We give a detailed study of the various aspects of the mixing effects
due to geodesic instability in compact negative curvature FLRW models,
as an explicit function of the cosmological parameters and the topolo
gical compactification scale. Our results show that the effect is: (i)
much less pronounced than some of the claims made previously; (ii) st
rongly dependent upon the current value of the cosmological density pa
rameter OMEGA0. Nevertheless it can, for reasonable values of the dens
ity parameter, produce appreciable mixing with a consequent reduction
in the measured CMWBR anisotropy on a range of angular scales. This ef
fect is expressible in terms of the curvature scalar and is therefore
gauge invariant. Furthermore, we show: (a) the usual observer area dis
tance routinely employed in cosmological studies also encodes all the
dynamical information relating to the geodesic instability; (b) the es
timates of the length scales on the surface of the last scattering dep
end significantly on the density parameter, and could be significantly
different in low density universes compared with a critical density u
niverse.