  The power spectrum of fluctuations in the momentum distributions of particles
have been estimated with optical Glauber and Monte-Carlo Glauber initial
conditions for relativistic heavy ion collisions. The evaluation procedure
adopted in this work is analogous to the one used in the calculation of power
spectrum in Cosmic Microwave Background Radiation (CMBR). The power spectrum
due to perturbations in the phase space distribution of the particles has also
been evaluated. The perturbation in phase space has been evolved through the
Boltzmann transport equation in an expanding quark gluon plasma (QGP)
background. The expansion of the QGP has been treated within the purview of
(3+1) dimensional relativistic hydrodynamics. We observe that the
non-equlibrium effects introduced as perturbations in the phase space
distributions can be traced from the enhancement of the power spectrum as well
as through its variation with temperature which is distinctly different from
the case of vanishing perturbation. A relation has been derived between the
power spectrum and the flow harmonics.
