  It is known that the conformal instability or bottomless problem rises in the
path integral method in quantizing the general relativity. Does quantum
spacetime itself really suffer from such conformal instability? If so, does the
conformal instability cause the collapse of local spacetime region or even
collapse the whole spacetime? The problems are studied in the framework of the
Quantum Spacetime Reference Frame (QSRF) and induced spacetime Ricci flow. We
find that if the lowest eigenvalue of an operator, associated with the
F-functional in a local compact (closed and bounded) region, is positive, the
local region is conformally unstable and will tend to volume-shrinking and
curvature-pinching along the Ricci flow-time t; if the eigenvalue is negative
or zero, the local region is conformally stable up to a trivial rescaling.
However, the local non-collapsing theorem in the Ricci flow proved by Perelman
ensures that the instability will not cause the local compact spacetime region
collapse into nothing. The total effective action is also proved positive
defined and bounded from below keeping the whole spacetime conformally stable,
which can be considered as a generalization of the classical positive mass
theorem of gravitation to the quantum level.
