Leptonic Photons and Nucleosynthesis

Abstract

Should $U(1)$ long-range forces be associated to electron, muon and/or tau quantum number then their ''fine structure constants" are seen to be bound by nucleosynthesis data to be less than about $1.7 \times 10^{-11}$. For $\tau$ and $\mu$ this is the best upper limit up to dateComment: 4 pages, LaTeX. Full postscript file available via anonymous ftp at ftp://ftp.ifae.es/preprint/ft/uabft402.p