The KeV Majoron as Dark Matter Particle

We consider a very weakly interacting KeV majoron as dark matter particle (DMP), which provides both the critical density $\rho_{cr} = 1.88 \times 10^{-29} h^{2}$ $g/cm^{3}$ and the galactic scale $M_{gal}$ $\sim m^{3}_{Pl}/m^{2}_{J} \sim 10^{12} M_{\odot} (m_{J}/1 KeV)^{-2}$ for galaxy formation. The majoron couples to leptons only through some new "directly interacting particles", called DIPS, and this provides the required smallness of the coupling constants. If the masses of these DIPS are greater than the scale $V_s$ characterizing the spontaneous violation of the global lepton symmetry they are absent at the corresponding phase transition ($T \sim V_s$) and the majorons are produced during the phase transition, never being in thermal equilibrium during the history of the universe. In the alternative case $m_{DIP} < V_{s}$ the majorons can be for a short period in thermal equilibrium. This scenario is not forbidden by nucleosynthesis and gives a reasonable growth factor for the density fluctuations compatible with COBE. A possible signature is an X-ray line at $E_\gamma = \frac{m_J}{2}$, produced by the decay $J \to \gamma + \gamma$. A model is described which realizes the possibility of the KeV majoron as DMP and may also lead to observable rates for decays such as \mu \ra e \gamma and \mu \ra 3e.Comment: 13 pages, 3 figures available upon request, FTUV/93-35, late

The fundamental constants and their variation: observational status and theoretical motivations

This article describes the various experimental bounds on the variation of the fundamental constants of nature. After a discussion on the role of fundamental constants, of their definition and link with metrology, the various constraints on the variation of the fine structure constant, the gravitational, weak and strong interactions couplings and the electron to proton mass ratio are reviewed. This review aims (1) to provide the basics of each measurement, (2) to show as clearly as possible why it constrains a given constant and (3) to point out the underlying hypotheses. Such an investigation is of importance to compare the different results, particularly in view of understanding the recent claims of the detections of a variation of the fine structure constant and of the electron to proton mass ratio in quasar absorption spectra. The theoretical models leading to the prediction of such variation are also reviewed, including Kaluza-Klein theories, string theories and other alternative theories and cosmological implications of these results are discussed. The links with the tests of general relativity are emphasized.Comment: 56 pages, l7 figures, submitted to Rev. Mod. Phy

The origin and abundances of the chemical elements revisited

The basic scheme of nucleosynthesis (building of heavy elements from light ones) has held up very well since it was first proposed more than 30 years ago by E.M. Burbidge, G.R. Burbidge, A.G.W. Cameron, W.A. Fowler, and F. Hoyle. Significant advances in the intervening years include (a) observations of elemental and a few isotopic ratios in many more extrasolar-system sites, including metal-poor dwarf irregular galaxies, where very little has happened, and supernovae and their remnants, where a great deal has happened, (b) recognition of the early universe as good for making all the elements up to helium, (c) resolution of heavy element burning in stars into separate carbon, neon, oxygen, and silicon burning, with fine tuning of the resulting abundances by explosive nucleosynthesis in outgoing supernova shock waves, (d) clarification of the role of Type I supernovae, (e) concordance between elements produced in short-lived and long-lived stars with those that increased quickly and slowly over the history of the galaxy, and (f) calibration of calculations of the evolution and explosion of massive stars against the detailed observations of SN 1987A. The discussion presupposes a reader (a) with some prior knowledge of astronomy at the level of recognizing what is meant by an A star and an AGB star and (b) with at least a mild interest in how we got to where we currently are. © 1991 Springer-Verlag