We review the landscape of QCD axion models. Theoretical constructions that extend the
window for the axion mass and couplings beyond conventional regions are highlighted and …

We elucidate the fate of classical symmetries which suffer from Abelian Adler-Bell-Jackiw
anomalies. Instead of being completely destroyed, these symmetries survive as …

We show that the upper bound of the classical QCD axion window can be significantly
relaxed for low-scale inflation. If the Gibbons-Hawking temperature during inflation is lower …

A bstract We point out that SO (2N) pure Yang-Mills theory provides a candidate for dark
matter (DM) without the explicit need to impose any additional symmetry. The DM candidate …

We study an axion-like particle (ALP) that experiences a first-order phase transition with
respect to its mass or potential minimum. This can be realized if the ALP obtains a potential …

A bstract We present a new mechanism to deplete the energy density of the QCD axion,
making decay constants as high as fa≃ 10 17 GeV viable for generic initial conditions. In our …

A bstract The Witten effect implies the electromagnetic interactions between axions and
magnetic monopoles, and the quantum electromagnetodynamics (QEMD) properly …

We show that axions interacting with Abelian gauge fields obtain a potential from loops of
magnetic monopoles. This is a consequence of the Witten effect: the axion field causes the …

Cosmic birefringence is predicted if an axionlike particle (ALP) moves after the
recombination. We show that this naturally happens if the ALP is coupled to the dark matter …

A bstract We present global fits of cosmologically stable axion-like particle and QCD axion
models in the mass range 0.1 neV to 10 eV. We focus on the case where the Peccei-Quinn …