  In a full solution for a scalar quantum field coupled to an accelerating
isotropic universe, all constituent non-autonomous modes of elementary
excitation cease to oscillate and become unstable at a discrete sequence of
times. After canonical quantization the time-frozen Hamiltonian has eigenstates
that can be viewed as neither particles nor oscillatory radiation. Under
standard canonical quantization, the Hamiltonian has a natural time dependent
partitioning into a light component and a dark component. Under equipartition
of energy, the energy density of the dark component remains constant. The dark
component consists of a finite number of low wave -number repulsive units with
time varying force constant. Although these unstable modes have no ground state
of minimum energy there exist only finitely many of them and so their quantum
Hilbert space representation, by the Stone-von Neumann theorem, is unique up to
unitary equivalence. The remaining infinite number of stable modes still have a
unique Fock-Cook representation and so overall there is still a preferred
physical representation.
