Throat Cosmology
  In this thesis, we study throats in the early, hot universe. Throats are a
common feature of the landscape of type IIB string theory. If a throat is
heated during cosmological evolution, energy is subsequently transferred to
other throats and to the standard model. We calculate the heat transfer rate
and the decay rate of throat-localized Kaluza-Klein states in a ten-dimensional
model. For the calculation, we employ the dual description of the throats in
terms of gauge theories. We discuss modifications of the decay rate which arise
in flux compactifications and for Klebanov-Strassler throats and emphasize the
role of tachyonic scalars in such throats in mediating decays of Kaluza-Klein
modes. Our results are also applicable to the energy transfer from the heated
standard model to throats. We determine the resulting energy density in throats
at our epoch in dependence of their infrared scales and of the reheating
temperature. The Kaluza-Klein modes in the throats decay to other sectors with
a highly suppressed rate. If their lifetime is longer than the age of the
universe, they are an interesting dark matter candidate. We show that, if the
reheating temperature was 10^10 - 10^11 GeV, throats with infrared scales in
the range of 10^5 GeV to 10^10 GeV can account for the observed dark matter. We
identify several scenarios where this type of dark matter is sufficiently
stable but where decays to the standard model can be discovered via gamma-ray
observations.
