  Based on particle physics, the fundamental CPT invariance suggests a Big Jets
model for the beginning of the universe, in which two oppositely directed jets
evolved into a gigantic "matter half-universe" and a gigantic "antimatter
half-universe" after annihilation and decay processes. In the geometric-optics
limit, quantum Yang-Mills gravity with $T_4$ translational gauge symmetry in
flat spacetime leads to an effective metric tensor in the Hamilton-Jacobi
equation for macroscopic objects. This effective metric tensor does not exist
in the wave equations of quantum particles. For cosmological expansion, we
assume that an "effective metric tensor" for spacetime geometry based on
Yang-Mills gravity corresponds to the usual FLRW form. Dynamical equations of
expansion for the matter half-universe are obtained and solved. The
time-dependent scale factors and the estimated age of the universes, $t^{YM}_o
\approx 15.3 \times 10^9 yr$, based on Yang-Mills gravity are consistent with
experiments. CPT invariance implies that the same evolution process and
dynamics of cosmic expansion also hold for the distant `antimatter
half-universe.'
