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FQXi FORUM
December 14, 2017

CATEGORY: It From Bit or Bit From It? Essay Contest (2013) [back]
TOPIC: Relative information at the foundation of physics by Carlo Rovelli [refresh]
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Author Carlo Rovelli wrote on Jun. 21, 2013 @ 15:50 GMT
Essay Abstract

I observe that Shannon's notion of relative information between two physical systems can effectively function as a foundation for statistical mechanics and quantum mechanics, without referring to any subjectivism or idealism. It can also represent the key missing element in the foundation of the naturalistic picture of the world, providing the conceptual tool for dealing with its apparent limitations. I comment on the relation between these ideas and Democritus.

Author Bio

Carlo Rovelli is professor of theoretical physics at the University of Aux-Marseille. His main interest is quantum gravity, but he has worked also on the foundations of quantum theory and general covariant statistical mechanics, and on the ancient history and philosophy of physics.

Download Essay PDF File




Edwin Eugene Klingman wrote on Jun. 21, 2013 @ 22:10 GMT
Dear Carlo Rovelli,

Thanks for submitting a very interesting essay. As I understand it, you begin by depicting entropy as emergent, which is then followed by "entropy is information". You certainly managed to link the two, as did ET Jaynes in 1957 when he presented the first information theory treatment of statistical mechanics. Yet he makes clear (quoted in my technical endnotes) that information entropy and thermodynamic entropy are not identical. In this respect I find your treatment of information as implying physical constraints on two interacting systems to be quite insightful.

Your discussion of information and quantum theory is succinct, but I was particularly pleased with your formulation that: "it is always possible to acquire new information about a system", thereby making the previous quantum information irrelevant. Very interesting.

Your summary of the relevance of information to life (i.e., to anything other than a dead universe) is fascinating and yet, if I understand your essay, you do not posit It from Bit, which is the question the essays address.

As a key player in quantum loop gravity I do not expect you to agree with my essay, but I still think you might enjoy a fresh perspective, and would hope you will read it and comment on it.

Thanks again, and good luck in the contest.

Edwin Eugene Klingman

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Author Carlo Rovelli wrote on Jun. 21, 2013 @ 23:35 GMT
Thank you Edwin for your very insightful comments. Indeed Jaynes views have affected me strongly (and I should have cited him!); but I found that there was still some bits missing in his account, and I am searching the missing element in Shannon's clean definition of relative information.

I certainly now will go read your essay.

best, carlo




Wilhelmus de Wilde wrote on Jun. 22, 2013 @ 08:22 GMT
Dear Carlo,

It is a pleasure to see that after 3 years you now entered with a exeptional essay.

I cannot but totally agree with your perceptions. Especially the phrase "an infinite game of mirrors reflecting one another" is a wonderful expression.

You also put limits to our so called "material universe" as we perceive it.

"The "particular configurations of atoms singled out because of the manner a given other system interacts with them" allows me to think that one of these systems is our consciousness.

The latest contribution of your co-creator of LQG Abhay Ashtekar mentioning that there cannot be a singularity in a black hole but that at the Panck-length we enter in a "different" dimension is actually paralel with my perception of the limit of our causal universe, only I use the term "Total Simultaneity" and "rimal Sequence" in my essay : "THE QUEST FOR THE PRIMAL SEQUENCE" (which I hope you will read and rate).

The limit however as Ashtekar put in a Black Hole, is in my perception at every point in our causal universe attainable, why only in a black hole ?

Wilhelmus

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Jacek Safuta wrote on Jun. 22, 2013 @ 10:11 GMT
Dear Professor Rovelli,

I am familiar with your publications for many years mainly concerning LQG. It is a pleasure to welcome so great physicist here as an entrant to the contest.

Your essay delivers a new interesting look for the thermodynamical entropy (at least for me).

However I would like to comment your example with colored and charged balls that seems to be...

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Lawrence B Crowell wrote on Jun. 22, 2013 @ 13:39 GMT
Carlo,

Great essay. Entropy has been considered as the number of ways one can rearrange microstates in such a way that a macrostate is preserved. Information I_n = log(P_n), for the occurrence of a state with probability P_n, when summed over P_n is

S = -k sum_n P_nI_n.

For P_n = 1/N one gets the standard result that S = k log(Ω), with small errors. In this case the system with equiprobable microstates is at maximum entropy. The maximum entropy is hard to define, but a black hole is probably as close as we can get. It is entropy defined for a maximum number of degrees of freedom or qubits on an event horizon or holographic surface bounding a volume.

A system at maximum entropy can only be assessed to have such entropy if some measurement is performed, say of temperature with T = ∂E/∂S, which necessitates some probe be coupled to the system. This means there is another system with some Hamiltonian that couples in with the thermal system of interest. In this case there is a change in entropy where in the adiabatic limit usually means δS \lt\lt S. This would then imply that a relative entropy exists with a small change in entropy.

Cheers LC

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Joe Fisher wrote on Jun. 22, 2013 @ 15:35 GMT
Professor Rovelli,

I found your essay exceptionally instructive even though I am a decrepit old realist. May I please make a comment about one sentence you used in your essay?

You wrote: “If we have measured a system, the information we have about a system allows us to predict its future." It is my contention that one real unique Universe is eternally occurring in one real here and now, once.

Respectfully Professor, unique cannot be measured. Unique cannot be systematic. Unique cannot be informed or conformed or deformed. Unique cannot be allowed or denied. Unique cannot be predicted.

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Author Carlo Rovelli replied on Jun. 22, 2013 @ 15:53 GMT
Dear Joe Fisher. Yours is an interesting idea, I think around the Mediterranean it goes back to Parmenides. There is one thing I have never understood about this idea: if the Universe is so happening only once and in such an unique and undifferentiated fashion, how can you and I be so talking and telling things one another, in a manner that could alter our thoughts?



Joe Fisher replied on Jun. 24, 2013 @ 14:29 GMT
Respectfully Professor Rovelli,

Unique is different once. It cannot be undifferentiatedly fashionable.

Joe

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Jochen Szangolies wrote on Jun. 22, 2013 @ 15:48 GMT
Dear Carlo Rovelli,

I've long thought about the relationship between subjective information and objective quantities relating to physical systems---the sun's heat, in your example. Your idea, I think, clears up that mystery completely, and it goes to show that there are still simple, but powerful answers out there to be found, of which you've provided one.

I've also been interested in your reconstruction of quantum mechanics for a long time. I've thought about the idea that Bell inequalities/the Kochen-Specker theorem/etc., are ultimately related to the fact that one cannot find a single (ordinary) probability distribution to cover all experimental predictions of QM, especially all correlations between observables---that is, there is no probability distribution such that its marginals reproduce all experimentally obtained probabilities. Unless, of course, you allow the distribution to take on negative values, generalizing to a pseudo-probability; then, you get something like the Wigner function on phase space. I keep thinking that this ought to be related, in some way, to your approach, but so far I haven't thought about it enough. Also perhaps of interest is Kochen's recent reconstruction of quantum mechanics along similar lines.

Anyway, thank you for posting this essay, it was a pleasure to read,

Jochen

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Author Carlo Rovelli replied on Jun. 22, 2013 @ 15:56 GMT
Thank you! Carlo




Member Matthew Saul Leifer wrote on Jun. 22, 2013 @ 16:17 GMT
Thanks for your insightful essay. I am wondering what the status of single molecule thermodynamics is in your approach, e.g. in the Szilard engine and the derivation of Landauer's principle. Clearly, a single molecule interacts with thermometers and the box walls in a very different way from a gas with a large number of molecules. It has no effect on them except on those rare occasions when it hits them causing a tiny fluctuation. Yet we are still able to use Gibbsian thermodynamics to reason about this system. Do you accept such arguments in your approach and, if not, do you have an alternative derivation of Landauer's principle or an alternative resolution of Maxwell's demon.

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Author Carlo Rovelli replied on Jun. 23, 2013 @ 11:00 GMT
Thanks for pointing out this. I do not know the answer. I will think about the Szilard engine and the derivation of Landauer's principle. c




Hoang cao Hai wrote on Jun. 22, 2013 @ 19:50 GMT
Dear Carlo

Maybe I did not yet understand the part of your argument - it's a bit more complicated and have many terminology not yet specifically defined - but I like:"The Universe is change, life is opinion that adapt it - self".

http://fqxi.org/community/forum/topic/1802

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Author Carlo Rovelli replied on Jun. 23, 2013 @ 10:44 GMT
Yes, it is a wonderful phrase. Of course is not me: it is Democritus...




Domenico Oricchio wrote on Jun. 23, 2013 @ 09:04 GMT
I read quickly your article, and it is interesting.

I am thinking that if it is possible to have a bijection between each statistical system and a thermodynamic system (for example the blind child and a thermodynamic process), then it is possible to associate to each statistical system some physical quantity, and it is possible to apply the law of thermodynamic.

So, if there are two boxes, with red balls (hot molecules) and white balls (cold molecules), and a blind child (no physical measure) that make a random choice for each time step, then asymptotically the system is in equilibrium; if we write the second law of thermodynamics (in equilibrium point) for the blind child, then we must write that is impossible the passing of N red balls (for example 20) from a boxe to an other boxes (Clausius say that the entropy fluctutations are impossible).

I can understand the impossibility of the perpetual motion: it is impossible the infinite reproduction of the same sequence of extractions from the two boxes, but I think that the Clausius statement is so weak.

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Member Alexei Grinbaum wrote on Jun. 23, 2013 @ 10:40 GMT
Ciao Carlo,

This is a nice statement of your ideas. Two questions:

1) It seems that on your account systems somehow "know" which degrees of freedom are going to be involved in their interaction. When you write, "If the coupling is such that it depends only on certain macroscopic variables of the gas, then the physical interactions of the gas and this system are objectively well described by thermodynamics", I feel that the coupling of systems somehow precedes its physical description. Who tells us which coupling is correct and which isn't?

2) On Democritus. I leave aside Democritus's argument about infinitely divisible space and no smallest magnitude, which your position obviously contradicts. Not everything in Democritus is the historic source of your account. However there's a contradiction that appears to me subtler than this. Democritus famously claimed that atoms can be any size, even the size of the Universe; they don't have to be small, like in Epicurus. This is good news, because you can favorably compare Democritus's notion of an atom and your notion of a system. Now, Democritus's systems are indivisible - this is absolutely fundamental for an atom. But aren't systems divisible? We routinely speak about subsystems, and this is as fundamental for quantum mechanics (e.g. entanglement) as indivisibility is for Democritus. So the analogy seems to fail on at least one very important point.

Hope to see you around soon.

Amicalement,

Alexei

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Author Carlo Rovelli replied on Jun. 23, 2013 @ 10:58 GMT
Hi Alex. Thanks for the comments. Here are answer to both:

1) I was not sufficiently clear. The point I am trying to make is that the relevant physical question is not which coupling is correct and which coupling is not correct. The question is which coupling happens to *actually* be there, and which does not. The *physically relevant* coarse graining is the one determined by the couplings of the system with a second system that actually exists; and it is physically relevant because it describes the interactions of the system with this second system. Therefore there is nothing to "know", or "choose".

2) Regarding Democritus, I spent the last year trying to bring together and understand what he might have said. I do not think he had any argument *for* infinitely divisibility of space. The other way around, I think that we can gather from what Aristotle says about him that he had argument *against* the infinite divisibility of anything. Regarding the fact that there are very large atoms, the attribution to him of this idea idea is widely disputed by many scholars. It is likely that it is a misunderstanding. In any case, I definitely not identify atoms with systems, for many reasons, including the one you say. Also, of course I am not defending Democritus naive physics here!




Philip Gibbs wrote on Jun. 23, 2013 @ 14:01 GMT
Carlo, it's good to see you bringing your expertise into the system. I like the idea of using Shannon's relative entropy to resolve the difference between Democritus and Plato/Aristotle.

Since you are interested in ancient philosophy have you heard much about the acataleptic philosophers? There does not seem to be much recorded and interpretations differ.

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Author Carlo Rovelli replied on Jun. 23, 2013 @ 14:33 GMT
I suppose this word refers mainly to Pyrrho. His skepticism has been taken into the modern era by Hume, and is still alive and kicking, for instance in Popper. I take it to make the point that we are never sure, a good point. But what we care is reliability, not certainty. This is what I think (reliably, but not with certainty.)



Philip Gibbs replied on Jun. 23, 2013 @ 17:09 GMT
In the essay I mentioned Carneades and Arcesilaus rather than Pyrrho. What was of interest to me was the debate around whether a skeptic could say anything reliable about their own ideas if they did not consider anything reliable. Hume was more important in my previous essay on causality. At least the ideas are linked.

I think a better modern development might be Bayesian Probability

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Author Carlo Rovelli replied on Jun. 24, 2013 @ 10:07 GMT
Carneade... chi era costui?

(Sorry, this is a joke only Italians understand ...)




Antony Ryan wrote on Jun. 24, 2013 @ 04:36 GMT
Carlo,

I found your essay extremely interesting and informative, rich and diverse. I like the closing paragraph, particularly "The world is not just a blind wind of atoms, or generally covariant quantum fields. It is also the infinite game of mirrors reflecting one another formed by the correlations among the structures formed by the elementary objects".

All the best,

Antony

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Author Carlo Rovelli replied on Jun. 24, 2013 @ 10:08 GMT
Thanks!



Antony Ryan replied on Jul. 3, 2013 @ 22:27 GMT
My pleasure Carlo,

Hopefully you get chance to read my essay based around the Fiboanacci sequence and Black Holes.

Best wishes for the contest,

Antony

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Akinbo Ojo wrote on Jun. 24, 2013 @ 13:55 GMT
Hi Carlo,

Your essay very worth reading…, I also love your analogy of the box full of balls, characterized by color and charge. Nothing much to criticize but you may wish to ponder the following to which I have not got any satisfactory answer.

1. Since your essay touches on thermodynamics, given the equation

dS = dE/T, if you are given a tiny amount of energy, E and a control knob that can regulate temperature, T, can you cause an astronomical-sized increase in entropy, S by manipulating the temperature, T at the time of energy introduction?

I asked, Anton Biermans, but didn’t get a satisfactory answer. I am looking at a cosmological implication.

2. On the discretization of space, which you also touched on… I have asked Edward Fredkin, but I am not fully satisfied with the answer and Stephen Wolfram didn’t respond.

It is easy to say planets, air, fish in water, the water itself, atoms, etc, are discrete. Space does the separation for us so that we are able to call them “discrete”.

But when the great SEPARATOR itself, space is said to be capable of taking a discrete form, who will do the separation for us? Certainly, the separator cannot separate itself or can it? That is between one discrete representation of space and the adjoining one, what makes us distinguish 1 from 2?

3. Then although you mention the atomism of Democritus, I suggest that you consider monads as well in future. Here is what Leibniz has to say about them, "… something that has no parts can’t be extended, can’t have a shape, and can’t be split up. So monads are the true atoms of Nature—the elements out of which everything is made".

I will be happy to have your expert opinion and criticism of my essay, where I discuss my ideas on how discrete nature of space can be realized.

Regards,

Akinbo

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Author Carlo Rovelli replied on Jun. 26, 2013 @ 16:26 GMT
1) No, you cannot make the entropy go up much. If you control the temperature, then this means that the system remains in equilibrium with a heat bath. At fixed temperature, if you add new energy, this is just going to go out as heat, so, there is no way you can increase S after it got to the maximum.

2) I do not think "space" is just a separator, if by "space" we mean what we mean in general relativity. It is more than that. In particular, it carries quantities that are expressed by the metric field. So for instance the space between two walls is not just the separation between the two walls: it also how many *meters* are there between the two walls. Now, in general relativity this is just the *amount of gravitational field* between the walls, because distance is a function of the gravitational field. Therefore what can be discrete is not the "separator" is is the gravitational field that determine this distance. The point is that there is no separation less than a minimal one.

3) There is a difference between atoms and monads. Atoms (in ancient atomism) have only their shape and relative position and order. Monads are much more complicate things, that can reflect the external world and hold a vision of the rest of the universe. I am fascinated by Leibniz ideas, but I also think that one should move ideas around with care.

Thanks for your comments!



Akinbo Ojo replied on Jul. 1, 2013 @ 13:31 GMT
Thanks Carlo for replying...

On 1), I did not mean to regulate the temperature during the entropy increase, but the temperature AT the time of energy introduction. From that equation, which I presume correct since you dont question it, if T is made very, very, very low, will the resulting entropy change following a small energy introduction not be very, very, very large?

On 2), I didnt want to mix up discreteness with gravitational theory. To avoid confusion, discreteness implies occurring in separate representations, so that we can count 1, 2, etc. What usually enables us to do this, e.g. for grains of sand is separation by space. Or if you like let us take the space far away from any walls or gravitational field, in order not to argue over the statement "...because distance is a function of the gravitational field", will that far away space have a discrete nature?

On 3), Leibniz did not originate Monads, the Pythagoreans did. Also apart from the initial 8 paragraphs of his Monadology, the remaining were more concerned with spiritual not with physics. Interestingly, an essayist here pointed out a reference that Wheeler suggested that his "elementary quantum phenomenon" was like a monad (JA Wheeler, The computer and the universe, International Journal of Theoretical Physics, vol.21, nos. 6/7, 1982)here.

I know you are a busy academic, but if you have the time you may reply on these points.

Regards,

Akinbo

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Mikalai Birukou wrote on Jun. 24, 2013 @ 19:18 GMT
Dear Carlo,

A concept that information is a relative phenomena goes against classical and intuitive view of the world, to the point that even well-meaning grads still try to find a "universal underlying information", were none is present. Not further then one month ago we had such conversation, in two long batches of posts in this very competition at...

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Author Carlo Rovelli replied on Jun. 26, 2013 @ 16:28 GMT
Thanks for pointing this out! c




Manuel S Morales wrote on Jun. 25, 2013 @ 06:35 GMT
Carlo,

I find that your statement, "Amon all systems, living systems are those that selection has lead to reproduce continuously their own structure by, in particular, making use of the information they have about the exterior world. This is why we can understand them in terms of finality and intentionality, because they are the ones that have permaned thanks precisely to the finality in their structure. Thus, it is not finality that drives structure, but the other way around, selected structures define finality." is indeed factual.

I have obtained evidence of what you have summarized about selected structures to map gravity with the strong, weak, and electromagnetic forces as one super-deterministc force. I invite you to review my findings and rate my essay when you get the chance:

http://fqxi.org/community/forum/topic/1809

Good luck with your entry of which I have rated highly for its insight.

Regards,

Manuel

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Cristinel Stoica wrote on Jun. 25, 2013 @ 16:01 GMT
Dear Carlo Rovelli,

I was very pleased to read your essay. Indeed, the context of a system has tremendous impact to the system, if we are interested in information, entropy, quantum mechanics, etc. Local depends on global, everything is relative to the context. I like your bold view that the context impacts reversibility even more than the intrinsic properties of the system. I find this...

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Author Carlo Rovelli replied on Jun. 26, 2013 @ 16:30 GMT
Thanks for everything. I did not know about Baez. I go look at that that. c




Roger Granet wrote on Jun. 26, 2013 @ 05:05 GMT
Dr. Rovelli,

Hi. Good essay! I do have one question, which may stem from my lack of knowledge, but if, as you say, "the information relevant in physics is always the relative information between two systems", how can there be information about the universe, or existence, as a whole because there shouldn't be another system outside the universe with which it can interact. Would the second system be an arbitrarily imposed size for the universe?

Also, there are tons of essays, but any feedback you might have on mine would be most welcome. It's at

http://fqxi.org/data/essay-contest-files/Granet_fqxiessay201
3final.pdf

and is basically about the idea that maybe we shouldn't argue so much about it or bit, analog or digital, etc., but should just accept that there is some generic existent state at the heart of existence and try to figure out how such an existent state can lead to the universe we see around us.

Anyways, I enjoyed reading your well written essay! Thanks!

Roger Granet

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Author Carlo Rovelli replied on Jun. 26, 2013 @ 16:32 GMT
In fact, I do think that it makes no sense to talk about the "relevant physical information" for the entire universe!




Walter Smilga wrote on Jun. 26, 2013 @ 09:29 GMT
Dear Carlo Rovelli,

Thanks for your very interesting essay. You make the point that information is relative. Linguistics, applied to informatics, tells us something very similar: A bit, implemented in computer hardware, is at first merely an abstract symbol without any meaning. Only, when we assign a meaning (semantics) to the bit, by agreeing that, e.g., it shall refer to the nth digit within a binary number, we can say that the bit carries information. So, at least on the binary level, information is always relative to an "agreement" or, in physical terms, relative to a "frame of reference". I think, this is in line with your position, although in a more abstract sense.

Now, being physicists, we are inclined to ask: What happens to the information contained in a bit, when we change the frame of reference? I have studied this question in my essay and encountered informational structures that qualitatively and quantitatively resemble the basic structures of elementary particle physics - similar to your findings.

Any feedback you might have on my essay would be most welcome.

Walter Smilga

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Author Carlo Rovelli replied on Jun. 26, 2013 @ 23:21 GMT
Dear Walter, thanks for this comment. I think that it is better if physics does not mix the two levels. The reason I refer constantly to Shannon's definition of information is that his definition is independent from semantics, as Shannon himself emphasizes in his 1948 work. The point I am trying to make is precisely the fact that there is are meaningful notions of information and relative information in simple physics, without need to refer to semantic, meaning, or mental or idealistic perspectives.

c



Walter Smilga replied on Jun. 27, 2013 @ 10:09 GMT
Dear Carlo,

thanks for your response. Certainly, Shannon gave a definition of information that is independent from semantics and this is a great intellectual achievement. However, physics generally deals not with abstract information, but with information about physical things, e.g., spin, position, mass. With my understanding of the word semantics, it therefore deals with information relative to a semantic frame of reference.

Of course, I agree with you that physical laws shall be formulated independent from a specific frame of reference and this includes also semantic frames of reference. However, to ensure this independency we must formulate them in such a way that the laws can easily be adapted to any specific frame of reference, whenever for practical reasons this is required.

Therefore, even though the laws do not refer to a specific frame of reference, we must implement the possibility to adapt the law to any specific frame of reference. This includes that we must be able to tell how this adaptation changes with a change of the frame of reference.

This consideration has motivated me to study the structure of binary information relative to a "semantic frame of reference", which I regard as a straight-forward generalization of the notion of a coordinate system.

Regards,

Walter

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Hoang cao Hai wrote on Jun. 27, 2013 @ 04:53 GMT
Send to all of you

THE ADDITIONAL ARTICLES AND A SMALL TEST FOR MUTUAL BENEFIT

To change the atmosphere "abstract" of the competition and to demonstrate for the real preeminent possibility of the Absolute theory as well as to clarify the issues I mentioned in the essay and to avoid duplicate questions after receiving the opinion of you , I will add a reply to you :

1 . THE...

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Sreenath B N wrote on Jun. 27, 2013 @ 16:37 GMT
Dear Dr. Carlo Rovelli,

I have down loaded your essay and soon post my comments on it. Mean while, please, go through my essay and post your comments.

Regards and good luck in the contest.

Sreenath BN.

http://fqxi.org/community/forum/topic/1827

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Eckard Blumschein wrote on Jun. 27, 2013 @ 16:40 GMT
Dear Carlo Rovelli,

Your suggestion to use Shannon's relative information at the foundation of physics may be very courageous after the use of relative information seems to be inappropriate for most ecological applications. Cf. R. K. Peet (1975) Relative Diversity Indices, Ecology 56, 496-498.

Good luck,

Eckard

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Author Carlo Rovelli replied on Jul. 1, 2013 @ 12:13 GMT
Eckard, is there an online version of the article you quote? We do not get that kind of journals in our physics lab. Or maybe could you explain the main point? Thanks, Carlo



Eckard Blumschein replied on Jul. 29, 2013 @ 18:25 GMT
Yes,

http://intranet.catie.ac.cr/intranet/posgrado/Agrof-Cult
-AyP/

Curso%20SAF%20A%20y%20P%202011/Propedeutico%20Agrofores
tal/Lecturas%20optativas/The

%20Measurement%20of%20Species%20
Diversity.pdf

Annual Reviews is cooperating with http://www.jstor.org

Eckard

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Satyavarapu Naga Parameswara Gupta wrote on Jun. 28, 2013 @ 01:39 GMT
Dear Cario,

Thank you for presenting your nice essay. I saw the abstract and will post my comments soon.

So you can produce material from your thinking. . . .

I am requesting you to go through my essay also. And I take this opportunity to say, to come to reality and base your arguments on experimental results.

I failed mainly because I worked against the main stream....

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Wilhelmus de Wilde wrote on Jun. 29, 2013 @ 14:08 GMT
Hi Carlo, Dear Prof Rovelli

On june 22, I sent you a post on this thread, perhaps you did not remark it because it was in the beginning, I am sill awaiting your very valued remarks.

best regards

Wilhelmus

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Author Carlo Rovelli replied on Jul. 1, 2013 @ 12:27 GMT
Thank you, Wilhelmus. Well, I di not reply because it was more a question to Ashtekar than to myself... c




Mikalai Birukou wrote on Jun. 29, 2013 @ 15:55 GMT
Dear Carlo,

Want to point a recent article http://arxiv.org/abs/1306.5471 with a very meticulous treatment of quantum theory and phenomenology. These guys actually come to realisation that at a fundamental, or postulate level "... All that we can assume is a fundamental quantum field ..."

Taking in your view of information (its creation and destruction by qm systems), and mine http://www.fqxi.org/community/forum/topic/essay-download/159
7/__details/Birukou_Birukou_essay_Bit_I.pdf
, all of it combined may finally give a sweet thing :)

Mikalai

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Author Carlo Rovelli replied on Jul. 1, 2013 @ 12:25 GMT
Thanks for point out this rather interesting book. Carlo




David Brown wrote on Jul. 1, 2013 @ 13:57 GMT
@Carlo Rovelli: "... for all quantum systems, the orthogonal states are in finite number per each finite region of phase space." If there is a multiverse finite automaton then all possible measurable states are a finite set. If the multiverse is infinite and really needs an infinite phase space, then what is the explanation for the space roar? The space roar is supported by: FIRAS and low frequency radio data, ARCADE2 and low frequency radio data, and combined data sets from ARACADE2 and FIRAS.

http://asd.gsfc.nasa.gov/archive/arcade/pubs/arc2_apj_
interp_2011.pdf INTERPRETATION OF THE ARCADE2 ABSOLUTE SKY BRIGHTNESS MEASUREMENT by M. Seiffert, D. J. Fixsen, A. Kogut, et al., The Astrophysical J., 734:6 (8pp.), 2011 June 10

Is any quantum theory of gravity that contradicts the space roar guaranteed to be wrong?

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Conrad Dale Johnson wrote on Jul. 1, 2013 @ 15:18 GMT
Dear Carlo -

I'm very glad to see a new essay of yours revisiting some themes of Relational Quantum Mechanics. I've always considered that paper a milestone, or rather a signpost pointing a way that remains to be explored. Maybe the time is ripe... there are a few other essays in this contest - Knuth's, for example - working with the idea that all of physics concerns "the information...

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Author Carlo Rovelli replied on Jul. 1, 2013 @ 16:23 GMT
Dear Conrad,

you touch something basic here. I agree that what you talk about is a central issue, and I am uncertain myself.

We certainly agree on the relevance of context, and I feel everybody would agree, at least after a good discussion clarifying what we mean. But I have tried to bring this down to good old physics. You are right that in quantum mechanics this affects the measurement issue and you are right that it affects the definition of what is a measurement context. But the central point of Relational Quantum Mechanics is to solve this issue by accepting the idea that *any* physical interaction is a measurement. When an atom in a SternGerlack apparatus is deviated by the magnetic field, the position of the atom is measuring the spin. This seems to me the only possible solution; I have never found a convincing alternative. The price to pay is of course the Relational Quantum Mechanics observation that events are indexed by the context. That is, in this case the spin is measured by the position, and does not take value with respect to a system not interacting with it. This allows interference to affect possible later interactions with position or spin. Thus, in this sense I agree with you that measurement is fundamental, but I prefer to view it as synonymous of interaction, rather than trying to view it, as you suggest to attribute it to "a very complex interactive environment".



Conrad Dale Johnson replied on Jul. 2, 2013 @ 14:36 GMT
Carlo - thanks for your response, and I get your point. In fact, I pulled out my old marked-up copy of the RQM paper and was reminded again what a thorough piece of work it is, given its limited scope. It lays out - more carefully than any work of philosophy I know of - the basic philosophical issues involved in the meaning of objectivity.

It is just the notion that events are indexed by...

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Author Carlo Rovelli replied on Jul. 2, 2013 @ 16:18 GMT
Ok, you definitely convinced me to read with care what you have written! I will now print it out and study it... thanks! carlo




Member Giacomo Mauro D\'Ariano wrote on Jul. 2, 2013 @ 08:44 GMT
Dear Carlo

I read your essay with pleasure. It is very well written, clear, and easy to understand. I share essentially all points, though just at the qualitative level, i.e. as a general philosophy. I have been always curious about your relational quantum theory, and I now understand that it is meant to be an axiomatization program. That's is even more interesting for me, since, pragmatically, I do not pay much attention at the purely opinionated interpretational issues. I will consider to which of our axioms your postulates may be connected (I'm referring to the Pavia axiomatization http://pra.aps.org/abstract/PRA/v84/i1/e012311). I just downloaded your IJTP paper of 1996, and I notice a third axiom, which looks quite quantum. You don't mention it in your essay. Do you have a more recent version of your derivation of QT without it?

Second, about LQG, it seems to me that, in a sense, you are not so far from my cellular automaton approach, and I was wondering if e.g. your loops maybe related to my loops on the Cayley graph. I'm very curious.

My best regards

Mauro

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Author Carlo Rovelli replied on Jul. 5, 2013 @ 05:38 GMT
Thanks Mauro. The two main "physical" axioms are:

1. Relevant information about a system is finite.

2. We can always gather new relevant information.

But as you say in the derivation at least a third axiom is needed. I have not followed up on this, but Alexei Grinbaum in Paris has worked on this extensively, with a more mathematical approach. My own expectation is that the key missing element is one that capture the tensorial structure of QM. Namely how more than two systems work together.

I will look at the axioms you have.

Yes, there might be a relation between the spin networks and the Caley graphs.

ciao, carlo




Sreenath B N wrote on Jul. 2, 2013 @ 09:33 GMT
Dear Dr. Carlo,

Your essay is short but contains enough information on ‘Information’, but you haven’t touched up on ‘reality’ in the same way; so I couldn’t see your valuable views on reality and disappointed. I hope you will make it up to it soon.

You have identified entropy with information, but is this identification universal? For example, if two systems are in equilibrium with each other there will be no change in the entropy of the two systems but yet there can be exchange of information between them.

You have reviewed the current trend prevailing in physics to unite such different fields as thermodynamics, gravitation and quantum physics on the basis of the concept of entropy as yourself being one of the champions of LQG. There are lots of expectations to see how far you succeed in your endeavor.

I also expect you to go through my essay and post your comments. http://fqxi.org/community/forum/topic/1827.

Best regards,

Sreenath

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Harlan Swyers wrote on Jul. 3, 2013 @ 10:46 GMT
Carlo,

Interesting essay. As I dwell on the same questions you are raising I focused on the following statement you make:

"The information contained in any fi nite region of the phase space of any system is fi nite."

I would agree this is true to the level of precision allowed to the level of error imposed upon us by the uncertainty principle. However, the error does represent information, a vast amount of it, and it is this information that ultimately forces us to only accept an approximate reality. In general, I have to agree with Democritus that life is change. In general I think these ideas seem to be manifest in several of the essay provided. I was wondering what your thoughts are on the apparent prevalence of the same ideas?

My essay if you're interested.

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James Lee Hoover wrote on Jul. 3, 2013 @ 18:08 GMT
Carlo,

If given the time and the wits to evaluate over 120 more entries, I have a month to try. My seemingly whimsical title, “It’s good to be the king,” is serious about our subject.

Jim

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Héctor Daniel Gianni wrote on Jul. 4, 2013 @ 22:21 GMT
Dear Professor Carlo Rovelli:

I am going to refer myself to the last part of your essay.The main finality of a living system is to survive, in the case of the Galapagos cormoran its “selected structure” which “original finality” was to be a “flying bird” is not flying, environment (as you said, making use of the information they have...

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Than Tin wrote on Jul. 5, 2013 @ 03:42 GMT
Dear Professor Carlo:

On my hard drive, you have existed as a bunch of arXiv articles; in my memory, your name is associated with the name of Professor Lee Smolin, the author of many books that I learned physics from.

You are on my hard drive, you are in my memory, and now you are here. It’s a pleasure to be in your company!

I have downloaded your article, and I’m reading it with as much intelligence and diligence that a non-physics major can muster about a topic “It from Bit” that is deep and has many facets to it. I dread making pronoucements about it, but having entered a public contest, I had to.

I am the author of FQXi essay entry titled “Analogical Engine”, and my belief is that ‘Nature is thoroughly Analogical,’ and to make it sound less of a slogan, I made a subsequent statement: “Planck's constant is the Mother of All Dualities, and a necessary condition for existence of thoughts and things.”

And to make the statement picturesque, I have included in the body of my essay a thought-experiment based on an intuitive distinction between the (subjective) and the (objective) by working out an interpretative, non-mathematical derivation of what I believe to be the simulacrum of Planck constant, different from the one that is in textbooks.

Within that framework, I find your essay greatly illuminating, especially section IV.

Than Tin

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Dipak Kumar Bhunia wrote on Jul. 5, 2013 @ 13:49 GMT
Dear Prof. Carlo Rovelli,

Let me quote you first from your essay:

"...I think, from the basis of genetics, to the

foundation of quantum mechanics, to the basis of ther-

modynamics, all the way to sociology and to quantum

gravity, it appears that the notion of information has a

pervasive and unifying role. The world is not just a blind

wind of atoms, or generally covariant quantum elds. It

is also the in nite game of mirrors reecting one another

formed by the correlations among the structures formed

by the elementary objects. To go back to Democritus

metaphor: atoms are like an alphabet, but an immense

alphabet so rich to be capable of reading itself and think-

ing itself".

Thanks for the sentences and also similar many others in your essay. I'm agree with you.

Moreover I think that its really a quantized mirror world. It simply depends on from which side we are looking that world on the mirror. I'also invite you to my essay if possible.

Regards

Dipak

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Member Ian Durham wrote on Jul. 8, 2013 @ 20:07 GMT
Hi Carlo,

Interesting essay. I have always had a certain affinity for your relational approach having studied Eddington's work in great detail (if you are not familiar with it, it might be worth a look despite its age). But I wonder about some of the specific conclusions you have reached. In addition to the concerns shared by Matt Leifer, I'm not sure I buy the argument that recovers objectivity in the macroscopic limit while maintaining a relative approach. While I agree that a relational view is inescapable, so too do I think is some level of subjectivity.

In regard to the favored "starting position" in dynamical evolution, it is entirely possible to explain that without any reference to a form of description. Large systems of random processes can be shown to favor very specific macrostates simply via combinatorics (e.g. a pair of dice are the classic example, but much larger systems can be shown to have even narrower distributions).

Related to your example of the broken cup, I think there are some subtle issues that you have missed. Certainly by redefining "information" I could create a situation in which the entropy of the broken cup appears to be less than the entropy of an unbroken cup. But I do not see how to do this without completely redefining information in which case you're not really talking about the same quantity anymore. I think the problem here is that the exact relation between Shannon entropy and thermodynamic entropy is not as well-understood on a foundational level as many people think it is. I have no doubt that they are, but I think there are some deep foundational issues that still need to be resolved here.

At any rate, my only other criticism is that you seem to have avoided taking a specific stance on the actual question of the essay contest itself: does your argument imply "it from bit" or "bit from it" or, perhaps, neither?

Cheers,

Ian Durham

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Yuri Danoyan wrote on Jul. 9, 2013 @ 00:34 GMT
Dear Carlo

Warren McCulloch an American neurophysiologist and cybernetician, known for his work on the foundation for certain brain theories and his contribution to the cybernetics movement once told:"Greatest riddle of the World "What is "the same information?"

That is modern version question of Plato.

Do you agree with him?

Regards

Yuri

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Author Carlo Rovelli replied on Jul. 28, 2013 @ 15:51 GMT
No, I do not. Shannon has provided a very strait-forward and well defined way to understand the meaning of "the same information". c



Yuri Danoyan replied on Aug. 6, 2013 @ 23:39 GMT
Carlo

Could you please comment my essay

Yuri

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Giacomo Alessiani wrote on Jul. 9, 2013 @ 02:38 GMT
Mr. Carlo Rovelli , I am sure You do not Know who I am, as any other

participant.



I can say , to be in this contest is an historical goal.

Can I ask to read my essay , actually with zero score ?

Into my best hope the basic idea of the script is the first classic law for

quantum physics. I also need suggestions about the idea.

Best Regards. Giacomo Alessiani.

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Ralph Waldo Walker III wrote on Jul. 9, 2013 @ 13:04 GMT
Dr. Rovelli,

I enjoyed reading your essay and appreciated several of your insights. In particular, I thought you pointed out a couple of vital distinctions, such as the fact that, “Objects are not just aggregate of atoms. They are particular configurations of atoms singled out because of the manner a given other system interacts with them.” You also noted that, in addition to the fact that inanimate objects are not simple an aggregate of atoms, that “living systems are those that selection has led to reproduce continuously their own structure by, in particular, making use of the information they have about the exterior world.”

It would seem, then, that both living things and inanimate objects in our universe somehow interact with information, which, as you also point out, “has a pervasive and unifying role.” I would be curious to know if you think it might be possible that the universe is, in fact, some sort of information system. The fact that, “The world is not just a blind wind of atoms, or generally covariant quantum fields,” and that so many various fields of study suggest there is an exchange of information occurring seem to suggest an information system of some sort. Might it be possible that quantum field theory offers us a description of a form of information software at work? Perhaps the Theory of Relativity describes the hardware?

Again, thank you for your thoughts on the matter. Best to you in the future.

Sincerely,

Ralph

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Valentin Koulikov wrote on Jul. 10, 2013 @ 23:58 GMT
Dear Carlo,

thank you for interesting essay; this kind of ideas lead to the theory of fundamental physical informational interaction between objects and other kind of objects selected and controlled by us to become experimental devices (material reference frames, etc.), which can be called "subjects". Your time would not be lost if you check my essay where I show that on this way one may unify quantum and relativity principles in one single principle based on Object-Subject informational interaction:

http://fqxi.org/community/forum/topic/1612

Valent
in Koulikov

P.S. I believe that I have mailed to you my article on this matter a couple of years ago, but unfortunately got no response ("Time Loops and Unification of Quantum and Relativity Principles"), you may find the link to it in References to my essay.

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Armin Nikkhah Shirazi wrote on Jul. 13, 2013 @ 22:32 GMT
Dear Carlo,

What a remarkable and insightful essay you have written! I found the example of the balls with color and charge especially eye-opening. It immediately made me wonder whether our universe which had to start off in a low entropy state was "prior to that" not in a maximum entropy state by virtue of some kind of interaction that is no longer present in our current universe. I'm sure you have considered that possibility already.

Your essay is short but packs a punch. I am delighted to have read it. I'm not so sure that you will appreciate my essay because in the second half it introduces a principle which I believe undermines the concept of background independence in a quantum theoretical context, which I know is a major focus of your work. I should emphasize that my claim only concerns the compatibility between such background independence and the principle, if the principle is not adopted, then the argument given does not apply. If you do read my paper and find some fault with my argument, I would certainly appreciate hearing from the top expert in the field about it.

Best wishes,

Armin

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KoGuan Leo wrote on Jul. 18, 2013 @ 08:27 GMT
Dear Carlo,

You are my model in doing theoretical physics especially your relationship interpretation of Quantum Mechanics. You made a bold declaration: "I suggest that this incorrect notion is the notion of observer-independent state of a system (or observer-independent values of physical quantities). I reformulate the problem of the "interpretation of quantum mechanics" as the problem of...

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Lorraine Ford wrote on Jul. 21, 2013 @ 03:00 GMT
Carlo,

In a recent article you have, in effect, pronounced that the future of our world is already fixed and set in stone. Game over. In the face of the likelihood of catastrophic climate change, your's is an uninspiring position.

The article, on the edge website, argues for determinism and complexity, and against free will. Of course no one would disagree that complexity means that...

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Author Carlo Rovelli replied on Jul. 28, 2013 @ 15:47 GMT
"In a recent article you have, in effect, pronounced that the future of our world is already fixed and set in stone. Game over. In the face of the likelihood of catastrophic climate change, your's is an uninspiring position."

Oh no! If this is what you read in my article, I really have not been able to explain my ideas !!

carlo



Lorraine Ford replied on Jul. 28, 2013 @ 17:27 GMT
Carlo,

please help me to understand: does ANYTHING change future outcomes? What DOES change future outcomes?

(Obviously I'm not referring to the issue of complexity, which means that future outcomes in real life usually cant be predicted)

Lorraine

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Vladimir F. Tamari wrote on Jul. 24, 2013 @ 02:32 GMT
Dear Carlo

I enjoyed your lucid essay. You make it clear that particles somehow exchange information, but you provide no 'mechanism' by which such information is transmitted - what would be the equivelant of Shannon's information channels, say at the Planck scale?

My Beautiful Universe Theory also found here suggests precisely how the presumed dielectric nodes making up a lattice of the Universe transmit angular momentum (one can call it information about angular momentum!):locally, causally and linearly, and without the need for any sort of observer.

With best wishes,

Vladimir

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Than Tin wrote on Jul. 24, 2013 @ 23:49 GMT
Dear Professor Rovelli

Richard Feynman in his Nobel Acceptance Speech (http://www.nobelprize.org/nobel_prizes/physics/laureates/19
65/feynman-lecture.html)

said: “It always seems odd to me that the fundamental laws of physics, when discovered, can appear in so many different forms that are not apparently identical at first, but with a little mathematical fiddling you can show...

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Akinbo Ojo wrote on Jul. 25, 2013 @ 19:54 GMT
Dear Carlo,

Sorry to trouble you. I am not a professional physicist but I have a question I will like to be enlightened about. I am taking advantage of this forum to ask an expert so I can be clear although this may not be the subject of your essay. Is it being implied by the relational view of space and as suggested by Mach's principle that what decides whether a centrifugal force would act between two bodies in *constant relation*, would not be the bodies themselves, since they are at fixed distance to each other, nor the space in which they are located since it is a nothing, but by a distant sub-atomic particle light-years away in one of the fixed stars in whose reference frame the *constantly related* bodies are in circular motion?

You can reply me here or on my blog. And please pardon my naive view of physics.

Accept my best regards,

Akinbo

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Author Carlo Rovelli replied on Jul. 28, 2013 @ 15:45 GMT
The answer is no. Not at all. Physics is local. Best, carlo



Akinbo Ojo replied on Jul. 29, 2013 @ 09:19 GMT
Thanks so much Carlo for replying. Your reply suggests then that what determines whether two constantly related bodies will experience centrifugal force is in their local environment? If so, since it cannot be the bodies themselves it must be in space even if you may want to call this a field.

Following additional insights I have gained from interacting with FQXi community members, including your respected self (on Jun 26 and other days), perhaps you will like to view the judgement in the case of Atomistic Enterprises Inc. vs. Plato & Ors delivered on Jul. 28, 2013 @ 11:39 GMT. Thanks

I wish I had full access to the Wheeler article I mentioned before. I understand he compared his elementary quantum phenomenon to monads.

All the best, sir

Akinbo

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William Amos Carine wrote on Jul. 26, 2013 @ 17:11 GMT
Hey C. Rovelli,

Neat short essay! I Like here that entropy and information is dealt with as a tool.

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Douglas Alexander Singleton wrote on Jul. 28, 2013 @ 09:30 GMT
Dear Prof. Rovelli,

A good and thought provoking essay. If I understand correctly the idea is first the primacy/importance of the macro variables in determining entropy (that the entropy is a function primarily/only of these marco variables like volume, temperature, pressure) and second the importance of the interaction of two systems and the degrees of freedoms that come into play in these interactions. For example, certainly ignoring interactions or back reaction in black hole evaporation is a bad idea at the end stages where a BH evaporates. But as well this is a difficult problem.

I did have one open ended question -- many times for quantum systems one discusses "entanglement entropy"/von Neumann entropy/fine grained entropy which is defined as -Tr (p log p) with p being the density matrix of the system (I'm am just looking in detail at this so do not have very good intuition which is why I use formulas instead of words). This entanglement entropy has some odd feature in certain situation -- for example unlike usual thermal entropy it is not additive. So my question is "What can one say about entanglement entropy in the context of your arguments?" A quantum entangled system is "interacting" (sort of) but I'm not sure in the sense you mean interaction. In any case I am just beginning to look into this type of entropy and it has some (to me) odd features and it seems your arguments may have something to say in this regards.

Best,

Doug

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Author Carlo Rovelli replied on Jul. 28, 2013 @ 15:40 GMT
Hi Dough.

Von Neumann entropy is quintessential "relative" information, of the kind I am talking. It is not just "entropy of a system": it is entropy to a system relative to another. I am trying to work out the precise relation in these days.

Best, Carlo




eAmazigh M. HANNOU wrote on Jul. 28, 2013 @ 15:17 GMT
Dear Carlo,

« Relative information at the foundation of physics »

This title is revealing that information is the basis of our reality.

If reality is made both wave and particle.

Why not « Quantum and Wave Mechanics » ?

And where is the binary « 0 » and « 1 », in nature.

Accordingly to eDuality, see my essay which is less scholarly.

I rated your essay accordingly to my appreciation.

Respectfully, and good luck.

Please visit My essay.

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Author Carlo Rovelli replied on Jul. 28, 2013 @ 15:43 GMT
Careful, "Relative information at the foundation of physics" does NOT imply that physics is nothing else than relative information. Foundations are often large and rich. Information is one of the ingredients for better understanding the world. I do not think (nor know) if it is the only one...c




Author Carlo Rovelli wrote on Jul. 28, 2013 @ 15:38 GMT
Sorry for absence.

I was at various conferences (Oxford on Quantum and Cosmology, Nottingham on Relativistic Quantum Information, GR20 in Warsaw, and LOOPS13 in Canada).

Now I am back, and I read agin the posts.

Carlo




Peter Jackson wrote on Jul. 29, 2013 @ 12:16 GMT
Dear Carlo,

I thank you for your excellent analysis making a fascinating essay. But I find an apparent contradiction I wish to resolve.

The finiteness at the Planck length I can agree as wavelength gamma, then you seem to assume this is equivalent to the binary 0,1 of Shannon. But then you also find, (agreeably) that; "it is always possible to acquire new information about a system."...

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Author Carlo Rovelli replied on Jul. 30, 2013 @ 06:54 GMT
The reason it is always possible to acquire new information is quantum mechanics. It is the same reason for which after you have measured the z-component of angular momentum you can still get new information by measuring its x-component. In doing so, the information about the z-component becomes irrelevant, therefore the new information is acquired without increasing the total amount of information available.

This I think characterizes quantum theory. I do not think that we learn more by trying to connect this to some underlying quantum fluctuation. Like we did not learn more about the Maxwell equations by trying to guess some underlying mechanical explanation of these equations. We learnt more about them by realizing that they were simply describing some simple fact about nature, which we had discovered.

c



Peter Jackson replied on Jul. 30, 2013 @ 16:03 GMT
Carlos,

Interesting. Can you explain what a 'virtual photon' is, or why Snell's Law fails at Maxwell's near'Far field transformation along with Fresnel's refraction? We have to call the unexplained non-linear effect 'Fraunhofer' radiation and slip it under the carpet to be rationalised later! Unless you can offer an explanation?

Do you not believe that understanding the underlying quantum mechanism to the transform will aid our comprehension, so remove the anomalies and paradoxes (including such as Kinetic Reverse Refraction, another well known effect from optical science with not consistent theoretical explanation).

A mathematical identity is of course not a true or even absolutely precise 'explanation' of natures uncertainties, just a good approximation, Yes?

So I am suggesting perhaps these are the things we DON'T yet fully understand, or do you truly believe we do?

Peter

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Patrick Tonin wrote on Jul. 29, 2013 @ 16:08 GMT
Dear Carlo,

You have written an entertaining essay but I think that things could be greatly simplified if theoretical physicists would be a bit more adventurous with subversive ideas.

For example, Hawking and Bekenstein showed that the entropy of a black hole is proportional to the area of its event horizon. t'Hooft and Susskind then came up with the Holographic principal but can't find a proper working scenario for it. The "divided by 4" in the BH entropy formula is giving us a clue.

I believe that a black hole is in fact a plain circle and its entropy is proportional to the area of the circle (there goes the "divided by 4").

Why don't you try to use your LQG in the context of successive 2D frames ?

(each 2D frame representing the "present" information for an internal observer in the frame, each frame being a scaled up version of the previous one and the "present" information is moving through the frames at the speed of light).

I have done this in my simple theory and I got some great results. I am only an amateur physicist, so I am sure that you would discover a lot more if you tried that approach.

For example, I have discovered (and I can show) that the proton's diameter is just a scaled up version of the Planck Length and that the proton's mass is just a scaled down version of the Planck mass.

By using this simple "holographic" principle and a simple scaling rule, I concluded that Dirac was correct when he came up with his Large Numbers Hypothesis, unfortunately not many current physicists want to even consider that he was right.

I know that you like to question the fundamentals (that's why I am one of your fans), so, please be even more adventurous and at least consider some of my ideas even if I am a nobody.

Best regards,

Patrick

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Author Carlo Rovelli replied on Jul. 30, 2013 @ 07:07 GMT
Hi Patrick.

Nobody is "a nobody" in science. Remember the patent office clerk... I looked at your UB's and CBU's. Quite surprising indeed your numbers! Id didn't check out the arithmetic. Does it really give that? It should not have been easy to find these formulas... I'll try to see if there is something I can use... Best! carlo



Patrick Tonin replied on Jul. 30, 2013 @ 08:34 GMT
Hi Carlo,

Thank you for your reply.

Yes, the arithmetic is correct.

No, it was fairly easy to find these formulas, it is all simple logic.

Have you checked out the proton's diameter and the proton's mass formulas?

If I am correct, wouldn't this give us a big clue about the current proton's radius measurement problem ?

A+

Patrick

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Anonymous wrote on Jul. 30, 2013 @ 09:21 GMT
Dear Carlo,

Re your answer (28th July) to my post: doesn't your determinism mean that all future physical outcomes are already fixed and "set in stone"? (Obviously I'm not referring to the issue of complexity, which means that future physical outcomes in real life usually cant be predicted).

Cheers,

Lorraine

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Author Carlo Rovelli replied on Jul. 30, 2013 @ 12:34 GMT
Well, the issue you mention is like that in christian theology: God knows everything, therefore He already knows if I will go to Even or to Hell. Therefore this is already fixed. Therefore why bother about being good?

Where is the mistake?

It is in mixing levels. Here you assume you can decide something (not doing anything) on the basis of the fact that you cannot decide anything. This obviously is contradictory.

Either you discuss in the appropriate high level terms, where choice and responsibility make sense. Or you refer to the underlying physical deterministic evolution, in which case if you are trapped in this false logic you are jus a self destroying system and too bad for you ...

In other words, it is a non sequitur. c



Lorraine Ford replied on Aug. 1, 2013 @ 14:12 GMT
Carlo,

thanks very much for your reply, but I must disagree with your reasoning.

I would contend that there is no dividing line between "the underlying physical" reality and the "high level" reality. There is a difference in complexity, but there is no difference in the essential nature of reality between the high level and the underlying level. No new properties can miraculously appear ex nihilo at the "high level" that do not have foundations in "the underlying physical" level.

So if the underlying reality is completely deterministic, then the "high level" is exactly the same. Determinism means that (due to laws of nature) only one physical outcome is possible for each next moment in time. That is, at the high level, no "choice and responsibility" is possible for human beings in a deterministic universe. Surely, in a deterministic universe, to believe that "choice and responsibility" is possible is to deceive oneself.

Cheers,

Lorraine

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Lorraine Ford wrote on Jul. 30, 2013 @ 09:25 GMT
Dear Carlo,

Re your answer (28th July) to my post: doesn't your determinism mean that all future physical outcomes are already fixed and "set in stone"? (Obviously I'm not referring to the issue of complexity, which means that future physical outcomes in real life usually cant be predicted).

Cheers,

Lorraine Ford

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Author Carlo Rovelli replied on Jul. 30, 2013 @ 12:35 GMT
Lorraine, I have answered to the previous post, without seeing you had corrected it with your name.

c




Torsten Asselmeyer-Maluga wrote on Jul. 30, 2013 @ 14:03 GMT
Dear Prof Rovelli,

very interesting essay. I completely agree with you about the role of information in physics. It is the relation between the objects which counts.

Your two principles (leading to quantum mechanics) are not totally new. von Weizsäcker also discussed the abstract derivation of quantum mechanics from finite Hilbert spaces (like C^2). I discuss it partly in my essay.

Maybe one point of disagreement: In my opinion, the relation between the discrete structure of spacetime (like the area quantization of LQG) and the smooth spacetime is not well enough understand. Is it really necessary, that the spacetime itself is discrete? Using diffeomorphism invariance, the information contained in a smooth 4-manifold is discrete (as I explained in my essay). Also the substructures like surfaces are partly regid (see for instance a incompressible surface in a 3-manifold which can be a topological expression for area quantization). Do not misunderstand me, I'm not an oponent of the discrete spacetime but the relation between discrete and smooth is not really explored (in dimension 4 or lower any triangulation (or PL structure) is uniquely determed by a smooth structure and back).

Maybe you have time to look in my essay.

Best wishes

Torsten

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Anonymous wrote on Jul. 31, 2013 @ 03:46 GMT
Dear Carlo,

Thank you for a most illuminating essay, which deserves top marks.

You explained how "selected structures define finality". There is clearly a Lagrangian cast to this statement if the action is bound globally and is time symmetric. It appears that the relative information gained by one system (i.e., an observer) about another system (i.e., a quantum state) is reflexive. In other words, the act of measurement defines both systems. The observer erases the entanglement information which encodes the global interconnectedness of herself and the other system. Both she, as perceiver, and the measured state, as the perception, emerge as ontic entities. (See my essay "A Complex Conjugate Bit and It".)

This "infinite game of mirrors reflecting one another" brings to mind the image of Indra's net, with a jewel glittering at every node.

Best wishes,

Richard

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John Brodix Merryman wrote on Aug. 1, 2013 @ 02:48 GMT
Professor Rovelli,

As the eminence grise of these conversations, may I ask why physics favors the concept of information, over that of energy?

As living organisms, we are the result of billions of years of evolution. The

consequence of this process is two fairly distinct systems. One is the central nervous

system, to absorb, organize and act on information. The...

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John Brodix Merryman replied on Aug. 1, 2013 @ 02:52 GMT
That second paragraph broke into line breaks because I cut and pasted it from my own essay.

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Jonathan J. Dickau wrote on Aug. 2, 2013 @ 01:14 GMT
Dear Professor Rovelli,

While you tell an enjoyable tale and make a good point; I found your essay a bit disappointing, playing as it does upon the common misconceptions about entropy, and the confusion that exists about the extent to which the different types of entropy are interchangeable. Of course; the Scientific American editors did it too, when they ran an article about non-linear...

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Jonathan J. Dickau wrote on Aug. 3, 2013 @ 03:33 GMT
Dear Professor Rovelli,

While you tell an enjoyable tale and make a good point; I found your essay a bit disappointing, playing as it does upon the common misconceptions about entropy, and the confusion that exists about the extent to which the different types of entropy are interchangeable. Of course; the Scientific American editors did it too, when they ran an article about non-linear...

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Jonathan J. Dickau replied on Aug. 3, 2013 @ 03:40 GMT
Please note; this comment was first posted here last night, but it disappeared with technical problems today. I have slightly edited the copy, which I respectfully submit for your attention Carlo. I respect your work greatly, and hope not to offend, but I want it known where I stand on the Physics involved - or the description thereof.

All the Best,

Jonathan

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CS Unnikrishnan wrote on Aug. 3, 2013 @ 12:27 GMT
Dear Carlo Rovelli,

It was good to highlight that what was important are relative entropy and relative information, needing a reference template or a reference physical system. For experimental physicists this is obvious for ALL measurable quantities - that is why they create 'standards of measurements', a stable and universal metric of measures, for basic as well as secondary quantities. All measurements and hence new quantitative knowledge is a relative measurement. Information is no exception since it is encoded in physical states.

I felt that the initial example of Colored and Charged balls and inadequate observers perhaps was not appropriate since one assumes good measurement or observational apparatus BEFORE an observation is claimed - otherwise a specific observer's handicaps are to be folded in (convoluted/traced) into the measurement, as some blur function or coarse graining, or tracing over some variable. So, while it is true that special initial states are required for apparent irreversible behaviour, the statement about irreversibility assumes that the observer to which the sytsem couples is genuine and not blind, not zombie and so on. Irreversibility is relative with respect to initial states, but the observer's handicaps should not enter its formulation in physics.

Unnikrishnan

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Anonymous wrote on Aug. 3, 2013 @ 13:39 GMT
Carlo, as you may be aware, FQXi has just been moved to a new server and many people have found that posts are missing. A post I sent to you on Aug. 1, 2013 @ 14:12 GMT (in reply to your post on Jul. 30, 2013 @ 12:34 GMT) is missing, so I am resending the post in case it never gets restored:

Carlo,

thanks very much for your reply, but I must disagree with your reasoning.

I would contend that there is no dividing line between "the underlying physical" reality and the "high level" reality. There is a difference in complexity, but there is no difference in the essential nature of reality between the high level and the underlying level. No new properties can miraculously appear ex nihilo at the "high level" that do not have foundations in "the underlying physical" level.

So if the underlying reality is completely deterministic, then the "high level" is exactly the same. Determinism means that (due to laws of nature) only one physical outcome is possible for each next moment in time. That is, at the high level, no "choice and responsibility" is possible for human beings in a deterministic universe. Surely, in a deterministic universe, to believe that "choice and responsibility" is possible is to deceive oneself.

Cheers,

Lorraine

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Lorraine Ford replied on Aug. 3, 2013 @ 13:42 GMT
The above post was from me. I was logged out in no time at all!!!

Lorraine

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Author Carlo Rovelli replied on Aug. 5, 2013 @ 15:14 GMT
I think that that the interesting question is not to give for granted the meaning of "choice and responsibility", as if it was completely clear, and ask whether it works or not with what we know about fundamental physics.

I think the interesting question is to ask what we actually mean by "choice and responsibility" (and "free will") when we talk about these things in a world like ours, which is the one described by physics.

c



Author Carlo Rovelli replied on Aug. 5, 2013 @ 15:20 GMT
Here is an example: I drive on the highway with my nice car that has the automatic speed control turned on. My friend sitting next to me sees something unclear ahead and tells me: "There is something ahead, take away the automatic speed control, do not let the car decide by itself, in this situation." Is he making a mistake? No, of course, he is using "deciding" with the car a s subject, in a sense which is fully coherent, in this context. Once we understand exactly what we mean, we realize that there is no contradiction between this use of the words and the fact that everything is fully programmed in the car driving system.

Same for "free will" used with ourselves as subjects.

carlo




Paul Borrill wrote on Aug. 4, 2013 @ 00:45 GMT
Dear Professor Rovelli - I am always inspired by your papers (and books); this essay is no different. Your review of entropy is very enlightening. It was perhaps an accident that I read your paper back to back with the essay by Christian Corda, in which he says something very similar:

[from Corda] “In principle, a process in which pure states evolve in completely mixed states does not contradict the laws of quantum mechanics because the apparent information loss is instead hidden by quantum entanglement. The term entanglement means that the quantum state of a quantum system composed by two (or more) subsystems depends on the quantum state of each subsystem even if they are spatially separated. When one sums up the information in the two subsystems the result will be less than the information in the original system. The apparent information loss results hidden inside correlations between the subsystems.”

My favorite paragraph form your paper was: “Thus, the systems formed by atoms have necessarily information about one another in the sense of Shannon. The negative information (in this sense) that a system have about another is precisely the relative entropy of the second, which is relevant for the interactions with the first, and is the conventional thermodynamical entropy.”

In my essay I introduced an idea that might first seem absurd. A trapped photon bouncing back and forth between two atoms will trap energy/information, and for all intents and purposes will be “dark”, i.e. outside of (classical) time. I introduce the concept of subtime to describe relative reversible evolution between measurements; much of this was inspired by your earlier writings.

I think you will find this idea to be quite different to thermal time and Tomita flow. I would be honored to receive your thoughts after reviewing it.

Kind regards, Paul

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Hugh Matlock wrote on Aug. 4, 2013 @ 08:24 GMT
Hi Carlo,

Thank you for such a clearly described investigation into the fundamentals. I especially like these:

> If they are like letters of an alphabet, to whom do they tell stories?

> The world is not just a blind wind of atoms, or generally covariant quantum fields. It is also the infinite game of mirrors reflecting one another formed by the correlations among the structures formed by the elementary objects.

In my essay Software Cosmos I show how we might work within the simulation paradigm to model a world of information. This discrete computational cosmos has properties that we observe of our own, and in fact, I have carried out a test to see whether we now inhabit such a world.

Interestingly enough, a world constructed of information has room for more than the "blind wind of atoms". Different architectural layers of the software cosmos can have quite different properties. The layers of Life and Mind can lie below the physical layer of Matter, and not be (as conventionally assumed) emergent from it. Life and Mind, then, can animate Matter, and so produce the phenomenology of consciousness.

I hope you get a chance to read my essay, as I would love to know what you think of my model.

Hugh

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Member Olaf Dreyer wrote on Aug. 4, 2013 @ 16:42 GMT
Dear Carlo:

What a well written essay. I enjoyed reading it a lot. I usually hate it when people use these comments to immediately point to their own essays but here it seems appropriate and here is why: You point out that thermodynamic quantities depend on a coarse graining and that the proper coarse graining is determined by how the two systems interact with each other. In the example of the box of differently colored and charged balls you then discuss the possibility that there could in fact be different coarse grainings. Maybe there is a way to interact with the broken cup on the floor that makes it look like it has less entropy than the whole cup. My point now is this:

There is a special interaction between the two systems. Not all conceivable interactions are relevant. One of them is singled out.

The interaction that is relevant is the one that is mediated by the generalized rigidity of the systems (I point this out in my essay). For the cup this generalized rigidity is the rigidity of the lattice of molecules that makes up the cup (this is original example of rigidity). If you kick it, it kicks back. There is just one of these and it chosen by the dynamics of the molecules not by the observer.

If you think about the classical examples that one finds in thermodynamics you can see the same thing. The volume of a system is relevant because of the rigidity of the box that encloses the volume. We interact with the piston in a certain way again because of its rigidity etc.

So I think that you are pointing to an important fact but you are missing one half of the story: there is a special interaction.

Cheers

Olaf

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Author Carlo Rovelli replied on Aug. 5, 2013 @ 15:09 GMT
Hi Olaf.

Interesting. But rigidity cannot be such a general issue. Rigidity is a special feature of the Earth. Had we lived on Jupiter or Saturn, there everything is fluid... and the same for the Sun. I think we would had still conceived a thermodynamics, no?

carlo




eAmazigh M. HANNOU wrote on Aug. 4, 2013 @ 17:46 GMT
Dear Carlo,

We are at the end of this essay contest.

In conclusion, at the question to know if Information is more fundamental than Matter, there is a good reason to answer that Matter is made of an amazing mixture of eInfo and eEnergy, at the same time.

Matter is thus eInfo made with eEnergy rather than answer it is made with eEnergy and eInfo ; because eInfo is eEnergy, and the one does not go without the other one.

eEnergy and eInfo are the two basic Principles of the eUniverse. Nothing can exist if it is not eEnergy, and any object is eInfo, and therefore eEnergy.

And consequently our eReality is eInfo made with eEnergy. And the final verdict is : eReality is virtual, and virtuality is our fundamental eReality.

Good luck to the winners,

And see you soon, with good news on this topic, and the Theory of Everything.

Amazigh H.

I rated your essay.

Please visit My essay.

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Kyle Miller wrote on Aug. 5, 2013 @ 19:23 GMT
Your essay was nice and short. It provided an eloquent, overarching argument for why information is very important in physics. And how, exactly, it is built into the foundations of the physical world. However, I think you sort of neglected the question posed in the essay prompt. It is clear, in my opinion, that "bits" and "its" are both in the foundation. They are are both very fundamental concepts. The question was/is what is more fundamental. I suggested in my essay that force(s) are even more fundamental than both, i.e., its and bits from forces.

Please check out my essay: All Your Base Are Belong To Math.

- Kyle Miller

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Yutaka Shikano wrote on Aug. 5, 2013 @ 21:11 GMT
Dear Carlo,

Thank you so much for your interesting essay. I doubt your last section on relativity based on the Shannon-sense information. As also mentioned in my essay, http://fqxi.org/community/forum/topic/1836 , Shannon originally consider the amount of information can be taken as the optimal compression rate of bit sequences. In relativity sense, this connection is not trivial. From this viewpoint, it seems to be conceptually mismatched. What do you think?

Best wishes,

Yutaka

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Laurence Hitterdale wrote on Aug. 5, 2013 @ 21:30 GMT
Dear Professor Rovelli,

I agree with you, "The universe is not just simply the position of all its Democritean atoms." I agree further that, if this be true, then the

additional facts (i.e., the facts which go beyond the simple Democritean-atomic facts) have to be objectively "out there." The additional facts

should not be just subjectively projected onto the cosmos. ...

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Giacomo Alessiani wrote on Aug. 6, 2013 @ 02:40 GMT
Professor Rovelli ,

I am sure You do not Know who I am, as many other

participant.

Let me say , to be in this contest is an historical goal.

Can I ask to read my essay for some opinion?

Into my best hope, the basic idea of the script is a "classic law"

for quantum physics. Well, I need suggestions about the idea.

http://fqxi.org/community/forum/topic/1903



My Best Regards. Giacomo Alessiani.

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Charles Raldo Card wrote on Aug. 6, 2013 @ 04:03 GMT
Late-in-the-Day Thoughts about the Essays I’ve Read

I am sending to you the following thoughts because I found your essay particularly well stated, insightful, and helpful, even though in certain respects we may significantly diverge in our viewpoints. Thank you! Lumping and sorting is a dangerous adventure; let me apologize in advance if I have significantly misread or misrepresented...

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James Lee Hoover wrote on Aug. 6, 2013 @ 04:18 GMT
Carlo,

"The world is not just a blind wind of atoms, or generally covariant quantum fields. It is also the infinite game of mirrors reflecting one another

formed by the correlations among the structures formed by the elementary objects."

In "It's Great to be the King," I claim that this mirror is a telescope taking humankind back in time,access that enables us to visualize an anthropomorphic interpretation of reality.

I never thought of information being a unifying force and the assembling of atoms like an alphabet into a macro system. I like the idea of selected structures defining finality but not reality.

You have a more nuanced concept of It and Bit.

Jim

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Carolyn Devereux wrote on Aug. 6, 2013 @ 11:09 GMT
Your comment that the Universe is the net information that all systems have about one another seems to be the Machian Principle regarding the global affecting the local. A network of dynamic space-time would create this, everything would be connected to everything else (and the interactions create information). In my essay I have assumed such a model to create matter from dynamic space. However I was interested in your comment that a dynamical space-time is necessarily discrete. As a last minute questons can I ask why this is so?

I enjoyed your essay. Thank you

Carolyn Devereux

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Anonymous wrote on Aug. 6, 2013 @ 12:11 GMT
Hello Carlo

Apologies for not making contact sooner. I had to read your essay several times.

You wrote the first principle that the information contained in any finite region of the phase space of any system is finite. This aligns exactly with the Harmony Set of my essay because the nature of that 1-space model implies a limited amount of information, and one cannot have a model from this system that brings more information that in the founding structure, as a matter of equivalence (that is, under the GPE).

You introduce the second principle that it is always possible to acquire new information about a system. Unexpectedly, I think this aligns with the Harmony Set, because every iteration of the set introduces new structure, although the proportional amount that is being introduced becomes tiny when the set has a great number of previous iterations (states).

You said: If the system S can be in two states, say a and b and the system O can be in two states, say A and B and there is a physical constraint that forbids the states (a;B) and (b;A), thus allowing only the two states (a;A) and (b;B), then we say that O has (one bit of) information about S.

I don't think this carries very well. To say that O has information about S seems to have an bother in the epistemology. To use your analogy, just because one is not standing and smiling does not mean one was knocked down by a tree, or indeed anything. Even when picking out O and S, while the system might deduce the case, O may know nothing of S. Indeed, I'm not sure that it can know or have access to this with any proper connection really, but the bothers I am seeing are abstract and foundational. You have read my essay, so you will have seen a little of how I view ontology, epistemology, and the majority of what are otherwise well thought out arguments. So these don't mean my arguments would be those of most of the community.

Best wishes

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Christian Corda wrote on Aug. 8, 2013 @ 14:15 GMT
Carlo,

This Essay is not at level of your previous works. It's a little lecture to students on the topic "The reality, information and Democritus". Yesterday I rated it according to my judgement. In any case, good luck in the Contest.

Sincerely,

Ch.

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Algernon kk wrote on Feb. 2, 2017 @ 12:40 GMT
travestis

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dani maz tare wrote on Feb. 2, 2017 @ 13:39 GMT
travestis vamos in essa galera

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dani maz tare wrote on Feb. 2, 2017 @ 13:44 GMT
traveco

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