Gravitational instability of Yang-Mills cosmologies

The gravitational instability of Yang-Mills cosmologies is numerically studied with the Hamiltonian formulation of the spherically symmetric Einstein-Yang-Mills equations with SU(2) gauge group. In the short term, the expansion dilutes the energy densities of the Yang-Mills fluctuations due to their conformal invariance. In this early regime, the gauge potentials appear oscillating quietly in an interaction potential quite similar to that of the homogeneous case. However, in the long term, the expansion finally becomes significantly inhomogeneous and no longer mimics a conformal transformation of the metric. Thereafter, the Yang-Mills fluctuations enter a complex nonlinear regime, accompanied by diffusion, while their associated energy contrasts grow.