#### DarMM

Science Advisor

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The other usage is centuries old as well, going back to at least Gibbs and Boltzmann and it's used in Statistical Mechanics and Cosmology as well. So both usages are prevalent in modern physics and centuries old. I don't know which is older, but I also don't see why this point matters if both are in common usage now and have been for used for centuries.I don't doubt that, but I think you are missing the point that the other usage of fine tuning is old, centuries old....

In any case, I will grant your usage of this unfortunate standard terminology in the novel and relatively secluded area of research that is the foundations of QM.

You're treating this like a serious proposal, remember the context in which I brought this up. This toy model isn't intended to be a scientific advance. It's intended to show how simple it is to replicate all the features of QM except for entanglement, i.e. post-classical correlations. The model isn't even remotely realistic and is mathematically trivial and it can still replicate them.I understand that this toy model is or may just be some random example, but I seriously think a few key points are in order. I will start by making clear that my following comments are regarding mathematical models in scientific theories of empirical phenomenon, but I digress.

I do hope you realize that there is anenormousqualitative difference between these kind of theoretical models and a theoretical model like Manasson's. This can be seen at multiple levels:

The reason I brought up such toy models was to focus on the fact that things like quantised values, superposition, solving the measurement problem, etc can be done quite easily and this model is just the simplest such model demonstrating that (more complex ones exist).

What isn't easy is replicating breaking of the Bell inequalities and any model that really attempts to explain QM should focus on that primarily, as the toy model (and others) show that the other features are easy.

There are less psi-epistemic models though, they are very hard to construct, especially now in light of the PBR theorem. I really don't understand this.All of these critique points w.r.t. theorisation of empirically based scientific models do not merely apply to the toy model you posted, but to all psi-epistemic models of QM. This is also why we see so much of such models and practically none of the other; making psi-epistemic models is a low-risk/low-payout strategy, while making psi-ontic models is a high-risk/high-payout strategy.

I didn't present the toy model as a candidate to replace QM, but as a demonstration of how easily all non-entanglement features can be replicated.When I said earlier, that I've never seen a new model which wasn't obviously wrong or completely unbelievable, I wasn't even counting such incrementally different models because they tend to be nowhere near even interesting enough to consider seriously as a candidate that will possibly supersede QM. Sure, such a model may even almost directly have way more applications; that however is frankly speaking completely irrelevant w.r.t. foundational issues. W.r.t. the foundations of QM, this leaves us with searching for psi-ontic models.

Again this is counter to virtually everything I've read in quantum foundations. Making Psi-Epistemic models is extremely difficult in light of the PBR theorem.Make no mistake; the foundational goal of reformulating QM based on another model is not to find new applications but to go beyond QM; based on all psi-ontic attempts so far this goal is extremely difficult. On the other hand, as I have illustrated, finding a reformulation of QM based on a psi-epistemic model tends to be neither mathematically challenging nor scientifically interesting for any (under)grad student with sufficient training

I don't think so, again not in light of the PBR theorem.one can almost literally blindly open any textbook on statistics, decision theory, operation research and/or data science and find some existing method which one could easily strip down to its mathematical core and try to construct an incrementally different model of QM.

This is what I am saying:So again, if you do know of some large collection of new psi-ontic (toy) models which do not quickly fall to fine-tuning and aren't obviously wrong, please, some references would be nice.

- Replicating non-entanglement features of Quantum Mechanics is very simple as all one needs is a classical theory with an epistemic limit. The toy model presented is an example of how simple this is.
- Hence something that replicates QM should explain how it replicates entanglement first, as the other aspects are easy
- However we already know that realist models will encounter fine-tuning from the Wood-Spekkens and Pusey-Leifer theorems.

**. That's actually one of my reasons for being skeptical regarding these sort of models, we already know they will develop unpleasant features. People present these models as if they will escape what they don't like about Bohmian Mechanics, however we know now that these features of Bohmian Mechanics are general to all such models.**

__because it has been proven not to exist, all realist models require fine tunings__The only really different theories would be superdeterministic, retrocausal or Many-Worlds, but all of those have fine tunings as well.

Acausal models might be different (i.e. where physics concerns multiscale 4D constraints), but they are truly different theories with little analysis on them as of now.

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