The forest of QSO absorption lines and cosmological models with unstable dark matter

Indications on clustering features in the two‐point correlation function of Ly α line separations in published high‐resolution spectra of quasars are presented. They are in contradiction to the self‐similar hierarchical clustering model, but they could be explained by a first generation of small‐scale pancakes in a model with unstable dark matter. A characteristic scale of velocity dispersion Δ v ≈ 150 km/s of absorption clouds within pancakes is described by corresponding coherent regions of positive correlation, while the structure adjacent on the lines of sight are separated by a comoving distance of (18 ± 6) Mpc ( H 0 = 50 km/s Mpc). The appropriate coherence length of the fluctuation spectrum may result from the free streaming length of (unstable) neutrinos of (100 … 200) eV rest mass.