We explore whether the axion which solves the strong CP problem can naturally be much lighter than the canonical QCD axion. The Z_N symmetry proposed by Hook, with N mirror and degenerate worlds coexisting in Nature and linked by the axion field, is considered and the associated phenomenology is studied in detail.
On a second step, we show that dark matter can be accounted for by this...
The Standard Model (SM) suffers from five shortcomings: Dark Matter, Neutrino masses and mixing, Baryon asymmetry, Strong CP-Problem and Inflation. The latter is regarded as the seeds for structure formation. In this talk, we introduce an inflationary $\nu$DFSZ-type axion model which is dubbed 2hdSMASH (Two-Higgs-Doublet SM * Axion * Seesaw * Higgs-Portal-Inflation). 2hdSMASH aims at giving a...
We consider supersymmetric extensions of DFSZ type axion models with the field content of the MSSM plus some extra vectorlike quark and lepton supermultiplets that simultaneously give a solution to the $\mu$ problem and the strong CP problem. The extra vectorlike content is chosen such that the perturbative gauge coupling unification is maintained. We identify Peccei-Quinn (PQ) symmetry that...
We propose a $SU(5) \times U(1)_X \times U(1)_{PQ}$ model, where $U(1)_X$ is the generalization of the $B-L$ (baryon minus lepton number) gauge symmetry and $U(1)_{PQ}$ is the global Peccei-Quinn (PQ) symmetry. There are four fermions families in $\bf{{\overline 5}} + \bf{10}$ representations of $SU(5)$, a mirror family in $\bf{5}+\bf{{\overline {10}}}$ representations, and three $SU(5)$...
We propose a model for the QCD axion which is realized through a coupling of the Peccei-Quinn scalar field to magnetically charged fermions at high energies. We show that the axion of this model solves the strong CP problem and then integrate out heavy magnetic monopoles using the Schwinger proper time method. We find that the model discussed yields axion couplings to the Standard Model which...
A large flux of axion-like particles can be produced in the solar core. While the majority of these particles will have high velocities and escape the Sun’s gravitational pull, a small fraction of low-velocity particles will become trapped on bound orbits. Over time, an appreciable density of slow-moving axions can accumulate in this “solar basin.” Their subsequent decay to two photons...
We show that axion-like particles that the only couple to invisible dark photons can generate visible B-mode signals around the reionization epoch. The axion field starts rolling shortly before reionization, resulting in a tachyonic instability for the dark photons. This generates an exponential growth of the dark photon quanta sourcing both scalar metric modes and gravitational waves that...
