Related papers: The Supersymmetric Axion and Cosmology
We explore whether the axion which solves the strong CP problem can naturally be much lighter than the canonical QCD axion. The $Z_\mathcal{N}$ symmetry proposed by Hook, with $\mathcal{N}$ mirror and degenerate worlds coexisting in Nature…
I describe how the QCD vacuum structure, necessary to resolve the $U(1)_A$ problem, predicts the presence of a P, T and CP violating term proportional to the vacuum angle $\bar{\theta}$. To agree with experimental bounds, however, this…
I discuss the essential features of the QCD axion: the strong CP solution and hence its theoretical necessity. I also review the effects of the QCD axion on astrophysics and cosmology, in particular with emphasis on its role in the dark…
If one simultaneously invokes the SUSY solution to the gauge hierarchy problem and the PQ solution to the strong CP problem, then one might expect mixed axion/neutralino dark matter (DM), i.e. two dark matter particles. In this case, dark…
Axions solve the Strong CP Problem and are a cold dark matter candidate. The combined constraints from accelerator searches, stellar evolution limits and cosmology suggest that the axion mass is in the range $3 \cdot 10^{-3} > m_a >…
The axion is a highly motivated elementary particle which could address two fundamental questions in physics - the strong CP problem and the dark matter mystery. Experimental searches for this hypothetical particle have started to reach…
The nature of dark matter is one of the longest-standing puzzles in science. Axions or axion-like particles are a key possibility, and arise in mechanisms to solve the strong CP problem but also in low-energy limits of string theory.…
Cosmology now provides unambiguous, quantitative evidence for new particle physics. I discuss the implications of cosmology for supersymmetry and vice versa. Topics include: motivations for supersymmetry; supersymmetry breaking; dark…
We present a novel framework of the post-inflationary composite axion to address the strong CP problem without the cosmological domain wall problem. Conventional composite axion models lead to the domain wall number greater than one,…
The Strong CP Problem and its resolution through the existence of an axion are briefly reviewed. The combined constraints from accelerator searches, the evolution of red giants and the duration of the SN 1987a neutrino pulse require the…
We derive two features of axion cosmology that may have cosmological implications, whether or not axions are dark matter: For the full range of allowed axion masses, the evolution of a cosmic axion background allows large CP violation until…
A small breaking of R-parity reconciles thermal leptogenesis, gravitino dark matter and primordial nucleosynthesis. We find that the same breaking relaxes cosmological bounds on the axion multiplet. Naturally expected spectra become allowed…
There is increasing evidence suggesting a discrepancy between the cosmic dipole observed in the number count of distant galaxies and the one derived from the cosmic microwave background (CMB). In this study, we investigate the possibility…
Axions provide a solution to the strong CP problem and are excellent dark matter candidates. The presence of additional sources of CP violation, for example to account for the matter/antimatter asymmetry of the universe, can lead to…
Outline: 1. Thermal axions 2. Axion field evolution 3. The domain wall problem 4. Cold axions 5. Axion miniclusters 6. Axion isocurvature perturbations
The axion has emerged in recent years as a leading particle candidate to provide the mysterious dark matter in the cosmos, as we review here for a general scientific audience. We describe first the historical roots of the axion in the…
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…
A cosmological model with total density close to critical (and flat geometry), dominated by dark matter and dark energy of unknown nature, and consistent with the basic predictions of the inflationary scenario is a very good fit to a…
The quest to understand the nature of dark matter and dark energy motivates a deep exploration into axion physics, particularly within the framework of string theory. Axions, originally proposed to solve the strong CP problem, emerge as…
In these lectures I examine some of the principal issues in cosmology from a particle physics point of view. I begin with nucleosynthesis and show how the primordial abundance of the light elements can help fix the number of (light)…