Speaker
Andreas Ringwald
(DESY)
Description
The saxion - the modulus of the Peccei-Quinn scalar - or a mixture
of it with the modulus of the Higgs - represents a viable
inflaton candidate, if one takes into account the possible non-minimal coupling
of the PQ scalar to gravity. Remarkably, reheating in saxion/Higgs inflation inevitably
restores the PQ symmetry and results therefore in a lower bound on the axion
mass around 30 micro-eV. Otherwise, the amount of axion dark matter exceeds
the observed amount of cold dark matter. This cosmological scenario
can be decisively tested by the next generation of CMB and axion experiments,
such as CMB-S4, MADMAX, and IAXO.
