Superhorizon fluctuations and acoustic oscillations in relativistic heavy ion collisions

We focus on the initial state spatial anisotropies, originating at the thermalization stage, for central collisions in relativistic heavy-ion collisions. We argue that the physics of fluctuations at the early stages of heavy ion collisions has strong similarities with the physics of density fluctuations in the early universe which give rise to remarkable acoustic peaks in the cosmic microwave background radiation (CMBR) power spectrum. Following the method of analysis in CMBR physics, we propose that a plot of root mean square values of the flow coefficients root V(n)(2) equivalent to V(n)(rms), calculated in a laboratory fixed coordinate system, for a large range of n from 1 to about 30, can give non-trivial information about the initial stages of the system and its evolution. We also argue that for all wavelengths lambda of the anisotropy (at the surface of the plasma region) much larger than the acoustic horizon size H(s)(ff) at the freezeout stage, the resulting values of V(n)(rms) should be suppressed by a factor of order 2H(s)(ff)/lambda.