Lattice Melting and Rotation in Perpetually Pulsating Equilibria

Abstract

Systems whose potential energies consists of pieces that scale as r^-2 together with pieces that scale as r^2, show no violent relaxation to Virial equilibrium but may pulsate at considerable amplitude for ever. Despite this pulsation these systems form lattices when the non-pulsational `energy' is low, and these disintegrate as that energy is increased. The `specific heats' show the expected halving as the `solid' is gradually replaced by the `fluid' of independent particles. The forms of the lattices are described here for N ~ 20 and they become hexagonal close packed for large N. In the larger N limit, a shell structure is formed. Their large N behaviour is analogous to a gamma=5/3 polytropic fluid with a quasi-gravity such that every element of fluid attracts every other in proportion to their separation. For such a fluid, we study the `rotating pulsating equilibria' and their relaxation back to uniform but pulsating rotation. We also compare the rotating pulsating fluid to its discrete counter part, and study the rate at which the rotating crystal redistributes angular momentum and mixes as a function of extra heat content.