Intrinsically Quantum-Mechanical Gravity and the Cosmological Constant
  Problem
  We propose that gravity be intrinsically quantum-mechanical, so that in the
absence of quantum mechanics the geometry of the universe would be Minkowski.
We show that in such a situation gravity does not require any independent
quantization of its own, with it being quantized simply by virtue of its being
coupled to the quantized matter fields that serve as its source. We show that
when the gravitational and matter fields possess an underlying conformal
symmetry, the gravitational field and fermionic matter-field zero-point
fluctuations cancel each other identically. Then, when the fermions acquire
mass by a dynamical symmetry breaking procedure that induces a cosmological
constant in such conformal theories, the zero-point fluctuations readjust so as
to cancel the induced cosmological constant identically. The zero-point vacuum
problem and the cosmological constant vacuum problems thus mutually solve each
other. We illustrate our ideas in a completely solvable conformal-invariant
model, namely two-dimensional quantum Einstein gravity coupled to a
Nambu-Jona-Lasinio self-consistent fermion.
