SciPost Phys. Proc. 4, 014 (2021) ·
published 13 August 2021
The scale of quantum mechanical effects in matter is set by Planck's constant, $\hbar$.
This represents the quantisation scale for material objects.
In this article, we present a simple argument why the quantisation scale for space, and hence for gravity, may not be equal to $\hbar$.
Indeed, assuming a single quantisation scale for both matter and geometry leads to the `worst prediction in physics', namely, the huge difference between the observed and predicted vacuum energies.
Conversely, assuming a different quantum of action for geometry, $\beta \ll \hbar$, allows us to recover the observed density of the Universe.
Thus, by measuring its present-day expansion, we may in principle determine, empirically, the scale at which the geometric degrees of freedom should be quantised.