Signatures of Pseudoscalar Photon Mixing in CMB Radiation

We model the effect of photon and ultra-light pseudoscalar mixing on the propagation of electromagnetic radiation through the extragalactic medium. The medium is modelled as a large number of magnetic domains, uncorrelated with one another. We obtain an analytic expression for the different Stokes parameters in the limit of small mixing angle. The different Stokes parameters are found to increase linearly with the number of domains. We also verify this result by direct numerical simulations. We use this formalism to estimate the effect of pseudoscalar-photon mixing on the Cosmic Microwave Background (CMB) polarization. We impose limits on the model parameters by the CMB observations. We find that the currently allowed parameter range admits a CMB circular polarization up to order $10^{-7}$.Comment: 17 pages, 5 figure

Alignments in quasar polarizations: pseudoscalar-photon mixing in the presence of correlated magnetic fields

We investigate the effects of pseudoscalar-photon mixing on electromagnetic radiation in the presence of correlated extragalactic magnetic fields. We model the Universe as a collection of magnetic domains and study the propagation of radiation through them. This leads to correlations between Stokes parameters over large scales and consistently explains the observed large-scale alignment of quasar polarizations at different redshifts within the framework of the big bang model.Comment: 12 pages, 5 figures, version published in PR

Constraints on the axion-electron coupling for solar axions produced by Compton process and bremsstrahlung

The search for solar axions produced by Compton ($\gamma+e^-\rightarrow e^-+A$) and bremsstrahlung-like ($e^-+Z \rightarrow Z+e^-+A$) processes has been performed. The axion flux in the both cases depends on the axion-electron coupling constant. The resonant excitation of low-lying nuclear level of $^{169}\rm{Tm}$ was looked for: $A+^{169}$Tm $\rightarrow ^{169}$Tm$^*$ $\rightarrow ^{169}$Tm $+ \gamma$ (8.41 keV). The Si(Li) detector and $^{169}$Tm target installed inside the low-background setup were used to detect 8.41 keV $\gamma$-rays. As a result, a new model independent restriction on the axion-electron and the axion-nucleon couplings was obtained: $g_{Ae}\times|g^0_{AN}+ g^3_{AN}|\leq 2.1\times10^{-14}$. In model of hadronic axion this restriction corresponds to the upper limit on the axion-electron coupling and on the axion mass $g_{Ae}\times m_A\leq3.1\times10^{-7}$ eV (90% c.l.). The limits on axion mass are $m_A\leq$ 105 eV and $m_A\leq$ 1.3 keV for DFSZ- and KSVZ-axion models, correspondingly (90% c.l.).Comment: 7 pages, 4 figure

Red giant bound on the axion-electron coupling reexamined

If axions or other low-mass pseudoscalars couple to electrons (``fine structure constant'' $\alpha_a$) they are emitted from red giant stars by the Compton process $\gamma+e\to e+a$ and by bremsstrahlung $e+(Z,A)\to (Z,A)+e+a$. We construct a simple analytic expression for the energy-loss rate for all conditions relevant for a red giant and include axion losses in evolutionary calculations from the main sequence to the helium flash. We find that \alpha_a\lapprox0.5\mn(-26) or m_a\lapprox 9\,\meV/\cos^2\beta lest the red giant core at helium ignition exceed its standard mass by more than 0.025\,\MM_\odot, in conflict with observational evidence. Our bound is the most restrictive limit on $\alpha_a$, but it does not exclude the possibility that axion emission contributes significantly to the cooling of ZZ~Ceti stars such as G117--B15A for which the period decrease was recently measured.Comment: 11 pages, uuencoded and compressed postscript fil