Physics Needs a Physical Theory of Observation by Chris Fields

Chris

You touched the perennial problem

"What is the same information?" is the modern version of oldest problem starting from Plato question: What makes beautiful things "beautiful". Problem of universals is an ancient problem in metaphysics. Bertrand Russel wrote that all Western philosophy is the comment to Plato.

In my Opinion Plato's question is tautological question and according to Wittgenstein does haven't sense,but....

major propositions in physics connected with notion"the same"

For example:

1.Einstein's relativity of simultaneity. The same time doesn't exist...

2 Heisenberg's uncertainty. The same time can't to measure....

3.Pauli's exclusion principle. The same energetic level only one fermion....

It seems to me very interesting.

Somebody thought of that?

Dear Chris

I´m deeply impressed by your essay. I will read it more carefully before making any comments though. I have also thought of relations between semantics and physics, but I found category theory was a better tool than model theory for investigating that. Please take a look at my essay

, for I think that there could be some link.

Best regards

Daniel

I found your paper interesting; I read it twice today. In comparing that you advocate a theory of observation with what I consider as the need for generalizing unitarity and removing quantum field locality, I would say your foundations are in some sense on a deeper level. A theory of observation, one which physically describes the observation process, I think leads into some bizarre territory,

The indefinability of a boundary in Hilbert space is really a way of saying that a trace operation is an arbitrary nonphysical process. This is something done by an analyst in order to isolate certain observables by fiat. This tracing defines the reservoir states or the environment where one "dumps" entanglement entropy. This connects in part with problems with quantum gravity. . The entropy of a black hole is given by the Bekenstein formula S = kA/4L_p^2. Here L_p = sqrt{Għ/c^3} is the Planck length, and L_p^2 is a unit of Planck area. A is the area of a black hole event horizon. The entropy is equal to the number of Planck units of area that comprises the event horizon S = Nk/4. This is given by the total density matrix of the black hole, where ρ is the quantum density matrix ρ_{op} = sum_n|ψ_n)(ψ_n|. A trace over the density matrix in the Khinchin-Shannon formula determines entropy. If you threw a bunch of quantum states into a black hole entropy of the black hole is

S = k sum_nρ_a log(ρ_n) S_{BH}

The black hole entropy increases. The S_{BH} is an initial entropy of the black hole, which if the analyst does not know the previous quantum states comprising the black hole is determined by a trace over states.

Your section "Observation as semantics" is where this could potentially jump off into strangeness. The Hilbert space description difficulty, or the inability to describe a boundary appears to be a form of Turing machine halting problem. The connection with Moore's work also appears to have this implication. This is an automata version of Godel's theorem. There is a form of Godel's second theorem in modal logic that constructs a semantic theory or semantic soundness. By including an observer into the description the eigenvalues of a Hilbert space become mapped to Godel numbers, and in this system you have quantum states which are codes for other quantum states.

I think this sort of thing may indeed underlie the structure of the universe. It could lead us to the end of physics itself. In some ways this leads into J.A Wheeler's idea of the observer-participator cosmology conjecture. Wheeler insisted there was "law without law," or that physical law was something that emerged from this process in the same way that mathematics consists of islands of axioms and theorem-proofs in a vast sea of self-referential propositions. To include the observer, where the ubiquitous observers are any type of quantum entanglement processor, into the physics seems to lead to a very difficult and strange direction.

Cheers LC

Chris

Well argued, but I disagree with some key concepts (I think). The first is your point 1. I claim that sophisticated observation can detect and define a physical boundary to all inertial frames, which are mutually exclusive. I agree that this; "distorts physical theory, renders our perspective special, turns the universe into a 'multiverse' and makes time objective." However all these are part of an ontological construct build on fully logical foundations which is more consistent with reality than current theory.

Also; "the "External Reality Hypothesis (ERH)": the claim that 'there exists an external physical reality completely independent of us humans' As an external reality "completely independent" of the physical states of human observers." I show how this need not violate energy conservation, because I find BOTH! Real and apparent. i.e. Light pulses that go PAST the observer in motion through a medium are observed as being at a different speed to the one measured after detection by interaction with the lens. I describe how this can be entirely self apparent and intuitive.

Nevertheless well written and a valuable contribution. I hope read my essay, fit the parts together and report on the outcome in your terms.

Best wishes.

Peter

Dear Chris,

I agree that the role of the observer is key in modern accounts of scientific theories that currently leave observers outside. And unfortunately, some researchers working in models that do take into consideration the observer, such as quantum mechanics (QM), often make adventurous claims about the properties of such observers by making interpretations about the model (such as free will theorems based in indeterministic randomness of QM).

Dear Daniel,

Please see my comment on your paper. From a category-theoretic perspective, a semantic model is just a mapping from a category being modeled (e.g. physical states and physical dynamics) to a "model" category in which the objects are descriptions encoded using classical information and the morphisms are operations defined over those descriptions. Classically-specified execution traces of classical algorithms as semantic models of the dynamics of physical systems that we call "computers" provide a canonical example.

Cheers,

Chris

Dear Lawrence,

Thank you for your comments. You say, "a trace operation is an arbitrary nonphysical process." I don't think this is really correct. When we do trace operations - when we choose to ignore certain degrees of freedom - we are doing something. The issue is to understand what we are doing, and then to ask if "trace" is an adequate mathematical model.

This is a place where Chris Fuchs' picture of an observer interacting with a system using a POVM (Fig.1 of his "Perimeter of QBism" paper) is useful as a guide. The observer physically acts on the world, and the world physically acts back on the observer. When we perform a trace, we are saying that we know what degrees of freedom of the world physically caused (or will or would physically cause) what Fuchs calls our "experience," but what we can just think of as our act of encoding the outcome in memory. I argue in my paper that we don't in fact know this, and that we can't know this, even in principle. But we nonetheless act as if we know it, and construct our formalism accordingly.

To assume that some fixed set of degrees of freedom, and no others, are causally relevant to our action of encoding an outcome is to "solve" the frame problem, either correctly if we are right, or wrongly if we are not. In point of fact we do not know, and cannot know, if our "solution" is right or not. If we regard humans as classical and hence allow ourselves to talk about neurocognitive architecture and the contents of memory, we know a good bit about how this solving of the frame problem works; not surprisingly, it involves informal causal reasoning (this is ref. 14 in my paper).

The question is: can we understand this process of assuming what degrees of freedom are relevant as a quantum computation? Can we understand the process of deciding that an "object" can be treated as separate from its environment as a quantum computation? Can we understand the process of deploying some particular finite-dimensional POVM as a quantum computation? Until we can do these things, we cannot claim to understand observation.

Cheers,

Chris

I called the trace operation unphysical because it is something we do by fiat. I agree there is something going on, but we in effect "trace over it." It is rather similar to the problem of metric back reaction with Hawking radiation. This is something one imposes, using classicality of spacetime, which is suggestive of some quantum gravity process. In fact the problem of measurement in quantum mechanics and the problem of quantum black holes share some remarkable similarities.

I am not as heavily marinated in problems on the foundations of quantum physics as apparently you are, and certainly not as much as Chris Fuchs. I do find something odd about this. I maintain that quantum mechanics is as simple a physics as one could ever want. It involves state spaces that are linear, linear operators, basic vector space operations of diagonalization, eigenvalues and eigenvectors and so forth. Nature could not possibly be any simpler. The problem is not the quantum but the classical. The existence of a classical world is the big mystery. All of the strangeness about quantum mechanics stems from the fact we observe things from a classical perspective.

I think it comes down to the fact that quantum mechanics describes states that have a representation in configuration variables, but quantum states or Hilbert space has no explicit dependency upon them. As a result we make measurements, such as "the electron appeared here" according to such variables in a way that quantum mechanics is blind to, or at least blind to as we understand. We measure these according to classical systems or represent them according to classical information.

If one were to quantize the observer, which I think requires understanding how quantum mechanics "builds up" the classical world, this seems to me to get into the problem of self reference. A self referential physics, one where maybe quantum numbers are Godel numbers, strikes me as the last possible theory after all else has been exhausted. We may well be heading in this direction though, with what ever dragons might appear.

Cheers LC

Dear Lawrence,

"The existence of a classical world is the big mystery." Indeed.

It is an irony of history that physicists, with the notable exception of Helmholtz, never seem to have become very interested in the "measurement problems" of classical physics - the problems of how observers differentiate systems from their environments and of how they determine that multiple observations are observations of the same system. Had they been, the variations introduced by quantum theory might not have seemed so surprising or shocking.

As far as I know, the first experimental studies of the object identification problem were those of Burke, who showed in the 1950s that how an object moves in part determines whether humans see it as remaining the same object over time. The frame problem wasn't formulated as such until McCarthy and Hayes in 1969. Now, however, these questions are an industry - much larger than the foundations of physics! If you really want to understand how humans implement the trace operator, you use an fMRI machine, or study the cytology of Alzheimer's disease.

Self-reference enters into this as the question: how does an observer know that part of the observation is observation of a memory? How is this tag implemented? It seems obvious when you're looking at your instrument and looking at a logbook page. But it's less obvious when the memory is in your head.

So yes, it is the classical versions that are the really hard ones. When we understand how someone knows that her coffee cup is the same thing as it was 10 minutes ago - really understand it - we'll be making progress.

Cheers,

Chris

Hi Chris,

I really enjoyed reading your essay. I'll have to give it a second read to wrap my head around it, but the question of the meaning, import and ontology of systems is fascinating. What are your thoughts on Carlo Rovelli's relational quantum mechanics? I've been impressed by the clarity of his thinking on this issue - in a nutshell, that quantum physics is about what information one system has about another, and that such relations exhaust what we can say about the world. In any case, you've put forward some intriguing ideas.

If you have a moment to look at my essay, it may be of some interest to you. While very different, it focuses on a kind of radical frame-dependence that also invokes a relational view of systems, and of the boundary between observer and observed, which clearly is itself frame-dependent. I'd love to hear your thoughts.

Best,

Amanda

Chris,

An observer can include any classical information recording system. Consider a cosmic ray that interacts with the atmosphere, scatters and its muon decay product is caught in a piece of flint. The rock has a path of the muon recorded in it, and serves as a type of particle detector. The set of possible quantum amplitudes for the cosmic ray interaction and subsequent decays has been in part recorded by this rock. The rock is in some sense a "classical observer." Of course the human geologist looking at the rock under a microscope constitutes a conscious observer.

BTW, I have proposed that if a spacecraft were to land on the Jovian moon Europa that possibly high energy cosmic ray events could be studied in the hard ice of the moon. Cosmic ray tracks could be frozen in place and "log" some very high energy physics.

The classical world, in the large N limit S = Nħ in a path integral setting

Z[φ] = ∫δ[φ] e^{-iS[φ]}

has a wild set of oscillations. The e^{-iS[φ]} is interpreted in the Euclidean Wick rotated form as a real valued function that becomes very small, and thus the quantum fluctuations around a classical trajectory become insignificant. Of course this assumes there is a classical trajectory, which is some stable eigenvalue in the large N limit. This is a sort of argument, but it is not entirely satisfactory. In part we don't entirely understand path integrals, the euclideanization is a bit of a sleight of hand, and the existence of this large N stable eigenvalue = classical trajectory is not proven.

Actually my essay involves degrees of freedom fundamental in a physical system. An elementary particle, such as an electron, is just a projection of one particle state in different configuration variables. This is a brane holography result. So ultimately there is only one electron in the entire universe, but multiple projections of it. If this is correct it is ultimately what Feynman initially thought of with respect to the path integral.

The role of a brain or conscious beings such as ourselves makes the issue far more difficult. Of course we have a poor idea about how the brain generates this subjective experience we call consciousness. It is maybe at this point one is thinking about some self-referential foundation to reality. The piece of rock above, or a computer memory that places a detector click into a histogram bin, or the manual written notes of an experimenter are classical information. The brain acting to understand this; to have some awareness of this information at least subjectively appears different. How does one know that a conscious perception is real? We all have those moments of doubt, such as walking back into the house to really check you turned off the stove, even if you have some memory of it. Some people in fact go a bit dysfunctional over this.

Cheers LC

Dear Chris,

your approach is very interesting to me. The idea that even in a single-"particle"-experiment the degrees of freedom aren't what we assume to be is really new to me. In fact, to model a realistic information transfer of Qubits on has to define things in a classical manner: environment, measurement device and the object of measurement (and probably the final observer). From a classical point of view this seems to be easily feasible. But as you outlined in your essay from the view of QM it is non-trivial.

So, in my own essay i come to similar conclusions as you ("Treating such boundaries as "given" distorts physical theory: it renders our perspective special, turns the universe into a multiverse and makes time appear objective.").

This non-triviality may be one reason why Hawking stated that, for him, "many-worlds" are "trivially true". In my own essay i refute the MW-assumption in favour of a more non-trivial explanation: Namely that entanglement does render every measured system to be consistent with logic and our trivial understanding of physical causality. I differenciate between this causality and non-physical reassons because i think to have found a new explanation of QM that at least is isomorphic to some other attempts here at fqxi and because i also think that Wheeler's "utterly simple idea" could be that the very framework of physics - the causality-concept - does no more fully hold in the domain of QM. How it can be nonetheless, that we experience strong causal effects in our classical world is outlined in my essay.

I would be happy if you could take a look at it!

Best wishes,

Stefan

Dear Chris Fields,

I agree very much with the title of your essay. I did read what I could of your essay but I'm afraid it became very difficult for me to follow as I got further into it. It is an interesting subject and no doubt those with an adequate training in the background science and mathematics will get far more from it than I managed.

Good luck in the competition. Kind regards Georgina.

"Neither the prestige of your subject, and the power of your instruments, nor the extent of your erudition and the precision of your planning, can substitute for the originality of your approach and the keeness of your observation."(Hans Selye)

Dear Chris,

That's a very interesting essay! You brought light and focus to a subject that is often overlooked by physicist: the Hilbert space itself. What defines what is the Hilbert space of a system? How do we know what is the Hilbert space of the specified system? I think almost nobody asks these questions, but they are very important. I wouldn't say I agree with all your answers, however, the most important here is not giving the right answers, but asking the right question. This is questioning the foundations. You have shown that there many problems on a fundamental notion that are often overlooked.

I have also tried to answer some of these questions in a previous work of mine (aXiv: 1208.4474). I suggest you using the identity of the Hilbert space as a mathematical tool for understanding these notions. The many Hilbert space can all be identified by their associated identities, which are projectors. Knowing which is the Hilbert space means knowing which is the identity associated with it. I also suggest you visiting and rating my essay: The Final Theory and the Language of Physics , you might find it interesting...

Great work! Regards,

Frederico

Dear Chris Fields,

I'm sorry if my review sounded unkind, it was not meant so. It was unnecessarily honest. My lack of comprehension is not any reflection on the quality of the material you have presented. Your reply to Lawrence Sep. 28, 2012 @ 10:44 GMT is really interesting to me. I also think Lawrence's point about observer's not having to be human is important. I talk about the output generated by artificial devices and sensitive materials as well organisms. The most important feature in all cases is the function of a Reality Interface, that converts input data into an output that is distinct from the source of the data and the data itself. That is what I regard the classic space-time to be, an emergent output reality. That overcomes a lot of problems in physics.

Just noticed this in your biography. "His current research focuses on describing how humans identify systems across observations at the implementation level, and on building a realistic representation of observation into a physical formalism." That sounds fascinating. How physics and the output of observation are related has been an interest of mine for a number of years. It has been mostly a philosophical/problem solving inquiry rather than the sort of in depth practical work I am imagining you are engaged upon.

I have enjoyed seeing how evidence from the study of biology, such as presented by David Eagleman at the last FQXi conference, fits with the "Reality in Physics" framework.I would very much appreciate you opinion of the summary of that framework, used in my essay to answer the essay question. There is a high resolution version in my essay discussion thread which is the correct way around. Kind regards Georgina

If you do not understand why your rating dropped down. As I found ratings in the contest are calculated in the next way. Suppose your rating is [math]R_1 [/math] and [math]N_1 [/math] was the quantity of people which gave you ratings. Then you have [math]S_1=R_1 N_1 [/math] of points. After it anyone give you [math]dS [/math] of points so you have [math]S_2=S_1+ dS [/math] of points and [math]N_2=N_1+1 [/math] is the common quantity of the people which gave you ratings. At the same time you will have [math]S_2=R_2 N_2 [/math] of points. From here, if you want to be R2 > R1 there must be: [math]S_2/ N_2>S_1/ N_1 [/math] or [math] (S_1+ dS) / (N_1+1) >S_1/ N_1 [/math] or [math] dS >S_1/ N_1 =R_1[/math] In other words if you want to increase rating of anyone you must give him more points [math]dS [/math] then the participant`s rating [math]R_1 [/math] was at the moment you rated him. From here it is seen that in the contest are special rules for ratings. And from here there are misunderstanding of some participants what is happened with their ratings. Moreover since community ratings are hided some participants do not sure how increase ratings of others and gives them maximum 10 points. But in the case the scale from 1 to 10 of points do not work, and some essays are overestimated and some essays are drop down. In my opinion it is a bad problem with this Contest rating process. I hope the FQXI community will change the rating process.

Sergey Fedosin

Hi Amanda,

Thanks for your comments. Please see my comments on your essay.

I think Rovelli is clearly on the right track. We just need to go farther, from a relational approach to quantum states to a relational approach to quantum systems. Both of our essays seem to be making this point, although from quite different perspectives.

Cheers,

Chris

Dear Georgina,

Thanks for your comments; please see mine on your essay.

Thinking about physics from a more biological viewpoint may indeed be useful. We as observers are in the position of individual neurons trying to figure out what the brain they are part of is doing. The brain is thinking about something or other, but all the neurons see are superimposed patterns of local excitation. What kinds of theories can such neurons build?

Cheers,

Chris