Interpretations of QM

[joigus]

I think we're living in an age of confusion and that this confusion must have been pretty much unavoidable all along. Copenhagen's interpretation works like a dream for anything that doesn't deeply involve questions of very early cosmology, quantum gravity, or vacuum energy. Little surprise there: Where does the universe come from? Why is there something rather than nothing? What is time? You can't get more essential than that.

I also think there's the social factor that not many high-profile theorists since the likes of Einstein and Schrödinger have been attracted to this problem nearly compellingly enough. That's probably because so far there hasn't been much at stake from the point of view of solving fundamental problems --or getting a university tenure. This particular factor, I feel, could be about to change in the decades to come.

As to interpretations, one possibility is that, wherever the description of physical systems & processes hinges on QM, we've finally hit a fundamental logical obstacle which could have to do with the completeness vs consistency of mathematics itself, which we know by now to be an actual issue. The reason being: Why not? If that's the case, we will have to give up on matters of interpretation.

My personal feeling is that we haven't taken the question seriously enough. And my battlecry --or baby cry, who knows--, is that we must change the attitude to that of the cartographer: Our quantum-state variables, and space-time and internal-gauge, spin variables, etc. would be but a parametrisation of physics that simply cannot do the job of explaining everything at every level. At some point we have to drop them, propose new variables, and explicitly build formulae connecting the different domains. This is very similar to what a cartographer who wants to faithfully describe Antarctica must do if she's been working only with the Mercator projection previously. In a way that's what we do all the time.

As to my own interpretation, I think there must be some kind of a non-linear dynamics of solitons, kinks and domain walls, etc, going on in the gauge degrees of freedom, that's not completely inconsequencial, complex enough that it's gone unnoticed for all these years as a possibility, and can perhaps under suitable ancillary hypothesis be statistically related with a De Broglie-Bohm model as an approximation. So in that sense I think the De Broglie Bohm interpretation, although it cannot be the whole story, does capture something important as a crude approximation.

Sorry for the split infinitive, and for so many words for what basically is my two cents.

[Genady]

2 hours ago, joigus said:

I also think there's the social factor that not many high-profile theorists since the likes of Einstein and Schrödinger have been attracted to this problem nearly compellingly enough. That's probably because so far there hasn't been much at stake from the point of view of solving fundamental problems --or getting a university tenure.

For example, a neighbor of mine, retired dentist, keeps asking, why do we spend money on origin of the universe and such. I came up with some answers, but he is not satisfied. What would you say?

2 hours ago, joigus said:

This particular factor, I feel, could be about to change in the decades to come.

Why do you feel so?

Edited January 1, 2023 by Genady

[Lorentz Jr]

12 minutes ago, Genady said:

why do we spend money on origin of the universe and such... What would you say?

Just to be on the safe side. The dinosaurs didn't know about asteroids, and look what happened to them.

[geordief]

17 minutes ago, Genady said:

For example, a neighbor of mine, retired dentist, keeps asking, why do we spend money on origin of the universe and such. I came up with some answers, but he is not satisfied. What would you say

We have millennia ahead of us to occupy our minds.We would be pretty stupid if we didn't attempt to answer questions like that  (and others)

 

At the present time though the priority must be to ensure we don't trash our planetary  home for our  future, and present generations

 

[joigus]

24 minutes ago, Genady said:

Why do you feel so?

Because a few decades is a long time for experiments not to end up catching up dramatically with our frontiers of knowledge, and because it's never been the case that a breakthrough in our basic understanding of scientific issues has left the technological landscape untouched. It's bound to happen sooner rather than later.

Seemingly unsolvable problems in basic science seem to be piling up, and something's got to give.

[Markus Hanke]

36 minutes ago, Genady said:

For example, a neighbor of mine, retired dentist, keeps asking, why do we spend money on origin of the universe and such. I came up with some answers, but he is not satisfied. What would you say?

Because the human condition doesn’t magically end with the surface of our skin. We are a part of the universe, and thus ultimately a product of its origin and all the various processes that have been going on since then. It is delusion to think that we are somehow separate from everything else, so that these questions have no relevance to us. Understanding the universe means understanding ourselves and our human condition better. 

Also, the question carries connotations that the value of something is defined solely by the financial benefits it yields. This is another common delusion. Too many people these days confuse the price of things with their actual value, which isn’t always readily quantifiable, nor even commonly recognised. 

But I think it’s also important to realise that not everyone will “get” this, no matter how well you try to explain it, and how good your arguments are. Sometimes you just have to leave them to it, and move on.

[swansont]

55 minutes ago, Genady said:

For example, a neighbor of mine, retired dentist, keeps asking, why do we spend money on origin of the universe and such. I came up with some answers, but he is not satisfied. What would you say?

You don’t know what you’re going to find, and what impact it will have.

[Genady]

8 minutes ago, Markus Hanke said:

the question carries connotations that the value of something is defined solely by the financial benefits it yields

Not in his case. He in fact very much values efforts to fight diseases, hunger in Africa (he is from Germany), etc.

 

8 minutes ago, swansont said:

You don’t know what you’re going to find, and what impact it will have.

This was my most effective argument so far. I told him, what if, for example, it will give us a way to get an unlimited energy from nothing?

[swansont]

1 hour ago, Genady said:

This was my most effective argument so far. I told him, what if, for example, it will give us a way to get an unlimited energy from nothing?

It’s one thing to say we can discover the unknown. It’s another thing to say what we know to be true will be overturned.

[geordief]

9 hours ago, Markus Hanke said:

The one that comes to mind is “Helgoland” by Carlo Rovelli; I found it to be a very good read. Do bear in mind though the final conclusion of the book does promote his own interpretation of QM, which is Relational Quantum Mechanics. But the historical overview is quite good.

Thanks

[Genady]

1 hour ago, swansont said:

It’s one thing to say we can discover the unknown. It’s another thing to say what we know to be true will be overturned.

The guy doesn't know that this particular thing would overturn anything 😉

[TheVat]

On 12/31/2022 at 11:20 AM, Lorentz Jr said:

So you can keep particles if you give up hidden variables, or you can keep hidden variables if you give up particles.

I thought DeB-B had both particles and pilot waves.  Not my field, so if I'm wrong or not even wrong that's par for me.

Am sorta a fan of DeB-B, due to my apelike gropings over, and cowering from, probabilistic theories.  

[Mordred]

I've always been curious as to why so many have issues with probability.

 If you have a system or state where you have more than one possible outcome it's only natural to model all possible outcomes and give the probability of those possible outcomes.

This is true in classical as well as quantum mechanics.

So why is probability in quantum mechanics an issue?

[Lorentz Jr]

4 hours ago, TheVat said:

I thought DeB-B had both particles and pilot waves.  Not my field, so if I'm wrong or not even wrong that's par for me.

Am sorta a fan of DeB-B, due to my apelike gropings over, and cowering from, probabilistic theories.  

DBB is a strange beast. The wave affects the particle, but not vice versa. So you have these unused ghost branches of the pilot wave floating around forever.

Personally, I don't believe particles exist at all in any meaningful ontological sense, so I like objective-collapse interpretations (see my signature, for instance). No data supporting them yet, but I'm glad someone is investigating them.

[Genady]

21 minutes ago, Lorentz Jr said:

particles [don't] exist at all in any meaningful ontological sense

To better understand this statement, or rather to understand it at all, may I ask if the computer in front of me exists in any meaningful ontological sense?

[Lorentz Jr]

36 minutes ago, Genady said:

may I ask if the computer in front of me exists in any meaningful ontological sense?

You know, I've gotten into a lot of arguments about this lately (my thread), because I find the things I've been reading about modern physics so horrifying (19th-century principles of science being displaced by quantum and relativistic ideas that IMO seem more like mysticism).

If you take quantum wave equations seriously as indications of what matter really is, your computer exists as a very complicated wave but not as a collection of particles. According to objective-collapse theories, quantized amounts of the wave keep collapsing repeatedly, creating the illusion of solid matter. The various theories differ in how and why the collapses occur.

So an electron flying through the vacuum is literally a wave packet that spreads out in space, while an electron in a bubble chamber is a wave that keeps getting re-localized by interactions with the fluid in the chamber, and an electron in an atom is an ordinary(-ish) standing wave.

These models seem radical because they reject the classical notion of matter as being made of "particles", which are just very small "objects". But classical ontology isn't a fundamental principle. It's just very familiar. It's an aspect of a specific class of models that are based on intuition developed from macroscopic observations.

Edited January 1, 2023 by Lorentz Jr

[Mordred]

  While I don't particularly bother with attempting to define a fundamental reality, I do support the view of particles being field excitations. At one time this would not have been the case. I used to be an avid supporter of the particle view. That view gradually changed as I studied QFT and various researches into the subject. However even then I recognize that the field excitation isn't fundamental either. In truth I cannot name anything truly fundamental. The thing is wave particle duality does describe what we observe, depending upon examination the point-like or wavelike characteristics will be involved. Sometimes the point-like is better suited other times the wave-like.

 The reason I don't feel fields are fundamental is that a field is simply a set of values under a geometric treatment. This describes all forms of fields, including physical vs mathematical. Many often forget that physical has the meaning of any measurable property as one of its numerous definitions. By that definition any measurable quantity can be described as physically real.  You often see that argument used in the distinction between real vs virtual particles, a real particle must be measurable and hence have a quanta of action.

as far as I can tell that's likely as close to fundamental as will ever be possible. Though we allow for virtual particles many consider them to be more a mathematical convenience than actuality. In QFT they don't typically refer to the term particle but rather a field state so virtual particles are simply field permutations that cannot be localized with well defined boundaries.

 

 

[Genady]

I am familiar with the models. I just wanted to understand what is

1 hour ago, Lorentz Jr said:

any meaningful ontological sense

I still don't know.

Maybe I do... Then my answer to 

 

1 hour ago, Genady said:

if the computer in front of me exists in any meaningful ontological sense?

is, No. This is regardless of waves, particles, strings, whatever.

[Genady]

6 hours ago, Mordred said:

So why is probability in quantum mechanics an issue?

Maybe the issue is not QM but rather probability? Entropy is another statistical concept that causes lots of confusion.

[Mordred]

4 minutes ago, Genady said:

Maybe the issue is not QM but rather probability? Entropy is another statistical concept that causes lots of confusion.

I agree on that at times I see numerous posters on various multimedia preferring no probability or statistics. Unfortunately they take it to such extremes that they refuse any theory that involves probability. May even be as simple as the preference for easy mathematics that are more readily understandable.

[Markus Hanke]

7 hours ago, Lorentz Jr said:

19th-century principles of science being displaced by quantum and relativistic ideas that IMO seem more like mysticism

Well, that happened because those 19th century principles turned out to not work so well - or rather, they only work well under a very specific and limiting set of circumstances. Thus it was necessary to find better descriptions of the world around us.

[Lorentz Jr]

58 minutes ago, Markus Hanke said:

those 19th century principles turned out to not work so well

Maybe. They haven't been quite disproven though. There's a theory of geometric gravity without relativity, and it seems very strange to me that physicists wax philosophical about abandoning cherished misconceptions, while at the same time clinging to the classical ontology of matter as being made of solid entities of one kind or another, in the face of wave-based quantum theories. Like throwing out the baby and keeping the dirty bathwater because we've gotten so used to it.

It's said that truth is stranger than fiction, and modern physics is one of the classic examples of that phenomenon. But I wonder if maybe 20th-century physics is the fiction and the truth is even stranger....

Edited January 2, 2023 by Lorentz Jr

[Markus Hanke]

4 hours ago, Lorentz Jr said:

Maybe. They haven't been quite disproven though.

They remain valid - within their respective domains of applicability (which is why we all learn Newtonian physics in high school). The issue was that these domains turned out to be limited, and if you go beyond them, you need different physics. This is why relativity, QM, and (later) QFT came about.

4 hours ago, Lorentz Jr said:

There's a theory of geometric gravity without relativity,

Alternative theories of gravity are legion, and the author(s) of each and every one of them generally insist that theirs is the only correct one, and solves all of GR’s problems. You need to take such claims with a huge grain of salt. What often happens is that these theories might match the data for one particular phenomenon very well, but then fail to do so for other aspects of gravity; or, which is worse, they flat out contradict some other aspect of known physics or observational data. For example, the model in the link you provided does not seem to be locally Lorentz invariant (AFAICS) in small regions if the extra parameters are anything other than identically zero - which is a huge problem, since local Lorentz invariance has been tested for to extremely high precision, and no preferred coordinate frames have ever been found.

If you compare all the currently known models for gravity against one another, then GR still remains both the simplest model, as well as the only one that matches all available experimental and observational data very well, so far as classical gravity is concerned. Have a look here for quick introduction:

https://en.wikipedia.org/wiki/Alternatives_to_general_relativity

This being said, it is, I think, safe to assume that the domain of applicability of GR is itself also limited. I just think that whatever more general model underlies GR (to which GR will be the classical limit) will involve a paradigm shift far more radical than just adding a couple of extra terms to the gravity Lagrangian; my guess is we’ll be in for a complete overhaul of our understanding of what “space” and “time” mean on a fundamental level. If you feel the shift from Newtonian to relativistic and quantum physics was too radical, then I don’t think you’ll like what I think is coming  

[joigus]

10 hours ago, Lorentz Jr said:

DBB is a strange beast. The wave affects the particle, but not vice versa. So you have these unused ghost branches of the pilot wave floating around forever.

Personally, I don't believe particles exist at all in any meaningful ontological sense, so I like objective-collapse interpretations (see my signature, for instance). No data supporting them yet, but I'm glad someone is investigating them.

DBB is a theory of point particles. It fails at several levels. But IMO we should not disregard the fact that it really offers a natural explanation of why objective collapse works so well for all practical purposes.

As to @Mordred's statement that he's happy with particles corresponding to just excitations in quantum fields, I agree that it's good enough for all practical purposes, including relativistic contexts in which the Born interpretation is not so easy to invoke unambiguously.

I would just keep a bunch of people examining this reasonable possibility, the very same way that people keep working on string theory, supersymmetry, etc, which are very reasonable possibility, although they probably don't work in the way they were formulated. The thing about physical hypotheses is one never knows what hidden assumption could be dropped and give way to a real breakthrough. It's very difficult to be precise about when it's worth spending the effort.

I tend to see these ideas that seem to be characterised by a spectacular --although very partial-- success as definitely worth keeping under scrutiny, and tinkering with a panoply of possibilities to modify them.

x-posted with @Markus Hanke

[Lorentz Jr]

42 minutes ago, Markus Hanke said:

They remain valid - within their respective domains of applicability (which is why we all learn Newtonian physics in high school). The issue was that these domains turned out to be limited, and if you go beyond them, you need different physics. This is why relativity, QM, and (later) QFT came about.

We're talking past each other, Markus. I was referring to fundamental scientific principles and alternatives to modern mainstream theory, not high-school physics.

42 minutes ago, Markus Hanke said:

Alternative theories of gravity are legion, and the author(s) of each and every one of them generally insist that theirs is the only correct one, and solves all of GR’s problems. You need to take such claims with a huge grain of salt.

This is ad hominem, Markus. I take comments by forum posters the same way.

42 minutes ago, Markus Hanke said:

For example, the model in the link you provided does not seem to be locally Lorentz invariant (AFAICS) in small regions if the extra parameters are anything other than identically zero - which is a huge problem, since local Lorentz invariance has been tested for to extremely high precision, and no preferred coordinate frames have ever been found.

Well, I don't know enough about the subject to judge the theory myself, but it's published, so I'm going to give it the benefit of the doubt.

42 minutes ago, Markus Hanke said:

If you compare all the currently known models for gravity against one another, then GR still remains both the simplest model, as well as the only one that matches all available experimental and observational data very well, so far as classical gravity is concerned.

There's also gauge theory gravity (with another article and a Wikipedia article), which, if I'm not mistaken, is virtually identical to GR at all experimentally observed field strengths, and has what seem to me to be the advantages of disallowing exotic sci-fi phenomena like wormholes and time loops.

42 minutes ago, Markus Hanke said:

If you feel the shift from Newtonian to relativistic and quantum physics was too radical, then I don’t think you’ll like what I think is coming  

Considering theories "radical" has nothing to do with my objections, Markus. My suspicion of current quantum theory is based on thinking it may not be radical enough (being formulated in terms of particles, which are derived from classical intuition), and my suspicion of relativity is based on thinking it may be unscientific (I'm not convinced by the "geometry" argument of time dilation in the twin paradox).

But of course no one has found a preferred frame, so I try not to be ideological about the subject. I won't mind any theories that are developed in the future, as long as they don't do unscientific things like making 10⁵⁰⁰ different predictions. 🙄

Edited January 2, 2023 by Lorentz Jr