It actually involves even fewer assumptions than the MWI because it rejects the commonly accepted postulate in Step 3 above.
I don’t see why we need any of the three. MWI assumes only wavefunction. PBR assumes perspective, actions, indeterminism and still wavefuntion, that describes behavior of actions.
PBR assumes perspective, actions, indeterminism and still wavefuntion
That’s a list of nouns rather than of ontological posits. Indeterminism is arguable a non-unicorn, an absence of something. Perspectives are hard to dispute, since we’ve all got one. Wave functions are explicitly regarded as a kind of map, rather than something out there.
I assumed at least laws themselves don’t change in PBR so we still need some things to be deterministic in addition to indeterministic things. Not sure if it requeries additional ontology, but still seems to result in more complex theory?
Perspectives in MWI can be derived.
I guess “actions behaving according to wavefuntion” in PBR do replace “wavefunction”, but would’t then laws of behavior became more complex to include that translation from wavefunction to actions?
The results of the laws are indeterministic, but laws themselves are kinda not—you always get the same probabilities. So I figured you would need additional complexity to distinguish between deterministic and indeterministic parts of description of the universe.
Forgive my ignorance, but why do we need projection postulate in MWI?
Forgive my ignorance, but why do we need projection postulate in MWI
Because if this you are trying to calculate the probabilities of future events, you need to treat anything you have already observed as probability 1 .or equivalently , discard anything unobserved.
It sounds useful but I don’t see any reason to include the way I treat anything into ontology. That wavefunction is nearly zero in all regions where Born statistics fails is just consequence, not postulate. Similarly you can derive that following Bayes rule will result in largest amount of spicemeasure for states where you know something. Whether you want this or not is purely ethical question and ethics today is as arbitrary as it was yesterday. You might as well only track uncertainty about wavefunction and not specific decoherence-path and decide to minimize worst ignorance or something.
You would need a postulate only if you want there to be some fundamental point-knowledge but there are no point-states in reality—everything is just amplitudes.
It sounds useful but I don’t see any reason to include the way I treat anything into ontology.
I didn’t say it had anything to do with ontology, and in MWI it doesn’t . In MWI , you disregard results from other branches that you haven’t observed in order to predict future probabilities correctly , but you don’t regard them as non existent.
The results of the laws are indeterministic, but laws themselves are kinda not—you always get the same probabilities. So I figured you would need additional complexity to distinguish between deterministic and indeterministic parts of description of the universe
Under subjective interpretations like rQM, there arent deterministic and indeteministic parts of the universe. You can use Schrödinger’s equation to model a part of the universe , and that will work until it stops being isolated—until it interacts with something not in the model. All models are ultimately indeteministic because they are always based on incomplete information. And the process by which this becomes apparent, by which the limited model is invalidated, isn’t anything special .
Observer 01 can model system A just fine until it interacts with system B, which they don’t know anything about. If observer O2 is more knowledgeable , they might be able to model the AB interaction using the SWE.
MWI suggests wavefuntion describes the objective world or wavefuntion is the objective world. That in itself assumes objectivity is perspective-independent. I.e. we can think about reality with a “view from nowhere”. I am arguing that is an assumption, that epistemically speaking, perspectives and actions are more fundamental than reality as an absolute conception.
Right, I confused epistemic assumptions with ontological assumptions. But does minimizing epistemic assumptions even makes sense? I mean we don’t start with PBR anyway—we start with what happened to be in our brains. So what’s the point then in selecting description of the universe that is epistemically nearest to our starting state as opposed to the least complex one? I guess it would be interesting if we actually could reach PBR QM without ever invoking complexity minimization...
I definitely see the value of choosing the least complex theory or Occam’s Razor. The problem is that it works really well in hindsight. But before the debate is settled it is hard to measure which theory is the simpler one.
The appeal of MWI is that it gives a very coherent explanation of quantum phenomenons (maybe not Born rule) without assuming anything extra. There is no additional collapse, there are no extra hidden variables. The existence of parallel worlds that many people find uncomfortable is not its assumption but the result of vigorous logical deductions. I would be lying by saying I don’t see the simplicity and beauty of it. However, I just want to point out MWI does need to assume perspective-independent objectivity. Which CI could (and I think should) go without. If Thomas Nagel’s steps are valid, then it can be argued that CI is less complex. But again, complexity is hard to compare, I have no problem if others find MWI simpler.
I also think we do start with perspective-based reasoning. Even thinking about what happens within my brain requires “a view from nowhere” (assuming perspective-independent reality, step 3), or an outsider’s perspective (step 2).
The existence of parallel worlds that many people find uncomfortable is not its assumption but the result of vigorous logical deductions
The existence of decoherent worlds is pretty hard to deduce from the SWE alone -- one pure state evolves into another. And a pure state doesn’t decompose into a set of objective worlds without a preferred basis .
I don’t see why we need any of the three. MWI assumes only wavefunction. PBR assumes perspective, actions, indeterminism and still wavefuntion, that describes behavior of actions.
That’s a list of nouns rather than of ontological posits. Indeterminism is arguable a non-unicorn, an absence of something. Perspectives are hard to dispute, since we’ve all got one. Wave functions are explicitly regarded as a kind of map, rather than something out there.
I assumed at least laws themselves don’t change in PBR so we still need some things to be deterministic in addition to indeterministic things. Not sure if it requeries additional ontology, but still seems to result in more complex theory?
Perspectives in MWI can be derived.
I guess “actions behaving according to wavefuntion” in PBR do replace “wavefunction”, but would’t then laws of behavior became more complex to include that translation from wavefunction to actions?
I dont see what you mean. What are the deterministic quantum laws?
That would just be the projection postulate that everything else uses .
The results of the laws are indeterministic, but laws themselves are kinda not—you always get the same probabilities. So I figured you would need additional complexity to distinguish between deterministic and indeterministic parts of description of the universe.
Forgive my ignorance, but why do we need projection postulate in MWI?
Because if this you are trying to calculate the probabilities of future events, you need to treat anything you have already observed as probability 1 .or equivalently , discard anything unobserved.
It sounds useful but I don’t see any reason to include the way I treat anything into ontology. That wavefunction is nearly zero in all regions where Born statistics fails is just consequence, not postulate. Similarly you can derive that following Bayes rule will result in largest amount of
spicemeasure for states where you know something. Whether you want this or not is purely ethical question and ethics today is as arbitrary as it was yesterday. You might as well only track uncertainty about wavefunction and not specific decoherence-path and decide to minimize worst ignorance or something.You would need a postulate only if you want there to be some fundamental point-knowledge but there are no point-states in reality—everything is just amplitudes.
I didn’t say it had anything to do with ontology, and in MWI it doesn’t . In MWI , you disregard results from other branches that you haven’t observed in order to predict future probabilities correctly , but you don’t regard them as non existent.
Under subjective interpretations like rQM, there arent deterministic and indeteministic parts of the universe. You can use Schrödinger’s equation to model a part of the universe , and that will work until it stops being isolated—until it interacts with something not in the model. All models are ultimately indeteministic because they are always based on incomplete information. And the process by which this becomes apparent, by which the limited model is invalidated, isn’t anything special .
Observer 01 can model system A just fine until it interacts with system B, which they don’t know anything about. If observer O2 is more knowledgeable , they might be able to model the AB interaction using the SWE.
MWI suggests wavefuntion describes the objective world or wavefuntion is the objective world. That in itself assumes objectivity is perspective-independent. I.e. we can think about reality with a “view from nowhere”. I am arguing that is an assumption, that epistemically speaking, perspectives and actions are more fundamental than reality as an absolute conception.
Right, I confused epistemic assumptions with ontological assumptions. But does minimizing epistemic assumptions even makes sense? I mean we don’t start with PBR anyway—we start with what happened to be in our brains. So what’s the point then in selecting description of the universe that is epistemically nearest to our starting state as opposed to the least complex one? I guess it would be interesting if we actually could reach PBR QM without ever invoking complexity minimization...
I definitely see the value of choosing the least complex theory or Occam’s Razor. The problem is that it works really well in hindsight. But before the debate is settled it is hard to measure which theory is the simpler one.
The appeal of MWI is that it gives a very coherent explanation of quantum phenomenons (maybe not Born rule) without assuming anything extra. There is no additional collapse, there are no extra hidden variables. The existence of parallel worlds that many people find uncomfortable is not its assumption but the result of vigorous logical deductions. I would be lying by saying I don’t see the simplicity and beauty of it. However, I just want to point out MWI does need to assume perspective-independent objectivity. Which CI could (and I think should) go without. If Thomas Nagel’s steps are valid, then it can be argued that CI is less complex. But again, complexity is hard to compare, I have no problem if others find MWI simpler.
I also think we do start with perspective-based reasoning. Even thinking about what happens within my brain requires “a view from nowhere” (assuming perspective-independent reality, step 3), or an outsider’s perspective (step 2).
The existence of decoherent worlds is pretty hard to deduce from the SWE alone -- one pure state evolves into another. And a pure state doesn’t decompose into a set of objective worlds without a preferred basis .
I think you are right. Preferred basis is another problem.