John Carlos Baez on Nostr: nprofile1q…ze5g0 wrote: ". It's certainly possible that effective QG gives a good ...
nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpqky223zcc4q69d8t0me4vg5uw8mw0yxeukjgvz6h92laqnenr0ajsgze5g0 (nprofile…e5g0) wrote: ". It's certainly possible that effective QG gives a good approximation, or that QG is asymptotically safe."
Asymptotic safety is irrelevant to my claim.
I said the coefficients of the infinitely many counterterms in perturbative QG are not numbers we can freely choose if we want a theory that reduces to exactly Einstein-Hilbert gravity in the low-energy limit. They must obey infinitely many constraints: namely, the requirements that the corresponding terms in the resulting low-energy effective Lagrangian must vanish, to leave only the 2 terms we actually see: the Ricci scalar term and the cosmological constant term.
"But the machinery of perturbation theory is horrifically complex."
That's true, but that's okay. I'm assuming above that we use a Poincare-invariant regularization. This restricts the nature of the possible counterterms
Asymptotic safety is irrelevant to my claim.
I said the coefficients of the infinitely many counterterms in perturbative QG are not numbers we can freely choose if we want a theory that reduces to exactly Einstein-Hilbert gravity in the low-energy limit. They must obey infinitely many constraints: namely, the requirements that the corresponding terms in the resulting low-energy effective Lagrangian must vanish, to leave only the 2 terms we actually see: the Ricci scalar term and the cosmological constant term.
"But the machinery of perturbation theory is horrifically complex."
That's true, but that's okay. I'm assuming above that we use a Poincare-invariant regularization. This restricts the nature of the possible counterterms