Dr
Keisuke Harigaya
(UC Berkeley)
23/05/2018, 14:00
The QCD axion is a good dark matter candidate. The observed dark matter abundance can arise from misalignment or defect mechanisms, which generically require an axion decay constant fa ~ O(10^11) GeV (or higher). We introduce a new cosmological origin for axion dark matter, parametric resonance from oscillations of the Peccei-Quinn symmetry breaking field, that requires fa ~ (10^8 − 10^11)...
Quentin Bonnefoy
(Centre de Physique Théorique, Ecole Polytechnique)
23/05/2018, 14:40
I will present QCD axion or cosmological Goldstone bosons, such as ultra-light dark matter or quintessence, in a model with global symmetry highly protected by gauge symmetries. The global symmetry is accidental, obtained from an abelian quiver with scalar bifundamental fields. The Goldstone boson mass may receive explicit breaking contributions, but these are already much suppressed for a few...
Pablo Quílez Lasanta
(UAM/CSIC)
23/05/2018, 15:00
A massless quark solution to the Strong CP problem is implemented with an extra confining gauge group that is unified with the SM QCD group in a CUT (Colour Unified Theory). A novel contribution to the axion mass (due to the small-size instantons at the CUT breaking scale) renders the dynamical axion heavy. This allows to protect the PQ symmetry from semi-classical gravitational effects that...
Fredrik Björkeroth
(INFN-LNF)
23/05/2018, 15:20
In Peccei-Quinn (PQ) solutions to the strong CP problem, a global $U(1)_{PQ}$ symmetry is typically added by hand. However, $U(1)_{PQ}$ need not be exact: it may arise from discrete symmetry, provided the PQ solution is protected to sufficient order. We present a rather complete model, based on Pati-Salam unification and $A_4$, wherein such discrete symmetries are the very same symmetries that...
