26 research outputs found
Black hole superradiance and polarization-dependent bending of light
An inhomogeneous pseudo-scalar field configuration behaves like an optically
active medium. Consequently, if a light ray passes through an axion cloud
surrounding a Kerr black hole, it may experience a polarization-dependent
bending. We explore the size and relevance of such effect considering both the
QCD axion and a generic axion-like particle.Comment: Bulk of 29 pages + 11 figures. v2: minor changes, version accepted
for publication in JCA
Dark matter and leptogenesis linked by classical scale invariance
In this work we study a classically scale invariant extension of the Standard Model that can explain simultaneously dark matter and the baryon asymmetry in the universe. In our set-up we introduce a dark sector, namely a non-Abelian SU(2) hidden sector coupled to the SM via the Higgs portal, and a singlet sector responsible for generating Majorana masses for three right-handed sterile neutrinos. The gauge bosons of the dark sector are mass-degenerate and stable, and this makes them suitable as dark matter candidates. Our model also accounts for the matter-anti-matter asymmetry. The lepton flavour asymmetry is produced during CP-violating oscillations of the GeV-scale right-handed neutrinos, and converted to the baryon asymmetry by the electroweak sphalerons. All the characteristic scales in the model: the electro-weak, dark matter and the leptogenesis/neutrino mass scales, are generated radiatively, have a common origin and related to each other via scalar field couplings in perturbation theory
On Anomaly-Free Dark Matter Models
We investigate the predictions of anomaly-free dark matter models for direct
and indirect detection experiments. We focus on gauge theories where the
existence of a fermionic dark matter candidate is predicted by anomaly
cancellation, its mass is defined by the new symmetry breaking scale, and its
stability is guaranteed by a remnant symmetry after the breaking of the gauge
symmetry. We find an upper bound on the symmetry breaking scale by applying the
relic density and perturbative constraints. The anomaly-free property of the
theories allows us to perform a full study of the gamma lines from dark matter
annihilation. We investigate the correlation between predictions for final
radiation processes and gamma lines. Furthermore, we demonstrate that the
latter can be distinguished from the continuum gamma ray spectrum.Comment: 21 pages, 9 figures. v2: minor changes to the text, references added,
version to appear in PR
Axion Dark Matter, Proton Decay and Unification
We discuss the possibility to predict the QCD axion mass in the context of
grand unified theories. We investigate the implementation of the DFSZ mechanism
in the context of renormalizable SU(5) theories. In the simplest theory, the
axion mass can be predicted with good precision in the range
neV, and there is a strong correlation between the predictions for the axion
mass and proton decay rates. In this context, we predict an upper bound for the
proton decay channels with antineutrinos, and . This theory can be considered as the minimal realistic
grand unified theory with the DFSZ mechanism and it can be fully tested by
proton decay and axion experiments.Comment: 17 pages, 4 figures. v2: minor comments and references added, matches
version published in JHE