  Understanding cosmic acceleration mechanisms, such as jet formation in black
holes, star collapses or binary mergers, and the propagation of accelerated
particles in the universe is still a `work in progress' and requires a
multi-messenger approach, exploiting the complementarities across all possible
probes: ultra-high energy cosmic rays (UHECR), gamma-rays and neutrinos. In
this report I will summarize some of the IceCube results concerning searches
for astrophysical neutrino point sources and diffuse fluxes from populations of
sources widely distributed in the sky or from the interactions of protons on
the cosmic microwave background producing the GZK cut-off in the cosmic ray
spectrum. I will compare the results to other neutrino telescopes and to
astrophysical models of neutrino production in sources. Another unresolved
question concerns the nature of dark matter. Indirect searches have the
opportunity to observe where it is located in the universe through the
observation of secondary photons, neutrinos or antiparticles such as positrons
and antiprotons. The potential for the search of neutrinos from the
annihilation of WIMPs in IceCube is greatly enhanced by the addition of more
compact strings, the DeepCore.
