Thanks, Peter -- good luck to you as well.
Frank, I'm afraid I don't really follow much of your comment, but good luck developing your ideas. Friedemann is an adjunct faculty member in our department, but he doesn't teach here, and is mostly at SETI. He's working on some very interesting things these days...
Hi Armin,
Yes, the LSU assumes a block universe, but so does the NSU and all of modern physics, as I see it. (With the exception of the measurement problem as applied to the standard quantum state; for more on this telling mismatch you'll have to dig up my entry to the very first FQXi contest.)
Denying a block universe is basically saying that we're parameterizing physics all wrong, and we shouldn't have functions that look like the classical Electric field E(x,y,z,t), but instead things like E(x,y,z,t_clock,t_obs), where t_clock is usual time and t_obs is the time at which one is discussing E. Maybe someone will develop such a physical theory, but until they do, physics assumes a block universe.
As for your second question, it depends on what you mean by "violations in causality". See the recent piece on my work with Huw Price.
Also, I'm not trying to "rationalize" away entanglement -- I'm trying to come up with a spacetime-based LSU model that quantitatively yields all of the same correlations as the standard configuration space version. I don't have it yet, but there are no conceptual show-stoppers. As for whether I'm 'giving up too soon'... I'm actually just exploring an alternate path towards the same goal. I don't think the century-old NSU-approach to quantum phenomena would suffer if a few researchers headed off in a new, promising direction. :-)
If your entry concerns the path integral, I'll put it near the top of my to-read-list... Thanks for the pointer!
Hi Yuri,
I think I disagree with Weinberg's response to your interesting question -- I don't think that you can discretize space while not discretizing time, at least not in any GR-friendly way.
That said, I'm not a particular fan of discretization at all -- at least not the conventional justifications for it. (That was the last essay contest, which I linked to above.)
My essay devoted at first to splitting space from time.
GR-is not completed theory,as SR.Why i must be friendly to her?
Some of the fundamental stuff:
(1.) Zaanen:
Quantum Critical Electron Systems: The Uncharted Sign Worlds
Mottness collapse and statistical quantum criticality
(From "Mottness collapse" above:) "For 'everything else' this connection with classical statistical physics is severed as the quantum partition sum contains both positive and negative 'probabilities': the fermion (or 'quantum') signs. On the one hand, these represent the greatest technical embarrassment of theoretical physics because there is not even a hint of mathematics that works in the presence of signs [30]."
Pacifying the Fermi-liquid: battling the devious fermion signs
Fermions, fermions, fermions! (PowerPoint converted to PDF)
(2.) Troyer and Wiese:
Computational complexity and fundamental limitations to fermionic quantum Monte Carlo simulations (Main paper ... cited in all Zaanen above)
Quantum Monte Carlo and the negative sign problem (PowerPoint converted to PDF)
Hi Michael,
Yes, lots of points of agreement. But let's take the disagreements one point at a time.
First, you bring up the block universe. This is a red-herring that has little to do with NSU, LSU, or anything directly related. In my mind, the arguments against the block universe (arguments for presentism, or the growing block) are simply are not consistent with SR, GR, or how we parameterize physical events (see my post to Armin above). I know that lots of philosophers (and some physicists) seem to think that presentism or the growing-block is potentially viable, but the burden of proof is on them, not me. Smolin is trying to change physics to add a "now", which is fine, but physics does not currently have a "now". And most of the anti-block arguments sneak in multiple time dimensions in practically every sentence. Even the way you phrased it --" But from this it doesn't follow that the future is equally real or 'already there' ", is using the word "already" that treats time as a subject while using the word "future" that treats time as an object. Those are two different times (the time at which the future is discussed, and the time of the future in question), ergo one needs a model with two time dimensions to even have a physics-based discussion about presentism.
I'm confused about your sentence that reads: " As far as we can see, someone could (and they do) still believe in NSU/reject block universe and adopt all your other suggestions." This baffles me, and leads me to think I didn't write a very good essay, given that my primary suggestion is to reject NSU. And while I maintain that ordinary NSU physics implies a block universe, LSU *certainly* implies a block universe. What do future boundary conditions mean to someone who doesn't think the future is "real"? Who is "someone"?
For your next big point, I grant that I have no detailed model, just some of the pieces. You guys are way ahead of me on that front. (Actually, I have a beautifully simple model (hinted at the end of my essay), but I'm having a devilish time working out the math, so I don't yet know if it generates the right probabilities.) I also would like to see how my (future) model deals with all these things, but it's always nice to map out potential show-stoppers before one gets that far. In my experience, all of the proposed show-stoppers come from people implicitly assuming NSU without realizing it. Therefore I wrote this essay to help lay out the fact that NSU is a pervasive assumption, not a necessary logical position.
You write: " you still assume there would always be a 3+1 type explanation of a NM sort between the measurements, you just have to work backwards to get it.", but that's not quite right. In an LSU model, once you work backward to fill in the 4D spacetime, you can translate that 4D description to a 3+1D *description* of what is going on between measurements. But I do not think it will be "Newtonian", in that it will not always be a solution to some master differential equation , and I do not think it will be an "explanation", just a movie-like description of what actually happened. For an *explanation*, one will have to consider the whole 4D-LSU picture. Hopefully this makes it clearer how much difference there is between the NSU and the sort of LSU that I envision.
You end that part with "Also notice that the use of future boundary conditions doesn't require that QM systems have definite worldlines and the only reason to assume they must is some sort of NSU prejudice." First of all, you know I'm looking for field descriptions, not particle descriptions, so "worldlines" is a bit misleading. But I'm not sure what you're getting at, exactly... asking the universe to have some particular reality between measurements doesn't seem NSU or LSU, just *realist*. Again, that intermediate solution need not, in general, solve a differential equation.
Finally, you seem to imply that your RBW gives up "more of the NSU-type" picture than I want to myself, but I think you're conflating much of the realism of standard classical physics with the Newtonian Schema, as defined in my essay. Classical physics works on a continuum; does this make the continuum in any way part of the Newtonian Schema? No -- see the definition of NSU in section I. (After all, my main example of the NS is a computer, which are typically digital!) I grant that RBW gives up more of standard physics than I want to, but let's not throw out perfectly valid concepts unless we need to. What quantum phenomena force a spacetime-realist to give up is the NSU, not spacetime itself. Maybe spacetime will have to go as well, but I'm never going to make that leap without first undertaking a much better exploration of the spacetime-realist-LSU landscape.
Best, Ken
You certainly don't have to be friendly to GR or SR -- many quantum theorists take the same view.
For me, I guess I just have too much respect for Einstein's hard-won insights, and too little respect for our human intuitions about time.
My favorite quote from Einstein is:
"What I am really interested in is knowing whether God could have created the world in a different way; in other words, whether the requirement of logical simplicity admits a margin of freedom."
Dear Professor Wharton,
Thank you for your eloquent essay. As I am one of those lay persons for whom the Lagrangian approach is "non-intuitive", I can't pretend to follow all of your arguments in its favor. Yet, your criticisms of the Newtonian approach seem clear enough to me. My corresponding thought is that the laws of physics are algorithms summarizing, after the fact, empirical data. One tends to forget that, in favor of a notion that they have some independent causal power to "determine" the future. This is so only to the extent they can be extrapolated to new situations. Otherwise, 'determine' can mean only the human sense in which one does one's best to determine what is, or will be, the case, or will be observed. In other words, dynamical equations do not have causal power and do not describe determinism in nature, only the logical determinism that belongs to mathematical systems, which are products of definition. Whether the sample of data used to fit the equation to reality consists of an 'initial condition' (NSU) or of 'boundary condition' (LSU) seems to me irrelevant to this point, though there may be, as you say, advantages to the latter approach.
In any case, it seems common sense that the universe can "compute itself" only in the trivial sense that it is an analogue of itself--an "analogue computer". Even if the universe is ultimately discretized, in no way can we assume that it is a digital computer that "processes information" in the way that our computers do, obeying the laws of physics as a computer obeys its program. Such beliefs are but the worst sort of anthropomorphism, embracing current technology as the metaphor for reality. But that is nothing new in physics, which early embraced clockworks and machines as models, and now the computer as universal machine.
Dan
Dear Ken
First of all it's great to know that we are neighbors living in San Jose. I also have been a part-time lecturer at San Jose State in the past and have several faculty friends there. I would like to get in touch with you and meet you if you would like to share the mutually beneficial results of our work.
Your conclusion -"The universe is not a computer" is fully vindicated by the results presented in my paper - -" From Absurd to Elegant Universe". It is shown that the observed universe behavior can be predicted via proper inclusion of the missing physics of the well-known spontaneous decay of particles. This new physical understanding that is missing from QM and GR provides a better alternative than merely using an alternative mathematical scheme to solve the QM mysteries, inconsistencies, and understanding the universe. Inclusion of this missing physics provides the degree of freedom in the universe that a computer does not have. The QM uncertainty is shown to be an artifact of this degree of freedom so far ignored in physics/cosmology theories. There is no need to "....assuming the NSU must be correct, and using suspiciously anthropocentric reasoning to recast the universe in an image of our quantum calculations" as you have rightly said in your paper.
My paper provides a new fundamental understanding of the Cosmological Constant and relativistic universe expansion based on spontaneous motion. The current QM and GR paradoxes and inconsistencies are shown to be artifacts of the missing (hidden) physics of the well-known phenomenon of spontaneous decay. A new Gravity Nullification Model for Universe Expansion (GNMUE) is proposed that integrates the missing physics of the spontaneous mass-energy conversion into a simplified form of general relativity. The model predicts the observed expansion of the universe and galaxies and other data. The model provides answers to key fundamental questions and resolves paradoxes among general relativity, quantum mechanics, and cosmology. It also bridges the gap between quantum mechanics and relativity theories via revealing relativistic understanding of the inner workings of quantum mechanics. The impact of the new understanding on widely-accepted fundamental assumptions is discussed and a new wholesome perspective on reality is provided.
I would greatly appreciate your comments on my paper. Please feel free to get in touch with me at avsingh@alum.mit.edu.
Best Regards
Avtar Singh
Dear Ken
Nice essay. I hadn't before given much thought as to why most physicists do not
like the idea of future boundary conditions. I like your anthropic explanation.
From reading some of your other work it seems you are mostly interested in Lagrangian field theory rather than Lagrangian mechanics. For this reason, I'm curious to know how you imagine describing an electron?
If you imagine the electron as being a soliton, then we agree on that. On the other hand, I think that looking for a nonlinear field theory of the electron is jumping way too far ahead in terms of our current knowledge of physics because the length scales are too small. The experimental bounds on detecting internal structure of the electron charge-center suggest it would be a rather small soliton (< 10^(-19)m), which is an awful lot smaller than the electron Compton wavelength and I think too small to be relevant in quantum mechanics.
So the way I imagine future boundary conditions most directly playing a role is through Lagrangian mechanics (2nd or higher order) not field theory. I touch on this in my essay (briefly in Section 2.1). Hope you find it interesting.
Good luck with the essay!
Andrew
Ken.
To simplify; I found mapping abstraction back to reality does not describe nature using present mathematics. Substituting the strict disciplines of logic however allowed a model which appears to give far more consistent results.
The model challenges a few assumptions which I identify. I assume you haven't yet read the essay? It's quite dense but mainly conceptual. Too many and too little time I know. (I'm mainly in astronomy and quantum optics so speak different languages anyway).
Your rationalisation of the theoretical background to my work is none the less very helpful and encouraging. I hope to cite your work.
I do hope you can read mine and comment, and forgive the Shakespearian metaphors to help kinetic visualisation!
Best wishes
Peter
Ken
I like your paper, and think that this issue of the universe being or not being a computer is important. I don't think there is any conflict if we say that evolution of the wave function is deterministic. So its not so much that there are future boundary conditions, its that we can know some probabilities with certainty. We know that we are mortal for instance. We can not escape the unbearable certainty of some outcomes. There are certain two state systems.
Determinism is a tricky thing. There are two types that I can articulate, one is cold determinism of the classical, and the other is the warm determinism of the quantum. Determinism is a foundation it seems, but the universe seems to prefer the latter over the former.
In any case, it seems that you would agree with the statement that quantum universe is certainly more relevant than the classical one, would you agree?
Hi Ken,
First, regarding your essay. Title not withstanding, you are not really arguing against the universe as literally a computer a la Lloyd or Wolfram. You only indirectly argue against them by positing a block universe, which certainly can't be computed. So my questions were about trying to pin down your main conclusion. Now, you admit in your reply to me that you don't have a novel argument for block universe, though I assume you want that to be a distinguishing feature of LSU. Another possibility is that you are really arguing for a new time-symmetric interpretation of QM but again, merely being a block universe is neither necessary nor sufficient for that. In other words, there can be block worlds without local time-symmetric processes and there are time-symmetric accounts of QM that are not block world. Yet another possible interpretation of your essay is that you see some necessary connection between LS and LSU or some ontological fact about reality, but of course any such inference would require extra premises not given in the essay. And finally, since we already knew that a time-symmetric psi-epistemic account of the QM could deflate the MP and provide a local picture of entanglement, that can't be your novel conclusion. I think the answer to what is novel in your essay comes at the end and again in your reply to me:
"In an LSU model, once you work backward to fill in the 4D spacetime, you can translate that 4D description to a 3+1D *description* of what is going on between measurements. But I do not think it will be "Newtonian", in that it will not always be a solution to some master differential equation, and I do not think it will be an "explanation", just a movie-like description of what actually happened. For an *explanation*, one will have to consider the whole 4D-LSU picture."
If you could find such a formalism, that might lend some extra credence to a block universe and could constitute a novel time-symmetric interpretation of QFT. If this is indeed the heart of your essay, here's my challenge to you. If the lagrangian density L is a function of the field f and its derivatives, S is stationary wrt to f (LS formalism), and f satisfies the boundary conditions (LS formalism), then L satisfies a differential eqn (NS formalism). If you want your LS soln to allow for a continuously mediated (3+1)D story, then I don't see how L won't be a function of f and its derivatives, thus allowing for an NS counterpart. Can you explain how you plan to avoid this LS-NS correspondence? Isn't there a theorem to this effect? See http://en.wikipedia.org/wiki/Lagrangian for example.
Of course what's interesting about our account http://fqxi.org/community/forum/topic/1393 with the SCC at bottom, is that it's exactly what you are looking for except you would have to give up the continuously mediated (3+1)D description. Even though you say such a description wouldn't be explanatory, you think the lack of such a description entails instrumentalism. An understandable worry, but our view isn't instrumentalism. The key to understanding why is seeing that our "fields" are such that matter/sources and spacetime (the metric) are inextricably connected. So it isn't that some independent dynamical QM entity disappears at one point in some spacetime arena and re-appears at another point in that arena. Our "fields" are spacetimematter fields, not some continuous medium between events. Spacetimematter fields on the graph are the fundamental ontological elements and these are not dynamical entities in some (3+1)D sense, they are inherently 4D. In other words, for you "between" necessarily means "between time-evolved entities." To see what we're saying just flip that perspective, i.e., let "between" give rise to "time-evolved entities involved in processes." Then you'll be asking the right questions, e.g., "What is happening between measurements?" becomes "What is between for measurements?" [Answer: spacetimematter fields on a graph.]. When you take spacetimematter seriously, you have to re-think what you mean by "between", "duration", "distance" and so on, in such situations. This is as big a difference in what it means to "explain" as when we went from Aristotelian to Newtonian physics. You worry that our model is needlessly extreme, but that depends on the pay off right? Gauge fields on links allow us to discharge the mysteries of QM with a psi-epistemic account that explains interference, entanglement, discrete outcomes, all consistent with SR and no MP. It also allows us to explain so-called dark energy and unify GR and QFT. Nor do we give up spacetime as you accuse in your reply, we simply give up the differentiable manifold as fundamental. You are so close to us in spirit, if only you can throw off the remaining chains of dynamism.
Ken,
Thanks for the detailed response. You have provided me with several pieces of information I didn't know, and several other ideas I will have to carefully consider. I share your preference for GR and its few simple principles. However, coming from a math background and working mostly with very nice things like algebraic schemes and complex manifolds, it is hard for me to believe that the physical world is based on similarly nice things. I expect successful theories beyond GR and the SM to still be based on simple principles, but possibly involving arbitrarily messy mathematics. Take care,
Ben
Dear Ken
very nice thoughtful essay, one of the best. A comment: I am a little surprised you do not mention Aharanov's "two-time" formalism (see for example this paper and references therein), as it seems very close to what you are proposing as regards the way time works.
As regards the LSU formalism, this non-local approach is very interesting. You state "Instead of initial inputs (say, position and angle), Fermat's principle requires logical inputs that are both initial and fi nal (the positions of X and Y). The initial angle is no longer an input, it's a logical output."
Yes indeed. What this approach does is very interesting: it puts dynamics into a framework that resembles the process of adaptive selection (the dynamics is offered a variety of choices, and selects one that it finds optimal according to some selection criterion, rejecting the others). This kind of process occurs in various contexts in physics, even though this is not widely recognised; for example it underlies both Maxwell's demon and state vector preparation (as discussed here ). I believe there may be a deep link to the dynamics you describe. This may be worth pursuing.
George Ellis
Hi Ken,
I'm very relieved that the Universe is not a computer! Sure, I need to re-read your essay many times to only partly understand it. But I need not know all the rules of hockey to see that a game is brilliantly played.
Best regards!
Hi Peter,
Sounds like you're going farther than I am, if you're discarding *all* present mathematics as a possible template for reality. I'm just targeting one particular style of mathematics (the Newtonian Schema), but I rather like the basic framework of the Lagrangian approach.
I guess I just don't see how one can even *do* physics without any mathematics at all...
Your essay is tough going to try to extract your main points, and I'm afraid I'm not having much success.
Best, Ken
Hi Ben,
Glad you found something useful here. And we're on the same page when it comes to the simple principles / messy mathematics - with GR being an excellent example.
Best, Ken
Hi Dan,
I agree that the usual focus on empirical data is one way that anthropocentrism finds its way into foundational arguments. But I didn't mean to imply that it was inherently impossible to map useful mathematics to reality. After all, *something* must determine the patterns we observe in the universe - it's not a random block of events. Still, I agree that this "something" is probably not the dynamical equations that we find so empirically useful. (And note the LSU does not merely put boundary data on such equations, but operates at a higher level than the equations themselves. In principle, the LSU can work without dynamical equations at all.)
Also, I trust you noticed that my main argument is completely distinct the analog/digital issue (for my views on that issue, see the previous contest). My main argument here is that the universe is not even an analog computer, at least not one that is governed by the 3-step Newtonian Schema.
Best, Ken
Hi Avtar,
On a quick scan, I'm afraid I can't find the connection between our essays, but I'll shoot you an email and see if we can cross paths this semester.
Cheers, Ken
Andrew,
It's great to see someone else pushing two-time boundary approaches to quantum problems... Section 2.1 definitely made me want to read more, and I hope to get to it soon. If you have any other drafts or preprints on this general topic, I'd love to take a look; please feel free to send them to me at whartonscience.sjsu.edu.
The continuous/discrete issue is an important one, and one on which I have fairly strong feelings, although that's outside the scope of this essay. (My entry in the previous contest is a pretty good summary.) But if you're looking for solitons, it sounds like you're aligned with me point of view that things are continuous at the most fundamental level... but it sounds like you want to treat these tiny solitons as discrete particles for all-practical-purposes?
But even if the structure of such a soliton appears to be less than 10^-19 m in high-energy collisions, would you agree that the structure of such a soliton passing through a double-slit interference experiment appears to be *much* bigger than that, on the order of the slit separation?
For the record, I do not see the electron as a soliton in the traditional sense as some tightly-bunched solution to some nonlinear differential equation. I think that it is best described by a field that corresponds to the classical Dirac Lagrangian Density, but doesn't necessarily solve any EOM, not even the Dirac equation. Such a field smoothly converges to a soliton-like bunch wherever such behavior maximizes its "relative volumes in the URT solution space" (to pick a quote from your 2.1 that meshes with my ideas fairly well). Such points are where we normally think that the "measurement" occurs, subject to caveats such as whether that measurement is erased in the future, as discussed in the previous contest entry. Inbetween measurements, one *wants* the electron-field to naturally spread out, or it becomes very difficult to describe interference in a "realistic" theory.
Welcome to the retrocausal club - I'll follow up on email soon!
Cheers,
Ken
Hi Harlan,
I don't much like the concept of "warm determinism"... I think (to paraphrase Jaynes) that's just scrambling together subjective and objective elements into a conceptual morass. If there's *any* part of the chain between measurements that's uncertain, why wouldn't you expect the whole length of the chain to be smoothly-uncertain? Why push all the uncertainty to the very end, at the moment when it makes the least physical sense?
As for your question, I'm not sure I can answer that without knowing what you mean by 'quantum universe'... There certainly shouldn't be two independent sets of physical theories, one applying to the microscopic world and one applying to the macroscopic. But I happen to think that the ultimate fundamental theory (which would govern both micro- and macro-) will in many ways look a lot more like classical Lagrangian field theory than standard quantum mechanics. We'll see... :-)
Hi George,
Thanks for the nice comments. I'm a bit of two-minds about the two-state formalism (:-) ... It's certainly a step in the right direction, with many elements that I like. But it's built so firmly on the standard QM foundation that it inherits too many of QM's traditional problems -- despite the fact that the retrocausal elements can in principle solve many of those same problems.
The biggest technical problem it inherits is the configuration-space of the standard quantum state. This isn't so evident in many of the papers as they usually only talk about single-particles, but if you delve into the details it only works if *both* the history- and the destiny-vector live in configuration space.
Now, these latest papers you mention are a step in the right direction, trying to fit entanglement experiments back into spacetime -- I was very pleased to see them when they were posted. But it's impossible to do this analysis in the traditional two-state formalism, because of the configuration-space problem. Basically they're pointing out what Huw Price and I have been arguing all along -- that the retrocausal elements can bring configuration space back to spacetime. But, by its very nature, the two-state formalism is not the right framework to accomplish this -- one needs something that departs from standard QM more radically.
I like the "adaptive selection" phrase, and might even use it as an easier-to-understand 3+1D description for the 4D physics I'm proposing. I'll be looking forward to reading both that preprint and your essay, which appears to be getting some very favorable feedback.
Cheers,
Ken
Hi Michael,
> Title not withstanding, you are not really arguing against the universe as literally a computer a la Lloyd or Wolfram. You only indirectly argue against them by positing a block universe, which certainly can't be computed.
I'm not sure I'm reading that correctly; surely you're not saying that there are no block universes that can be computed? Wolframs universes are block universes, and can be computed. Newtonian clockwork universes are also in that category. But as I said above, the block-universe has little or nothing to do with any of this.
>Now, you admit in your reply to me that you don't have a novel argument for block universe, though I assume you want that to be a distinguishing feature of LSU.
No, please don't assume that. Again, re-read my first response; physics is *all* block-universes, NSU, LSU, the lot. I don't need to argue for it, because it's not a distinguishing feature.
> In other words, there can be block worlds without local time-symmetric processes and there are time-symmetric accounts of QM that are not block world.
Yes on the first, no on the second (at least, any such account would also have a corresponding block-world account). At least, no one has ever come up with such a physical theory. (One would need two time dimensions, at which point time-symmetry would mean something quite different.)
> since we already knew that a time-symmetric psi-epistemic account of the QM could deflate the MP and provide a local picture of entanglement, that can't be your novel conclusion.
Maybe you know this, but this is still heresy in much of the foundations community. Regardless, I was more trying to answer the essay question than provide a 'novel conclusion'. The question is what flawed assumption we might be making without realizing it, and the answer is the assumption that the universe operates according to the Newtonian Schema. You may be one of the few people who have already internalized this point, but even many people in the retrocausal-quantum-camp still lapse into NSU-style thinking with alarming regularity. And people not in the camp are repelled from it, I think, because they think NSU is the only way to do physics.
> here's my challenge to you. If the lagrangian density L is a function of the field f and its derivatives, S is stationary wrt to f (LS formalism), and f satisfies the boundary conditions (LS formalism), then L satisfies a differential eqn (NS formalism). If you want your LS soln to allow for a continuously mediated (3+1)D story, then I don't see how L won't be a function of f and its derivatives, thus allowing for an NS counterpart. Can you explain how you plan to avoid this LS-NS correspondence?
The mistake is that you are assuming S has to be stationary with respect to small variations of f. True, this is how one gets classical field equations in classical physics, but it's simply not true when you look at the full quantum path integral (unless you take the hbar->0 limit, which is not physical.) Without that assumption, one cannot derive any equations of motion at all, and there simply is no NS version of a generic LS approach where the action isn't extremized. (We can debate whether the standard path integral still maps to the Schrodinger equation, but this is again beside the point, because LS is a broad framework that subsumes more than just the standard path integral; there will be other ways to use the action that lead to no general equations at all.)
I'm denying the existence of some master equation of motion that applies in all cases. No equations, no NS. It's that simple.
I'll tackle the RBW discussion back in email... but as I've told you, I'm not about to throw out all continuously-mediated LSU approaches until I have no other choice.
Cheers,
By the way I forgot to say that I totally agree with your critique of the idea of the universe as a computer. It's a totally overstretched analogy. And what is quite interesting is that if you analyse the flow of causality in computers, they are a classical case of top down action (I sketch this in my own essay). What drives them is the logic of the algorithms they employ - which are abstract entities.
Cheers
George
Dear Dr Wharton,
Your essay is clearly heading in the right direction. But, should this discussion stop at the physical aspect of the spacetime, which is still derived from a mathematical framework? Or have we missed the big picture precisely because of an even deeper bias we have about the spacetime at its most fundamental -- and physical -- level?
In my essay I introduce a model of the universe that resides entirely in ordinary spacetime. In this model, quantum spaces are explained as real but independent spaces, similar to the space of the universe.
However, something is less than ordinary: the hypothesis about the nature of this wrong assumption, which changes the way we see reality. Surprisingly, the hints about this wrong assumption were provided by Minkowski himself, but the scientific community ignored them for the last century.
Cheers,
Gene
Ken,
I agree a Lagrangian approach, indeed I've argued that the centre of a large mass such as a SMBH should not be a singlarity but a point of equilibrium. This is precisely a Lagrangian point, and gives a toroid form of gravitational potential, a form common to all em fields, tokamaks (fusion) and which I deal with every day as an astronomer, as AGN's etc.
So of course maths (see my end note terms) but far more warily. Information theory shows your idea can be taken further (See McEachern essay) because the information possible in a mathematical abstraction is tiny compared to that contained in what it is trying to model (nature). I'm thus far more rigorous in applying the order; Correct concept first, Maths second. This requires the structures of logic, and a fully consistent ontological basis, which few of our theories posses. Expecting maths to accurately match reality is then foolish.
My main point is that, if we drop the series of related and unproven assumptions identified, the gap between SR and QM disappears. SR is derived direct from QM, and consistent with GR. CSL, curved space-time etc are all natural and inevitable consequences and effects of a single and well evidenced (but poorly understood) series of real mechanistic quantum interactions. The picture is Einstein's Local Reality, with causality conserved and paradoxes resolved.
The strict construction of truth propositional logic (hierarchical frames), and Dynamic Logic (interleaved but non interfering modes) are followed.
The evidence is overwhelming, but the big issues with it are that it's;
1. Entirely unfamiliar.
2. So self apparent we can't possibly not already know it.
3. Hiding so close in front of our eyes it forms a layer on our lenses.
4. Far to 'big' and fundamentally important to be recognised or acceptable.
5. Does not require complex mathematics to initially find, just visualisation of the evolution of kinetic effect (a new way of thinking).
6. Although it agrees with the SR postulates, it finds a fault in one of the the assumptions used for SR so must of course be wrong.
Could you see any of that? I'm considering reverting to the incremental approach (paper on resolving the Kantor interferometer issues accepted and due soon). Any other ideas?
best wishes
Peter
Great essay, Ken. Had it been posted early enough, we would've made yours a prerequisite for ours and detailed how we satisfy your desideratum for an LS-only approach to new fundamental physics. Unfortunately, it wasn't in the blockworld cards so (with your permission) I'll have to do so here.
If you're interested in new LSU-inspired approaches (LS formalisms) to fundamental physics which have been vetted and shown to have empirical consequence, read our essay. The LS approach outlined therein was inspired by our LSU interpretation of QM called Relational Blockworld (Foundations of Physics (2008, 2012,) and Studies in History and Philosophy of Modern Physics (2008)). In RBW, the manner by which we satisfy Ken's desire for an LS-only formalism (to the extent that it's possible, anyway) is to abandon dynamism altogether, i.e., get rid of (3+1)D time-evolved stories. The fundamental ingredients are relations, as advocated in Rickle's essay. In a sense, we're getting rid of the background/matter distinction in the spirit of Dreyer's essay. Among other things, this idea suggests correlations on a cosmological scale as Weinstein promotes in his essay. Such correlations suggest corrections to Regge calculus cosmology that we used to explain the Union2 supernova data without accelerating expansion or dark energy (Classical & Quantum Gravity (2012)) in direct opposition to the 2011 Physics Nobel Prize citation (Honorable Mention in Gravity Research Foundation 2012 Awards for Essays on Gravitation, http://users.etown.edu/s/STUCKEYM/GRFessay2012.pdf).
Thanks for letting me use your essay to connect with others in the competition, Ken. Good luck!
Ken
Beautiful essay, and a very good point to get across. I hope you can get to read my own, and commend you to the other I refer therein, and particularly the Jackson and McEachern essays, the first for the mechanisms, both that and the second with some extended proof of your appraoch.
Interesting times!
Well done.
Rich
Ken,
I've been trying to put my finger on what strikes me as inconsistency in your desiderata. Perhaps you can help me understand where I'm missing the boat.
Desiderata: An LS formalism that does not admit an NS formalism but does admit a (3+1)D continuously mediated story between Source and sink that explains the measurement outcome.
My confusion: The way one obtains NS from LS is to demand the extremum condition of LS be satisfied instant by instant. This leads to the local as well as global conservation of some property or characteristic of the fields involved; in classical physics it's energy and in quantum physics it's probability. Thus, in order to avoid an NS characterization of your ultimate LS formalism, there can be nothing conserved instant by instant. But, if no field property or characteristic -- absolutely *nothing* -- is locally conserved, what *is* being mediated in a (3+1)D continuous fashion?
I can imagine a field filling spacetime between initial and final hypersurfaces (and therefore between the worldtubes of the equipment). This field has some 4D global property that satisfies an LS constraint, but this field does not possess any property or characteristic that satisfies any constraint instant by instant (for any foliation). Trying to mathematically model such a field strikes me as a perfectly reasonable thing to do (it's what we're doing graphically). But, the very field property that rules out the possibility for an NS formalism also rules out the possibility of a (3+1)D story. At least, that's the way it strikes me. Perhaps you can dispel my confusion :-)
Dear Prof. Wharton,
I very much enjoyed the essay and realize you are looking at this from primarily a mathematical perspective as it relates to the physics more so than from the philosophical bend. Never the less once the Lagrangian perspective is taken it's hard not to wonder about what it all means as opposed to simply what observable results it has mandated. That is while metaphorically you say the universe is not a computer, yet stop there as not to share with us how you actually would have it imagined.
As for instance I recall reading one of the first criticisms of such a perspective written by one of Fermat's contemporaries, Claude Clerselier, in him saying "Fermat's principle can not be the cause, for otherwise we would be attributing knowledge to nature: and here, by nature, we understand only that order and lawfulness in the world, such as it is, which acts without foreknowledge, without choice, but by a necessary determination". So although the LSU is certainly not a computer it presents as universe mandated to follow a central rule where the nature of the outcome is predecided. The deeper question for me then is to ask how a universe underpinned by predecision can have physical outcomes present as being so seemingly lawless respective to their certainty. That's not that I think we might ever be able to have such a question answered simply I find it as one interesting to think about.
"Our intuition, going back forever, is that to move, say, a rock, one has to touch that rock, or touch a stick that touches the rock, or give an order that travels via vibrations through the air to the ear of a man with a stick that can then push the rock-or some such sequence. This intuition, more generally, is that things can only directly affect other things that are right next to them. If A affects B without being right next to it, then the effect in question must be indirect-the effect in question must be something that gets transmitted by means of a chain of events in which each event brings about the next one directly, in a manner that smoothly spans the distance from A to B. . . . We term this intuition 'locality.'
Quantum mechanics has upended many an intuition, but none deeper than this one. And this particular upending carries with it a threat, as yet unresolved, to special relativity-a foundation stone of our 21st-century physics."
-Albert, D.Z. & Galchen, R., 2009. "A quantum threat to special relativity", Scientific American, 300, 32-39.
Kind regards,
Phil
Dr Wharton
I would like reminding you my last essay
http://www.fqxi.org/community/forum/topic/946
I don't know -- I'm quite suspicious of attempts to 'start with logic', as that's exactly how anthropocentric mistakes are most likely to sneak into the foundations in the first place. This goes doubly so for efforts built on information theory.
Now, I am a big fan of Einstein's method of building theories from big-idea principles, but at the end of the day it's the comparison of the math with reality that is the only way to determine if those ideas were right in the first place.
And I'm afraid I disagree with your sentiments concerning a derivation of SR from QM in an ordinary causal (NSU) framework. Your essay dismisses Bell's theorem far too cavalierly for my liking. If you really want to tackle Bell inequality violations in a spacetime framework, check out my essay references [6] and [12] to see how an LSU can do the trick.
Thanks, Inger, for the kind words!
Gene,
There certainly may be other anthropocentric biases built into physics, and it also is true that I only experience this one universe, so that might unfairly bias me against your ideas.
That said, as a physicist, I want to explain the particular universe that I observe. Maybe it will turn out that the best explanation will require the use of other places and times outside "my universe", but I can't see myself seriously pursuing that possibility until I've ruled out some simpler options.
Here's a quote I still kind of like from my entry to FQXi's very first contest:
"Looking to quantum theory for answers about spacetime is like looking to a roadmap for answers about geology: it's a tool designed for something else entirely. In general, quantum theory tells us nothing about spacetime except what its formulators put into it in the first place."
Best, Ken
Hi Mark,
Yes, you and Silberstein are further along than any other LSU-style approach that I know of, and it's great to see some new cosmological results coming out of it. For now I hope we can agree to disagree about the continuum/discrete issue, and keep finding points of contact, such as this essay. More to come...
Rich,
Thanks for the kind words -- although I think both you and Jackson may be misreading my main point to some extent. From what I can tell about your essay (and Jackson's, and McEachern's), you're still working in a conceptual framework aligned with the NSU. If there's some LSU approach buried in any of those essays, I must have missed it, but I'm certainly interested in any such efforts.
Best, Ken
Hi Mark,
I'm not sure if by "story" you mean "explanation" or mere "description"... If the former, we're not on the same page: LSU explanations don't make much sense when viewed sequentially in 3+1D -- they require 4D "stories". But I'll assume you're merely using "story" to refer to my hoped-for-3+1D representation of what is happening between measurements.
As for whether giving up NS for LS means that *nothing* can be conserved instant-by-instant... That seems way too strong a conclusion. After all, there are aspects of Noether's theorems that provide conservation-type-rules (from the symmetries of the Lagrangian) even if the Euler-Lagrange equations are not strictly adhered to. There's a nice paper by Harvey Brown to this effect...
If you ask me about ontology, "what is being mediated", my best guess right now is the classical Lagrangian density itself, and the classical fields that comprise it. (Bearing in mind that those fields need not strictly adhere to the Euler-Lagrange equations, just as single-photon experiments obviously don't adhere to Maxwell's equations.)
On your last point, perhaps the problem is what you mean by "story" (see first paragraph above). Otherwise, I think we're on the same page. Also, note that LS approaches can give meaning to *new* instant-by-instant constraints, that don't make any sense in an NS framework -- such as enforcing a zero total Lagrangian density throughout spacetime (to pick a not-so-offhand example... :-).
Cheers, Ken
Phil,
Yes, lots of great philosophical questions at the heart of this stuff. Usually I just point people to Huw Price at this point, but I'll venture a few comments of my own.
Very nice quote about Fermat's principle, but if you'll look closely, the claim that "nature... acts without foreknowledge" is precisely the NSU assumption that the universe is just as limited as us humans.
When you get into words like "predecided", I'll direct you to my discussions concerning the block universe in response to Silberstein, above. The very word "predecided" refers to two different times (its subject and object), and therefore has no physics translation -- the philosophical concept of predecision doesn't make sense in the block universe of modern physics.
As for your excellent question: "The deeper question for me then is to ask how a universe underpinned by predecision can have physical outcomes present as being so seemingly lawless respective to their certainty." I certainly have a few thoughts. At one level, the hidden variables that I'm proposing (and that are necessary in any LSU) answers this to a large extent. Just because it's a block universe doesn't mean that we *know* the block; to the extent it's unknown, it appears probabilistic.
But I've only recently come to realize this isn't the whole story. You can't get all quantum phenomena simply by constraining deterministic fields at two times. And the path I'm going down right now -- departing from deterministic equations of motion, underconstraining the intermediate physics between the LSU constraints -- provides plenty of uncertainty all around. (Although one must also relax the Principle of Sufficient Reason to the point where our universe is just one of many possible solutions to the same ultimate constraints.)
As for that great quote you ended with, you may be surprised to see that we used that very quote to start Ref. [12]. We like the intuition of locality (as defined in that quote), and the LSU allows us to keep it, quantum phenomena notwithstanding.
Best, Ken
