Essay Abstract

Simple questions can have profound answers and profound implications. We ask: why is a chair never seen in more than one place at the same time? Remarkably, the answer implies limits on unpredictability, and a fundamental upper bound on computability.

Author Bio

Priyanka Giri is a graduate student at the EGO-Virgo collaboration and at the Department of Physics, University of Pisa, affiliated with Istituto Nazionale di Fisica Nucleare, Pisa, Italy.聽 She is currently working on the Advanced Virgo+ commissioning. Her interests are in tests of general relativity, future GW detectors, and fundamentals of quantum mechanics and gravitation, and understanding the聽problem of time. She also enjoys discussing philosophy聽of physics.聽Tejinder P. Singh is Professor of Theoretical Physics at the Tata Institute of Fundamental Research, Mumbai, India. He has recently proposed the theory of Spontaneous Quantum Gravity, a promising new candidate theory of quantum gravity.

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"We well know that the gravitational effects of bodies are described by Newton's inverse square law of gravitation. Or, in the relativistic case, by Einstein's general theory of relativity." Is something seriously wrong with Newtonian-Einsteinian gravitational theory? I say that Milgrom's MOND has many empirical successes and requires a new paradigm in physics.

"The MOND paradigm of modified dynamics" by Mordehai Milgrom, Scholarpedia

Perhaps the most important unanswered question is: What is relativistic MOND?

7 days later

Hi Tejinder and Priyanka,

you (Tejinder) invited me in the blog of Stephen Klein to see your essay, because I asked, where the randomness, that is so fundamental in some of our main theories, comes from. Thanks for that.

But I also wrote, that I was looking for an explanation, where the randomness is not merely epistemological. But it seems to me, that is exactly the case in your essay.

But first things first. I really like the analogy of the pollen and the electron. If I understand you right, it is exactly the same mechanism, that causes the collapse of an electron into a random position, that also causes macroscopic objects to have well defined positions and deterministic classical behaviour.

This is somehow strange, but also very attractive in the sense of explanatory power of the theory.

Also very interesting to me, that you let us in, in your investigation of quantum gravity, for which I am grateful. Are there already any observable predictions that come from your theory? Or are the consequences still in the making? What are the difficulties you face? I got a lot of questions.

For the question about the randomness you seem to propose an underlying classical, deterministic and realistic theory at the cost of locality. Objects have predefined properties that are independent of observation. That is in a way, how most of us picture the world, and exactly this what I criticise in my essay. (Now it comes. But you invited me!) There I try explore the possibility of a view, that is realistic, but where objects emerge from relations between objects, which are described by symmetries. I speculate, that different environments different objects and laws might emerge. This might have as a consequence that near a black hole other objects emerge that in free space ...

But the problem of the origin/necessity of randomness in our physical description is still puzzling me.

Best regards,

Luca

    Hi Tejinder and Priyanka,

    Thank you both for an engaging and well written essay. I think you both are considering an interesting line of enquiry considering the notion of predictability at the limits of our physical theories. There are certainly some very big (and very small) numbers floating around!

    I'm curious to know how your discussion might fit into the broader conversation of quantum contextuality? In an SG experiment, assuming the electron and measurement procedure are drawn from classical local hidden variable distributions, you should be able to uncover this classicality in non-contextual . However, experimental results would suggest this is not the case and QM is non-contextual. How do you reconcile your results with those of contextuality, given that you wrote ``We have shown that fundamentally,

    nature is deterministic and predictable''?

    In liue of this comment, I am very interested in your ideas and I think you might find the discussion around the induced decoherence when a quanitsed mass is coupled to a gravitational field very helpful! I made reference to this in my essay.

    Good luck in the competition!

    Thanks,

    Michael

    Thanks so much Luca, for reading our essay.

    There indeed are predictions from my quantum gravity theory:

    1. The phenomenon of spontaneous localisation.

    2. Minimum length uncertainty: If a device is used to measure a length L, there will be a minumum uncertainty, which grows as L^(1/3).

    3. Dark energy is predicted to be a quantum gravitational phenomenon.

    4. An explanation as to why a charged rotating black hole has the same gyromagnetic ratio as the electron.

    If you would like to see a detailed basic introduction to this theory, kindly see this preprint Spontaneous Quantum Gravity, arXiv:1912.03266 And for more details you could please visit my website www.tifr.res.in/~tpsingh

    As regards randomness in my theory, it is only a consequence of not probing the underlying deterministic theory precisely enough. Precisely as in coin-tossing.

    Thank you for pointing me to your essay which I will now read.

    Best wishes,

    Tejinder

    Thanks so much Michael, for reading our essay. Your comment is very interesting, and gives us authors an opportunity to highlight an important point - quantum contextuality despite underlying determinism.

    Contextuality arises during a quantum measurement because we need to take into account the underlying Planck scale dynamics at the moment the interaction between a quantum system and the apparatus takes place. To help us visualise, let us consider a set-up such that over some time interval, say T, the measuring apparatus pointer has a (at Planck scales) periodic evolution in which a variable q of STM atoms completes one oscillation. Since the measurement is happening at energies below Planck energies, we have no knowledge of evolution of this variable q. It does not change at all, as far as we can tell. So the *time of arrival* of the electron at the SG is irrelevant in QM. But for the deterministic dynamics, what outcome will ensue upon measurement depends exactly when during this oscillation period T, did the electron arrive. In our example, we can assume that if the electron arrives during 0 to T/2, the outcome is spin-up, and if it arrives during T/2 to T, the outcome is spin down. Contextuality arises by way of the time of arrival - this will determine which path of the matrix dynamics gets chosen. We may want to think of time of arrival as the hidden variable, except that its not really hidden - a Planck scale probe would measure the exact time of arrival [there is something interesting going on here too..any such probe becomes a black hole, and cannot convey the information outside...in that sense, to answer Luca's query above, the randomness IS NOT merely epistemic].

    Thanks again for bringing up this important point. I will surely see your essay soon.

    Best,

    Tejinder

    Dear Tejinder,

    Thanks for your reply. And also for your questions in my blog to which I tried to answer. I certainly will have a look at your arxiv article.

    I slowly started to incorporate objective collapse theories into my framework in my replies to Flavio Del Santo and Christinel Stoica. Although maybe not in the way you would.

    Luca

    Dear Tejinder and Pryanka,

    It was a pleasure reading your contribution.

    We are all struggling with the essence of our reality, being time, space and gravity. You approached the subject in a new and clear way in your "Proposal for a new quantum theory of Gravity".

    "Randomness is a consequence of coarse-graining". All mini influences that are at the origin of sequence in our emerging reality are based on a lap of time or the flow of time. I think that without a conscious observer there is no flow of time observed, so the reality is unobserved and brought back into the for our reality unapproachable TOTAL SIMULTANEITY. There it is still a probability to become an observed sequence by a conscious agent.

    STM, space - time-matter, Maybe it could also be described as STG, space-time-gravity., which is more congruential with your latest publications. Furthermore, it is my humble opinion that the essence of matter is just probability (wave) and "at a large collection of (STM) atoms " in our emerged reality. It is gravity that at a certain grade of probability gives rise to the "dimension" of gravity.

    When you mention "predictability is regained at the Planck scale", I am afraid I cannot agree. When we are approaching the Planck scale we are approaching (in my interpretation) Total Simultaneity, the collection of all probabilities (futures, pasts, now's). The past of a conscious agent in a specific life-line is deterministic. The future that lies ahead can include each probability and therefore is not predictable.

    "At the Planck scale, we have a deterministic matrix dynamics of atoms of space-time-matter. These evolve with respect to Connes time τ ." Both Matrix dynamics and Thermal time hypothesis from Rovelli Connes are dealing with sequences of time from the past. When observed they already "happened". We always tend to mention that an experiment is taking place "NOW", but everything observed is history and gives no certainty about the future.

    The "singularity" that is placed always at the centre of a BH, is in my opinion not only present at the centre of the BH. The BH is a space-time-gravity emergence in our reality. Our reality is an emergent phenomenon that originates from Total Simultaneity (TS). TS is also compared to our reality a singularity, a for us non-achievable Point. In our emergent reality we can reach out at ANY POINT to the Planck Scale. After this LIMIT we are entering the singularity, so at any point in our reality, at any point of a BH we will find a singularity. (not only at the centre).

    Your essay gives a lot more opportunities to discuss, but then it becomes too long.

    Of course these are all interpretations based on my own understanding of reality. There is a multitude of theories and interpretations, yours and mine are just two of them. I learn every day and especially from your interpretation of gravity Tejinder. I hope that you will take some time to read my essay and leave a comment.

    Best regards

    Wilhelmus

      Dear Tejinder and Pryanka,

      Thanks for your essay. I found it really very interesting. Your deductions are completely sound, but they are based upon a particular interpretation of the maths of Quantum Theory. This interpretation was originally built around the electron which is quite a complicated particle, and is an interpretation which, after nearly a hundred years of thinking, is generally accepted as the one that fits the best.

      However, if you take the simplest particle, the photon, it is possible to build a completely different interpretation of what is really happening but still uses exactly the same maths (and is based on Schrodinger's idea that the wavefunction is something real rather than a mathematical device). This is is a totally unexpected surprise. Moreover, there are good reasons to then believe that this alternative interpretation has the potential to apply to the electron and to other particles as well.

      What I think is really interesting is that a simple reinterpretation of the maths like this can have really profound effects on further thinking. Indeed, I think, if you were a proponent of this reinterpretation, you would have written a completely different essay. As each interpretation uses the same maths the question then becomes which essay to write.

      If you are interested, there are further details in my essay. What do you think?

      All the best,

      David

        Dear Priyanka and Tejinder

        Thanks for a very well written essay whose basic conclusion I agree with.

        However, you stated: "A large collection of STM atoms, together with their dynamics, defines the fundamental universe. This dynamics is deterministic and time-reversible. Predictability is regained at the Planck scale!"

        I would argue that the dynamics of space-time-matter particles is not time-reversible as commonly thought, as all charged particles radiate when in motion and the radiation is governed by Maxwellian rules and is divergent in nature. (See my essay,

        I also make other arguments for and against determinism.

        You ask the question: " Is the quantum mechanical description of nature like how we describe water as a thermodynamic fluid, and is there a deeper deterministic microscopic theory underlying QM, same way as atomic theory underlies the fluid that is water?" to which I would answer absolutely yes. My branch of physics, structural physics, looks at the basic preon structure of protons, neutrons and electrons, and shows how this structure can explain many things beyond QM. The basic quantum numbers of particle physics can be totally simplified and this leads to a much better understanding of particle interactions, removing many so called violations of quantum numbers. In this case I would argue that reductionism works, and there is an end to the 'stack of turtles'.

        Regards

        Lockie Cresswell

          Dear Lockie,

          Its very kind of you to read our essay and comment on it. Thanks so much. It is wonderful that we agree that there is a deterministic theory underlying quantum indeterminism. We will definitely read your essay and compare notes.

          Regarding whether the deterministic dynamics is time reversible or not: actually there is no disagreement between us, because the level that you are referring to (radiation from a charge) is an emergent level in our theory. The underlying Planck scale dynamics is deterministic in our case. However, the emergent dynamics, based on our expanding universe, in all likelihood, arose from an asymmetric initial condition [at the big bang] in response to a spontaneous localisation event. These asymmetric and time-irreversible initial conditions give rise to the expanding universe, an arrow of time, and the so-called retarded solutions in Maxwell's electrodynamics. These ought to account for radiation (as opposed to absorption) from an accelerating electric charge.

          Hope we are in agreement about this now.

          Our best wishes to you in this contest.

          Tejinder

          Dear Priyanka and Tejinder,

          Very impressive essay, with a lot of ideas which are not just ideas, but well developed into a physical theory which connects many aspects of physics. I liked the idea to obtain the spontaneous collapse from a more fundamental theory, I find this a good point because I think the original GRW idea is quite artificial. But even if I think the original idea of GRW was artificial, it's brilliant and brave, and it seems to work well as an interpretation of QM, and makes testable predictions, unlike other interpretations that try to fly under the radar. I like to have the dynamics and the collapse emerge from a single law, rather than being distinct and even conflicting laws. I didn't continue with reading Adler's book, which I started at some point, but I think the idea of trace dynamics is great, and if it can connect with Alain Connes's noncommutative geometry then this is something! Also, the ideas you discuss about a quantum computer at Planck scale, and the relations with computability and predictability, are very thought provoking. I also have a question, do you have a way to recover spacetime from this theory?

          I wish you all the best in this contest!

          Cheers,

          Cristi

          Dear Wilhelmus,

          Thanks so much for reading my essay and for your detailed comments on it. I think we are in agreement on many things, even if not all.

          So I have a time-reversible matrix dynamics at the Planck scale, evolving in Connes time tau. Maybe this can be thought of as what you refer to as TOTAL SIMULTANEITY? I definitely do not have a past, present and future here.

          When coarse-graining is done, quantum theory emerges. This also is time-reversible dynamics. However, if sufficiently many d.o.f. are entangled, rapid spontaneous localisation occurs. That is because the anti-self-adjoint part of the Hamiltonian, originally negligible, now becomes significant, because of enormous entanglement.

          I believe you can have total simultaneity here too, only, it is hidden under the coarse-graining, I think.

          I am reading your essay - thanks for pointing me towards it.

          Take care Wilhelmus.

          Kind regards,

          Tejinder

          Dear David,

          It is very kind of you to read my essay and comment on it. Thanks so much. For me as well, the wave-function is more than a mathematical device. I woud say the wave-function is the same thing as the thing it describes! :-) At the deepest level, nature does not distinguish between the material world, and the mathematics that describes it, in my opinion.

          I shall surely read your essay soon.

          My best wishes,

          Tejinder

          Dear Cristi,

          Thanks so much for your kind comments and good wishes. You write so well in this post - its a pleasure to read your writings, and I am enjoying reading your essay currently.

          About the recovery of space-time: yes, we do. Space-time and gravity arise from the spontaneous localisation of material bodies, and actually this is shown mathematically. In a simplistic way, we say - space-time arises from collapse of the wave-function, or, space-time is what is left behind / generated, when macroscopic objects undergo the GRW localisation. More precisely, each space-time-matter atom in the matrix dynamics can be thought of as a sum of a bosonic part and a fermionic part. When a large number of STM atoms get entangled, their fermionic part undergoes rapid spontaneous localisation, giving rise to macroscopic bodies, and leaving behind the net bosonic part as classical space-time / gravity.

          It was always a worry for me that QM and GRW take an external classical space-time as given, and for the latter to exist the universe must be dominated by classical (macroscopic) objects. But these objects are supposedly classical because of GRW. So it is like...GRW depends on GRW, which of course is not satisfactory. Now though, classical spacetime and classical objects emerge concurrently, from a state in which neither were present, through spontaneous localisation. In my theory, space-time does not have to be present a priori, for material localisation to be formulated.

          I know that you have a deep understanding of these matters. So your appreciation means a great deal to me. Thank you Cristi. Despite COVID, hope we meet again soon.

          Best,

          Tejinder

          Dear participants,

          I am in this unenviable situation that all the comments on my essay are glowing and positive, but my score is going down and down. A participant just gave me a 4.0

          Whereas all the essays I have rated thus far, I have rated in the range 7-10. Strange are the ways of some participants :-) Sometimes I wonder if an Indian participant in the midst of many Western brothers and sisters comes in for special treatment, despite being an FQXi member?! May truth speak for itself, no matter which part of the world it comes from.

          I and my coauthor have presented a new deterministic theory that underlies quantum indeterminism.

          Thank you, and best wishes to all participants for success in this contest,

          Tejinder

            Dear Tejinder,

            I wouldn't worry too much. I'm an archetypal Westerner but my essay is scoring considerably less than yours. You might like to know that it is at least clear to me that you are saying something quite radical and interesting: that, although at a larger scale the Universe appears not to be deterministic, at the Planck scale it is actually deterministic, just as Brownian motion appears random but is deterministic. If that's correct it's obviously of major importance. I wanted to understand it all in more detail, but some of the crucial parts of what you say depend on things which I don't know about (my fault, not yours). I often wonder if there are wonderful, insightful, and revolutionary ideas that are just lost because they are never recognized as such.

            This is the first time I've entered a FQXi contest. I've enjoyed reading the essays, they've really made me think, even if some don't seem to hang together very well and others I don't understand. It's good to be able to encourage people and suggest a few more things they could think about. It's has also been good to have some feedback on my own ideas, even if some of it is rather challenging. Writing the essay has also really helped develop my ideas and given me lots more to think about. Despite my fairly low score, I'm still proud of my ideas, just like I'm sure you're proud of yours.

            As to marking, I haven't a clue how to do it, and have given up after marking one essay. I think it's great you have given people high marks - it's good to reward the enormous effort that most of the contributors have clearly made.

            Anyway, you could still win the contest!

            All the best,

            David

            Dear David,

            Thank you, that is very kind of you, to put it like that. I am very happy that you see it clearly that there is a new idea here - it builds on Stephen Adler's work I should say: he was the first (I think) to propose that Planck scale determinism underlies quantum indeterminism. I added gravitation to his framework.

            I agree the scoring has little to do with eastern or western, it is what it is. I am sorry I got carried away.

            I adopt the philosophy that good new ideas, once created, belong to humanity, not so much to the person who created them. So if I have a good idea, I expect other experts to look at it and examine it, no matter who gave it. How soon that will happen unfortunately depends on who proposed it. An influential physicist from a top-ranking university will have it heard much more easily than otherwise. I think eventually radical new ideas find their way into the mainstream, but the sociological path is quite random :-)

            I appreciate your honest conversation, and it is good to have participants such as you in the contest. And like you rightly said, we are proud to have gotten the ideas we had, notwithstanding the ratings. I also totally agree that each and every participant here has worked very hard on their essay, and everyone needs a fair appraisal - nobody deserves low scores like 1 and 2 on their hard work.

            My best wishes,

            Tejinder

            Tejinder,

            I can understand your concern about scoring of essays. I have the same concern about scoring for superior essays like yours. I have experienced the same frustration. My scores range from 5 that are 4 or less to 4 10s, and my essay does not rival yours.

            Your essay more clearly describes the quantum world and its transition to the classical world than any explanation I've seen. The pollen and the electron is the perfect metaphor and you use it skillfully. And you are not wedded to one interpretation such as the Copenhagen. I like that. Also like your quantum gravity discussion. I hope you share your descriptive capabilities with students. You have a great penchant for teaching. Saying that quantum unpredictability is only a consequence of our ignorance of the Planck-scale world like the pollen grain is an effective comparison. I make note of research that effectively links quantum and classical world in my essay. I hope you can read it: https://fqxi.org/community/forum/topic/3396. My rating is a 10 and is your 10th. Ambushers usually take advantage of comments to strike.

            Regards,

            Jim Hoover