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How do you get rid of renormalization? Are those not incompatible paradigms to the best of our knowledge? About string theory, "really not any different" and "

How do you get rid of renormalization? Are those not incompatible paradigms to the best of our knowledge? About string theory, "really not any different" and "strings instead of point particles" don't seem compatible. I agree that it is largely an attempt to explain the fine-tuning in the Standard Model, not to overthrow it. But it is in conflict with other paradigms that attempt to "complete" the Standard Model in other ways.

pdonis 6y ago
> How do you get rid of renormalization? First, why do you need to? Second, renormalization only has to be done at all in perturbation theory, and perturbation theory is just an approximation anyway. There is plenty of work done in non-perturbative QFT, in which renormalization doesn't even arise at all. > Are those not incompatible paradigms to the best of our knowledge? I'm not sure what you mean. Different approximations to the same underlying theory don't have to be compatible unless their domains of validity overlap, and even then the only compatibility they have to have is that they have to make predictions that are consistent with each other. More generally, s/approximations/models/ in the above, since approximations are one kind of model. > "really not any different" and "strings instead of point particles" don't seem compatible Why not? There's nothing about the fundamentals of QFT that says it can only apply to point particles, or that applying it to point particles and applying it to strings are inconsistent. They're different models. > it is in conflict with other paradigms that attempt to "complete" the Standard Model in other ways. To the extent that the different attempts at a fundamental theory are inconsistent with each other (e.g., string theory vs. loop quantum gravity, which AFAICT are not consistent with each other), yes, I suppose they could be considered different paradigms. But there will never be a transition from one of them to the other. The most that could happen is that we transition from our current theories as the best we have, to our current theories being approximations to whichever more fundamental theory wins out. (Or it's possible that none of the current candidates will win out.)
- guscost 6y ago
  > why do you need to [get rid of renormalization]? What does renormalization actually represent? Why does nature do that? Those rules seem kinda tacked-on after the fact, to me... > There's nothing about the fundamentals of QFT that says it can only apply to point particles String Theory does not present a serious challenge to QFT or the Standard Model yet, but it is a massive set of additional ideas that are completely unnecessary for either one, and it is a paradigm in vigorous conflict with all of the other proposed completions to the Standard Model right now. If any of these completions ever wins conclusively, it will also "win" against the Standard Model, in the sense that the Standard Model will turn out to be a higher-level approximation of some truer lower-level theory, one which will never explain any of its fine-tuning, and therefore one which will fail. It's very similar to GR vs. Newtonian Dynamics, and I would argue that Newtonian Dynamics is in fact a failed paradigm, and it has been replaced by a better paradigm, no matter how useful it may remain.
  - guscost 6y ago
    Oh, also: > There is plenty of work done in non-perturbative QFT, in which renormalization doesn't even arise at all. Yes, because that stuff doesn't even attempt to be compatible with GR. There is no conflict between the probably-incompatible paradigms of GR and non-perturbative QFT because their respective predictions have zero overlap.
    - pdonis 6y ago
      > that stuff doesn't even attempt to be compatible with GR Sure it does. You can do non-perturbative QFT in curved spacetime.
      - guscost 6y ago
        When you say "do non-perturbative QFT in curved spacetime" you don't mean "make a risky prediction that could be falsified in non-curved spacetime", right? As I understand it the whole purpose of perturbation is to approximate QFT so that it can predict macro-scale things.

pdonis 6y ago

> How do you get rid of renormalization? First, why do you need to? Second, renormalization only has to be done at all in perturbation theory, and perturbation theory is just an approximation anyway. There is plenty of work done in non-perturbative QFT, in which renormalization doesn't even arise at all. > Are those not incompatible paradigms to the best of our knowledge? I'm not sure what you mean. Different approximations to the same underlying theory don't have to be compatible unless their domains of validity overlap, and even then the only compatibility they have to have is that they have to make predictions that are consistent with each other. More generally, s/approximations/models/ in the above, since approximations are one kind of model. > "really not any different" and "strings instead of point particles" don't seem compatible Why not? There's nothing about the fundamentals of QFT that says it can only apply to point particles, or that applying it to point particles and applying it to strings are inconsistent. They're different models. > it is in conflict with other paradigms that attempt to "complete" the Standard Model in other ways. To the extent that the different attempts at a fundamental theory are inconsistent with each other (e.g., string theory vs. loop quantum gravity, which AFAICT are not consistent with each other), yes, I suppose they could be considered different paradigms. But there will never be a transition from one of them to the other. The most that could happen is that we transition from our current theories as the best we have, to our current theories being approximations to whichever more fundamental theory wins out. (Or it's possible that none of the current candidates will win out.)

guscost 6y ago
> why do you need to [get rid of renormalization]? What does renormalization actually represent? Why does nature do that? Those rules seem kinda tacked-on after the fact, to me... > There's nothing about the fundamentals of QFT that says it can only apply to point particles String Theory does not present a serious challenge to QFT or the Standard Model yet, but it is a massive set of additional ideas that are completely unnecessary for either one, and it is a paradigm in vigorous conflict with all of the other proposed completions to the Standard Model right now. If any of these completions ever wins conclusively, it will also "win" against the Standard Model, in the sense that the Standard Model will turn out to be a higher-level approximation of some truer lower-level theory, one which will never explain any of its fine-tuning, and therefore one which will fail. It's very similar to GR vs. Newtonian Dynamics, and I would argue that Newtonian Dynamics is in fact a failed paradigm, and it has been replaced by a better paradigm, no matter how useful it may remain.
- guscost 6y ago
  Oh, also: > There is plenty of work done in non-perturbative QFT, in which renormalization doesn't even arise at all. Yes, because that stuff doesn't even attempt to be compatible with GR. There is no conflict between the probably-incompatible paradigms of GR and non-perturbative QFT because their respective predictions have zero overlap.
  - pdonis 6y ago
    > that stuff doesn't even attempt to be compatible with GR Sure it does. You can do non-perturbative QFT in curved spacetime.
    - guscost 6y ago
      When you say "do non-perturbative QFT in curved spacetime" you don't mean "make a risky prediction that could be falsified in non-curved spacetime", right? As I understand it the whole purpose of perturbation is to approximate QFT so that it can predict macro-scale things.