Stupid Questions Open Thread Round 3

OpenThreadGuy

From Costanza's original thread (entire text):

"This is for anyone in the LessWrong community who has made at least some effort to read the sequences and follow along, but is still confused on some point, and is perhaps feeling a bit embarrassed. Here, newbies and not-so-newbies are free to ask very basic but still relevant questions with the understanding that the answers are probably somewhere in the sequences. Similarly, LessWrong tends to presume a rather high threshold for understanding science and technology. Relevant questions in those areas are welcome as well. Anyone who chooses to respond should respectfully guide the questioner to a helpful resource, and questioners should be appropriately grateful. Good faith should be presumed on both sides, unless and until it is shown to be absent. If a questioner is not sure whether a question is relevant, ask it, and also ask if it's relevant."

Meta:

How often should these be made? I think one every three months is the correct frequency.

Costanza made the original thread, but I am OpenThreadGuy. I am therefore not only entitled but required to post this in his stead. But I got his permission anyway.

Meta:

I still haven't figured out a satisfactory answer to the previous meta question, how often these should be made. It was requested that I make a new one, so I did.
I promise I won't quote the entire previous threads from now on. Blockquoting in articles only goes one level deep, anyway.

From the last thread:

From Costanza's original thread (entire text):

"This is for anyone in the LessWrong community who has made at least some effort to read the sequences and follow along, but is still confused on some point, and is perhaps feeling a bit embarrassed. Here, newbies and not-so-newbies are free to ask very basic but still relevant questions with the understanding that the answers are probably somewhere in the sequences. Similarly, LessWrong tends to presume a rather high threshold for understanding science and technology. Relevant questions in those areas are welcome as well. Anyone who chooses to respond should respectfully guide the questioner to a helpful resource, and questioners should be appropriately grateful. Good faith should be presumed on both sides, unless and until it is shown to be absent. If a questioner is not sure whether a question is relevant, ask it, and also ask if it's relevant."

Meta:

How often should these be made? I think one every three months is the correct frequency.

Costanza made the original thread, but I am OpenThreadGuy. I am therefore not only entitled but required to post this in his stead. But I got his permission anyway.

Meta:

I still haven't figured out a satisfactory answer to the previous meta question, how often these should be made. It was requested that I make a new one, so I did.
I promise I won't quote the entire previous threads from now on. Blockquoting in articles only goes one level deep, anyway.

Quantum field theory (QFT) is closer to the truth, but there are a number of barriers to a straightforward importation of MWI into the language of QFT

This is important if true, and I would like to know more. What are the barriers?

I'm reasonably confident that an MWI-like interpretation of QFT can be constructed, but it does not exist in any rigorous form as of yet

On the other hand, my understanding is that QFT itself doesn't exist in a rigorous form yet, either.

On the other hand, my understanding is that QFT itself doesn't exist in a rigorous form yet, either.

Depends on what you mean by rigorous. (OTOH, it's not fully compatible with general relativity, so we know it doesn't exactly describe the world -- or that GR doesn't, or that neither does.)

14pragmatist14y

This article (PDF) gives a nice (and fairly accessible) summary of some of the issues involved in extending MWI to QFT. See sections 4 and 8 in particular. Their focus in the paper is wavefunction realism, but given that MWI (at least the version advocated in the Sequences) is committed to wavefunction realism, their arguments apply. They offer a suggestion of the kind of theory that they think can replace MWI in the relativistic context, but the view is insufficiently developed (at least in that paper) for me to fully evaluate it. A quick summary of the issues raised in the paper: * In NRQM, the wave function lives in configuration space, but there is no well-defined particle configuration space in QFT since particle number is not conserved and particles are emergent entities without precisely defined physical properties. * A move to field configuration space is unsatisfactory because quantum field theories admit of equivalent description using many different choices of field observable. Unlike NRQM, where there are solid dynamical reasons for choosing the position basis as fundamental, there seems to be no natural or dynamically preferred choice in QFT, so a choice of a particular field configuration space description would amount to ad hoc privileging. * MWI in NRQM treats physical space as non-fundamental. This is hard to justify in QFT, because physical space-time is bound up with the fundamentals of the theory to a much greater degree. The dynamical variables in QFT are operators that are explicitly associated with space-time regions. * This objection is particularly clever and interesting, I think. In MWI, the history of the universe is fully specified by giving the universal wavefunction at each time in some reference frame. In a relativistic context, one would expect that all one needs to do in order to describe how the universe looks in some other inertial reference frame is to perform a Lorentz transformation on this history. If the history reall

0Douglas_Knight14y

If you bug physicists enough, they will admit that the standard model has some problems, like the Landau pole. However, there are toy QFTs in 2 spacial dimension that have models rigorous enough for mathematicians. That should be adequate for philosophical purposes.

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Stupid Questions Open Thread Round 3

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Stupid Questions Open Thread Round 3

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