-gluon plasma that filled the microseconds-old universe have established that it is a nearly perfect liquid that flows with such minimal dissipation that it cannot be seen as made of particles. String theory provides a powerful toolbox for studying matter with such properties. This book provides a comprehensive introduction to gauge/string duality and its applications to the study of the thermal and transport properties of quark-gluon plasma, the dynamics of how it forms, the hydrodynamics of how it flows, and its response to probes including jets and quarkonium mesons. Calculations are discussed in the context of data from RHIC and LHC and results from finite temperature lattice QCD. The book is an ideal reference for students and researchers in string theory, quantum field theory, quantum many-body physics, heavy ion physics and lattice QCD.

Models of medium-induced radiative parton energy loss account for the strong suppression of high-pT hadron spectra in √ sNN = 200 GeV Au-Au collisions at RHIC in terms of a single "jet quenching parameter"q. The available suite of jet quenching measurements makeq one of the experimentally best constrained properties of the hot fluid produced in RHIC collisions. We observe thatq can be given a model-independent, nonperturbative, quantum field theoretic definition in terms of the short-distance behavior of a particular light-like Wilson loop. We then use the AdS/CFT correspondence to obtain a strong-coupling calculation ofq in hot N = 4 supersymmetric QCD, findingqSYM = 26.69 √ αSYMNc T 3 in the limit in which both Nc and 4παSYMNc are large. We thus learn that at strong couplingq is not proportional to the entropy density s, or to some "number density of scatterers" since, unlike the number of degrees of freedom,q does not grow like N Ultrarelativistic nucleus-nucleus collisions are studied at RHIC and at the LHC to determine the properties of QCD matter at extreme energy density and temperature [1,2]. If we could do the gedanken experiment of deep inelastic scattering on the hot fluid produced in a heavy ion collision, we could learn a lot. Even though the short lifetime of the transient dense state precludes the use of such external probes, a conceptually similar method is available at RHIC and LHC energies. This method is based upon internally generated probes: energetic partons produced in rare high transverse momentum elementary interactions in the initial stage of the collision, which then interact strongly with the hot, dense fluid produced in the collision as they plough through it [3]. The characterization of the resulting mediuminduced modification of high-p T parton fragmentation ("jet quenching") and its connection to properties of the hot, dense matter that is the object of study have become one of the most active areas of research stimulated by RHIC data [3]. Models which supplement the standard perturbative QCD formalism for high-p T hadron production with medium-induced parton energy loss successfully account for the strong (up to a factor ∼ 5) suppression of hadronic spectra in √ s N N = 200 GeV Au-Au collisions at RHIC, its dependence on centrality and orientation with respect to the reaction plane, and the corresponding reduction of back-to-back hadron correlations [4,5]. These models typically involve one medium-sensitive "jet quenching parameter" denotedq. This parameter is usually defined only perturbatively, and is often thought of as proportional to 1/(λ 2 D λ MFP ), with λ D the Debye screening length and λ MFP some perturbatively defined transport mean-free path [6]. In the present paper, we address the question of howq can be defined and calculated from first principles in nonperturbative quantum field theory, without assuming the existence of quasiparticles with a well-defined mean-free path.There are many indications from data at RHIC and from calculations of lattice-discretized QCD th...