Insights Interview with Astrophysicist: Adam Becker - Comments

[vanhees71]

How come it's not ok to talk about "reality", but it is ok to talk about "Nature"?

Is Nature different from reality?

It's ok to talk about reality with physicists, but with philosophers you never know what they mean!

 

[vanhees71]

atyy's comment,

is perhaps too much a cute fussing about words, but I'll further note that there are no “objective reproducible quantitative observations in nature” insofar as events never repeat perfectly. Of course pragmatically a given experimenter makes their choice of what is close enough (perhaps quantitatively, a formal choice of a distance between events, but even in the most meticulous experiments there are also judgement calls), there are "good" experimenters who serve as exemplars of best practice, and there are social conventions that have been honed over centuries that make intersubjective seem objective to those who have been trained in those social conventions, but there is a gap. Research is arguably about getting "out of the box" —or, for some, the straightjacket— that we find ourselves trained into, and creating a new and beautiful box for students to have to get out of in their turn. All of us have some groups of outsiders, people who have been trained into different social conventions than those we have been trained into, to whom we pay some attention. We can and should make our own choices, and perhaps it's OK even to disdain some other groups, but, I suggest, philosophers of physics are too diverse a group, at least as I find them, for physicists to dismiss all of them.
I'll also add that there's no such thing as “pure qualitative "philosophical" thought”, except as a straw man. Most of the philosophers I pay attention to engage in quantitative mathematics of one kind or another.

Well, particularly due to quantum mechanics we have some things that are really reproducible exactly. E.g., any electron is precisely as any other, they are even indistinguishable in a very strict sense. Thus to the best of our knowledge each electron has precisely the same mass, magnetic moment, and charges of the standard model as any other. Of course, these quantities can be measured only with some finite accuracy, but so far even by getting this accuracy down to up to 12 significant digits (for the magnetic moment), there's no deviation from the assumption of indistinguishability. In this sense we have objective reproducible quantitative observations in nature in much better approximation than within classical physics.

That natural sciences are not sheer convention within a science community can be seen that indepedent researchers find the same result, measuring, e.g., the properties of elementary particles.

Mathematics is not philosophy. The mathematicians for already some time like to group mathematics into the category of "structural sciences" rather than "philosophy". Of course, mathematical physics (like axiomatic QFT) is not philosophy but an important part of physics (maybe also mathematics, but that the mathematicians have to judge). If I was a mathematical physicist I'd consider it an insult to be named a philosopher of science!

 

[vanhees71]

Again, one of Einstein’s fallacies, merely based on his psychological predispositions and his desire to return to the ontology of materialism.

In his book “Chemistry, Quantum Mechanics and Reductionism: Perspectives in Theoretical Chemistry“ Hans Primas cites Fock:

“The deeper reason for the circumstance that the wave function cannot correspond to any statistical collective lies in the fact that the concept of the wave function belongs to the potentially possible (to experiments not yet performed), while the concept of the statistical collective belongs to the accomplished (to the results of experiments already carried out) (Fock 1952, 1957).”

It's well known, why Fock wrote quite "interesting" philosophical articles concerning QT in Soviet times! I don't know, whether it's also in the English edition of Blokhintsev's famous QM textbook, but in the (then Eastern!) German edition there was also a "philosophical appendix"...

 

[zonde]

Einstein believed “that the notions of physics would refer to a real external world and that these ideas would be set by things that claim a "real existence" independent of the perceiving subjects.” And then he tried to force quantum physics into the corset of his conceptions. Everybody knows how successful he was. “Physics” cannot establish that such beliefs are true, but it can establish that such beliefs are not true. But, instead of learning from Einstein’s convoluted and ultimately entirely unsuccessful attempts, some are still on the quest to find some good elements of “objective reality” in quantum theory. And the “interpretative game” goes on. It’s not the word "reality" that has almost lost its usability, it’s the concept of a physical reality that has lost all its usability.

Scientific approach is based on assumption of realism (defined as "there is mind independent reality" or as opposite of solipsism). So the realism is common basis for any meaningful scientific discussion (this applies to positivists too). If you reject realism there can be no meaningful discussion with you about any science topic.

 

[Lord Jestocost]

Scientific approach is based on assumption of realism...

The scope of physics and its operational formalism is limited to pointer readings (the experience of what is called “observations”), which physics can study and connect to other pointer readings. There is no need for any assumption of realism or anti-realism or anything else. All these assumption belong to the realm of beliefs, personal “hypotheses” about yourself and about your experiences of “observations”.

 

[zonde]

The scope of physics and its operational formalism is limited to pointer readings (the experience of what is called “observations”), which physics can study and connect to other pointer readings.

I'm not sure what do you mean with "pointer readings". Do you mean either:
1) direct experience of expermentalist;
2) any type of record from which one can learn about certain measurement result?

 

[mattt]

The scope of physics and its operational formalism is limited to pointer readings (the experience of what is called “observations”), which physics can study and connect to other pointer readings. There is no need for any assumption of realism or anti-realism or anything else. All these assumption belong to the realm of beliefs, personal “hypotheses” about yourself and about your experiences of “observations”.

I would use a slightly different wording but...yes, that is exactly correct.

 

[Peter Morgan]

I'm not sure what do you mean with "pointer readings". Do you mean either:
1) direct experience of expermentalist;
2) any type of record from which one can learn about certain measurement result?

In modern experiments, it will usually mean a record in a computer, not any direct experience, microsecond by microsecond. For experimental data to be really out there, it should be in "Supplementary Material", or at least available to other physicists on application. Where things get edgy is in the instrumental details of how the experimental apparatus was constructed, including how whatever exotic materials were used were exotically processed, where apparatus was sourced, what sources of noise were shielded and corrected for, et cetera, whchi all in all should be as much as is needed to reproduce the results.

 

[zonde]

In modern experiments, it will usually mean a record in a computer, not any direct experience, microsecond by microsecond. For experimental data to be really out there, it should be in "Supplementary Material", or at least available to other physicists on application. Where things get edgy is in the instrumental details of how the experimental apparatus was constructed, including how whatever exotic materials were used were exotically processed, where apparatus was sourced, what sources of noise were shielded and corrected for, et cetera, whchi all in all should be as much as is needed to reproduce the results.

So do the records of experimental data and setup details have mind independent existence?

 

[vanhees71]

I'd say, if anything is free of prejudices it's a "machine read" record of experimental results. Of course, these records are of no value, if one doesn't know, how the measurement devices and DAQ (i.e., both hard and software) has been constructed. E.g., at the LHC even the best DAQ technology cannot produce "raw data", i.e., there are hardware triggers already in the detectors before anything is stored to electronic storage. These triggers are to a certain extent constructed using models. It's not so clear to me, whether one really could perhaps through away interesting signals by such cuts. Recently there was an interesting article concerning the still mute search for particles beyond the Standard Model concerning possible long-lived candidates in the Quanta Magazine:

https://www.quantamagazine.org/how-the-hidden-higgs-could-reveal-our-universes-dark-sector-20170926/

So one should be aware that there is indeed a subjective element in objective observations, that cannot be eliminated, namely the "arbitrary choice" of the observational apparati. I you'd say, e.g., only the direct human senses are valid, you'd miss a lot of stuff, which objectively exists: e.g., of the electromagnetic spectrum, restricting yourself what can be seen by the human eye, you'd exclude all em. waves at wavelenths outside the one octave from about 400 too 800 nm that can be seen directly by the human eye.

Nevertheless there's some objective reality in observations (particularly those not related to direct involvement of the human senses), because they are reproducible everywhere and at any time independently from each other, given a precise enough description of what is observed in terms of possible setups for measuring the concerning quantities. That becomse, of course, the more convincing if two or more such setups are also using different technology to measure the very same observable.

 

[Peter Morgan]

So do the records of experimental data and setup details have mind independent existence?

I'll mostly defer to vanhees71's account, comment #70. I think of triggers as a definite lossy data compression, but how the data is compressed is presumably decided by some committee, which hopefully has some minds. One could perhaps say that once an experiment has been constructed as an automated object, the data collected can be automated and be mostly independent of mind. Indeed, if human intervention is required to keep an experiment on track because of an error condition that lies outside the automation specified, one would expect that any data during the period during which human intervention was required ought to be discarded (unless, perhaps the human intervention can be formally modeled).
I'll paste in an account I wrote last night to a correspondent, which seems to be a propos:

Consider an Avalanche PhotoDiode, an APD: we set up an exotic state of matter so that the output signal is almost always near zero current, but occasionally it is some obviously non-zero value. Hardware is usually set up to record the time at which a transition from zero to non-zero current happens (we could instead record the current as a 14-bit output from an Analog-to-Digital Converter, an ADC, every nanosecond, say, but the record of current transition times is essentially a very compressed, very lossy record of the same information.) Also of interest in experiments is the dead time, the time it takes the hardware to restore the current to near zero so that another transition can be noticed and the time recorded.
Suppose we have this device. When it's set up in a dark room, there is a low rate of current transitions, called the dark rate; when we enter the room and turn on a dim light, the rate of current transitions changes; when we move around the room, the rate of current transitions changes; when we change the intensity of the light or introduce new lights, the rate of current transitions changes. If we set up some barriers, again the rate of current transitions changes, and again when we move the barriers around. If we set up two or more APDs, we can calculate more elaborate statistics, cross-correlations at the same or at different times.
If we ask what could be causing these events, one answer is that we've set up a ridiculously exotic state of matter, so of course weird stuff will happen. More than that, however, we notice that as we continuously change the conditions of the experiment, the current transition statistics change more-or-less continuously, if we collect enough data. Even though the events are discrete, the statistics change continuously. Historically, elementary physics has said that each current transition is caused by a particle, but more sophisticated physics works with a quantum field, which can be understood to make no claims about what happens outside the APD, nor about details of the APD current, but does discuss the statistics one would observe for a given theoretical model of an APD, and how those statistics would change continuously as we move the lights or the barriers or the APDs around.
For what it's worth, my YouTube video from last February, Quantum Mechanics: Event Thinking, deliberately short at 4'26", presents more-or-less this story.

One additional note, keying into vanhees71's account, is that triggers for large experiments are usually much more elaborate (and can slip into dangerously ad-hoc territory) than just whether one electrical signal transitions from zero to non-zero.

I think it's best not to get too hung up on the Bishop Berkeley problem. Ultimately I can't see that it helps much to be solipsist about the world. Go to the world of extreme positivism for a visit if you like, which I've found occasionally useful as a way to get out of the box, but best to come back. I've been peppering everything I've written on PF with links to my arXiv:1709.06711 (comment #30 has a more up to date version attached) because that's how I think about QM/QFT (for which sorry, I guess) and it's not yet well-known, but for this specific question, I think its mathematical derivation of a random field as a subalgebra of a free quantum field algebra more reconciles a classical perspective and a quantum field perspective than any other math I've seen in the literature (there's a parallel with the de Broglie-Bohm approach, deriving trajectory probabilities from the wave function, but there are also fundamental differences, that I keep to the mathematics of operators acting on Hilbert space as a model for signal analysis, manifest Poincaré invariance is maintained, and I keep to an operational interpretation of the math as far as possible). One significant point, however, is that the philosophy of classical probability has become significantly less settled than it used to be. I'm happy with an instrumental, construct-an-ensemble-and-compute-statistics approach, which I think is what physicists do, but philosophers have worries that I find significant about that approach, and physicists who want to construct a model for the whole observable universe obviously can't construct an ensemble (also, if we take away the background Minkowski space, constructing an ensemble becomes quite fraught, AFAICT —amongst other worries, of course).

 

[Lord Jestocost]

So do the records of experimental data and setup details have mind independent existence?

You have to find an answer for yourself to such a question. To my mind, it’s beyond the scope of "Physics" to answer this question or questions like “What is real?”. You can conceive that in course of experiments photographic plates have been blackened or that cloud droplets have been formed, without the intrusion of a conscious observer, but how should "Physics" prove your idea.

From an instrumentalist' point of view, such questions are idle ones. "In science we study the linkage of pointer readings with pointer readings." (Arthur Stanley Eddington). That’s all. The confusion begins when one tries on base of a schedule of pointer readings to draw conclusions as to the nature of “NATURE”.

Nevertheless, "Modern physics" now indicates that one cannot arbitrarily cut “NATURE” into – so to speak – subjective or objective parts or – let’s say – into Descartes’ mind and matter. Here I follow Bohr who said: I consider those developments in physics during the last decades which have shown how problematical such concepts as "objective" and "subjective" are, a great liberation of thought.

 

[AlexCaledin]

 

[RUTA]

You have to find an answer for yourself to such a question. To my mind, it’s beyond the scope of "Physics" to answer this question or questions like “What is real?”. You can conceive that in course of experiments photographic plates have been blackened or that cloud droplets have been formed, without the intrusion of a conscious observer, but how should "Physics" prove your idea.

From an instrumentalist' point of view, such questions are idle ones. "In science we study the linkage of pointer readings with pointer readings." (Arthur Stanley Eddington). That’s all. The confusion begins when one tries on base of a schedule of pointer readings to draw conclusions as to the nature of “NATURE”.

Nevertheless, "Modern physics" now indicates that one cannot arbitrarily cut “NATURE” into – so to speak – subjective or objective parts or – let’s say – into Descartes’ mind and matter. Here I follow Bohr who said: I consider those developments in physics during the last decades which have shown how problematical such concepts as "objective" and "subjective" are, a great liberation of thought.

I just finished Part I of Adam's book. Did you read it? It speaks precisely against this attitude.

 

[zonde]

You have to find an answer for yourself to such a question. To my mind, it’s beyond the scope of "Physics" to answer this question or questions like “What is real?”.

Sure

You can conceive that in course of experiments photographic plates have been blackened or that cloud droplets have been formed, without the intrusion of a conscious observer, but how should "Physics" prove your idea.

Why should physics prove anything?

Nevertheless, "Modern physics" now indicates that one cannot arbitrarily cut “NATURE” into – so to speak – subjective or objective parts or – let’s say – into Descartes’ mind and matter. Here I follow Bohr who said: I consider those developments in physics during the last decades which have shown how problematical such concepts as "objective" and "subjective" are, a great liberation of thought.

Science requires two things to do it. First, you have to have creative thinking to come up with possible explanations of phenomena. And second, you have to have critical thinking to throw away useless explanations.
"Great liberation of thought" is good for creative thinking, but if you loose the critical thinking part as a result of this liberation ... well, it's just not going to work.

 

[vanhees71]

Indeed. Even the most appealing creative thought has to be confronted with observations and accurate measurements. If you cannot make contact to observables, it's a nice mathematical idea at best or just philosophical gibberish at worst. If your predictions are clearly countered by observation, it's a physical theory that's wrong and needs to be modified (at best) or abandoned (at worst)! As all natural sciences physics after all is an empirical science.

 

[Lord Jestocost]

I just finished Part I of Adam's book. Did you read it? It speaks precisely against this attitude.

Sir Arthur Stanley Eddington in "The Nature of the Physical World“:

"Scientific instincts warn me that any attempt to answer the question “What is real?” in a broader sense than that adopted for domestic purposes in science, is likely to lead to a floundering among vain words and high-sounding epithets."

 

[Peter Morgan]

Indeed. Even the most appealing creative thought has to be confronted with observations and accurate measurements. If you cannot make contact to observables, it's a nice mathematical idea at best or just philosophical gibberish at worst. If your predictions are clearly countered by observation, it's a physical theory that's wrong and needs to be modified (at best) or abandoned (at worst)! As all natural sciences physics after all is an empirical science.

vanhees71, I can't see which comment you're referring to here. I understand if you might not want to use QUOTE, but it would help a lot if you would cite a comment number. TBH, I'm saying this because I've been unsure what or who you've been referring to a number of times, not just because of this one comment. Sorry! I won't say this again until I forget that I said it.

 

[RUTA]

Sir Arthur Stanley Eddington in "The Nature of the Physical World“:

"Scientific instincts warn me that any attempt to answer the question “What is real?” in a broader sense than that adopted for domestic purposes in science, is likely to lead to a floundering among vain words and high-sounding epithets."

Did you read Adam's book?

 

[Peter Morgan]

Did you read Adam's book?

I look forward to reading a review from you, RUTA. Having been to the talk Adam gave last night in New York, I'm not very enthusiastic. The last time I remember someone landing hard on a conversation at a foundations of physics conference with "Copenhagen says X, so everything you're saying is nonsense", was in the early 90's, and my sense is that physicists now more often fall back on decoherence (notwithstanding that the last mile from a mixed state to actual events is glossed), an interpretation which Adam didn't mention in his talk (I suppose because many philosophers would be loath to call decoherence an interpretation at all). Furthermore, I just read that Feyerabend in 1962 said (cited in arXiv:1509.09278, page 43)

. . . many physicists are very practical people and not very fond of philosophy. This being the case, they will take for granted and not further investigate those philosophical ideas which they have learned in their youth and which by now seem to them, and indeed to the whole community of practicing scientists, to be the expression of physical common sense. In most cases these ideas are part of the Copenhagen Interpretation.
A second reason for the persistence of the creed of complementarity in the face of decisive objections is to be found in the vagueness of the main principles of this creed. This vagueness allows the defendants to take care of objections by development rather than a reformulation, a procedure which will of course create the impression that the correct answer has been there all the time and that it was overlooked by the critic. Bohr's followers, and also Bohr himself, have made full use of this possibility even in cases where the necessity of a reformulation was clearly indicated. Their attitude has very often been one of people who have the task to clear up the misunderstandings of their opponents rather than to admit their own mistakes.

which seems a clear statement, 56 years ago, of what seemed to be a large part of Adam's argument for why Copenhagen is still given lip service today.
Adam at one point said that he hopes to give his talk to physics departments, but TBH with nothing at all said about QFT (is there anything about QFT in the book?), and decoherence unmentioned, I can't see physicists taking him seriously. One high point of going to Adam's talk was that I talked to several Masters and PhD students and postdocs, all of whom seemed quite knowledgeable about and willing to talk about the interpretation of QFT.

 

[RUTA]

I'm in Adam's chapter 6 on Bohm and Everett. I haven't seen anything about QFT mentioned in the other reviews and he has made little mention of it so far in his book, so I doubt he talks about interpretations of QFT. We offer an interpretation of QFT in chapter 5 of our book and that chapter opens with the following:

As for progress in this area, Healey notes, “no consensus has yet emerged, even on how to interpret the theory of a free, quantized, real scalar field” [Healey,
2007, p. 203]. And, “There is no agreement as to what object or objects a quantum field theory purports to describe, let alone what their basic properties would
be” [Healey, 2007, p. 221].

Foundations of physics (FoP) doesn't spend much time on this subject. FoP's attitude is that the weird/fun stuff is in QM, the only mysteries about QFT are technical, e.g., Haag's theorem, so FoP deals almost exclusively with QM. In my 24 years of attending FoP conferences and talks, I don't remember even one presentation on QFT issues. I'm very interested in your interpretation of QFT, as you know, because it looks to fill in technical gaps with my interpretation of QFT. With your help, I'll figure it out :-)

In the first 5 chapters, Adam has focused on the history of the Copenhagen interpretation (in its many variations) and why we're stuck with it now. His coverage of interpretational issues of QM has been sparse to this point. Based on reviews I've read, I'm assuming he'll plug those holes in part 3 of the book.

 

[Peter Morgan]

Foundations of physics (FoP) doesn't spend much time on this subject. FoP's attitude is that the weird/fun stuff is in QM, the only mysteries about QFT are technical, e.g., Haag's theorem, so FoP deals almost exclusively with QM. In my 24 years of attending FoP conferences and talks, I don't remember even one presentation on QFT issues. I'm very interested in your interpretation of QFT, as you know, because it looks to fill in technical gaps with my interpretation of QFT.

Different circles! I think you're right, although I haven't been to a Foundations of physics conference, $lo$, the last ten years. Perhaps it's more the philosophers who have taken up the philosophy of QFT, and there are several mathematicians who have tried to make sense of the mathematics of renormalization/interacting QFT with what seem almost philosophical motivations. I filter out a majority of non-QFT foundations these days, so it seems quite the opposite way round. QFT changes the game totally, IMO, makes everything much easier, partly because there are already fields, so it's fields/waves duality, which I think is easier to live with, but of course I have to convince anyone of that.

 

[RUTA]

I just finished Adam's analysis of the Bell inequality via a roulette wheel. I've heard this before in a different context, but it's a very nice way to introduce the Bell inequality to laymen. His claim afterwards is that only one of three logical possibilities exists: nonlocality, superdeterminism, or QM is wrong. Most people accept the experimental results vindicating QM, so few if any argue for the third option anymore (it was more common when I started working on this in 1994). I'm assuming he believes retrocausality falls into the SD camp? It's semantics, but I'd disagree with that since the "common cause" resides in both the future and past. I wouldn't say that any of the three options applies to the ontology of Relational Blockworld (RBW) where explanation is adynamical and QM is certainly correct. Therein, the fundamental ontological element is 4-dim and QM provides a distribution function for these 4D "spacetimesource elements" in the context of a classical block universe. So, we do have "realism" and there are no superluminal signals required in the explanation of the distribution of these real 4D objects in spacetime. I'm not even sure that the concept of nonlocality is relevant when discussing 4D objects (careful, this nonlocality has to do with superluminal signaling, not the locality assumed in differentiable manifolds). Silberstein and I are giving a talk to the foundations group at the Univ of MD next Wed, so I'll solicit their opinions. But, he and I agree that the standard analyses of Bell inequalities tacitly assume dynamism and are meaningless for adynamical explanation. Continuing, there is certainly no SD in RBW because there is no dynamical causation in adynamical explanation. In other words, when Adam claims to have exhausted all logical possibilities for the implications of Bell's inequality, he has failed to consider adynamical explanation.

 

[vanhees71]

vanhees71, I can't see which comment you're referring to here. I understand if you might not want to use QUOTE, but it would help a lot if you would cite a comment number. TBH, I'm saying this because I've been unsure what or who you've been referring to a number of times, not just because of this one comment. Sorry! I won't say this again until I forget that I said it.

I only quote if I refer to a posting not immediately before the posting I'm answering to.

 

[vanhees71]

I just finished Adam's analysis of the Bell inequality via a roulette wheel. I've heard this before in a different context, but it's a very nice way to introduce the Bell inequality to laymen. His claim afterwards is that only one of three logical possibilities exists: nonlocality, superdeterminism, or QM is wrong.

He forgot the third, which is the contemporary solution of this apparent problem, which is local microcausal relativistic QFT. It's local (i.e., fulfilling the linked-cluster principle) and allows for the long-range correlations described by entanglement of parts of quantum systems that are observed at far-distant points. Of course, you have to give up naive collapse interpretations, which introduce an artificial action at a distance, which is in clear contradiction to the very foundations the Standard Model rests upon, namely locality and microcausality. Of course QM is only a non-relativistic approximation of the relativstic QFT and thus becomes wrong when applied to situations where the approximation is invalid.

 

[RUTA]

He forgot the third, which is the contemporary solution of this apparent problem, which is local microcausal relativistic QFT. It's local (i.e., fulfilling the linked-cluster principle) and allows for the long-range correlations described by entanglement of parts of quantum systems that are observed at far-distant points. Of course, you have to give up naive collapse interpretations, which introduce an artificial action at a distance, which is in clear contradiction to the very foundations the Standard Model rests upon, namely locality and microcausality. Of course QM is only a non-relativistic approximation of the relativstic QFT and thus becomes wrong when applied to situations where the approximation is invalid.

That's not true, the formalism maps beautifully onto the experimental set-ups and data. There are many analyses, but one for undergrads that I use in my QM course is attached. There's nothing in the formalism that resolves this issue.

 

[Peter Morgan]

That's not true, the formalism maps beautifully onto the experimental set-ups and data. There are many analyses, but one for undergrads that I use in my QM course is attached. There's nothing in the formalism that resolves this issue.

Quantum theory, being probabilistic, only makes predictions about statistics associated with recorded measurements. As a probabilistic theory, it has nothing to say about individual recorded events, only about their statistics. As a statistical theory, it includes the notion of microcausality, that measurements associated with space-like separated regions commute, but this is consistent with us being able to prepare states in which there are correlations at space-like separation.
I see this as resolving the difference between vanhees71 and yourself, that quantum theory is microcausal as a probabilistic theory, whereas a theory that non-stochastically predicts the precise timings of individual recorded events would appear to have to be either nonlocal or superdeterministic (or some combination thereof: any such model might require infinite information to be predictive if there's any chaos, so I can't see how we could determine what a non-stochastic theory would be, I think we have no honest choice but to say "hypotheses non fingo").

I can see some merits to the paper you attach, but, of course, I'd like something better. In particular, IMO the role played by the incompatibility of the pairs of measurements at each end should be emphasized: if we were to perform only compatible measurements at each end separately, there would be no violation of any Bell inequalities. That there are incompatibilities means that there are time-like dependencies, but between the two measurements at A and between the two measurements at B, not between the ends (that is, if we have two measurements at A and two measurements at B, $[A_i,B_j]=0, [A_1,A_2]\not=0, [B_1,B_2]\not=0$.) And I'd prefer "particles" not to be mentioned at all (instead of the word appearing 34 times): to be trite, for the quantized EM field there's just a wave/field duality. But that's a different paper altogether.

 

[Lord Jestocost]

I just finished Part I of Adam's book. Did you read it? It speaks precisely against this attitude.

As I haven't read the book yet, I don't know Adam Becker's attitude.

 

[Boing3000]

Quantum theory, being probabilistic, only makes predictions about statistics associated with recorded measurements. As a probabilistic theory, it has nothing to say about individual recorded events, only about their statistics.

That is a nice refresher for those who think that quantum theory is a description of reality, instead of just a description of what would happens to "equally prepared state", that is "in a laboratory"

As a statistical theory, it includes the notion of microcausality, that measurements associated with space-like separated regions commute, but this is consistent with us being able to prepare states in which there are correlations at space-like separation.

As a layman, do you know of any resource that will explains how QFT micro-causality is supposed to solve the EPR macro stochastic causality behaviors ?

Also Ruta's point on block -universe "interpretation" seems quite interesting, I'll try to dig into that also...

I see this as resolving the difference between vanhees71 and yourself, that quantum theory is microcausal as a probabilistic theory, whereas a theory that non-stochastically predicts the precise timings of individual recorded events would appear to have to be either nonlocal or superdeterministic (or some combination thereof: any such model might require infinite information to be predictive if there's any chaos, so I can't see how we could determine what a non-stochastic theory would be, I think we have no honest choice but to say "hypotheses non fingo").

Aouch .. Latin hurts more than math On this topic of timing, isn't Bohmian's mechanic supposed to have more predictive power over classical QM ? If some spin value is observed to be X by Alice, isn't the (entangled?) pilot wave time dependency suppose to make more accurate prediction over the entangled value over time (and space) at Bob's end ?

 

[Peter Morgan]

That is a nice refresher for those who think that quantum theory is a description of reality, instead of just a description of what would happens to "equally prepared state", that is "in a laboratory"

What I said, that QM/QFT is a probabilistic theory —which can be understood to model, and hence in appropriate circumstances to predict, statistics of recorded experimental events—, seems to me not inconsistent with quantum theory being "a description of reality". I think of QM/QFT, admittedly loosely, as being as much as we can say about "reality" because to predict individual events in a chaotic world would require more information than I think we can plausibly have access to, perhaps even might require infinite information.

As a layman, do you know of any resource that will explains how QFT micro-causality is supposed to solve the EPR macro stochastic causality behaviors ?

I have a terrible memory, I'm afraid. I retain concepts more-or-less, once I've grokked them, but I too often forget where I learned about them and where the good references are. That said, I don't think of microcausality as solving EPR. Microcausality —that measurements are compatible with and don't change the statistics of other measurements that are at space-like separation— is apparently consistent with experiment, whereas in fact we can set up states in which there are correlations and Bell inequality violations between space-like separated measurements.

On this topic of timing, isn't Bohmian's mechanic supposed to have more predictive power over classical QM ?

I think of Bohmian mechanics more as retrodicting a trajectory, given an individual actual event, if we know (or think we know) the quantum dynamics. That is, if the event is caused by a particle, that particle must have come from somewhere, because that's what particles do. We can massage the quantum dynamics to give us an equation that determines a trajectory when it's given just a single point on that trajectory (it's sometimes cited as a conceptual difficulty for Bohmian mechanics that we don't need to know the velocity as well as the position to determine the trajectory —differently from the case for classical mechanics, that is). BUT, at least in those cases where we do not observe more than one point (not high energy physics, and not a football or anything else large, in other words, but for most low energy experiments, because then the particle is absorbed and doesn't carry on along the same trajectory), that's not a prediction. To claim that de Broglie-Bohm is empirically equivalent to QM, one has to say that de Broglie-Bohm is a probabilistic theory.
Personally, I'm OK with de Broglie-Bohm trajectories for the non-relativistic case, except that, crucially, the math is a mess compared to just using Hilbert spaces. When we use QFT, however, I've not seen de Broglie-Bohm work out well enough. Most physicists just cite the QFT case as a one-line dismissal.