Quantum vacuum fluctuations and dark energy
  It is shown that the curvature of space-time induced by vacuum fluctuations
of quantum fields should be proportional to the square of Newton's constant
$G$. This offers a possible explanation for the success of the approximation $G
m^6 c^2 h^{-4}$ for the dark energy density, with $m$ being a typical mass of
elementary particles.
