Questions re Cramer's Transactional Interpretation?

rkastner

As I've indicated earlier, it's possible for a photon to exist in spacetime via an absorberless transaction (e.g. as suggested in Cramer 1983). In that type of transaction, the role of 'confirmation' is played by the reflected advanced wave from the emitter at the t=0 boundary condition. Perhaps it's not the kind of 'confirmation' you have in mind, but it functions in the same way, to build up the OW to full strength and allow for asymmetric propagation. Davies' comments that you've cited here consider the standard emitter-absorber picture of a direct action theory, and his approach generally includes the usual DA idea that the field does not exist as an independent entity. In contrast, as I've tried to make transparent in my 'PTI and Relativity,' PTI differs from this ontology by taking the field as physically real and thus leaves open the possibility of other ways in which transactions can be realized, such as this t=0 reflecting boundary condition, which are not typically considered in connection with DA theories. Thus, PTI is not just a 'DA theory' in the traditional sense. My p. 29 sentence that you quoted can be understood as encompassing an absorberless, t=0 perfectly reflecting boundary condition resulting in an effective confirmation in the sense I've described above.

rkastner

Just a note that I've uploaded my "On Delayed Choice and Contingent Absorber Experiments" to the PhilSci archive: http://philsci-archive.pitt.edu/8963/

This paper argues that Maudlin-type experiments present no more of a challenge to TI than delayed choice experiments present for standard qm. Question/comments welcome at my website, rekastner.wordpress.edu.

RUTA

Quote by rkastner

As I've indicated earlier, it's possible for a photon to exist in spacetime via an absorberless transaction (e.g. as suggested in Cramer 1983). In that type of transaction, the role of 'confirmation' is played by the reflected advanced wave from the emitter at the t=0 boundary condition. Perhaps it's not the kind of 'confirmation' you have in mind, but it functions in the same way, to build up the OW to full strength and allow for asymmetric propagation. Davies' comments that you've cited here consider the standard emitter-absorber picture of a direct action theory, and his approach generally includes the usual DA idea that the field does not exist as an independent entity. In contrast, as I've tried to make transparent in my 'PTI and Relativity,' PTI differs from this ontology by taking the field as physically real and thus leaves open the possibility of other ways in which transactions can be realized, such as this t=0 reflecting boundary condition, which are not typically considered in connection with DA theories. Thus, PTI is not just a 'DA theory' in the traditional sense. My p. 29 sentence that you quoted can be understood as encompassing an absorberless, t=0 perfectly reflecting boundary condition resulting in an effective confirmation in the sense I've described above.

So, there are no advanced waves representing a completed/actual transaction, only advanced waves from sources that will not receive the photon, and these still manage to "build up the OW to full strength" allowing for an ... emission? I wouldn't can't call it a transaction, since the photon will never be received. So, if all possible ... whatevers ... aren't represented by advanced waves, what's the point of advanced waves? Why not simply use the standard retarded wave explanation? We have photon paths in spacetime, presumably all equally 'real', some of which are represented by both retarded and advanced waves while some are only represented by retarded waves. And what happens to your basis for the Born rule when you have actual spacetime paths without the overlap of advanced and retarded waves?

rkastner

As Cramer discussed in his 1986 and in the 1983 to which I've repeatedly referred you, there can be different types of 'transactions'. The crucial aspect of an actualized transaction in PTI is just the actualization of a quantum of the respective field that can carry away energy from a source. It's your inference, not mine, that this process *requires* that the energy be received somewhere. I've discussed it in terms of energy transfer from a source to an absorber because that is the situation we deal with in all experiments, and what any interpretation must address. You now apparently would like to extend this approach to more speculative questions about the large-scale structure of the universe. If the universe really is not a (mostly) light tight box, and you demand that PTI account for how stars can radiate away energy into infinite future (which again is not established incontrovertible fact), I have already provided a mechanism involving a less typical type of transaction, which Cramer proposed nearly 30 years ago, so clearly TI’s originator has long been aware of this consideration. Whether or not you'd like to call this a ‘transaction’ is a matter of taste (and evidently is not to your taste) but it contains the same physical properties associated with the typical transaction: cancellation of advanced waves for time less than the emission time and reinforcement of retarded waves for times greater than the emission time.

As for the Born Rule, this applies to situations involving the physical possibility of the detection of a quantum. An infinitely propagating quantum cannot possibly be detected, by definition. If what you are arguing is that the object |x><x| does not seem to apply to this atypical kind of transaction, that would be consistent with the idea that its probability of detection must be undefined, since by definition is has no possible detector.

Re your statement begnning with "if all possible ....whatevers....aren't represented by advanced waves'' : I'm not sure what you are trying to say here. Typical incipient transactions are represented by encounters between OW and CW, viz: |x><x|, not just advanced waves. Also recall that any emitter emits both OW and CW (or at least 'emitter advanced waves') and it is cancellation of the emitter's advanced waves together with reinforcement of its OW that makes possible the transport of a real quantum in the form of retarded radiation. So there are still advanced waves involved in the atypical transaction; and it is their overlap with their out-of-phase reflected retarded component that builds up the field to full retarded strength and defines a quantum being emitted from the emitter and continuing on to the infinite future without being absorbed.

There are many reasons why I think the purely retarded picture of radiation is insufficient. Among these is the ad hoc nature of the ‘free field’ needed to account for loss of energy by a radiating source, and the complete lack of a physical basis for the Born Rule and for a solution to the measurement problem. Here’s a place to start for anyone wishing to consider these issues: http://rekastner.wordpress.com/the-b...metry-of-time/ ; particularly sections 3 and 4; and of course this is also discussed in my http://philsci-archive.pitt.edu/8959/ .

RUTA

Quote by rkastner

... there are still advanced waves involved in the atypical transaction; and it is their overlap with their out-of-phase reflected retarded component that builds up the field to full retarded strength and defines a quantum being emitted from the emitter and continuing on to the infinite future without being absorbed.

This explains my confusion -- I didn't know you could have CWs connecting x to infinity. Thus, there is no problem posed by the fact that the current reigning cosmology model (LambdaCDM) permits emission to infinity. This is very different than direct particle interaction (obviously), and I didn't realize you had made this change.

I don't have any other questions for you now ... maybe I'll generate more for your presentation in Miami next month. Have a safe trip down!

rkastner

If you look at Cramer 1983, he explains how the 'absorberless' transaction works. It all looks physically consistent to me. The reflected advanced wave from the emitter continues on to t=infinity in an open universe. We do have to keep in mind, however, that the 'current reigning cosmology' is not incontrovertible fact and should not be taken as ruling out any given interpretation even if the latter does not seem obviously harmonious with it. We are continually learning new things in cosmology and who knows how that will ultimately turn out...

RUTA

Quote by rkastner

We do have to keep in mind, however, that the 'current reigning cosmology' is not incontrovertible fact and should not be taken as ruling out any given interpretation even if the latter does not seem obviously harmonious with it. We are continually learning new things in cosmology and who knows how that will ultimately turn out...

If a strong interpretation of QM is incompatible with the reigning cosmology model, I would say cosmology is probably wrong. That's actually how I expected you to respond

rkastner

As I explained , however, the interpretation (PTI) is *not * incompatible. But thanks for characterizing it as a strong interpretation.

RUTA

Quote by rkastner

As I explained , however, the interpretation (PTI) is *not * incompatible.

To my surprise.

Quote by rkastner

But thanks for characterizing it as a strong interpretation.

You're welcome.

HelpNowPlease

Quote by Demystifier

If yes, then why there is an appearance of the wave function collapse?

There is only something to collapse, if it has something to deflate in the first place.

Maybe the real question is, whether the wave function is objective or subjective. In other words, it is merely a field which is there for us to keep track of our calculations? Early quantum field theorists thought exactly that. But of course, we can't truely believe this today. What we might really believe is there is a battle to prove maybe the wave function is physical and tangible, not some ethereal field of probabilities.

HelpNowPlease

There is already evidence pointing to the physical interpretation of the wave function.

Maui

The biggest objection to a probability wave being real seems to be that the majority can not believe it(that the world is like that based on their personal preferences, despite all the evidence to the contrary).

rkastner

There is a recent proof by Pusey et al that the wave function cannot be considered merely as a statistical quantity describing our incomplete knowledge of quantum entities with real (but unknown) properties. See: http://arxiv.org/abs/1111.3328.

There was also a reply on the arxiv pointing out that the Pusey et al proof depends on realism about quantum objects (i.e., that they do have real but unknown properties). I do not recall the author(s) of that paper, but it argues that the proof does not rule out instrumentalist views of the wave function (or quantum state). As is probably evident from my work, I think that the quantum state does indeed refer to a real entity and that's what explains the predictive power of quantum theory. I am almost finished writing a book on my 'possibilist' variation of TI (PTI) and I hope you'll stay tuned for that. These possibilities may seem 'ethereal' compared to concrete events, but they are crucially important for the inception of a concrete event. I invite anyone interested to drop in to my blog, rekastner.wordpress.com. Happy New Year, everyone!

bohm2

Quote by rkastner

There is a recent proof by Pusey et al that the wave function cannot be considered merely as a statistical quantity describing our incomplete knowledge of quantum entities with real (but unknown) properties. See: http://arxiv.org/abs/1111.3328.

There was also a reply on the arxiv pointing out that the Pusey et al proof depends on realism about quantum objects (i.e., that they do have real but unknown properties). I do not recall the author(s) of that paper, but it argues that the proof does not rule out instrumentalist views of the wave function (or quantum state).

I didn't think the PBR theorem (or any theorem) can rule out the instrumentalist view. Leifer argues that such views are next to impossible to rule out:

I would classify the Copenhagen interpretation, as represented by Niels Bohr, under option 2 (e.g. Wavefunctions are epistemic, but there is no deeper underlying reality). One of his famous quotes is:

There is no quantum world. There is only an abstract physical description. It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature…[4]

and “what we can say” certainly seems to imply that we are talking about our knowledge of reality rather than reality itself. Various contemporary neo-Copenhagen approaches also fall under this option, e.g. the Quantum Bayesianism of Carlton Caves, Chris Fuchs and Ruediger Schack; Anton Zeilinger’s idea that quantum physics is only about information; and the view presently advocated by the philosopher Jeff Bub. These views are safe from refutation by the PBR theorem, although one may debate whether they are desirable on other grounds, e.g. the accusation of instrumentalism.

Can the quantum state be interpreted statistically?
http://mattleifer.info/2011/11/20/ca...statistically/

Not that I buy this author's arguments but maybe you mean this paper?

Pusey, Barrett and Rudolph claim to prove that statistical interpretations of quantum mechanics do not work. In fact, their proof assumes that all statistical interpretations must be based on hidden variable realism. Effectively, the authors demand from the start that reality must be decided by mathematics, and not by measurements. If this unjustified assumption is dropped, the quantum formalism has a natural statistical interpretation that fully explains the paradox presented by the authors.

The quantum state should be interpreted statistically
http://lanl.arxiv.org/PS_cache/arxiv...112.2446v1.pdf

rkastner

Yes, thanks, that's the paper I was thinking of. I agree that pure instrumentalist views are hard to rule out via the kind of proof presented by Pusey et al.

rkastner

Update: My book on the possibilist approach to TI and its relativistic extension is forthcoming this fall, http://www.cambridge.org/us/knowledg...e_locale=en_US

Also I uploaded the audio and ppt from my recent talk on how TI solves the measurement problem, here: http://transactionalinterpretation.org

bohm2

This is an interesting paper/EPR experiment that seems compatible with the Transactional Interpretation. Then again, I might be misunderstanding it?

The only reasonable resolution seems to be that of the Two-State-Vector Formalism, namely that the weak measurement's outcomes anticipate the experimenter’s future choice, even before the experimenter themselves knows what their choice is going to be. Causal loops are avoided by this anticipation remaining encrypted until the final outcomes enable to decipher it...Ergo, the weak measurements’ agreement with the strong measurements could have been obtained only by the former anticipating the spin orientation to be chosen for the latter. This result indicates the existence of a hidden variable of a very subtle type, namely the future state-vector...Therefore, when a weak measurement precedes a strong one, the only possible direction for the causal effect is from future to past.

The authors also suggest support for free will but I don't understand their argument:

Finally, this experiment sheds a new light on the age-old question of free will. Apparently, a measurement's anticipation of a human choice made much later renders the choice fully deterministic, bound by earlier causes. One profound result, however, shows that this is not the case. The choice anticipated by the weak outcomes can become known only after that choice is actually made. This inaccessibility, which prevents all causal paradoxes like “killing one's grandfather,” secures human choice full freedom from both past and future constraints.

Can a Future Choice Affect a Past Measurement's Outcome?
http://arxiv.org/ftp/arxiv/papers/1206/1206.6224.pdf

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rkastner	Just a note that I've uploaded my "On Delayed Choice and Contingent Absorber Experiments" to the PhilSci archive: http://philsci-archive.pitt.edu/8963/ This paper argues that Maudlin-type experiments present no more of a challenge to TI than delayed choice experiments present for standard qm. Question/comments welcome at my website, rekastner.wordpress.edu.

HelpNowPlease	There is already evidence pointing to the physical interpretation of the wave function.

Maui	The biggest objection to a probability wave being real seems to be that the majority can not believe it(that the world is like that based on their personal preferences, despite all the evidence to the contrary).