Against Spacetime by Giovanni Amelino-Camelia

The problem is straightforward, Giovanni. You seem to reject the consequent (spacetime) but then refuse to question the truth of the antecedent (Einstein's 1905 postulates). Such a behaviour is incorrect when the theory is DEDUCTIVE.

Best regards, Pentcho

I totally agree with Joy Christian

And I totally agree with your cool name!

it is well Darth Vador, you make a good job.

Interesting strategy.

Wawww impressing, you are si intelligent.Wawww all people are very impressed.Wawww incredible of revolutions and innovations. Incredible intelligence. Incredible checking of algorythms.Wawww probably still genius of net. wawww you are strong. Impressing, really. I am so impressed by the eqautions also, wawww the maths are incredible. I have never seen that.Even Euler will not understand. Impressing dear team.Really. There is no words for your intelligence. You are probably elected. So impressing.

Incredible lesson of life. I have understood the humility due to your sincerity and of course your incredible intelligence. I am not the same man due to your high intelligent strategy. I thank you, really, without you, never I will understand this Universe.

ps It is not like this that I am going to be less parano.

spherically yours.

what a world.

Giovanni,

You did question the truth of Einstein's 1905 postulates in the past:

http://discovermagazine.com/2008/mar/13-e-nste-n

"Six iconoclasts who could revolutionize physics - again. (...) 4. Giovanni Amelino-Camelia: 42, University of Rome-Sapienza, Italy. Body of work: His "doubly special relativity" posits that the supposedly constant speed of light actually depends on its wavelength and that space has a minimum distance. His theory could unify physics and help explain the early growth of the universe, but experimental proof seems to be a tall order. Einsteinian trait: Rejects accepted physics on the basis of logic arguments."

Why are you so timid now?

Pentcho Valev pvalev@yahoo.com

Hi Giovanni:

I thoroughly enjoyed your well-written paper and fully agree with your conclusion - " .....in some of the contexts where quantum mechanics is most significant, such as quantum tunneling through a barrier, the spacetime abstraction proves to be cumbersome. And I argue that in quantum-gravity research we might limit our opportunities for discovery if we insist on the availability of a spacetime picture."

Not only the above conclusions are vindicated in my paper - -" From Absurd to Elegant Universe", but also it is shown (figure 1) that since spacetime dilates at quantum particles' speeds (V close to C), observing or limiting quantum phenomena to fixed or classical spacetime departs from physical realty leading to the well-known inconsistencies and QM paradoxes. My paper proposes a new model for the missing physics of spontaneous decay that explains the inner workings of QM and demystifies the quantum observations resolving many of its paradoxes and inconsistencies with relativity theory. As you point out, this has never been done, and hence, the QM mysteries and misinterpretations continue to prevail.

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. 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.

Best Regards

Avtar Singh

Hi Giovanni

I read your interesting and thought-provoking essay. I have some comments and doubts about some issues that I would be grateful if you could make some comments. You mention that:

But in some sense we never actually "see" spacetime, we never "detect spacetime", and over the last century we gradually came to appreciate that there would be no spacetime without particles.

You argue against space-time, but it was not clear to me what new conceptual framework or formulation you propose to replace space-time. For instance, in thermodynamics time is not an indispensable item for the calculation of the physical quantities, by only knowing the pressure, the temperature and the volume one can predict the outcome of a system no matter how much time elapses. To be honest, I did not get well why you see space-time redundant, the arguments you lay down appear to me somewhat messy, in what sense you think they are redundant?

On the other hand, I have been studying the problems of the measurement of the one-way speed of light and of clock synchronization and one of your statements call my attention particularly this: "Alice and Bob establish that they are in relative rest at a distance L with synchronized clocks."

According to my research the one-way speed of light has been never measured and clock synchronization a la Einstein assumes that the one-speed of light is isotropic which turns out to be redundant and thus a dead end. I have realized that clock synchronization has become a non-trivial task as at first sight it may seem.

Moreover, you mentioned in relation to the aether that:

I shall leave these questions to the appetites of philosophers... And then quote Poincaré:...Whether the ether exists or not matters little - let us leave that to the metaphysicians... Later you argue that the concept was rule out from physics because it turned out to be useless.

However, in my essay I hold the opposite opinion that reviving the aether it is more useful to solve most of the present problems of physics. Bell, Dirac and others contented that the situation of the aether in 1905-1915 was quite different from the situation of the aether in the middle of the XX century. This seems to me very plausible and I discuss in my essay some of the misconceptions around this concept. I claim that certain assumptions should be revived in physics because of their usefulness. One case of this was the notion of light as a particle brought back to life by Einstein. I would like to quote what Newton thought about the aether and its connection with gravity (Vesselin Petkov also holds that gravity is not a force and thus quantization of gravity is chimera), which I think it could be of great relevance to physics:

"Gravity is the result of a condensation causing a flow of ether with a corresponding thinning of the ether density associated with the increased velocity of flow..."

To make even clearer that Newton was actually Cartesian in the philosophical matters of gravity, in a letter to Bentley in 1692 Newton wrote:

"It is inconceivable that inanimate brute matter should, without the mediation of something else which is not material, operate upon and affect other matter, without mutual contact, as it must do if gravitation in the sense of Epicurus be essential and inherent in it. And this is one reason why I desired you would not ascribe 'innate gravity' to me. That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance, through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an ABSURDITY, that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it."

Making the assumption that the quantum vacuum is some sort of fluid (as the CERN experiments have revealed) it has been shown that the bending of light due to the presence of a massive object can be equivalently explained by a gradient in the refractive index of the vacuum.

Finally you mention that:

But how should one describe the position of the particle when it is formally "inside" the barrier? And especially how much time does it take a particle to quantum-tunnel through a barrier?

Besides reconsidering the aether in physics one should get rid of the notion of particle. Instead, I propose to use solitons which, as it is well known in several field of mathematics and physics, behave as particles in all aspects. The essay of Jarek Duda explains all the similitudes and at the same time the advantages of dealing with solitions in physics instead of particles. If one incorporates these two ingredients into physics the wave-particle duality disappears and experiments such as the double-slit experiment become quite intuitive and easy to handle.

I wish you good luck in the contest and I would be grateful if you could leave me some comments about my essay.

Israel

Hi Giovanni

Thanks you for your reply and your comments. I think I will read again your essay to grasp the detail. Anyway, I hope you get a chance to leave some comments in my entry.

Good luck in the contest

Best regards

Israel

Giovanni,

I liked your essay, for it makes a point similar to mine in a simple fashion. Your equation for the translation of the Alice coordinate to Bob

x(3)^μ_B = x(3)^μ_A b^ν{p(3)_ν()p(4)_ν, x(3)^μ}

is such that the last term looks very similar to a Yangian commutator. A Yangian is a quantum deformation of a universal enveloping operator. In fact I am working on precisely a formula of this type. This is equivalent to the Yang-Baxter relationship so that spacetime relationships have a quantum group structure.

I did not discuss Yangians in my essay, though they are a part of this overall work. I instead focused on the BCFW recursion relationship. The implication is that locality is an approximation. In the Yangian system there is aduality, where one set of variables given a spacetime relationship or configuration variables is dual to another set which have no explicit reference to spacetime.

Cheers LC

I still think you cannot fight spacetime without questioning the truth of Einstein's 1905 postulates, Giovanni:

http://philsci-archive.pitt.edu/2408/

Vesselin Petkov: "This paper pursues two aims. First, to show that the block universe view, regarding the universe as a timelessly existing four-dimensional world, is the only one that is consistent with special relativity."

http://www.pitt.edu/~jdnorton/papers/OntologyOUP_TimesNR.pdf

John Norton: "When Minkowski (1908) introduced the routine use of spacetime into physics, it seemed that this represented the victory of a particular view of time. Minkowski's spacetime represented all there was: past, present and future, and all at once. Did this finally vindicate an idea whose pedigree traces back to Parmenides in antiquity: time and change are mere illusions? (...) Might there be something special in the nature of the relativistic spacetime that supports the illusory character of change? An ingenious line of analysis suggests there might be."

If there is "something special in the nature of the relativistic spacetime that supports the illusory character of change", this "something special" could be the false constancy of the speed of light. That is, you may try to admit that Einstein should not have "resisted the temptation to account for the null result in terms of particles of light and simple, familiar Newtonian ideas":

http://www.amazon.com/Relativity-Its-Roots-Banesh-Hoffmann/dp/0486406768

"Relativity and Its Roots", Banesh Hoffmann: "Moreover, if light consists of particles, as Einstein had suggested in his paper submitted just thirteen weeks before this one, the second principle seems absurd: A stone thrown from a speeding train can do far more damage than one thrown from a train at rest; the speed of the particle is not independent of the motion of the object emitting it. And if we take light to consist of particles and assume that these particles obey Newton's laws, they will conform to Newtonian relativity and thus automatically account for the null result of the Michelson-Morley experiment without recourse to contracting lengths, local time, or Lorentz transformations. Yet, as we have seen, Einstein resisted the temptation to account for the null result in terms of particles of light and simple, familiar Newtonian ideas, and introduced as his second postulate something that was more or less obvious when thought of in terms of waves in an ether."

Pentcho Valev pvalev@yahoo.com

Dear Giovanni,

This is copied on my page as well.

I just started reading Relative locality in a quantum spacetime and the pregeometry of _-Minkowski http://arxiv.org/pdf/1206.3805v1.pd. You seem to be pointing to a similar end. Noncommutative geometry and Hopf algebras are a main tool in the work with Yangians. I will write more when I complete reading your paper.

Equation 1 is interesting, for it proposes a noncommutative relationship between time and the spatial coordinates. This in my opinion harkens back to an old argument by Bohr. In 1930 there was a famous Solvay conference where Einstein and Bohr sparred over the reality of quantum mechanics. Einstein was convinced of reality and locality and argued staunchly for an incompleteness of quantum mechanics. Quantum theory could only be made complete if there are some hidden variables that underlay the probabilistic, nonlocal quirky aspects of quantum mechanics. At the 1930 Solvay conference Einstein proposed an interesting thought experiment. Einstein considered a device which consisted of a box with a door in one of its walls controlled by a clock. The box contains radiation, similar to a high-Q cavity in laser optics. The door opens for some brief period of time t, which is known to the experimenter. The loss of one photon with energy E = ħω reduces the mass of the box-clock system by m = E/c^2, which is weighed. Einstein argued that knowledge of t and the change in weight provides an arbitrarily accurate measurement of both energy and time which may violate the Heisenberg uncertainty principle ΔEΔt ~ ħ.

Bohr realized that the weight of the device is made by the displacement of a scale in spacetime. The clock's new position in the gravity field of the Earth, or any other mass, will change the clock rate by gravitational time dilation as measured from some distant point the experimenter is located. The temporal metric term for a spherical gravity field is 1 - 2GM/rc^2, where a displacement by some δr means the change in the metric term is ~ (GM/c^2r^2)δr. Hence the clock's time intervals T is measured to change by a factor

T --> T sqrt{(1 - 2GM/c^2)δr/r^2} ~ T(1 - GMδr/r^2c^2),

so the clock appears to tick slower. This changes the time span the clock keeps the door on the box open to release a photon. Assume that the uncertainty in the momentum is given by the Δp ~ ħΔr < TgΔm, where g = GM/r^2. Similarly the uncertainty in time is found as Δ T = (Tg/c^2)δr. From this ΔT > ħ/Δmc^2 is obtained and the Heisenberg uncertainty relation ΔTΔE > ħ. This demands a Fourier transformation between position and momentum, as well as time and energy.

Consider an example with the Schwarzschild metric terms. The metric change is then ~ 1x10^{-12}m^{-1}δr, which for δr = 10^{-3}m is around 10^{-15}. Thus for a open door time interval of 10^{-2}sec, the time uncertainty is around Δ t ~ 10^{-17}sec. The uncertainty in the energy is further ħΔω, where by Fourier reasoning Δω ~ 10^{17}. Hence the Heisenberg uncertainty is ΔEΔt ~ ħ.

This argument by Bohr is one of those things which I find myself re-reading. This argument by Bohr is in my opinion on of these spectacular brilliant events in physics.

This holds in some part to the quantum level with gravity, even if we do not fully understand quantum gravity. Consider the clock in Einstein's box as a black hole with mass m. The quantum periodicity of this black hole is given by some multiple of Planck masses. For a black hole of integer number n of Planck masses the time it takes a photon to travel across the event horizon is t ~ Gm/c^3 = nT_p, which are considered as the time intervals of the clock. The uncertainty in time the door to the box remains open is

ΔT ~ Tg/c(δr - GM/c^2),

as measured by a distant observer. Similarly the change in the energy is given by E_2/E_1 = sqrt{(1 - 2M/r_1)/(1 - 2M/r_2)}, which gives an energy uncertainty of

ΔE ~ (ħ/T_1)g/c^2(δr - GM/c^2)^{-1}.

Consequently the Heisenberg uncertainty principle still holds ΔEΔT ~ ħ. Thus general relativity beyond the Newtonian limit preserves the Heisenberg uncertainty principle. It is interesting to note in the Newtonian limit this leads to a spread of frequencies Δω ~ sqrt{c^5/Għ}, which is the Planck frequency.

The uncertainty in the ΔE ~ ħ/Δ t does have a funny situation, where if the energy is Δ E is larger than the Planck mass there is the occurrence of an event horizon. The horizon has a radius R ~ 2GΔE/c^4, which is the uncertainty in the radial position R = Δr associated with the energy fluctuation. Putting this together with the Planckian uncertainty in the Einstein box we then have

ΔrΔt ~ (2Għ)/c^4 = L^2_{Planck}/c.

So this argument can be pushed to understand the nature of noncommutative coordinates in quantum gravity.

Cheers LC

Dear Giovanni,

You discuss spacetime in the way entropy is discussed in today's science. That the entropy increases in an isolated system was RIGOROUSLY deduced by Clausius in 1865, from a few premises. Those premises are long forgotten - nobody knows them, nobody cares whether they are true or false. Rather, people just redefine the entropy - e.g. "entropy is disorder" or "entropy is energy dispersion" - and then like or dislike the new definitions.

Pentcho Valev pvalev@yahoo.com

Dear Giovanni

What an essay! Congratulations! It is extremely clear and simple, while the questions you address are certainly very deep and complex. My essay and yours have a lot in common, as I will explain, and there are some points you might find interesting to discuss.

Like you and many other physicists, I feel the space-time abstraction is not fundamental. I find your arguments for the ''cumbersomeness'' of it whitin the context of QM very interesting. Your proposal of ''detectors'' first is compelling, and resembles a lot the Machian arguments against Newton´s classical mehanics, which I assume you´re aware of.

For instance, time is an abstraction we have built upon the notion of motion of obejcts. If everything in the universe speeded up, including clocks, the flow of an invisible paramater t seems meaningless; it becomes more easy to see that time may be just a practical abstraction and not a fundamental theoretical building block for physics.

So look at your example: ''x = vt (1)

Of the infinitely many ''otential truth'' codified in this equation only two facts are established experimentally: the particle is emitted at Alice at time t = 0 of Alice's clock and the particle is detected at Bob at time t = L=v of Bob's clock''

You see the space/time abstraction renders more information than a ''minimalist physical description'' would require. But also, we can ask: what is a clock? Shouldn´t we also remember that time is derived concept from motion in order ro provide a ''minimalist description''?

Since your proposal is a ''detectors first'' type, we should be well aware about what we mean by an instant of time and a position in space. This leads directly to Julian Barbour´s relational physics. In my essay Absolute or Relative Motion...or Something Else? I have also serached, just like you, for a minimalist description of the universe and speculated about a possible substitute for space-time. I think we can have an awesome discussion.

Best regards,

Daniel

Actually there are reasons for questioning space/time other than quantum gravity itself. My essay is just about this Absolute or Relative Motion...or Something Else?