  In this dissertation we use the D3/D7 model in gauge/gravity duality to
investigate the effects of finite temperature and particle density on matter in
strongly coupled super-Yang-Mills gauge theories, which we interpret as models
for the quark-gluon plasma (QGP).
  We start with an introduction to the AdS/CFT correspondence and the setup we
use subsequently. We then investigate the effects of finite temperature and
particle density on fundamental matter from three different viewpoints.
  (i) We study meson spectra. Our observations at finite temperature and
particle density are in qualitative agreement with phenomenological models and
experimental observations. They agree with previous publications in the
according limits.
  (ii) We study the temperature and density dependence of transport properties
of fundamental matter in the QGP. In particular, we obtain diffusion
coefficients. Furthermore, in a kinetic model we estimate the effects of the
coupling strength on meson diffusion and therewith equilibration processes in
the QGP.
  (iii) We observe the effects of finite temperature and density on the phase
structure of fundamental matter in the holographic QGP. We trace out the phase
transition lines of different phases in the phase diagram.
