Abstract:Année de publication : 2011
In this thesis, we apply the gauge/string duality in its supergravity limit to infer some properties of field theories at strong coupling. Experiments at RHIC and at the LHC indeed suggest that the quark–gluon plasma behaves as one of the most perfect fluid ever achieved in any controlled experimental setup. Perturbative approaches fail at accounting for its properties, whereas lattice QCD methods face technical as well as conceptual difficulties in computing dynamical aspects of this new state of matter. As a result, the AdS/CFT correspondence currently is the best tool at our disposal for analytically modelling this phase of QCD. One of the contributions of this thesis amounts to deriving a stochastic Langevin equation for a heavy quark moving across a maximally supersymmetric Yang–Mills plasma at strong coupling. Even though this theory seems to describe in a surprisingly satisfactory way the high–energy, deconfined phase of QCD, it is also of much interest to try and search for a string theory dual making closer contact with QCD at lower energies. As such, the other main focus of this thesis deals with supergravity solutions of lesser supersymmetry, without conformal invariance and exhibiting confinement. We build for the first time the gravity dual to metastable states of such theories. In particular, we find the contribution from anti–branes to the inflation potential in some general scenario of string cosmology.