New Constraints on Primordial Minihalo Abundance Using Cosmic Microwave
  Background Observations
  It was proposed that the massive compact halo objects (MCHOs) would be
produced during an earlier epoch of cosmology if the density perturbations are
between $3 \times 10^{-4}$ and 0.3. Then these objects can accrete dark matter
particles onto them due to their high density. If the dark matter is in the
form of the weakly interacting massive particles, the MCHOs can have a
significant effect on the evolution of cosmology due to the dark matter
annihilation within them. Using the WMAP-7 years data, we investigated the
constraints on the current abundance of MCHOs ($f_{MCHOs}$) formed during the
$e^{+} e^{-}$ annihilation phase transition. We have found that the $2\sigma$
constraint is $f_{MCHOs} \lesssim 10^{-4}$ for dark matter masses in the range
between 1 GeV and 1 TeV.
