Abstract
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.
Publication
Physical Review Letters 113, 011802 (2014)
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Tenure-track Assistant Professor, Università degli Studi di Salerno.
PhD in Physics, working on Particle Astrophysics and Dark Matter modeling.
