In general relativity we have free falling observers who feel no gravity. and equations for geodesics. There are tools that describe the strength of gravitation field for a given observer.

In Are loop quantum cosmos never singular? by Parampreet Singh from the Perimeter Institute I read:

An open question is the way quantum gravitational effects change the picture near above extremal events. This can be asked in different ways: Does quantum gravity resolve all spacelike singularities? Do quantum gravity effects always bound the spacetime curvature? Are geodesics complete (if their notion exists in a quantum spacetime)? What does the singularity resolution or the lack of it tell us about the underlying theory? Since we do not yet have a complete theory of quantum gravity these questions cannot yet be answered in full generality. However, they can be posed for cosmological singularities in a simplified setting such as a homogeneous universe where mini-superspace quantizations are available.

what are the tools in LQG that enable to describe the strength of gravity?

  • $\begingroup$ Does “passing to the classical limit” count as an answer? $\endgroup$ – Prof. Legolasov May 30 '18 at 10:40
  • $\begingroup$ we have conservation laws in physics which of them can be deduced by passing to classical limit? $\endgroup$ – Naima Jun 3 '18 at 14:59
  • $\begingroup$ not sure what the context of your comment is. Conservation laws are associated through Noether theorem with global symmetries of your theory. E.g. QED doesn’t explicitly depend on the external time parameter $t$ and thus energy in it is conserved. In the background independent context of GR or LQG there are no global symmetries to begin with. This is actually a point which isn’t specific to LQG itself, a similar situation also arises in GR. You end up with no real definition of gravitational energy. That is ok though, because usual physics is restored in the limit of small gravity field $\endgroup$ – Prof. Legolasov Jun 3 '18 at 15:30
  • $\begingroup$ how can i see that a situation in lqg has a limit to small gravity field? my question was about this strengrh. $\endgroup$ – Naima Jun 3 '18 at 17:14
  • $\begingroup$ do you know how to get the low energy limit of the LQG spinfoam amplitude? It reduces to the Einstein-Hilbert action. If not, try Rovelli’s textbook “Covariant LQG”. $\endgroup$ – Prof. Legolasov Jun 3 '18 at 17:15

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