  A key ingredient of hydrodynamical modeling of relativistic heavy ion
collisions is thermal initial conditions, an input that is the consequence of a
pre-thermal dynamics which is not completely understood yet. In the paper we
employ a recently developed energy-momentum transport model of the pre-thermal
stage to study influence of the alternative initial states in nucleus-nucleus
collisions on flow and energy density distributions of the matter at the
starting time of hydrodynamics. In particular, the dependence of the results on
isotropic and anisotropic initial states is analyzed. It is found that at the
thermalization time the transverse flow is larger and the maximal energy
density is higher for the longitudinally squeezed initial momentum
distributions. The results are also sensitive to the relaxation time parameter,
equation of state at the thermalization time, and transverse profile of initial
energy density distribution: Gaussian approximation, Glauber Monte Carlo
profiles, etc. Also, test results ensure that the numerical code based on the
energy-momentum transport model is capable of providing both averaged and
fluctuating initial conditions for the hydrodynamic simulations of relativistic
nuclear collisions.
