Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Not even wrong: Why does nobody like pilot-wave theory? [pdf]

tcm.phy.cam.ac.uk

Post reply on HN
Print view View original

41–50 of 80 posts

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#41

Post by jamesrcole »

hasenj wrote: post #16
quickben wrote: post #15

Earlier quoted context omitted.

You have to consider his concept as an analogy. Infinity is a thing inside this universe, it may not be outside .

The problem is not with infinity per se. If the universe gets cloned one time every second that would still be a huge claim. A million times every nanosecond is even a bigger claim. Now imagine how many states the universe can be in, and how many times a second can be meaningfully divided. If you can solve the "one clone every second" then I would be satisfied.

Note that you're assuming that a nanosecond is a tiny amount of time. It's tiny relative to what we're used to, but as far as what "implements the universe" goes, a nanosecond could be enough time for a huge amount of occurrences to happen within. We don't know.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#42

Post by millstone »

AgentME wrote: post #23

My understanding of QM is only surface-level, so there may be subtleties I'm missing, but this presentation's arguments against the many-worlds interpretation seem pretty weak. Page 28 grudgingly alludes to the idea that MWI could be simpler than other theories ("Objection based on surprisingly common misconception that standard QM defined solely by Schrödinger's equation ... It is only within a many-worlds framework…

The "nonsense news headline" and followup discussion are less critiquing MWI than poking fun at David Deutsch. This is because Deutsch is a prominent critic of PWT.

The arguments against MWI from Occam's Razor are indeed weak. The stronger critiques are the difficulty of deriving the Born rule, or indeed quantum randomness at all, from the deterministic MWI. This is presumably what the authors hint at in their "doubtful it [pure Hamiltonian evolution] makes sense even there (in MWI)".

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#43

Post by hasenj »

jamesrcole wrote: post #41
hasenj wrote: post #16

Earlier quoted context omitted.

The problem is not with infinity per se. If the universe gets cloned one time every second that would still be a huge claim. A million times every nanosecond is even a bigger claim. Now imagine how many states the universe can be in, and how many times a second can be meaningfully divided. If you can solve the "one clone every second" then I would be satisfied.

Note that you're assuming that a nanosecond is a tiny amount of time. It's tiny relative to what we're used to, but as far as what "implements the universe" goes, a nanosecond could be enough time for a huge amount of occurrences to happen within. We don't know.

I did not assume nor imply it's tiny in any "absolute" sense.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#44

Post by jamesrcole »

justinpombrio wrote: post #33
Xcelerate wrote: post #26

Earlier quoted context omitted.

> if you make some reasonable assumptions Not everyone agrees on what is "reasonable". I have no problem giving up locality, but "true" randomness (i.e., information generated without an algorithm) seems like a philosophical cop out. Note that something can also be globally deterministic but indeterministic from the perspective of a subsystem. In this sense, the universe would appear random as far as we're concerned,…

The probability of an event depends on your knowledge. Whether something is deterministic is a question of probability. Hence whether something is deterministic can depend on your knowledge. If the universe is deterministic to its simulator but random to us, I would call it random. Besides this difference in terminology, I think we agree.

Your knowledge of something can't change or determine whether it is deterministic or not.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#45

Post by jamesrcole »

hasenj wrote: post #43
jamesrcole wrote: post #41

Earlier quoted context omitted.

Note that you're assuming that a nanosecond is a tiny amount of time. It's tiny relative to what we're used to, but as far as what "implements the universe" goes, a nanosecond could be enough time for a huge amount of occurrences to happen within. We don't know.

I did not assume nor imply it's tiny in any "absolute" sense.

Then why is "every second" a "huge claim" and "every nanosecond" "even a bigger claim"?

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#46

Post by justinpombrio »

jamesrcole wrote: post #44
justinpombrio wrote: post #33

Earlier quoted context omitted.

The probability of an event depends on your knowledge. Whether something is deterministic is a question of probability. Hence whether something is deterministic can depend on your knowledge. If the universe is deterministic to its simulator but random to us, I would call it random. Besides this difference in terminology, I think we agree.

Your knowledge of something can't change or determine whether it is deterministic or not.

Do you agree that the probability of an event depends on your knowledge? For example, what is the probability that the bottom card of a shuffled deck is an ace? Peek at the top card, it's an ace of spades, now what is the probability?

Would you agree that something is determined iff its probability is zero or one? I'm guessing the disagreement is here - what definition would you use?

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#47

Post by AgentME »

millstone wrote: post #42
AgentME wrote: post #23

My understanding of QM is only surface-level, so there may be subtleties I'm missing, but this presentation's arguments against the many-worlds interpretation seem pretty weak. Page 28 grudgingly alludes to the idea that MWI could be simpler than other theories ("Objection based on surprisingly common misconception that standard QM defined solely by Schrödinger's equation ... It is only within a many-worlds framework…

The "nonsense news headline" and followup discussion are less critiquing MWI than poking fun at David Deutsch. This is because Deutsch is a prominent critic of PWT. The arguments against MWI from Occam's Razor are indeed weak. The stronger critiques are the difficulty of deriving the Born rule, or indeed quantum randomness at all, from the deterministic MWI. This is presumably what the authors hint at in their "doubt…

Why do you say that quantum randomness is a problem in MWI? I thought it was one of the neat things of MWI that it doesn't require randomness. There are no random events: instead you have a branch for each outcome. The only randomness is which branch you find yourself in as an individual.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#48

Post by cool_shit »

justinpombrio wrote: post #46
jamesrcole wrote: post #44

Earlier quoted context omitted.

Your knowledge of something can't change or determine whether it is deterministic or not.

Do you agree that the probability of an event depends on your knowledge? For example, what is the probability that the bottom card of a shuffled deck is an ace? Peek at the top card, it's an ace of spades, now what is the probability? Would you agree that something is determined iff its probability is zero or one? I'm guessing the disagreement is here - what definition would you use?

You are right, according to quantum mechanics. If you have a pair of electrons in a product state and measure the spin of one of them, you instantly know what the "other particle's" spin is going to be (if you knew what the initial state was). When you "peek at a card", you "make a measurement" and alter the system.

For anything that exists outside of a light-cone around the first electron, a measurement of the second electron will be truly random from the measurer's perspective.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#49

Post by jamesrcole »

justinpombrio wrote: post #46
jamesrcole wrote: post #44

Earlier quoted context omitted.

Your knowledge of something can't change or determine whether it is deterministic or not.

Do you agree that the probability of an event depends on your knowledge? For example, what is the probability that the bottom card of a shuffled deck is an ace? Peek at the top card, it's an ace of spades, now what is the probability? Would you agree that something is determined iff its probability is zero or one? I'm guessing the disagreement is here - what definition would you use?

There's two kinds of probability in question.

One concerns a lack of knowledge, like in your cards example. In that case, the probability is an expression of your state of understanding of the deck, and is not a property of the deck itself. The physical details of the deck and the situation it is part of could be entirely deterministic and we could still talk about this kind of probability. In this case your knowledge is independent of whether it is probabalistic or not.

The other is whether the universe contains fundamental randomness, such that you could say it is literally "probabalistic". And in this case whether that is true or not is independent of our knowledge of the probabilities.

Re: Not even wrong: Why does nobody like pilot-wave theory? [pdf]

#50

Post by justinpombrio »

jamesrcole wrote: post #49
justinpombrio wrote: post #46

Earlier quoted context omitted.

Do you agree that the probability of an event depends on your knowledge? For example, what is the probability that the bottom card of a shuffled deck is an ace? Peek at the top card, it's an ace of spades, now what is the probability? Would you agree that something is determined iff its probability is zero or one? I'm guessing the disagreement is here - what definition would you use?

There's two kinds of probability in question. One concerns a lack of knowledge, like in your cards example. In that case, the probability is an expression of your state of understanding of the deck, and is not a property of the deck itself. The physical details of the deck and the situation it is part of could be entirely deterministic and we could still talk about this kind of probability. In this case your knowledg…

There's a third kind -- indexical randomness, or not knowing who you will be -- that appears in many-worlds. Many worlds is in some sense completely deterministic. Yet with indexical uncertainty you still cannot possibly ever know which way you will see a photon go in a half-silvered mirror. Is that fundamental randomness or not?

http://lesswrong.com/lw/jlb/logical_and_indexical_uncertaint...

Post reply on HN