Rigidity and stability of cold dark solid universe model

The large scale dynamics of the universe appears to be dominated by a "dark energy" constituent with negative pressure to density ratio w=P/rho, which could be stable if sufficiently rigid, but not if purely fluid. It was suggested by Bucher and Spergel that such a cosmological solid might be constituted by a cold (static) distribution of cosmic strings with w=-1/3, or membranes with the observationally more favored value w=-2/3, but it was not shown that the rigidity actually would be sufficient for stability. For cases in which the defect lattice is formed from even junctions, it is found that the rigidity to density ratio will be given by mu/rho=4/15 in both the string and membrane cases, and it is confirmed that this is indeed sufficient for stabilisation with respect to sufficiently small perturbations.