  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. On 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 the one of the
homogeneous case. However, on the long term, the expansion finally becomes
significantly inhomogeneous and no more mimics a conformal transformation of
the metric. Thereafter, the Yang-Mills fluctuations enter a complex non-linear
regime, accompanied by diffusion, while their associated energy contrasts grow.
