  In this thesis, we study the physics of the quark gluon plasma (QGP) using
holographic methods borrowed from string theory. We start our discussion by
motivating the use of such machinery, explaining how recent experimental
results from the LHC and RHIC colliders suggests that the created QGP should be
described as a strongly coupled liquid with small but nonvanishing bulk and
shear viscosities. We argue that holographic dualities are a very efficient
framework for studying transport properties in such a medium.
  Next, we introduce the underlying physics behind all holographic dualities,
the AdS/CFT correspondence, and then motivate the necessity of implementing
conformal invariance breaking in them. After this, we present the
phenomenologically most successful holographic model of the strong interactions
- Improved Holographic QCD (IHQCD).
  Working within IHQCD, we next move on to calculate energy momentum tensor
correlators in the bulk and shear channels of large-Nc Yang-Mills theory. In
the shear channel, we confront our results with those derived in strongly
coupled N=4 Super Yang-Mills theory as well as weakly interacting ordinary
Yang-Mills theory. Close to the critical temperature of the deconfinement
transition, we observe significant effects of conformal invariance breaking. In
the bulk channel, where the conformal result is trivial, we make comparisons
with both perturbative and lattice QCD. We observe that lattice data seem to
favor our holographic prediction over the perturbative one over a wide range of
temperatures.
