Related papers: A Light QCD Axion with Hilltop Misalignment
In this paper, we consider a possibility that the temperature anisotropy of cosmic microwave background (CMB) is dominantly generated by the primordial fluctuations of QCD-axion like particles under a circumstance that inflaton's…
Axion-like particles (ALPs) are interesting dark matter candidates both from the theoretical as well as from the experimental perspective. Usually they are motivated as pseudo-Nambu-Goldstone bosons. In this case one of their most important…
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…
The QCD Lagrangian contains a CP violating gluon density term with a physical coefficient $\bar{\theta}$. The upper bound on the electric dipole moment of neutron implies that the value of $\bar{\theta}$ should be extremely small rather…
In the presence of QCD axion dark matter, atoms acquire time-dependent electric dipole moments. This effect gives rise to an oscillating current in a nuclear spin-polarized dielectric, which can resonantly excite an electromagnetic mode of…
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 show that very compact axion mini-clusters can form in models where axion-like-particle (ALP) dark matter is produced via the kinetic misalignment mechanism, which is well-motivated in pre-inflationary $U(1)$ symmetry breaking scenarios.…
We discuss relaxation solutions to the dark matter - baryon coincidence problem in the context of QCD axion dark matter. In relaxation solutions, a moduli dynamically adjusts the mass of dark matter and baryons until their energy densities…
We explore the interplay of the post-inflationary QCD axion and a light scalar field for the axion domain wall decay and dark matter (DM). The scalar field possesses a nonzero vacuum expectation value (VEV) during inflation, so that its…
Unveiling the dark sector of the Universe is one of the leading efforts in theoretical physics. Among the many models proposed, axions and axion-like particles stand out due to their solid theoretical foundation, capacity to contribute…
If dark matter is made of QCD axions, its abundance is determined by the vacuum expectation value acquired by the axion field during inflation. The axion is usually assumed to follow the equilibrium distribution arising from quantum…
We investigate the possibility that the Peccei-Quinn phase transition occurs at a temperature far below the symmetry breaking scale. Low phase transition temperatures are typical in supersymmetric theories, where symmetry breaking fields…
When the inflaton is coupled to the gluon Chern-Simons term for successful reheating, mixing between the inflaton and the QCD axion is generally expected given the solution of the strong CP problem by the QCD axion. This is particularly…
We argue that demanding a consistent cosmological history, including the absence of domain walls and strongly interacting relics at the Peccei-Quinn scale, singles out two concrete realizations of hadronic QCD axions as viable dark matter…
Under the expectation that nature is natural, we extend the Standard Model to include SUSY to stabilize the electroweak sector and PQ symmetry to stabilize the QCD sector. Then natural SUSY arises from a Kim-Nilles solution to the SUSY mu…
The interaction between the dark/mirror sector and the ordinary sector is considered, where the two sectors interact with each other by sharing the same QCD axion field. This feature makes the mixing between ordinary and dark/mirror photons…
The QCD axion stands as one of the most promising candidates for resolving the strong CP problem. However, the value of the axion's decay constant $f_a$ and, by extension, its mass $m_a$, remain uncertain within the framework of effective…
Despite considerable experimental progress large parts of the axion-like particle (ALP) parameter space remain difficult to probe in terrestrial experiments. In some cases, however, small-scale structure of the ALP dark matter (DM)…
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 show that relaxion, that addresses the hierarchy problem, can account for the observed dark matter (DM) relic density. The setup is similar to the case of axion DM models topped with a dynamical misalignment mechanism. After the…