  Heavy flavor observables provide valuable information on the properties of
the hot and dense Quark-Gluon Plasma (QGP) created in ultra-relativistic
nucleus-nucleus collisions. Various microscopic models have successfully
described many of the observables associated with its formation. Their
transport coefficients differ, however, due to different assumptions about the
underlying interaction of the heavy quarks with the plasma constituents,
different initial geometries and formation times, different hadronization
processes and a different time evolution of the QGP. In this study we present
the transport coefficients of all these models and investigate systematically
how some of these assumptions influence the heavy quark properties at the end
of the QGP expansion. For this purpose we impose on these models the same
initial condition and the same model for the QGP expansion and show that both
have considerable influence on $R_{AA}$ and $v_2$.
