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Anonymous: on 2/17/10 at 3:41am UTC, wrote Dear Dr. Gambini, When nature put the squeeze on the degrees of freedom of...

amrit: on 12/25/08 at 10:17am UTC, wrote Dear Prof. Gambini Time exists only when we measure it. Universe is...

Adam Helfer: on 12/22/08 at 14:53pm UTC, wrote Dear Professors Gambini and Pullin, I enjoyed your essay. You miht take a...

Robert Sadykov: on 12/22/08 at 1:02am UTC, wrote Dear Rodolfo Gambini, In the future quantum theory of gravitation in...

Tevian Dray: on 12/7/08 at 22:58pm UTC, wrote I love it -- a way around the decoherence problem without invoking a many...

J. Smith: on 12/2/08 at 19:43pm UTC, wrote Dear Rodolfo, I believe that your contribution contains an implicit and...

F. Le Rouge: on 12/2/08 at 15:34pm UTC, wrote -My ‘Libertarian’ objection against this D. Hume ‘revival’ is more...

Cristi Stoica: on 12/1/08 at 16:20pm UTC, wrote Dear Prof. Gambini, Your solution to the time problem in Quantum Gravity,...


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Georgina Woodward: "On obtaining the singular, relative, measurement product it replaces the..." in The Present State of...

Steve Dufourny: "The paper of Wilczek of course is very relevant considering the idea about..." in The Noise of Gravitons

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February 6, 2023

CATEGORY: The Nature of Time Essay Contest (2008) [back]
TOPIC: Free will, undecidability, and the problem of time in quantum gravity by Rodolfo Gambini [refresh]
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Rodolfo Gambini wrote on Sep. 10, 2008 @ 09:33 GMT
Essay Abstract

In quantum gravity there is no notion of absolute time. Like all other quantities in the theory, the notion of time has to be introduced "relationally", by studying the behavior of some physical quantities in terms of others chosen as a "clock". We have recently introduced a consistent way of defining time relationally in general relativity. When quantum mechanics is formulated in terms of this new notion of time the resolution of the em measurement problem can be implemented via decoherence without the usual pitfalls. The resulting theory has the same experimental results of ordinary quantum mechanics, but every time an event is produced or a measurement happens two alternatives are possible: a) the state collapses; b) the system evolves without changing the state. One therefore has two possible behaviors of the quantum mechanical system and physical observations cannot decide between them, not just as a matter of experimental limitations but as an issue of principle. This first-ever example of fundamental undecidability in physics suggests that nature may behave sometimes as described by one alternative and sometimes as described by another. This in particular may give new vistas on the issue of free will.

Author Bio

Rodolfo Gambini is professor of physics at the University of the Republic in Montevideo, Uruguay. He is a member of the Academy of Sciencies of Latin America, the Argentine Academy of Exact Sciences and the Third World Academy of Sciences. He is a fellow of the American Physical Society. Jorge Pullin is the Horace Hearne Chair in theoretical physics at the Louisiana State University. A Fulbright, Guggenheim and Sloan fellow, he is a member of the National Academies of Science of Argentina, Mexico and the Latin American Academy. He received the Bouchet award of the American Physical Society.

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matthew kolasinski wrote on Oct. 28, 2008 @ 05:04 GMT
Dear Prof. Gambini,

i enjoyed reading your paper. i find in it something of an intuitive resonance with my personal experience of reality in it.

i do, however, have one minor issue with what you have written here.


"In the first case the system would keep its entanglement with the rest of the

universe (i.e. the environment), in the second it will lose its entanglement. The availability of this choice opens the possibility of the existence of free acts."

i've run into this curious perspective here in the presentations twice now, that a theory will determine wheather we have free will or not.

i have the distinct impression that this is taking theories a little too seriously. theories have absolutely no impact on what actually is. they cannot permit or deny anything actualizing.

to hinge a determination of free will, be it yeah or nay, upon a theory enslaves what little free will you may have had to start with to that theory, building a whole new conceptual prison, apparently voluntarily, for the will.

it's a jail break; i'm here to spring ya.

of course, you have the option to remain in that lovely prison you've built, if you so desire.

i must admit, it's not half bad as far as prisons go; looks pretty comfey - an open door policy honor system. you might even find people wanting to join you in there, get to looking more like a clubhouse. just be mindful that it's subject to having the door unexpectedly locked come the next scientific revolution.


"In fact if quantum mechanics only implies a mere lack of causal determination in the occurrence of events, this is not sufficient to ensure that it makes sense to consider a free act for which responsibility is possible."

ah, glad you noticed that here; i was about to say something about this also. nice treatment. fun prison. :-)


"It would be quite disappointing if a universe that naturally includes in the laws of physics the capability for free acts will end up disallowing them for human beings."

well, it does and it doesn't. my personal experience with 'free will' strongly suggests that it has some distinct limitations. i don't seem to be permitted to choose to both sit here at the computer typing away and take a walk around the block at the same time. in fact, i don't appear to be allowed any more than one discrete action set at any given moment. i don't seem to be able to walk to the moon. my experience is also that the exercise of what 'free will' one might have is somewhat negotiated - this feature comes into sharp focus under such circumstances as crossing busy streets.

it would be significantly more disappointing if bright minds continue to fail to notice the conceptual limitations they impose upon themselves.

be free.

be well.

stay out of jail ;-)

glad to meet you.


matthew kolasinski.

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Dr. E (The Real McCoy) wrote on Oct. 31, 2008 @ 17:00 GMT
Hello Rodolfo,

Thanks for the paper!

Your abstract begins with:

"In quantum gravity there is no notion of absolute time."

Would it not be more proper to write, "In our universe there is no absolute notion of quantum gravity." By that I mean there is no experimental nor theoretical evidence for quantum gravity. Gravitons have never been seen, and gravity has never been...

view entire post

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Doug wrote on Nov. 1, 2008 @ 15:47 GMT
Wow. This is a tremendous essay Rodolfo. It will be a course of study for me for some time to come, because I think I can see a way to use the physical principle of undecidability in my own work, as a description of something I have been struggling to articulate.

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F. Le Rouge wrote on Nov. 6, 2008 @ 18:09 GMT
You are true when you explain that 'the evolution is trivial'; better is to say that Probability Theory is trivial (and proved its inefficacy in Economics recently): symmetry points the extrapolation and the (absolute) 'fake' Time between 'a priori' and 'a posteriori'.

But the Relativity Theory is a symmety too and it is based on extrapolation that is to say (absolute) fake time.

(I must add that I do not agree when you write that can happen something physical on a point. Points are ony measurements.)

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Narendra Nath wrote on Nov. 26, 2008 @ 07:02 GMT
Dear Rodolpho,

Sorry that i missed going through your essay till this day. i admire the way you have introduced freshness through some holistic considerations and have expanded the Paradigms in Physics. I also feel strongly that new Physics has become static for over a decade and most studies are mere minor modifications of major studies done in the past. It is clear that there is something non-physical behind the physical world. The question of what existed before Big Bang dominates still. What do you feel about the 'consciousness' playing a role and we have not developed linkage with it in a scientific manner? As time left is short, i ccclose here

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Cristi Stoica wrote on Dec. 1, 2008 @ 16:20 GMT
Dear Prof. Gambini,

Your solution to the time problem in Quantum Gravity, as well as the surprising result of evolving with or without collapse, is of real interest. And indeed, it seems to have implications on the free-will problem. I cannot help comparing your results, with the direction I am exploring. My version of Quantum Mechanics replaces the discontinuous collapse with delayed initial conditions, combined with entanglement, without violating the unitary time evolution (at least at the larger level). It is deterministic, but allows free-will exactly like the indeterministic QM, via the delayed initial conditions (and not by “compatibilism”). I refrain here discussing my ideas on your thread.

Congratulations for your work,

Cristi Stoica

“Flowing with a Frozen River”,

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F. Le Rouge wrote on Dec. 2, 2008 @ 15:34 GMT
-My ‘Libertarian’ objection against this D. Hume ‘revival’ is more general than the one that R. Gambini is pointing at the end of his essay.

Major objection against Gambini is that there is no Freedom at all in randomisation which is a binary algebraic system entirely based on Symmetry. Standard Model of this symmetric system is a Mirror and the deductions are just the hypothesis Reflex to which a factor is sometimes applied.

Some Scientists will take the Sunset (or Particle and Wave), some others will only take the Set, although the sole Sun is part of Nature.

Closer you are to the Nature, narrow the Mirage (and the LHC is so far away from Natural things!). Fragmenting Energy as M. Planck is doing with Boltzmann Quanta Arithmetic is only possible at the algebraic theoretical level.

‘The abrupt change in the wave function’ as Gambini says, this ‘broken wave’ is just a ‘coming back to Nature’: Inflexion of the Reflex!

-Wether it is made on purpose or not, the Question of the Nature of Time is cleverly skipped in Gambini’s theory. How? Just because Time presumption is still there in his Epistemology.

A few explanations about this: D. Hume is quoted but E. Kant after or saint Augustine before could be too who are deducing a model of Scientific ‘Understanding’ FROM Time Reference, i.e.: Memory (Past), Intelligence/Contemplation (Present) and Free Willing (Future). Put a dot on a circle for Present or Observer and you have a sketch of this ‘trigonometric’ epistemology -with the Infinity idea above of course.

-The Question of the Nature of Time is vanishing in the Epistemology but Time does resuscitate everywhere in the Probability Theory, the Quanta Physics and, last but not least, in Einstein’s Theory as arrows, vectors, cells, blocks, entirely conventional scales or variables.

-Two examples: 1. How can Gambini says that ‘In general relativity there is no notion of Absolute Time’?? Relative Time is splitting of ‘Absolute Time’ -that is to say an analogy with Infinity in distance or addition…

Or does ‘Absolute Time’ means ‘Objective Time’ for Gambini? And in this case if ‘Objective Time’ is not in Einstein’s Reference it is not in Gambini’s Theory either except as an implicit Postulate.

2. ‘A classical non-fluctuating Time is an idealization’: what the hell does that mean? Poincaré or Einstein elastic or fluctuating Time is the same ‘idealization’. It is classical algebraic geometry of Newton against variable algebraic geometry of Einstein or Poincaré. There is no real elasticity or flow. H. Poincaré admitted it in one of his last books, underlining the contradiction between the conclusion of General Theory and its absolutely necessary postulate.

-I want to say as a conclusion that bad news is that LHC-Experience is just a gigantic video-game for rich Scientists. But good news is that I demonstrate also that Science is cheap Sports, not Golf (I do not even have high speed web-connection!)

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J. Smith wrote on Dec. 2, 2008 @ 19:43 GMT
Dear Rodolfo,

I believe that your contribution contains an implicit and wrong assumption. When you state "Acknowledging that the real clocks and rods that one may use to measure space-time are not arbitrarily accurate requires reformulating the theory in terms of such clocks and rods." it becomes clear that you consider clock as a tool for measuring something a-priori given. You can say that something is fluctuating only if you consider that there is some real value with respect to which you fluctuate. Later you also talk about unitary evolution of QM as somthing given. I believe that, on the contrary, the point consists of understanding what is a clock, and how it observable quantities are related to other quantities. When talking about the nautre of time, evolution is a word with no meaning.


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Tevian Dray wrote on Dec. 7, 2008 @ 22:58 GMT
I love it -- a way around the decoherence problem without invoking a many worlds interpretation. But what rules (if any!) would control whether a state "chooses" to decohere?

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Robert Sadykov wrote on Dec. 22, 2008 @ 01:02 GMT
Dear Rodolfo Gambini,

In the future quantum theory of gravitation in addition to a problem of time the solution of a problem of gravitational energy is necessary. This question still remains open in the general theory of relativity. In the essay The Theory of Time, Space and Gravitation the problem of localization of gravitational energy is solved.

Yours faithfully

Robert Sadykov

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Adam Helfer wrote on Dec. 22, 2008 @ 14:53 GMT
Dear Professors Gambini and Pullin,

I enjoyed your essay. You miht take a look at mine, which has some elements in common (it focusses on reduction.)

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amrit wrote on Dec. 25, 2008 @ 10:17 GMT
Dear Prof. Gambini

Time exists only when we measure it.

Universe is atemporal.

From that point gravity force is carried by the atemporal space where time is a "coordinate of motion".

yours amrit

attachments: In_The_Theory_of_Relativity__Time_is_a_Coordinate_of_Motion__Sorli__FOUNDATIONS_OF_PHYSICS_2009.doc

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Anonymous wrote on Feb. 17, 2010 @ 03:41 GMT
Dear Dr. Gambini,

When nature put the squeeze on the degrees of freedom of some particle, this particle exhibits a quantized behavior. And when we make a measurement on that particle,we too are putting the squeeze on the particle`s freedom and change its quantization state.

Measurement necessarily introduce a new constraint on the system which is by that fact totally redefined. Adding constraint on a quantum system creates a new temporary quantization of the system. Any constraint on a system creates a new quantum number and quantization. Here is, I believe, a not so recognized example.

A photon can travel in any direction. If one squeezes the direction of the photon along its path, like with a slit, "direction" becomes a "quantum number" and past the slit, this "direction is now quantized i.e. a fringe pattern emerges.

This is the essence of quantum mechanics: constraints define the states of the quantum system. Measurement adds constraint which in turn redefines the system.

After this measurement, the new temporary quantization is gone and the system reverts to what it was before.

This make sense to you?


Marcel-Marie LeBel

fqxi_limits of physics contestant

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