Multiple dark matter scenarios from ubiquitous stringy throats
  We discuss the possibility of having multiple Kaluza-Klein (KK) dark matter
candidates which arise naturally in generic Type-IIB string theory
compactification scenarios. These dark matter candidates reside in various
throats of the Calabi-Yau manifold. In principle, they can come with varied
range of masses in four-dimensions depending upon the hierarchical warping of
the throats. We show that consistency with cosmological bounds and
four-dimensional effective theory description imposes strong constraints on the
parameter space and the geometry of the throats. With a rather
model-independent approach, we find that the mass scales allowed for the KK
dark matter particles in various throats can vary between 0.1 eV and 10 TeV,
depending upon the throat geometry. Thus, there could be simultaneously more
than one kind of cold (and possibly warm and hot) dark matter components
residing in the Universe. This multiple dark matter scenario could weaken the
bound on a conventional supersymmetric dark matter candidate and could also
account for extra relativistic degrees of freedom in our Universe.
