Speaker
Enrico Nardi
(INFN - Laboratori Nazionali di Frascati (IT))
Description
A pseudo Nambu-Goldstone boson (PNGB) coupled to a confining gauge group via an anomalous term is characterised, during the confining phase transition, by a temperature dependent mass $m(T) \propto T^{-n}$ with values of $n$ not far from $n\sim 3$. We study the possibility that a hidden gauge group undergoing confinement at present time could provide a suitable time-varying mass to a dark PNGB. The occurrence
of a diabatic level crossing between this PNGB and the QCD axion during $m(T)$ evolution can convert a tiny fraction of dark matter axions into dark PNGB, which will then drive the accelerated expansion.
