I Superdeterminism and the hidden variable

[Sunil]

I fail to see how it does so, since Weinberg does not even mention any such argument.

Weinberg was quoted to show that SM and GR considered as effective field theories is mainstream. That's all. Once you have conceded this, there is no further need to consider Weinberg.

If introducing a preferred frame into an effective field theory makes no difference, why would anyone bother doing it?

Need for what?

To show the viability of all the realistic interpretations of quantum theory, given that they require a preferred frame in the relativistic context. Correspondingly, to show the viability of EPR realism (given that together with Einstein causality one could prove the Bell inequalities, while with the Lorentz ether one cannot prove it), the viability of Reichenbach's common cause principle (same reason).

Moreover, to argue that even thinking about superdeterminism, quantum logic and other such "theories" is unreasonable, given that much simpler realistic causal alternatives exist.

This is one point I have liked in that paper recommended by RUTA: The point against superdeterminism that it has to be a very complicate theory. But to reject superdeterminism because it is too complex means one needs simpler alternatives. They exist, in form of the realistic interpretations, but require a preferred frame. Thus, to present a viable alternative we need a viable theory with preferred frame able to replace GR + SM.

I would phrase this a bit differently. Since we cannot currently experimentally test for Lorentz invariance below a finite length and time scale (about 1/10 the size of an atomic nucleus, or the corresponding light travel time, IIRC), we cannot say that we have experimentally confirmed that Lorentz invariance holds below that scale (or, if you prefer, above the corresponding energy and momentum scale). So if some theory claims that Lorentz invariance is not fundamental, but is an approximate symmetry that is broken above some energy and momentum scale beyond what we can currently test, that theory is consistent with currently known experimental data.

That's correct but too weak. It would be valid also if there would be no GR and the QFT would be described by some AQFT. But the situation looks much worse for relativistic symmetry. There is not even a single viable candidate for an AQFT, and given the situation with gravity AFAIU we have even sufficient evidence that below Planck length existing field theory (GR + SM) fails. There exist simple, straightforward replacements for more fundamental theories - lattice regularizations. But they have no relativistic symmetry. So, there exist sufficiently simple viable theories with only effective relativistic symmetry but none with fundamental relativistic symmetry.

 

[PeterDonis]

It would be valid also if there would be no GR

I'm not sure what you mean by "if there would be no GR". What symmetries do and do not exist physically does not depend on what theories humans do or do not discover.

given the situation with gravity AFAIU we have even sufficient evidence that below Planck length existing field theory (GR + SM) fails

I don't know what evidence you are talking about.

there exist sufficiently simple viable theories with only effective relativistic symmetry but none with fundamental relativistic symmetry.

Your definition of "viable" is rather idiosyncratic.

 

[Sunil]

I'm not sure what you mean by "if there would be no GR". What symmetries do and do not exist physically does not depend on what theories humans do or do not discover.

I mean a hypothetical world, where a viable AQFT would exist, not the real world.

I don't know what evidence you are talking about.

In this case the theoretical one. The quantization of GR as an effective field theory (see Donoghue) does not seem to suggests that it works below Planck length. That's AFAIU quite typical for non-renormalizable theories, they work fine for some time until the counterterms one has to add become large.

Your definition of "viable" is rather idiosyncratic.

You think so? Any evidence for this?

 

[PeterDonis]

You think so? Any evidence for this?

The theories you are calling "viable" are not supported by any experimental evidence at all. They simply agree with your own theoretical preferences. You even admit that you are talking about hypothetical worlds instead of the real world.

 

[Sunil]

The theories you are calling "viable" are not supported by any experimental evidence at all. They simply agree with your own theoretical preferences. You even admit that you are talking about hypothetical worlds instead of the real world.

The reference to the hypothetical world was part of a side remark - some fantasy world were the hypothesis of fundamental Lorentz covariance would have been reasonable, to illustrate how this differs from the actual world where the hypothesis of fundamental Lorentz covariance is simply unreasonable. Given that your remark suggests something completely different, it is [self-censored].

Then, "viable" means viable, that means, no falsifying empirical evidence is known. "Empirical evidence" also means simply empirical evidence, independent of the time it was made (prediction or postdiction). So, all the empirical evidence supporting GR also supports Schmelzer's Lorentz ether, and all the empirical evidence supporting the SM supports also the part obtained from Schmelzer's model (fermion and gauge content of the SM).

The claim "not supported by any experimental evidence at all" is therefore plainly wrong. You can argue that postdictions are less valuable than predictions, but they are, nonetheless, some experimental evidence.

And even if you compare the empirical content, which is something much more subtle than simply support by some experimental evidence, this looks not that bad. The SM is essentially purely phenomenological, it predicted essentially nothing beyond what was observed. Ok, one can disagree here, given that quarks themselves have not been observed, but are theoretical objects. Whatever, they were a guess based on the experimental data. The properties of the quarks, their number, the number of colors and so on were essentially taken from observation. In Schmelzer's model they follow from the model. This model predicts the fermion and gauge content of the SM. Competitors like supersymmetry have predicted additional such particles at LHC and failed, other competitors (like strings) predict nothing. For gravity, Schmelzer introduces additional terms (- in empirical content) but restricts the topology to $\mathbb{R}^4$ and requires the existence of a global harmonic time coordinate (+ in empirical content), thus, no clear advantage.

 

[PeterDonis]

The reference to the hypothetical world was part of a side remark - some fantasy world were the hypothesis of fundamental Lorentz covariance would have been reasonable, to illustrate how this differs from the actual world where the hypothesis of fundamental Lorentz covariance is simply unreasonable.

Your definition of "unreasonable" is your personal opinion. Evidently my personal opinion differs from yours. But PF discussions should not be based on personal opinions. Discussions of what predictions various models make are fine. Claims that one model is "unreasonable" are not.

"viable" means viable, that means, no falsifying empirical evidence is known

By this criterion, lots of nonsense theories are "viable", such as Russell's teapot.

If different theoretical models make exactly the same predictions, so that there is no way to distinguish them experimentally, then the usual scientific criterion that is applied is Occam's razor.

If different theoretical models make different predictions, but the difference is not testable with our current technology and powers of observation, then we are in much the same position as above (i.e., most scientists will use Occam's razor) until our technology or our powers of observation improve to the point where we can test the different predictions.

 

[Sunil]

Your definition of "unreasonable" is your personal opinion. Evidently my personal opinion differs from yours. But PF discussions should not be based on personal opinions. Discussions of what predictions various models make are fine. Claims that one model is "unreasonable" are not.
...
By this criterion, lots of nonsense theories are "viable", such as Russell's teapot.

That empirical viability includes a lot of nonsense theories is simply fact. You cannot get rid of it (except with Orwellian renaming). Logical consistency allows even much more nonsense, nonetheless it remains a useful criterion (say, against MWI and similar nonsense). And that's why you have to allow the use of other criteria to get rid of the nonsense.

So what do you propose? Either you restrict yourself to empirical predictions and their agreement with observation, and reject arguments going beyond this as "personal opinions" with no place in science, then Russel's teapot is fine.

I allow them, and accept the usefulness of criteria like simplicity, predictive power, compatibility with fundamental principles like causality and realism, which go, indeed, beyond viability.

If different theoretical models make exactly the same predictions, so that there is no way to distinguish them experimentally, then the usual scientific criterion that is applied is Occam's razor.

The problem with Occam's razor is that it is not that well-defined as it should be. Say, the spacetime interpretation adds a whole dimension to what actually exists. But somehow the theory which uses only a three-dimensional space, where the past no longer exists and the future not yet exists, is rejected using Occam's razor. IMHO that's complete nonsense, but that's the problem with Occam's razor that one can reinterpret it in such a way that it somehow sounds acceptable.

Then, don't forget that "exactly the same predictions" is a more an urban myth than reality. Say:
EPR realism + SR spacetime interpretation ===> Bell's inequality for spacetime-separated events.
EPR realism + SR pref. frame interpretation =/=> Bell's inequality for spacetime-separated events.
There are other examples. So, there is the Wallstrom objection against some realistic interpretations of QM, which is that the realistic "interpretations" are, in fact, different theories which make different predictions (namely they exclude some QM solutions).

If different theoretical models make different predictions, but the difference is not testable with our current technology and powers of observation, then we are in much the same position as above (i.e., most scientists will use Occam's razor) until our technology or our powers of observation improve to the point where we can test the different predictions.

That's the problem of modern physics. The new devices which have given the SM have reached their limit, and all those speculations beyond the SM are evaluated in a completely unprofessional way. Because the evaluation with the standard methods, namely experiments, gives nothing, nada, nitschewo, nix. And the professional discussion of other ways to evaluate theories has been essentially suppressed as evil "metaphysics" or "philosophy". As a consequence, what is used is bad philosophy. Unprofessional because professional philosophy is already much better than the philosophy used by physicists.

And if we would follow your philosophy, there would be no discussion about philosophy in the future too, and as a consequence, I guess, the philosophy used to evaluate theories beyond the SM would remain as bad and unprofessional as it is today.

 

[PeterDonis]

And that's why you have to allow the use of other criteria to get rid of the nonsense.

I gave another criterion: Occam's razor. That's generally what scientists use.

That's the problem of modern physics.

It's not a problem, it's a fact of life: we always have more to learn. We might have different personal opinions about which direction we should go next to try to learn more, but, as I've already said, PF is not about personal opinions.

As a consequence, what is used is bad philosophy.

Philosophy is out of scope for this forum. Here we discuss physics.

 

[PeterDonis]

The OP question has been sufficiently discussed, and personal opinions are off topic. Thread closed.