Axions and other very light axion-like particles appear in many extensions of the Standard
Model, and are leading candidates to compose part or all of the missing matter of the …

We study the leading effective interactions between the Standard Model fields and a generic
singlet CP-odd (pseudo-) Goldstone boson. Two possible frameworks for electroweak …

Very weakly interacting slim particles (WISPs), such as axion-like particles (ALPs) or hidden
photons (HPs), may be non-thermally produced via the misalignment mechanism in the …

Abstract Axion-like particles (ALPs), relatively light (pseudo-) scalars coupled to two gauge
bosons, are a common feature of many extensions of the Standard Model. Up to now there …

We consider axions coupled to nucleons and photons only through the nucleon electric-
dipole moment (EDM) portal. This coupling is a model-independent feature of QCD axions …

Recently, indications for an emission line at 3.55 keV have been found in the combined
spectra of a large number of galaxy clusters and also in Andromeda. This line could not be …

Abstract Light pseudo-Nambu-Goldstone bosons (pNGBs) such as, eg axion-like particles,
that are non-thermally produced via the misalignment mechanism are promising dark matter …

Hidden photons are dark matter candidates motivated by theories beyond the standard
model of particle physics. They mix with conventional photons, and they can be detected …

We study the propagation of photons in a homogeneous axion dark matter background.
When the axion decay into two photons is stimulated, the photon field exhibits a parametric …

We study in detail MSW-like resonant conversions of QCD axions into hidden axions,
including cases where the adiabaticity condition is only marginally satisfied, and where …