  We explore the low energy cosmological dynamics of feebly self-interacting
cold dark matter and propose a new simple explanation for the rotation curves
of the core-halo model in massive LSB (Low Surface brightness)galaxies. We
argue in favor of the truly collisionless nature of cold dark matter,which is
feebly,self-interacting at small scales between epochs of equality and
recombination.For this, we assume a model, wherein strongly coupled
baryon-radiation plasma ejects out of small regions of concentrated cold dark
matter without losing its equilibrium. We use the Merscerskii equation i.e. the
variable mass formalism of classical dynamics.We obtain new results relating
the oscillations in the CMB anisotropy to the ejection velocity of the
baryon-radiation plasma,which can be useful tool for numerical work for
exploring the second peak of CMB. Based on this model, we discuss the growth of
perturbations in such a feebly self-interacting,cold dark matter both in the
Jeans theory and in the expanding universe using Newton's theory.We obtain an
expression for the growth of fractional perturbations in cold dark matter,which
reduce to the standard result of perturbation theory for late recombination
epochs. We see the effect of the average of the perturbations in the cold dark
matter potential on the cosmic microwave background temperature anisotropy that
originated at redshifts between equality and recombination i.e. 1100 < z <
z_{eq}. Also we obtain an expression for the Sachs-Wolfe effect,i.e. the CMB
temperature anisotropy at decoupling in terms of the average of the
perturbations in cold dark matter potential.
