  Event by event fluctuations of particle multiplicities and their ratios are
considered to be sensitive probes to the exotic phenomena in high energy heavy
ion collisions like phase transtion or the occurence of critical point. These
phenomena might take place at different time after the collision based on
fulfilling the required conditions at a particular time. Fluctuations are
therefore expected to show non-monotonic behaviour at the of time of occurence
of these phenomena. Experimentally, fluctuations are measured at freezeout. In
this work, using the hybrid version of the UrQMD event generator, we have
investigated the propagation of fluctuations of particle multiplicities, their
ratios and the ratio of total positive and negative charges in AuAu collisions
at E_{lab} < 90 AGeV. Two commonly used experimental measures i.e.,
{\sigma^2}/mean and {\nu_{dyn}} have been used in the analysis in a given
acceptance. The hybrid model, i.e., UrQMD with hydrodynamic evolution has been
used to study the effect of hydrodynamic evolution on these conventional
fluctuation measures. It is observed that the fluctuations as measured by
{\sigma^2}/mean and {\nu_{dyn}} gets reduced considerably at freezeout. The
dominat structures present at the initial stage of the evolution get smoothen
out. However, the energy dependence of the fluctuations remain preserved till
the freezeout. The hydrodynamic evolution of the model with chiral equation of
state shows considerably higher fluctuation at lower collision energy as
compared to pure hadronic transport version or the hybrid version with hadronic
equation of state. The time evolution of the higher order moments of net-proton
distributios for particles in a specified coverage showed similar behaviour.

High Energy Physics - Phenomenology;Nuclear Theory