Question

Criteria for being able to work with gravity in quantum mechanics, without a full theory of quantum gravity?

Answer 1

Quantum gravity. ... Although some quantum gravity theories, such as string theory, try to unify gravity with the other fundamental forces, others, such as loop quantum gravity, make no such attempt; instead, they make an effort to quantize the gravitational field while it is kept separate from the other forces.

Answer 2

Follow the criteria given below:

●Experiments, such as the ones above, involving quantum mechanics, that can be described in flat spacetime using the equivalence principle. Curvature of spacetime is negligible.

●Experiments in which curvature is nonnegligible, but the analysis is still trivial. For example, I could imagine, at least in principle, doing gravitational lensing with neutrons and observing quantum interference effects between different parts of the beam. (In reality, I'd guess this example wouldn't work due to decoherence.)

●Semiclassical gravity, e.g., Hawking radiation.

●Planck-scale physics.