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. 
Yupeng Yang, Xiaoyuan Huang, Xuelei Chen and Hongshi Zong
astro-ph.CO