Peaks in the CMBR power spectrum. II. Physical interpretation for any
  cosmological scenario
  In a previous paper (part I), the mathematical properties of the cosmic
microwave background radiation power spectrum which presents oscillations were
discussed. Here, we discuss the physical interpretation: a power spectrum with
oscillations is a rather normal characteristic expected from any fluid with
clouds of overdensities that emits/absorb radiation or interact gravitationally
with the photons, and with a finite range of sizes and distances for those
clouds. The standard cosmological interpretation of "acoustic" peaks is just a
particular case; peaks in the power spectrum might be generated in scenarios
within some alternative cosmological model that have nothing to do with
oscillations due to gravitational compression in a fluid.
  We also calculate the angular correlation function of the anisotropies from
the WMAP-7yr and ACT data, in an attempt to derive the minimum number of
parameters a polynomial function should have to fit it: a set of polynomial
functions with a total of six free parameters, apart from the amplitude, is
enough to reproduce the first two peaks. However, the standard model with six
tunable free parameters also reproduces higher order peaks, giving the standard
model a higher confidence. At present, while no simple function with six free
parameters is found to give a fit as good as the one given by the standard
cosmological model, we may consider the predictive power of the standard model
beyond an instrumentalist approach (such as the Ptolemaic astronomy model of
the orbits of the planets).
