4 research outputs found
Axion cold dark matter in view of BICEP2 results
The properties of axions that constitute 100% of cold dark matter (CDM)
depend on the tensor-to-scalar ratio at the end of inflation. If
as reported by the BICEP2 collaboration, then "half"
of the CDM axion parameter space is ruled out. Namely, the Peccei-Quinn
symmetry must be broken after the end of inflation, and axions do not generate
non-adiabatic primordial fluctuations. The cosmic axion density is then
independent of the tensor-to-scalar ratio , and the axion mass is expected
to be in a narrow range that however depends on the cosmological model before
primordial nucleosynthesis. In the standard CDM cosmology, the CDM
axion mass range is , where is the fractional contribution to the
cosmic axion density from decays of axionic strings and walls.Comment: fixed colors in figure, references adde
Axion cold dark matter in view of BICEP2 results
The properties of axions that constitute 100% of cold dark matter (CDM)
depend on the tensor-to-scalar ratio at the end of inflation. If
as reported by the BICEP2 collaboration, then "half"
of the CDM axion parameter space is ruled out. Namely, the Peccei-Quinn
symmetry must be broken after the end of inflation, and axions do not generate
non-adiabatic primordial fluctuations. The cosmic axion density is then
independent of the tensor-to-scalar ratio , and the axion mass is expected
to be in a narrow range that however depends on the cosmological model before
primordial nucleosynthesis. In the standard CDM cosmology, the CDM
axion mass range is , where is the fractional contribution to the
cosmic axion density from decays of axionic strings and walls.Comment: fixed colors in figure, references adde
The moment of truth for WIMP Dark Matter
We know that dark matter constitutes 85% of all the matter in the Universe,
but we do not know of what it is made. Amongst the many Dark Matter candidates
proposed, WIMPs (weakly interacting massive particles) occupy a special place,
as they arise naturally from well motivated extensions of the standard model of
particle physics. With the advent of the Large Hadron Collider at CERN, and a
new generation of astroparticle experiments, the moment of truth has come for
WIMPs: either we will discover them in the next five to ten years, or we will
witness the inevitable decline of WIMP paradigm.Comment: To appear in Nature (Nov 18, 2010