Related papers: Using $\Delta N_{\rm eff}$ to constrain preferred …
We study for what specific values of the theoretical parameters the axion can form the totality of cold dark matter. We examine the allowed axion parameter region in the light of recent data collected by the WMAP5 mission plus baryon…
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 symmetry is broken before the end of inflation, such that the initial…
A model of high scale inflation is presented where the radial part of the Peccei-Quinn (PQ) field with a non-minimal coupling to gravity plays the role of the inflaton, and the QCD axion is the dark matter. A quantum fluctuation of…
The properties of axions that constitute 100% of cold dark matter (CDM) depend on the tensor-to-scalar ratio $r$ at the end of inflation. If $r=0.20^{+0.07}_{-0.05}$ as reported by the BICEP2 collaboration, then "half" of the CDM axion…
We revisit the cosmological aspects of axion models. In the high-scale inflation scenario, the Peccei-Quinn (PQ) symmetry is likely to be restored during/after inflation. If the curvature of the PQ scalar potential at the origin is smaller…
The strong CP problem was solved by Peccei & Quinn by introducing axions, which are a viable candidate for DM. Here the PQ approach is modified so to yield also Dark Energy (DE), which arises in fair proportions, without tuning any extra…
The clockwork axion refers to a family of aligned multi-axion models that lead to an exponential hierarchy between the scale of Peccei-Quinn symmetry breaking and the scale of the axion decay constant. The clockworking can bring the…
In the Standard Model a Dark Matter candidate is missing, but it is relatively simple to enlarge the model including one or more suitable particles. We consider in this paper one such extension, inspired by simplicity and by the goal to…
We review a class of models which generalize the traditional Peccei-Quinn (PQ) axion solution by a St\"uckelberg pseudoscalar. Such axion models represent a significant variant with respect to earlier scenarios where axion fields were…
A major fraction of the mass content of the universe is composed of dark matter (DM), i.e. particles not interacting significantly with electromagnetic radiation, with ordinary matter or self-interacting (cold dark matter). The axion is…
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…
The QCD axion is widely studied as a dark matter (DM) candidate and as a solution to the strong CP problem of the Standard Model. In conventional field-theoretic models, a much larger mass scale than the electroweak (EW) scale is typically…
We examine the cosmological consequences of the heavy quarks in KSVZ-type axion models. We find that their presence often causes an early matter domination phase, altering the evolution of the Universe. This extends the axion mass into the…
The recent detection of B-modes by BICEP2 has non-trivial implications for axion dark matter implied by combining the tensor interpretation with isocurvature constraints from Planck. In this paper the measurement is taken as fact, and its…
In this paper, we propose a bubble filtering-out mechanism for an asymmetric dark matter scenario during the Peccei-Quinn (PQ) phase transition. Based on a QCD axion model, extended by extra chiral neutrinos, we show that the PQ phase…
Although the axion is the most compelling solution to the strong CP problem, the ad hoc introduced global Peccei-Quinn symmetry suffers from a severe fine-tuning problem known as the quality problem. In this Letter, we show that the…
We study for what specific values of the theoretical parameters the axion can form the totality of cold dark matter. We examine the allowed axion parameter region in the light of recent data collected by the WMAP5 mission plus baryon…
A QCD axion with a decay constant below $ 10 ^{ 11} ~{\rm GeV} $ is a strongly-motivated extension to the Standard Model, though its relic abundance from the misalignment mechanism or decay of cosmic defects is insufficient to explain the…
Although the standard {\Lambda}CDM model describes the cosmic microwave background radiation and the large scale structure of the Universe with great success, it has some tensions with observations in the effective number of neutrino…
By eschewing finetuning from the electroweak and QCD sectors of supersymmetry (natural supersymmetry or SUSY), and by invoking the Kim-Nilles solution to the SUSY mu problem, one is lead to models wherein the dark matter is comprised of a…