Related papers: Altered Axion Abundance from a Dynamical Peccei-Qu…
In recent work we showed that the relic dark matter abundance of QCD axions can be altered when the Peccei-Quinn (PQ) field is coupled to very light scalar/s, rendering the effective axion mass dynamical in the early universe. In this work…
In the framework where the strong coupling is dynamical, the QCD sector may confine at a much higher temperature than it would in the Standard Model, and the temperature-dependent mass of the QCD axion evolves in a non-trivial way. We find…
We study the experimental constraints on a model of a two-component dark matter, consisting of the QCD axion, and a scalar particle, both contributing to the dark matter relic abundance of the Universe. The global Peccei-Quinn symmetry of…
The clockwork axion refers to a family of aligned multi-axion models that lead to an exponential hierarchy between the scale of Peccei-Quinn symmetry breaking and the scale of the axion decay constant. The clockworking can bring the…
We study cosmological effects of explicit Peccei-Quinn breaking on the QCD axion dark matter. We find that the axion abundance decreases or increases significantly depending on the initial position, even for a tiny Peccei-Quinn breaking…
We propose a minimal extension of the Standard Model with the Peccei-Quinn (PQ) scalar field and explain the relic density of the QCD axion through the kinetic misalignment with a relatively small axion decay constant. To this purpose, we…
It is shown that the post-inflationary quantum chromodynamics (QCD) axion need not lead to a unique one-parameter prediction for the dark matter abundance whenever small explicit Peccei-Quinn symmetry breaking becomes dynamically relevant…
It was shown that the required high quality of the Peccei-Quinn (PQ) symmetry can be a natural outcome of the multiple QCD axions model. In the axiverse, a hypothetical mass mixing between the QCD axions and axion-like particles (ALPs) can…
We review a class of models which generalize the traditional Peccei-Quinn (PQ) axion solution by a St\"uckelberg pseudoscalar. Such axion models represent a significant variant with respect to earlier scenarios where axion fields were…
Axion-like particles (ALPs) are often considered as good candidates for dark matter. Several mechanisms generating relic abundance of ALP dark matter have been proposed. They may involve processes which take place before, during or after…
The axion field, the angular direction of the complex scalar field associated with the spontaneous symmetry breaking of the Peccei-Quinn (PQ) symmetry, could have originated with initial non-zero velocity. The presence of a non-zero angular…
We show that the required high quality of the Peccei-Quinn symmetry can be naturally explained in the aligned QCD axion models where the QCD axion arises from multiple axions with decay constants much smaller than the axion window, e.g.,…
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 $f_a \sim \mathcal{O}(10^{11})$ GeV (or higher). We…
We discuss production of QCD axion dark matter in a novel scenario, which assumes time-varying scale of Peccei-Quinn symmetry breaking. The latter decreases as the Universe's temperature at early times and eventually stabilises at a large…
We explore how the Peccei-Quinn (PQ) axion parameter space can be constrained by the frequency-dependence dimming of radiation from astrophysical objects. To do so we perform accurate calculations of photon-axion conversion in the presence…
We present a new mechanism for producing the correct relic abundance of dark photon dark matter over a wide range of its mass, extending down to $10^{-20}\,\mathrm{eV}$. The dark matter abundance is initially stored in an axion which is…
We propose two models where a U(1) Peccei-Quinn global symmetry arises accidentally and is respected up to high-dimensional operators, so that the axion solution to the strong CP problem is successful even in the presence of…
Slightly extending a right-handed neutrino version of the $3-3-1$ model, we show that it is not only possible to solve the strong CP problem but also to give the total dark matter abundance reported by the Planck collaboration.…
We revisit the cosmological aspects of axion models. In the high-scale inflation scenario, the Peccei-Quinn (PQ) symmetry is likely to be restored during/after inflation. If the curvature of the PQ scalar potential at the origin is smaller…
We consider QCD axion models where the Peccei-Quinn symmetry is badly broken by a larger amount in the past than in the present, in order to avoid the axion isocurvature problem. Specifically we study supersymmetric axion models where the…