Cosmology with light axions from technicolor

We consider cosmological consequences of the spontaneous breaking of a global symmetry that is anomalous under technicolor interactions, leading to the emergence of a light axion-like particle. Avoiding overclosure of the universe by such axions yields the upper bound fa≲1010GeV on the symmetry breaking scale, corresponding to keV-scale axions. However, diffuse X-ray background data typically require larger values of fa. The overclosure and X-ray bounds can be reconciled if the axion initial amplitude of oscillations Ai∼fa/10. In this case, a viable axionic dark matter candidate with a mass in the 50-100 eV range emerges. The detection of this type of dark matter may pose a challenge.