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Beyond the standard glosses of QM (the realistic clock interpretation)

  1. Feb 23, 2010 #1


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    We've been watching this development taking shape ever since the tentative Gambini Pullin papers about it in 2006. It represents a fundamentally new way to address the problem of interpreting Quantum Mechanics. One person who worked on this back in 2006, with Gambini and Pullin, used to post occasionally here at Beyond forum.

    Complete quantum mechanics: an axiomatic formulation of the Montevideo interpretation
    Rodolfo Gambini, Luis Pedro Garcia-Pintos, Jorge Pullin
    21 pages
    (Submitted on 22 Feb 2010)
    "We make a first attempt to axiomatically formulate the Montevideo interpretation of quantum mechanics. In this interpretation environmental decoherence is supplemented with loss of coherence due to the use of realistic clocks to measure time to solve the measurement problem. The resulting formulation is framed entirely in terms of quantum objects without having to invoke the existence of measurable classical quantities like the time in ordinary quantum mechanics. The formulation eliminates any privileged role to the measurement process giving an objective definition of when an event occurs in a system."
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  3. Feb 23, 2010 #2


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    I should mention that Gambini and Pullin are longtime leaders in LQG research. Pullin is currently teaching an undergrad Introduction to LQG course at his university. He also runs the weekly International LQG Seminar, that links researchers in a teleconference that we listen to online. Background independent quantum gravity tends to favor a relational form of QM (there is no privileged time for example). The problem has been to combine realism with relationalism in a way that the universe is completely quantum (does not need a classical island where the observer sits with his classical clock and measuring instruments).
    Gambini and Pullin call their new interpretation complete QM.

    Basically complete QM is motivated by Quantum Gravity concerns and comes out of QG research. It addresses both the "problem of time" in quantum gravity and the "measurement problem" of QM.

    It may also be helpful in the application of QG to cosmology---that is, in a Quantum Cosmology context. In QC there has always been the problem of providing for an "outside observer". If the quantum model comprises the full universe, where is "outside"?

    Problems like these have been bugging the QG community for a long time and Gambini Pullin have been gradually working away at a solution---since at least as far back as 2006.
    It's nice to see they now have it crystalized in the form of a list of axioms.
  4. Feb 24, 2010 #3


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    Marcus, thanks for the posts. This is yet antoher idea that seems to contain very attractive traits. I'll try to skim those papers more later. The undecidability beeing a key distinction between classical and quantum is something that I can relate to and I needt to look into their details.

    I associate to how I envision it: simply that "classicality" is simply where further uncertainty is unresolvable or undecidable. Ie. the "classical certainty" is not be be interpreted as a "massive confidence", but rather the "LACK" of distinguishable measure of uncertainty (entropy) as measured from the "inside".

    This goes well with "relative entropy" ideas.

    The main challange for these ideas I see is how to infer the network of several such interacting systems. Most network inspired ideas postulate constraints that "force" desired structures that one expects semiclassically (ie. local rules + global or network-level constraints) and I haven't yet seen something to my liking. I like to see the constraints removed and instead follow from local rules as the complexity of the local system is increasing.

    The risk of removing all constraints is also that one ends up with a landscape without a defined probability measure.

    What's the middle road here which keeps the inside view, and makes progress without using ad hoc global consistency constraints, when the global view is non physical? I guess non-decidable inconsistences, are in fact not physical inconsistencies, just mathematical artifacts?

    I very much enjoy the recent stream of foundational reflections that have more non-program specific character!

  5. Feb 24, 2010 #4


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    I like your point that decoherence need not be an exact classical state but instead an average minimum - so inconsistency is minimised rather than actually being zero.

    But this then conflicts with your concern over global constraints as what constraints are exactly the kind of mechanism which can minimise, without actually being able to completely control, eradicate, or local degrees of freedom.

    An excellent review of such statistics is....

    However your basic concern could arise out of a misunderstanding of how global constraints are to be thought of in a dynamically self-organised system.

    When we talk about the constraints in a thermodynamic system, we usually imagine the box that physically constraints the motions of a collection of particles - the ideal gas model - and so is the kind of deus ex machina imposed boundary you object to.

    But emergent constraints, as in a scalefree network, would arise out of collective local actions. So the global constraints would exist everywhere, and nowhere, in the system.

    Take a turbulent stream. The emergent attractor would be the vortex. And in a very energetic stream, vortexes arise over all scales. Everywhere water molecule motions are being entrained into whorls that collectively dissipate the maximum energy.

    Only an analogy, but in approaches claiming to be background independent, we would be expecting both the local constructive actions (the events) and the global constraints (the context) to emerge together.
  6. Feb 25, 2010 #5


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    Philosophically we are quite close, as concluded previously.

    No doubt am I convinced that there is a road. My expressed concernt about landscape was mainly to illustrate what can happen, and has happened in some programs, it's not really something I worry about in the program I envision. Instead, we get undecidability. So the predictive power is constrained. This is exactly what the only rational rememdy seems to be to combine these ideas with evolving laws and constraints.

    I fully agree that also the constraints must be emergent. But the open problem is still to take what you and med are reasonably in agreement with on the philosophical level, to the complete quantiative prediction level. I have my own pet projects on this, but I'm an amateur and I really have very little time for this so progress is slow. This is what I'm curious about all the recent trends to see if some of the professionals has developed this in a direction that is in line with how I think it must be done.

    I've printed a few of Gambinis and Pullins papers to be read, but I fell asleep again last night. So I'll try again today.

  7. Feb 25, 2010 #6


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    An alternative view on ST can illustrate the prolem of missing p-measures:

    If we take the string and the string action to represent the elementa of which information is encoded.

    Then then problem of emergent spacetime in ST, is what is the structure of the "relations" between several of these units that are "interacting". How can two strings be "consistenct" with each other when they interact?

    Obvioulsy ST has a pack of consistency constraints here, that says that the consistencty requirements implies higher dimensional spaces etc. But there is no intrinsic measure of the confidence in these constraints that could be understood by the string itself.

    I think this ambigousness makes it not surprised that they end up with a landscape of consistent solutions, but without physical interpretation of the landscape.

    I think this should not happen if the constraints are reformulated in terms of intrinsic physics rather than "mathematical level consistencies".

    If the "strings" (or more generally whatever microstructure that encodes information) could be understood as also emergent from something simpler (not that a continuum string is anything but simple informationwise) then one should also understand that the emergent spacetime that should be implied from relations between strings might be better thought of as emergent communication channels between observers. And neither the communication channels nor the observers are given, the evolve together. This is why one breaks the idea if one pulls out of nowhere a nontrivial microstructure and postulates that it's fundamental and then requires some kind of "consistency" requirements from this when it is in fact not true that we know that strings are fundamental.

  8. Feb 26, 2010 #7


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    I've been extremely busy lately so I still only made it through two older papers of Gambini & Pullin, covering some interpretational but non-technical implementation issues. So far I like it.

    Their reasoning strikes me as very sound, in particular the "undecidability in physical law". This is exactly how I view the reason for "evolving law".

    Hopefully I'll get to look into the more critical papers where their ideas are translated into a formalism and see if they loose me, like Rovelli did :)

  9. Feb 27, 2010 #8


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    I made the first skim of the new february paper and some concerns arise to me, which show close similarities to my objection to Rovellis RQM and makes me less optimistic. I will try to read the paper more properly before commenting, to see if it's correct or if it was due to my skimming.

  10. Mar 1, 2010 #9


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    After reading more I can't see I share the continued reasoning.

    I certainly think it's sound to acknowledge that there are no "external clocks", where external means (outside of the universe) - this should be obivous, I don't think so either. However, I don't like the way things developed here, the "no external clocks" can be done in several ways.

    To mention one thing they seem to leave the physical basis of probability almost like Rovelli does.

    I still thinks that it's not wrong to think of the clock as beeing defined external to the *observed system*, it's just that both the observer and the observed system are of course constrained to within the universe. It's rather I think that if we take the "screen analogy", the clock is represented on the observer side of the screen, not the system side.

    Edit: I think if we consider real clocks on the system side, then I think technically that is not really measureing observers time. This "clock-time" is something different, and more on par with "rod-readings" than is the observers "cosmological time". AT least it's a clear distinction to me conceptually.

    They after all seem to seek observer an independent core? I think the observer indepdendent objectivity can only be emergent. And there is no objective view of this process. Only a set of inside views.

    I'm curious to hear if anyone else finds their ideas extraordinary.

  11. Apr 15, 2010 #10
    Hi everyone!
    Sorry, Fra, I didn't quite understand when you said "It's rather I think that if we take the "screen analogy", the clock is represented on the observer side of the screen, not the system side.". Why don't you agree with this situation of putting the clock on the observer side?
    Sorry I bring this up like a month after the discussion was "hot"...
  12. Apr 15, 2010 #11


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    Luis it is a real privilege for us to have someone who knows something about this new interpretation of QM show up here willing to explain and discuss.
    I regret to say I don't have specific questions at the moment. I sense that it is in some sense a more realistic and rational interpretation and consequently that it might contribute to the resolving some difficulties with the formulation of QG.

    Can you say anything, even in the most general terms, about what might be the consequences of the MV interpretation? Can you anticipate any substantial affect. Imagine the next book that comes out similar to Oriti's "Approaches to Quantum Gravity--towards a new understanding of space time and matter". Suppose a book like that were being written in, say 2011 or 2012. Would there be a chapter developing and presenting the MV interpretation as applied to our basic thinking about space time and matter?

    Or is it more of a detached line of investigation, how one interprets QM?
    Last edited: Apr 15, 2010
  13. Apr 15, 2010 #12
    Well, thank you Marcus! Im not sure if ill be able to explain, but Im definitely in for the discussion! I've been meaning to post for some time now... Im really interested in the critics people have on the ideas.

    Ok, complicated questions there. I should first say that I know nothing of quantum gravity. My motivation so far has been pure QM and its interpretation puzzles. So I can't answer your question. But as you know Gambini are Pullin are in the QG thing, I guess they see it as a more general thing than I do.
    Anyway, I don't think any of these discussions will be even close to being settled by 2012, hehe.
    Last edited: Apr 15, 2010
  14. Apr 16, 2010 #13


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    Hello Luis, thanks for commenting!

    I realise that some of the scentences in my posts are not proper english, I also note some critical typos of mine.

    I do think that the clock representing observers time (more closely related to the thermodynamical time, and cosmological time), must be on the observer side (that is EXTERNAL of the observed system). This isn't to be confued though, with me thinking there is a universal newtonian time. My point is the opposite. Instead of saying there is no time, and point to a timeless symmetries from with time is a gauge choice, I think time is for real, but observer dependent, and instead the symmetries are emergent in time, and evolving. But there is no global time evolution, but I do not see that as a problem.

    Clock time of devices beeing part of the system, is a different kind of time, which is more like the non-physical clock time we have in SR and GR, not cosmological time.

    I'll expand a little in a while, since I think my objection wasn't clear... it would be very interesting to hear your response to these objections, given that I can convey them...

  15. Apr 16, 2010 #14


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    Another possible source of confusion is that may the problem isn't on which side the "clock" is, but on which side the observer is? In my meaning of the word here, the observer is by definition on the opposite side of the screen relative to the system. The screen "is" the communication channel. If both observer and obserbed system are on the same side, there is no communication and no "measurement theory". Maybe the measurement problem is solved, by "removing the screen" but at the cost of also killing the core of a inference/measurement model.

    Last edited: Apr 17, 2010
  16. Apr 17, 2010 #15


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    Luis, I read your post again and although I see thay my own expressions of my objections may be unreadable, I'm not sure where to expand. Did any of the last two posts make anything clearer?

    I'm attraced to the notion of undecidability in that paper, because it's partly I also envision how objectivity is attained/emergent from communicating subjective observers - when due to limiting information(each observer can not hold/process all information) it's not possible to make an inference (to decide) of say a violation of a prior expected symmetry. When this happens the action of the observer will act to stabilise and preserve the symmetry, since it would not be rational to act upon something that's not decided.

    But I think there is still no birds view of this entire picture, this is why I think it's not enough to just say that the state of information of the complete system can't be known by an inside observer - I think not even the STATE SPACE can be known.

    I have a feeling with this paper, as with rovelli's past reasoning that they are trying to merge some very sound reasoning similar to rovelli's RQM paper (about relational notions, no absolute relations etc) with the idea that the structure of QM, with hilbert spaces etc, is correct and must not be modified. So there seems to take place a compromise here that I find objectionable. I really share some of the relational arguments, but the point is that the QM structure itself (set aside spacetime stuff) is in itself not relational, so I'm more rational and think thta QM itself is emergent. The starting points of timeless hilbert spaces etc, are just very counterintuitive to me since it breakes the inference model. The hilbert spaces must themselves be infered, and this is a evolving cycling processes that taks place everywhere and anytime.

    I'll stop there to see if you have feedback, otherwise I'll constrain myself from adding more ramblings to the thread.

  17. Apr 17, 2010 #16
    Hi! I found your comments interesting and clarifying Fredrik.

    So, I had been reading some things on models were some internal time is considered, and had some doubts myself. That is why I wanted to come back to your question.

    After reading your further comments I believe we think similarly on this point.

    This is how I see it, with your screen argument. On one side one has the observer, and on the other the quantum system with the measurement apparatus, like you said. Then there are two cases: in the first the clock is on the observer side and in the second in the system’s side.
    This second case would be when one needs the clock to interact with the whole device. For instance, I believe there is somewhere an example where one wants to measure how long some spin points in some direction (the spin is precessing in some magnetic field). In this case, one is asking about some time period, and of course I can’t be looking at the spin and pressing “start/stop” on some clockwatch, so what is needed is some sort of interaction between clock and spin (and probably some more devices). This interaction will produce backaction on the clock, and therefore time uncertainties.
    In the case where the clock is on the observer’s side of the screen then there is no interaction, but the time uncertainties just come from the fact that the clock is some quantum system, etc.
    So, I think both situations are contemplated on our work, even if we don’t need to distinguish them (we just talk of uncertainties in time).

    And then comes our point. When taking into account these errors in time measurement, and writing everything in terms of this “realistic time”, the information that the whole system + measurement apparatus is in a quantum superposition is inaccessible. So even if it is in a superposition, no process will show this.

    And then in the last comment you say:
    “I have a feeling with this paper, as with rovelli's past reasoning that they are trying to merge some very sound reasoning similar to rovelli's RQM paper (about relational notions, no absolute relations etc) with the idea that the structure of QM, with hilbert spaces etc, is correct and must not be modified. So there seems to take place a compromise here that I find objectionable.”
    There I agree with you. We have thought all the process in terms of plain QM, without ever questioning its basics. I guess in this respect I was thinking all the work one step less fundamentally than you. Changing how one sees QM, but not so drastically, hehe. I have no idea how this could be achieved though… are you thinking in something in particular?

    I’ll stop here, I’ve written too much already (maybe saying things that were already understood). Hope I haven’t bored anyone. Just in case, I should say that I am just thinking along here, we have not particularly discussed all of these ideas with Gambini or Pullin.

    Hope to hear what you guys think…
    Luis Pedro
  18. Apr 18, 2010 #17


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    Thanks for your comments Luis, this clarifies some things for for me. If I "pretend" to accept the premise that QM formalism is perfected, and take as my quest to merge the relational ideas with the QM formalism, then I can appreciate alot of the way of reasoning better! It's in this light your paper should be seen I think.

    But my own thinking has led me to a different starting point for my quest: Seeking an intrinsic inference model, I've come to question the QM formalism itself, so my objections are not so much against your inference, as it is against the premises.

    I have a set of personal ideas in mind, how it could be done differently but nothing mature and there is alot of work left before I would consider fleshing it out in a paper but it's in the plan. There are a few people that I think have presented good arguments that are all building blocks of something new. Part of Rovelli's initial reasoning in his RQM paper, Smolin's evolving law, Ariel Catichas "physics from inference" etc. I also see connections to the gravity as an entropic force, as well as holographic ideas.

    Maybe these furher comments are at least indicative of how I see it differently. My way of seeing it feeds new problems, but I think it's problems we have to face and they have physical interpretation.

    The way I see it, the "measurement apparatous" IS the observer, and this is always interacting with it's environment. The environment thus is "the system".

    But sometimes we consider that we observer only a subsystems of the environment. But IMO, this is only an idealisation, as it's not possible in general. I think the different notions of time, cosmological time vs "clock time" appear when the observer focues on the entire environment vs a subsystem. I also think that the symmetries of a subsystem can relatively speaking be inferred by the observer, to be more stable (~ timeless). The evolution of a subsystem may fit into the timless framework, but the evolution of he entire environment can't.

    To me your scenario of observer of one side and the apparatous on the other side, represents in my abstractions, one observer interacting with a second observer, which in turn interacts with another the system, but then "the system" with respect to the first observer, is really then just composite, which systems always tend to be anyway.

    So to address what I think is the real problem, the observer IS the apparatous, and the screen is what separates it from the system. And it's over this screen the measurement takes place as I see it, not between the apparatours(observer2) and the system, becayse the observer2 is just part of the system beeing observed by observer1.

    From the most general point of view, there is just one system and that is the entire environment. So I think the natural decomposition is an observer, and the screen, beyond there is the environment. The question I ask in my starting point, is what the action is of the observer, as a function of the inferred expectations on it's own environemnt. The action form encoding the action is them, is encoding the _expected_ symmetries of the environment, and is then also evolving due to backreaction from the environment. Since the environment produces a back-reaction for each action of the system. This means that the observer, can instrinsically only "decide" or infer an expected evolution, which I think of more as a differential evolution.

    Yes, but the two casess represent different things. The case where the clock is "in the environment" so to speak, is not the observers intrisic time. It's more like a "clock time".

    With intrinsic time, I mean a parameterisation of the expected flow of changes. This is entagled with the production of the "expectation" which in turns I see related to an subjective entropic flow on the observer side. This way of thinking requires that the "clock" is on the observer side.

    To me, even in the case where the clock is on the observer side, there IS interactions, because I seek the action of the observer, and it's evolution due to back-reactions for the environment. But thta's not fully decidable, tht's what I think in terms of evolution, not determinisitc dynamics. Even if there was a determinisitc dynamics in some silly sense, this predictive power is inaccessible to the observer. I think this is closely related to your point as well, it's just tht maybe you have a little different view. But my impression is that conceptually the idea behind it, is the same, and THIS I share, and i one form or of the other, I think this may be a key. Although I think me might need to be more radical.

  19. Apr 18, 2010 #18

    OK. But, for example, we are also thinking that the idea of isolated events are also included. By isolated events I mean just some system interacting with some environment (no other apparatus, and no interaction with any sort of observer). So, rewritting evolution in terms of real time, and in certain cases, the information of whether it is in a quantum superposition or not is not accesible. Then we say an event happens (a kind of "measurement")
    The cases in which this would occur is when the system is energetic enough, and the interaction with the environment is not too small, so that the effect of measuring time with real clocks is not tiny.
    So we are thinking about events happening all around us, without need of some sort of apparatus or observer.

    Do you agree with this? Am I understanding correctly what you were saying...?
  20. Apr 18, 2010 #19


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    My hunch is we are disagree about something since I don't follow what's the notion of an event, when there is no observer. It sounds like using notions/formalisms that are usually tied to an observer (events, eventspace etc), when there is no observer and giving it the status of some mathematical elements with unclear physical basis. This is what I'm trying to avoid.

    This critic I have also to rovelli's RQM - he (IMHO) rightly argues that the only way for two observer to compare their experiences of reality, is by communication=interaction. So far so good. But then he just says, the structure of this communication is supplied by QM and thus assigns this "relation" a status of structural realism, when he previously said there are no absolute relations. But this is indirectly what QM is in his usage, as I see it. I think if his spirit of no absolute relations are to be taken seriously, QM structure itself should be emergent as a negotiated CONSEQUENCE of interactions after equilibrations, following from underlying principles of ractional actions upon backreactions.

    But since you take your time to respond, which I really appreciate! I'll try to read your paper again and think another round to try to be more precise. I was just responding now based on the stores impressions in my memory of a previous read about a month ago.

    I'll try to respond again when I re-read the paper.

  21. Apr 19, 2010 #20
    Hello Fra,
    Yesteday i printed this paper by volovik a few years ago i readed the book "universe in a helium droplet" by Volovik. He also mentioned the emergence of QM.


    The Superfluid Universe
    G.E. Volovik
    (Submitted on 5 Apr 2010)
    We discuss phenomenology of quantum vacuum. Phenomenology of macroscopic systems has three sources: thermodynamics, topology and symmetry. Thermodynamics of the self-sustained vacuum allows us to treat the problems related to the vacuum energy: the cosmological constant problems. The natural value of the energy density of the equilibrium the self-sustained vacuum is zero. Cosmology is discussed as the process of relaxation of vacuum towards the equilibrium state. The present value of the cosmological constant is very small compared to the Planck scale, because the present Universe is very old and thus is close to equilibrium. momentum space topology determines the universality classes of fermionic vacua. The Standard Model vacuum both in its massless and massive states is topological medium. The vacuum in its massless state shares the properties of superfluid 3He-A, which is topological superfluid. It belongs to the Fermi-point universality class, which has topologically protected fermionic quasiparticles. At low energy they behave as relativistic massless Weyl fermions. Gauge fields and gravity emerge together with Weyl fermions at low energy. This allows us to treat the hierarchy problem in Standard Model: the masses of elementary particles are very small compared to the Planck scale because the natural value of the quark and lepton masses is zero. The small nonzero masses appear in the infrared region, where the quantum vacuum acquires the properties of another topological superfluid, 3He-B, and 3+1 topological insulators. The other topological media in dimensions 2+1 and 3+1 are also discussed. In most cases, topology is supported by discrete symmetry of the underlying microscopic system, which indicates the important role of discrete symmetry in Standard Model.
  22. Apr 23, 2010 #21


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    I've been travelling and not had time to respond. I'll be back shortly where I left off.

    Thanks for that link John.

  23. Apr 23, 2010 #22


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    Hello Luis, there are alot of premises in the paper that I do not accept as irrreducidle starting points, these are essentially several of the QM axioms, for example the notion of timeless hilbertspaces (I assume you think of them as timeless, right? My question is for example, how can anyone _decide_ if they are timless? and if these decisions are physical processes, doesn't the decision process itself take time? I think they do. So for me, the evolving structures are the only ones really possible. it's just that we idealized and think of structures where we can not decide that they are evolving, as timeless, when in fact that is nothing but an expectations - _maybe_ this is another sort of way to implement your decision argument, but I still think I have a quite different angle, but I could be mistaken about yours. To me the difference is important.).

    In my picture it doesn't make sense to do away with the observer, since even if we picture as you say "isolated interactions" where say two subsystems, or one subsystem and it's immediate environment are communicating "in isolation", it does not make sense to speak about this, unless there is a second observer that is indirectly observing this by means of how the action of the total system evolves; in this sense the "isolated interactions" are still indirectly observed (in the abstract sense that some limited but still incompelte inference of information about them takes place).

    In the intrinsic information and inference perspective Ithink is necessary, not only is an observer needed for communication/interaction, an observer is also needed to encode and store/hold information. So to make the inference complete, I think the measurement process needs to be combined with a model for sourcing and sinking the code. This is where I see the link to a kind of holographic perspective.

    So if I understand you right, you picture say a state space of an isolated system. But if it was properly isolated we would not be able to speak of it, and make no preparations. I think the entire history (preparation included) must be accounted for as this should yield the effective inferred state space of the almost isolated systems.

    These things are to me more basic than the clock issue.

    So if we picture an "almost" isolated system, there must still be an observer to formulate this representation, and encode information about the "hidden state space". A _completely isolated_ system clearly makes no sense, as it would be completely detached to anything that makes a difference. So we are discussing I think "almost isolated" or say "weakly interacting" observers right? (ie where we can imagine the isolated-interactions to be stronly interacting, but the mandatory observer may be weakly interacting with this isolated complex) But then the history or the interactins are I think crucial and some analysis is still missing.

    Last edited: Apr 23, 2010
  24. Apr 24, 2010 #23


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    From page 4 of the paper is an expression of a point of view that I find hard to digest.

    "The resulting description will be strongly objective in the sense indicated above without referring any time to observers or measurements."

    As I see it, there is a paradox between try to "do away" with external items, such as clocks or observers, and at the same time insist on the "structural realism" that is implicit in the strong objectivity, because the objectivity is then itself, in the structural realism sense - also an "an external view".

    What's your opinon of this? Is this not disturbing?

    I think the rational argument before seeing a structural realist view is that it's somehow connected to predictability. Without solid objectivity, there is no solid predictions. But I think solid predictions are not possible. I doubt it's not the nature works. Nature is more inductions made up on always incomplete information, and this includes the inference structure, and physical law itself.

    So relative to my own position, this Montevideo intepretation or view, seems so conceptually closely related to Rovelli's RQM view that I tend to group them. Although there are variations in the group.

    Does that sound fair? or how you see RQM?

    I do like like the sound of the undecidability idea, but I also like the sound to Rovelli's "no absolute relations". But then I feel that the spirit that I read into those phasings are broken as progress is made. Rovelli's uses the axiomatic structure of QM, more or less as an element of strucutral realism that its not questioned. I find this to be in contradiction to the generalised spirit contained in several of his introductory arguments (which I like alot and feel are very well formulated).

  25. Apr 24, 2010 #24
    Hi everyone, sorry I took so long to answer, I've been busy.
    I believe I have like I million questions / critics left unanswered... I'll go slow.

    First about what we mean by event. Event is just one we can say that some observable takes a definite value (so it's basically a measurement). When you have a quantum superposition (in the observables eigenbasis) there is no definite value.
    What we say is that since the evolution when there is an environment and taken the effect of time into account makes it undecidable if there has been a collapse or not (predictions are exactly the same in every conceivable sense), then you might as well think there has been a collapse. This is when we say an event occurs.

    And in the sense of what I just mentioned is that we believe that "The resulting description will be strongly objective in the sense indicated above without referring any time to observers or measurements." like you quoted in your last post.
    The basic idea I'm thinking about is this: the evolution of systems, even when there is no observer, leeds to undecidability. So basically the information of whether the system is in a superposition or not dissappears. I dont need to come in contact with the system to check if there has been some "event". This would be complicated, because then events (measurements) would only occur in certain situations. Most systems are not in contact with observers, just in contact with environments, and I prefer to think that events can happen everywhere without the need for us. So, IF the observer wanted to try to check if some system is in a superposition (of course, he would have to prepare states and measure and all that), he would not be able to because of how the evolution goes. But even if he didn't, evolution would lead to the loss of the information, so observer is not neccessary.

    Do you see this as wrong from a phylosophical point of view, or you are just not convinced about the way we are putting it?

    About the notion of timeless hilbert spaces. Yes, we assume that I believe; we left the background of QM intact. In what sense are you thinking about non-timeless hilbert spaces?

    I dont think I answered any of your critics after re-reading, but let me know what you think, and I'll keep posting anyway...
  26. Apr 24, 2010 #25
    Of course, if I wanted to make the experiment some preparation would be needed, but I dont think that to speak about some system and it's evolution I need to make a preparation to do the whole experiment.

    I find the evolution of the density matrix given an initial state, and see that the information of whether it is in a superposition is lost. Then an event takes place, I conclude. If i wanted to check if what I think is correct (maybe some other weird affect we haven't considered is going on and I do have a superposition ) I could for once do the experiment and see. But then I dont need to repeat it, the event takes place anyway.
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