Axions at the International Axion Observatory

QCD axions with meV mass can be behind some stellar cooling anomalies and form all or part of the cold dark matter of the universe. We discuss on a proposed experiment to discover the solar flux of meV mass axions: the International AXion Observatory: IAXO.Comment: 6 pages, 4 figures, Contributed to the 11th Patras Workshop on Axions, WIMPs and WISPs, Zaragoza, June 22 to 26, 201

The Sun in Hidden Photons

We present some aspects and first results of the emission of sub-eV mass hidden photons from the Sun. The contribution from a resonant region below the photosphere can be quite significant, raising previous estimates. This is relevant for the Telescope for Hidden Photon Search, TSHIPS I, currently targeting at meV-mass hidden photons with O(10^-6) kinetic mixing with the photon. These particles could account for the large effective number of neutrinos pointed at by the cosmic microwave background and other large-scale structure probes, and are motivated in some scenarios of string theory.Comment: 4 pages, 4 figures. Contribution to the 7th Patras Workshop on Axions, WIMPs and WISPs, 27 June - 1 July 2011, Mykonos, Greec

Atlas of solar hidden photon emission

Hidden photons, gauge bosons of a U(1) symmetry of a hidden sector, can constitute the dark matter of the universe and a smoking gun for large volume compactifications of string theory. In the sub-eV mass range, a possible discovery experiment consists on searching the copious flux of these particles emitted from the Sun in a helioscope setup \`a la Sikivie. In this paper, we compute the flux of transversely polarised HPs from the Sun, a necessary ingredient for interpreting such experiments. We provide a detailed exposition of photon-HP oscillations in inhomogenous media, with special focus on resonance oscillations, which play a leading role in many cases. The region of the Sun emitting HPs resonantly is a thin spherical shell for which we justify an averaged-emission formula and which implies a distinctive morphology of the angular distribution of HPs on Earth in many cases. Low mass HPs with energies in the visible and IR have resonances very close to the photosphere where the solar plasma is not fully ionised and requires building a detailed model of solar refraction and absorption. We present results for a broad range of HP masses (from 0-1 keV) and energies (from the IR to the X-ray range), the most complete atlas of solar HP emission to date.Comment: 45 pages, 18 figure

Book review: L'allevamento ecologico del coniglio (Organic rabbit farming)

González-Redondo, P. (2011). Book review: L'allevamento ecologico del coniglio (Organic rabbit farming). World Rabbit Science. 19(3). doi:10.4995/wrs.2011.869.SWORD19

Hochschild cohomology via incidence algebras

Given an algebra A we associate an incidence algebra A(\Sigma) and compare their Hochschild cohomology groups.Comment: 16 pages, Section 3.2 deleted, Section 4 adde

Axion results: what is new?

The PVLAS collaboration has obtained results that may be interpreted in terms of a light axion-like particle, while the CAST collaboration has not found any signal of such particles. Moreover, the PVLAS results are in gross contradiction with astrophysical bounds. We develop a particle physics model with two paraphotons and with a low energy scale in which these apparent inconsistencies are circumvented.Comment: 10 pages, 4 figures. Based on two talks given at the International Workshop "The dark side of the Universe", Madrid, June 2006: "Evading astrophysical bounds on axion-like particles in paraphoton models" by J. Redondo and "Axion results: what is new?" by E. Masso. To be published in the Proceeding