Constraints on decaying particles from Virgo infall

Decaying particles have been proposed to reconcile inflationary models of the early Universe with observations which suggest that the Universe is open. The bulk of the present mass-density is assumed to be in relativistic particles resulting from the non-radiative decay of massive weakly interacting particles. The relativistic component would be unclustered and therefore undetected in dynamical studies of virialized systems. The decays must have occurred recently $$(1+z_\text d)\lt5$$, otherwise the cores of rich galaxy clusters would not be in virial equilibrium. However, this model is not compatible with recent estimates of our peculiar velocity relative to the Virgo cluster unless $$(1+z_\text d)\gtrsim20$$.