I What's the best reference for learning about MWI?

[PeroK]

I'd like to learn about the MWI. I know undergraduate level QM (Copenhagen) and can, within reason, cope with a mathematical formulation of it.

What's the best reference for learning the MWI?

Thanks

 

[George Jones]

I'd like to learn about the MWI. I know undergraduate level QM (Copenhagen) and can, within reason, cope with a mathematical formulation of it. What's the best reference for learning the MWI?

The choice of "best reference" for any subject is very subjective!

I do not know much about MWI, but I have just ordered "Foundations of Quantum Mechanics: An Exploration of the Physical Meaning of Quantum Theory" by Travis Norsen. This is more general than what you want, i.e., it has a chapter on MWI, and it also contains chapters on other interpretations: Copenhagen; pilot_wave; spontaneous collapse.

The review
http://www.ijqf.org/wps/wp-content/uploads/2017/12/IJQF2018v4n1p5.pdf

says that Norsen favours pilot-wave. Another review:
http://www.academia.edu/36011436/Review_of_Foundation_of_Quantum_Mechanics_by_Travis_Norsen

Amazon:
https://www.amazon.com/dp/3319658662/?tag=pfamazon01-20

This book does not have an index! Springer seems to encourage this, as this will be my third "blue Springer" that does not have an index. This is unacceptable,

 

[DarMM]

I agree with @George Jones , the chapter in Norsen's book is probably the best reference for learning about MWI.

 

[PeroK]

The choice of "best reference" for any subject is very subjective!

I did not know much about MWI, but I have just ordered "Foundations of Quantum Mechanics: An Exploration of the Physical Meaning of Quantum Theory" by Travis Norsen. This is more general than what you want, i.e., it has a chapter on MWI, and it also contains chapters on other interpretations: Copenhagen; pilot_wave; spontaneous collapse.

The review
http://www.ijqf.org/wps/wp-content/uploads/2017/12/IJQF2018v4n1p5.pdf

says that Norsen favours pilot-wave. Another review:
http://www.academia.edu/36011436/Review_of_Foundation_of_Quantum_Mechanics_by_Travis_Norsen

Amazon:
https://www.amazon.com/dp/3319658662/?tag=pfamazon01-20

This book does not have an index! Springer seems to encourage this, as this will be my third "blue Springer" that does not have an index. This is unacceptable,

Thanks George. Bohmian Mechanics again! In the Alps this summer I was talking to someone who had a PhD in Quantum Magnetism. There had been a thread on PF about Bohmian Mechanics, and I asked him what he thought about it. He'd never heard of it; and felt that since he had done his PhD and never encountered it, it wasn't worth worrying about!

It's interesting to me, especially, as I see randomness and probabilities everywhere. I've never understood the need to have determinism restored to physics and probabilities banished, as I don't see much determinism in nature outside of a few well-controlled experiments and simple cases like the solar system.

I'd be interested to hear what you think about Norsen's book.

The MWI on the other hand, I thought, was the favoured interpretation of many well-respected physicists, like Sean Carroll, so I've been meaning for some time to get a better understanding of it.

 

[atyy]

The MWI on the other hand, I thought, was the favoured interpretation of many well-respected physicists, like Sean Carroll, so I've been meaning for some time to get a better understanding of it.

It is the favoured attempted interpretation. Even advocates like Carroll are not sure that is intellectually coherent. Also, different advocates have different versions of MWI. For this reason there are no standard texts for MWI. There are good discussions in
http://www.preposterousuniverse.com...ion-of-quantum-mechanics-is-probably-correct/
https://arxiv.org/abs/0712.0149
https://www.amazon.com/dp/3527403914/?tag=pfamazon01-20
https://plato.stanford.edu/entries/qm-manyworlds/
https://www.amazon.com/dp/0198707541/?tag=pfamazon01-20

 

[DrChinese]

It's interesting to me, especially, as I see randomness and probabilities everywhere. I've never understood the need to have determinism restored to physics and probabilities banished, as I don't see much determinism in nature outside of a few well-controlled experiments and simple cases like the solar system.

Well said, I couldn't agree more.

And yes, Norsen is a well known Bohmian/dBB/Pilot Wave advocate. In some of his work, that's not relevant. But it certainly is in other of his pieces. His historical viewpoint (especially 1926-1935) is quite different than what is usually presented. I'm not saying its wrong, but it can be a small shock on some items. He's a very bright guy, occasionally comments here too.

Obviously, the reviews of his book are excellent.

 

[akvadrako]

https://www.amazon.com/dp/0198707541/?tag=pfamazon01-20

I would recommend starting with that one, Emergent Multiverse: Quantum Theory According to the Everett Interpretation by David Wallace. He's a prominent advocate and researcher of many worlds. If you want to understand why others find the theory appealing, better to get it from the horse's mouth.

 

[zonde]

It's interesting to me, especially, as I see randomness and probabilities everywhere. I've never understood the need to have determinism restored to physics and probabilities banished, as I don't see much determinism in nature outside of a few well-controlled experiments and simple cases like the solar system.

Sorry, but are you still talking about Bohmian Mechanics here or do you mean it as criticism of MWI ... or both?

 

[zonde]

Determinism of MWI as I see it.
We have a string of numbers: 52, 30, 2, -1, -24 ,-77, -98, 82, 28, 69, -23, -89, 18, -50, -26, 85
We say it's random, as we can't see any system behind these numbers.
But let's imagine there is another string of numbers: -52, -30, -2, 1, 24 ,77, 98, -82, -28, -69, 23, 89, -18, 50, 26, -85
We pairwise add numbers from both strings at respective positions and we get perfectly predictable string: 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Have we explained randomness of the first string? No. But we can entertain ourselves with another perfectly predictable string.

In MWI we can't explain random outcomes of measurement events we experience, but wavefunction is deterministic. Isn't it neat?

 

[PeroK]

Sorry, but are you still talking about Bohmian Mechanics here or do you mean it as criticism of MWI ... or both?

It's not a criticism. It's just that probabilities seem to chime with some of us and upset, or even offend, others. If someone has an aversion to probabilities, then I can understand why they get interested in a theory that provides a deterministic underpinning of QM. But, it doesn't interest me so much, because it doesn't trouble me that probability is at the heart of QM.

 

[Demystifier]

I agree with @George Jones , the chapter in Norsen's book is probably the best reference for learning about MWI.

People who actually believe in MWI would probably disagree. But for me, MWI also clicked when I have seen an explanation by a Bohmian. It was the explanation of MWI in the book D. Bohm, The Undivided Universe.

As an explanation by an actual believer in MWI, I like Tegmark's https://arxiv.org/abs/quant-ph/9709032

 

[akvadrako]

It's not a criticism. It's just that probabilities seem to chime with some of us and upset, or even offend, others. If someone has an aversion to probabilities, then I can understand why they get interested in a theory that provides a deterministic underpinning of QM. But, it doesn't interest me so much, because it doesn't trouble me that probability is at the heart of QM.

It doesn't really follow that a theory would be uninteresting just because one of the problems it "solves" is a non-problem.

 

[Demystifier]

It's not a criticism. It's just that probabilities seem to chime with some of us and upset, or even offend, others. If someone has an aversion to probabilities, then I can understand why they get interested in a theory that provides a deterministic underpinning of QM. But, it doesn't interest me so much, because it doesn't trouble me that probability is at the heart of QM.

Contrary to a wide misconception, the main motivation for Bohmian mechanics is not determinism. The main motivation is clear microscopic ontology. The determinism is a byproduct.

 

[PeroK]

Contrary to a wide misconception, the main motivation for Bohmian mechanics is not determinism. The main motivation is clear microscopic ontology.

Even worse!

 

[Demystifier]

Even worse!

Why?

 

[PeroK]

Why?

Just another failed attempt at ironic humour!

 

[DarMM]

I would recommend starting with that one, Emergent Multiverse: Quantum Theory According to the Everett Interpretation by David Wallace. He's a prominent advocate and researcher of many worlds. If you want to understand why others find the theory appealing, better to get it from the horse's mouth.

You're probably right, most recommend this text, but I personally found Wallace's book a bit hard to follow, mixing Wallace's personal philosophy of physics with formal (in the sense of non-rigorous) mathematics and various proposals for how MWI might be brought into a fully coherent interpretation.

I personally think it's better to read Norsen's book first and maybe then read Wallace.

For an actual overview of Wallace's work on the Born rule, there is a philosopher Florian Boge whose
Bachelor thesis (On Probabilities in the Many Worlds Interpretation of Quantum Mechanics) has a better summary. The section in his recent book "Quantum Mechanics Between Ontology and Epistemology" has an even shorter summary.

It's not a criticism. It's just that probabilities seem to chime with some of us and upset, or even offend, others. If someone has an aversion to probabilities, then I can understand why they get interested in a theory that provides a deterministic underpinning of QM. But, it doesn't interest me so much, because it doesn't trouble me that probability is at the heart of QM.

I'd bear in mind that the main thing hard to understand about QM is the non-classical correlations. Even a fundamentally stochastic but local world, where the probabilities are the typical ones with the state drawn from a sample space (i.e. Kolmogorov probability), wouldn't have entanglement.

 

[A. Neumaier]

probabilities seem to chime with some of us and upset, or even offend, others. If someone has an aversion to probabilities, then I can understand why they get interested in a theory that provides a deterministic underpinning of QM.

The problem with probability is that the notion is not really well-defined outside a deterministic pre-context.