  In this talk presented at the 5th Rencontres du Vietnam 2004, we discuss our
preliminary investigations into voids of primordial origin. We show that if
voids in the cold dark matter distribution existed at the epoch of decoupling,
they could contribute significantly to the apparent rise in cosmic microwave
background (CMB) power on small scales detected by the Cosmic Background Imager
(CBI) Deep Field. Here we present the preliminary results of our improved
method for predicting the effects of primordial voids on the CMB in which we
treat the voids as an external source in the cold dark matter (CDM)
distribution, employing a Boltzmann solver. Our improved predictions include
the effects of a cosmological constant (Lambda) and acoustic oscillations
generated by voids at early times. We find that models with relatively large
voids on the last scattering surface predict too much CMB power in an
Einstein-de Sitter background cosmology but could be consistent with the
current CMB observations in a Lambda CDM universe.
