According to the TI, offer waves are sent forward in time from particle sources to absorbers. Each absorber responds by sending a confirmation wave backwards in time to the source. One of these transactions is selected with a probability given by the amplitude of the confirmation wave.
If I’m understanding this correctly, this implies that TI needs a “transaction eater” analogous to the “world eater” in the Collapse theory. This seems to be a liability of TI that isn’t matched by any liability of MWI.
But I’d never heard of TI before this post, so I could easily be missing something.
If I’m understanding this correctly, this implies that TI needs a “transaction eater” analogous to the “world eater” in the Collapse theory. This seems to be a liability of TI that isn’t matched by any liability of MWI.
Yeah, it does require something like that. Proponents of the TI claim that ultimately every interpretation that actually accounts for the success of the Born rule will have to include some such component, and so MWI advocates are deluding themselves if they think they can avoid it.
There is a version of the TI (called the possibilist TI), where transactions aren’t actually “eaten”, in the sense that all possible transaction really occur in some possible world (and these possible worlds are real, they exist). But only one of these transaction occurs in the actual world. As for how to make sense of this, your guess is as good as mine.
As for accounting for the Born Rule - if the wavefunction is real, then any minds it implements, in any way, will have associated subjective experience. Among the minds implemented by the wavefunction are ours, and ours happen to be those that are associated to the wavefunction by applying the Born Rule.
It’s not, as far as I can tell. Proponents of the TI (and the PTI) explicitly say that one advantage of their interpretation over the MWI is that it is a one-world theory, because only one world is actualized. Spacetime is treated as fundamental, rather than emergent (as it would be in non-relativistic MWI, at least). I think there are aspects of MWI and TI that are vaguely specified enough that it might end up being the case that one can be translated into the other, but I don’t think this is obvious.
As for accounting for the Born Rule—if the wavefunction is real, then any minds it implements, in any way, will have associated subjective experience. Among the minds implemented by the wavefunction are ours, and ours happen to be those that are associated to the wavefunction by applying the Born Rule.
This approach seems inadequate. Part of our evidence for the truth of QM is that we get experimental results in line with the Born rule. In order for this to actually count as evidence, we need to show that QM is the sort of theory that should lead us to expect these relative frequencies. Simply saying, “Well, in MWI observers will see all sorts of different frequencies in experimental results, including Born-rule compliant ones” doesn’t tell us why observers should expect to see Born-rule compliant frequencies in a QM-governed world. And if you don’t have a story about that, then I don’t see how you can claim that the observed frequencies confirm QM (and by extension MWI).
Proponents of the TI (and the PTI) explicitly say that one advantage of their interpretation over the MWI is that it is a one-world theory
Even the PTI? With the given description, that’s really really weird.
Simply saying, “Well, in MWI observers will see all sorts of different frequencies in experimental results, including Born-rule compliant ones” doesn’t tell us why observers should expect to see Born-rule compliant frequencies in a QM-governed world.
Not ALL sorts of frequencies. Many—most—ways of looking at the wavefunction won’t reveal causal structures isomorphic to observers. For instance, you can consider the wavefunction in the energy basis and interpret it as an infinite number of wheels of various sizes, spinning at different constant speeds. No observers are apparent when viewed this way.
I suspect that the Born Rule is the only rule that leads to observers, but we don’t need to prove that it’s the only one, and I’m open to the possibility that there are others. GAZP again—if it’s in there, it’s in there, whether or not you’re aware of it.
And if you don’t have a story about that, then I don’t see how you can claim that the observed frequencies confirm QM (and by extension MWI).
I think you’ll agree that the observed frequencies confirm the conjunction of Schrodinger’s Equation with the Born Rule. The question at hand is whether the Born Rule needs to be a rule of the universe. Whether collapse is ontologically real or based solely on our parochial viewpoint as observers.
Suppose it is real. That’s nice. We get everything we see.
Suppose it isn’t, and collapse isn’t a real thing. The wavefunction is just doing its thing, and that’s all there is. The causal structures in the wavefunction that correspond to people are still there.
The way of looking at us that brings us into focus is the Born Rule. Removing the Born Rule is just like removing a P-zombie’s consciousness. It’s that switch you flip to grant or remove subjective experience from a computation that implements consciousness.
Even the PTI? With the given description, that’s really really weird.
Weird, but true! See the discussion of PTI in the paper I link to in this comment. As far as I can tell, PTI is just a relabeling of the original TI. Where TI would have said only one branch is real and the other branches do not exist, PTI says only one branch is actual and the others are real but not actual. Our universe consists only of that which is actual, so the other branches are not part of our universe. They exist in other possible universes, which (and this is the innovation, I take it) happen to be real. I don’t see how merely renaming the selection procedure from “collapse” to “actualization” helps, but I will admit to not having read that much about the PTI.
I’m reminded of David Lewis’s response to Armstrong’s theory of laws of nature. According to Armstrong, two properties are associated in a law-like manner if and only if there is a specific second-order relation that holds between them. Armstrong labels this relation the “necessitation relation” and claims to have thereby accounted for the ineluctable character of the laws. Lewis responds: “I say that [Armstrong’s ‘necessitation relation’] deserves the name of ‘necessitation’ only if, somehow, it really can enter into the requisite necessary connections. It can’t enter into them just by bearing a name, any more than one can have mighty biceps just by being called ‘Armstrong.’”
I think you’ll agree that the observed frequencies confirm the conjunction of Schrodinger’s Equation with the Born Rule.
This is actually a tricky claim to adjudicate from the perspective of MWI. It’s certainly true that the relative frequencies of experimental results in our world support the Born rule. But why should the reference class be restricted to our world? For someone who has seriously absorbed MWI, this is akin to declaring that you only care about the frequencies of experimental results in North America. If you include all experimental results in your reference class, including those from other worlds, it is no longer the case that they confirm the Born rule unless you already assign weights to worlds based on the Born rule. But of course, assigning weights to worlds in this way would be question-begging if you were trying to provide evidence for the Born rule itself.
To put it another way, as a proponent of the MWI you believe that there are real scientists out there, in other branches of the wave function, who perform their experiments with just as much care and diligence as you do and who end up with wholly different observed frequencies within their world. What makes you think you have the right frequencies and they don’t?
But of course, assigning weights to worlds in this way would be question-begging if you were trying to provide evidence for the Born rule itself.
You have completely missed my point. It’s the difference between, on the one hand: proving that there is life on Earth, and on the other proving that if there is life in the universe, it must be on Earth.
Where TI would have said only one branch is real and the other branches do not exist, PTI says only one branch is actual and the others are real but not actual.
actual = the branch we’re observing.
real = part of the wavefunction of the universe.
I maintain my position that it’s the same thing as MWI.
To put it another way, as a proponent of the MWI you believe that there are real scientists out there, in other branches of the wave function, who perform their experiments with just as much care and diligence as you do and who end up with wholly different observed frequencies within their world. What makes you think you have the right frequencies and they don’t?
Please clarify the question. Do you identify these scientists using the Born Rule to interpret the wavefunction so as to provide the basis for their consciousness, and making them just really unlucky in the outcomes? Because in that case, for every one of them, there are sixty gazillion jillion squillion ridiculillion others that get the same frequencies we get. This is very unlucky for them. Prospectively, we could expect their frequencies to fall in line immediately (and of course we can also expect that a vanishingly small measure of them will continue to fail to do so).
OR, are you finding these scientists out there in the wavefunction without using the Born Rule to interpret the wavefunction when identifying their consciousness, but using some other rule instead? If so, then the Born Rule isn’t right for them.
Suppose it isn’t, and collapse isn’t a real thing. The wavefunction is just doing its thing, and that’s all there is. The causal structures in the wavefunction that correspond to people are still there.
Following that logic why not go even further and remove Schrodinger’s Equation? All possible observer moments exist, we just happen to be observers whose history happens to correspond to the conjunction of Schrodinger’s Equation with the Born Rule.
That notion doesn’t bother me in the least, but if we’re talking about the physics that happen for us, it’s the Schrodinger Equation, and the Born Rule is the ‘angle’ to take on finding us in it. Anything else isn’t us, and we can’t do experiments on it, so we ought to avoid making strong claims.
If I’m understanding this correctly, this implies that TI needs a “transaction eater” analogous to the “world eater” in the Collapse theory. This seems to be a liability of TI that isn’t matched by any liability of MWI.
But I’d never heard of TI before this post, so I could easily be missing something.
Yeah, it does require something like that. Proponents of the TI claim that ultimately every interpretation that actually accounts for the success of the Born rule will have to include some such component, and so MWI advocates are deluding themselves if they think they can avoid it.
There is a version of the TI (called the possibilist TI), where transactions aren’t actually “eaten”, in the sense that all possible transaction really occur in some possible world (and these possible worlds are real, they exist). But only one of these transaction occurs in the actual world. As for how to make sense of this, your guess is as good as mine.
That sounds like it’s simply MWI all over again.
As for accounting for the Born Rule - if the wavefunction is real, then any minds it implements, in any way, will have associated subjective experience. Among the minds implemented by the wavefunction are ours, and ours happen to be those that are associated to the wavefunction by applying the Born Rule.
It’s not, as far as I can tell. Proponents of the TI (and the PTI) explicitly say that one advantage of their interpretation over the MWI is that it is a one-world theory, because only one world is actualized. Spacetime is treated as fundamental, rather than emergent (as it would be in non-relativistic MWI, at least). I think there are aspects of MWI and TI that are vaguely specified enough that it might end up being the case that one can be translated into the other, but I don’t think this is obvious.
This approach seems inadequate. Part of our evidence for the truth of QM is that we get experimental results in line with the Born rule. In order for this to actually count as evidence, we need to show that QM is the sort of theory that should lead us to expect these relative frequencies. Simply saying, “Well, in MWI observers will see all sorts of different frequencies in experimental results, including Born-rule compliant ones” doesn’t tell us why observers should expect to see Born-rule compliant frequencies in a QM-governed world. And if you don’t have a story about that, then I don’t see how you can claim that the observed frequencies confirm QM (and by extension MWI).
Even the PTI? With the given description, that’s really really weird.
Not ALL sorts of frequencies. Many—most—ways of looking at the wavefunction won’t reveal causal structures isomorphic to observers. For instance, you can consider the wavefunction in the energy basis and interpret it as an infinite number of wheels of various sizes, spinning at different constant speeds. No observers are apparent when viewed this way.
I suspect that the Born Rule is the only rule that leads to observers, but we don’t need to prove that it’s the only one, and I’m open to the possibility that there are others. GAZP again—if it’s in there, it’s in there, whether or not you’re aware of it.
I think you’ll agree that the observed frequencies confirm the conjunction of Schrodinger’s Equation with the Born Rule. The question at hand is whether the Born Rule needs to be a rule of the universe. Whether collapse is ontologically real or based solely on our parochial viewpoint as observers.
Suppose it is real. That’s nice. We get everything we see.
Suppose it isn’t, and collapse isn’t a real thing. The wavefunction is just doing its thing, and that’s all there is. The causal structures in the wavefunction that correspond to people are still there.
The way of looking at us that brings us into focus is the Born Rule. Removing the Born Rule is just like removing a P-zombie’s consciousness. It’s that switch you flip to grant or remove subjective experience from a computation that implements consciousness.
Weird, but true! See the discussion of PTI in the paper I link to in this comment. As far as I can tell, PTI is just a relabeling of the original TI. Where TI would have said only one branch is real and the other branches do not exist, PTI says only one branch is actual and the others are real but not actual. Our universe consists only of that which is actual, so the other branches are not part of our universe. They exist in other possible universes, which (and this is the innovation, I take it) happen to be real. I don’t see how merely renaming the selection procedure from “collapse” to “actualization” helps, but I will admit to not having read that much about the PTI.
I’m reminded of David Lewis’s response to Armstrong’s theory of laws of nature. According to Armstrong, two properties are associated in a law-like manner if and only if there is a specific second-order relation that holds between them. Armstrong labels this relation the “necessitation relation” and claims to have thereby accounted for the ineluctable character of the laws. Lewis responds: “I say that [Armstrong’s ‘necessitation relation’] deserves the name of ‘necessitation’ only if, somehow, it really can enter into the requisite necessary connections. It can’t enter into them just by bearing a name, any more than one can have mighty biceps just by being called ‘Armstrong.’”
This is actually a tricky claim to adjudicate from the perspective of MWI. It’s certainly true that the relative frequencies of experimental results in our world support the Born rule. But why should the reference class be restricted to our world? For someone who has seriously absorbed MWI, this is akin to declaring that you only care about the frequencies of experimental results in North America. If you include all experimental results in your reference class, including those from other worlds, it is no longer the case that they confirm the Born rule unless you already assign weights to worlds based on the Born rule. But of course, assigning weights to worlds in this way would be question-begging if you were trying to provide evidence for the Born rule itself.
To put it another way, as a proponent of the MWI you believe that there are real scientists out there, in other branches of the wave function, who perform their experiments with just as much care and diligence as you do and who end up with wholly different observed frequencies within their world. What makes you think you have the right frequencies and they don’t?
You have completely missed my point. It’s the difference between, on the one hand: proving that there is life on Earth, and on the other proving that if there is life in the universe, it must be on Earth.
actual = the branch we’re observing.
real = part of the wavefunction of the universe.
I maintain my position that it’s the same thing as MWI.
Please clarify the question. Do you identify these scientists using the Born Rule to interpret the wavefunction so as to provide the basis for their consciousness, and making them just really unlucky in the outcomes? Because in that case, for every one of them, there are sixty gazillion jillion squillion ridiculillion others that get the same frequencies we get. This is very unlucky for them. Prospectively, we could expect their frequencies to fall in line immediately (and of course we can also expect that a vanishingly small measure of them will continue to fail to do so).
OR, are you finding these scientists out there in the wavefunction without using the Born Rule to interpret the wavefunction when identifying their consciousness, but using some other rule instead? If so, then the Born Rule isn’t right for them.
Following that logic why not go even further and remove Schrodinger’s Equation? All possible observer moments exist, we just happen to be observers whose history happens to correspond to the conjunction of Schrodinger’s Equation with the Born Rule.
That notion doesn’t bother me in the least, but if we’re talking about the physics that happen for us, it’s the Schrodinger Equation, and the Born Rule is the ‘angle’ to take on finding us in it. Anything else isn’t us, and we can’t do experiments on it, so we ought to avoid making strong claims.
Then I don’t understand on what grounds you reject the Born Rule but keep the Schrodinger Equation.
Because the Schrodinger Equation governs the absolute dynamics.
Let me draw an analogy to what things would be like if the world weren’t quantum.
Schrodinger Equation + form of the Hamiltonian : Born Rule + neuroscience
::
Newton’s 2nd Law + force rules : “Some of those masses are what we’re made of..” + neuroscience
Isn’t this sort of like the Tegmark multiverse?