Axion Dissipation Through the Mixing of Goldstone Bosons

By coupling axions strongly to a hidden sector, the energy density in coherent axions may be converted to radiative degrees of freedom, alleviating the ``axion energy crisis''. The strong coupling is achieved by mixing the axion and some other Goldstone boson through their kinetic energy terms, in a manner reminiscent of paraphoton models. Even with the strong coupling it proves difficult to relax the axion energy density through particle absorption, due to the derivative nature of Goldstone boson couplings and the effect of back reactions on the evolution of the axion number density. However, the distribution of other particle species in the hidden sector will be driven from equilibrium by the axion field oscillations. Restoration of thermal equilibrium results in energy being transferred from the axions to massless particles, where it can redshift harmlessly without causing any cosmological problems.Comment: 20 pages, Latex, (3 uuencoded compressed tarred postscript figures attached

Axions and the pulsation periods of variable white dwarfs revisited

Axions are the natural consequence of the introduction of the Peccei-Quinn symmetry to solve the strong CP problem. All the efforts to detect such elusive particles have failed up to now. Nevertheless, it has been recently shown that the luminosity function of white dwarfs is best fitted if axions with a mass of a few meV are included in the evolutionary calculations. Our aim is to show that variable white dwarfs can provide additional and independent evidence about the existence of axions. The evolution of a white dwarf is a slow cooling process that translates into a secular increase of the pulsation periods of some variable white dwarfs, the so-called DAV and DBV types. Since axions can freely escape from such stars, their existence would increase the cooling rate and, consequently, the rate of change of the periods as compared with the standard ones. The present values of the rate of change of the pulsation period of G117-B15A are compatible with the existence of axions with the masses suggested by the luminosity function of white dwarfs, in contrast with previous estimations. Furthermore, it is shown that if such axions indeed exist, the drift of the periods of pulsation of DBV stars would be noticeably perturbed.Comment: Accepted for publication in Astronomy & Astrophysic

An Automatic Invisible Axion In The SUSY Preon Model

It is shown that the recently proposed preon model which provides a unified origin of the diverse mass scale and an explanation of family replication as well as of inter-family mass-hierarchy, possesses a Peccei-Quinn symmetry whose spontaneous breaking leads to an automatic invisible axion. Existence of the PQ-symmetry is simply a consequence of supersymmetry and requirement of minimality in the field-content and interactions, which propose that the lagrangian should possess only those terms which are dictated by the gauge principle and no others. In addition to the axion, the model also generates two superlight Goldstone bosons and their superpartners which are cosmologically safe.Comment: (TeX file) 16 Page

A Quintessential Axion

The model independent axion of string theory has a decay constant of order of the Planck scale. We explore the properties of this quintessence candidate (quintaxion) in the scheme of hidden sector supergravity breakdown. In models allowing for a reasonable $\mu$ term, the hidden sector dynamics may lead to an almost flat potential responsible for the vacuum energy of $(0.003 {\rm eV})^4$. A solution to the strong CP-problem is provided by an additional hidden sector pseudoscalar (QCD axion) with properties that make it an acceptable candidate for cold dark matter of the universe.Comment: 11 pages, Revtex, 1 figur

Spontaneous CP Violation at the Electroweak Scale

Utilizing results on the cosmology of anomalous discrete symmetries we show that models of spontaneous CP violation can in principle avoid the domain wall problem first pointed out by Zel'dovich, Kobzarev and Okun. A small but nonzero $\theta_{QCD}$ explicitly breaks CP and can lift the degeneracy of the two CP conjugate vacua through nonperturbative effects so that the domain walls become unstable, but survive to cosmologically interesting epochs. We explore the viability of spontaneous CP violation in the context of two Higgs models, and find that the invisible axion solution of the strong CP problem cannot be implemented without further extensions of the Higgs sector.Comment: 10 page

Spontaneous CP Violation, Small Instanton and Invisible Axion

I propose a variant invisible axion model of spontaneous CP violation at the electroweak scale without CP domain wall and `strong CP' problems. Both large size QCD and small size non-QCD instantons break CP and Peccei-Quinn symmetries, and render cosmologically harmful CP domain walls unstable. The decaying epoch depends on size of small instanton effects, and is around 100 eV if the current neutron electric dipole moment bound is maximally saturated. The model satisfies constraints from primordial D and He photo-dissociation and black hole formation, while producing cosmologically interesting size of gravitational waves and galaxy-scale density perturbations.Comment: 10 page