Dissipationless clustering of neutrinos around a cosmic-string loop

The dissipationless clustering of weakly interacting massive neutrinos about a nonadiabatic pointlike seed perturbation (e.g., a cosmic-string loop) is studied. The clustering is described by the Liouville equation in an expanding universe which can be transformed into an integral equation for the density perturbation in Fourier space (the Gilbert equation). The analysis yields an accurate determination of the density profile about a seed, and a value for the maximal effective Jeans length 8h₅₀{}^{{{-}}2}$ Mpc, where ${h}₅₀$ is the expansion rate in units of 50 km ${s}^{{{-}}1}$ ${Mpc}^{{{-}}1}$.