atyy said:
... So would it be possible that there are an infinite number of parameters for arbitrarily high energies, but we only need to measure a few more parameters each time to gain predictivity whenever we want to step up the energy scale?
Yes I think that is right. I am not an expert but I believe that situation would NOT be what Weinberg was thinking of in 1976 and gave the name "asymptotic safe".
That would a series of "effective theories" getting better and better.
But no one theory would be "fundamental" in the sense that you can take it all the way, as high energy as you like, and it stays applicable.
And what you describe sounds like a practical and reasonably satisfactory situation.
But Weinberg, and Reuter and Percacci after him, and all the others are not talking about that. They want something that is what they call "nonperturbatively
renormalizable" where it is renormalizable in the sense that you only have to determine a finite number of parameters experimentally and then you are good to go all the way.
You never have to adjust and plug in another number.
That is what Weinberg meant when he said it's possible that something like string theory is not needed, and is not how the world is. It's possible that the way the world is is just what we are used to. Geometric general relativity and QFT combined in the effective unification we already have, or something like that, and it turns out to be predictive/fundamental in other words (nonperturbatively) renormalizable after all. You remember where he was saying things like that in his talk.
The november Perimeter workshop on that will probably be interesting and I bet they post videos of some or all of the talks. Loll will be there, Weinberg, Smolin, Percacci, Litim, Reuter. Quite a group!
+++++++
About your post #53, I am not ready to assume that any of these preliminary results are right, or anything more than an accident if they are right. I don't have the trained intuition and vision of someone who actually researches this stuff. You are thinking some interesting "what if" stuff, but it is too complex for me right now. I think they are clearly on to something that should be pursued full force, and get funding and workshop support and all that. I hope they attract grad student and postdoc brainpower, and I think they will. But I can't assume they are right and project ahead like that. Have to wait and see.
Also this is a big challenge to Rovelli to see if there is any scale-dependence in LQG (I mean spinfoam of course). Another thing to wait-see about.