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Davide: on 12/26/12 at 17:39pm UTC, wrote hallo there, I came across this paper during these Christmas holydays,...

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FQXi FORUM
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CATEGORY: Questioning the Foundations Essay Contest (2012) [back]
TOPIC: Against Spacetime by Giovanni Amelino-Camelia [refresh]

Author Giovanni Amelino-Camelia wrote on Aug. 28, 2012 @ 16:43 GMT
Essay Abstract

The notion of ``location" physics really needs is exclusively the one of ``detection at a given detector" and the time for each such detection is most primitively assessed as the readout of some specific material clock. The redundant abstraction of a macroscopic spacetime organizing all our particle detections is unproblematic and extremely useful in the classical-mechanics regime. But I here observe that 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.

Author Bio

Researcher in Theoretical Physics as Sapienza University of Rome. Previously worked at CERN, Univ Neuchatel, Oxford Univ, MIT. PhD from Boston University. Was awarded an FQXi Large Grant in 2008

Pentcho Valev wrote on Aug. 28, 2012 @ 22:15 GMT
Minkowski spacetime is a consequence of Einstein's 1905 two postulates. Are you suggesting the postulates are true but the consequence should be rejected?

Pentcho Valev pvalev@yahoo.com

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Yuri Danoyan replied on Aug. 28, 2012 @ 22:56 GMT
Dear Giovanni,

I am not contra to the spacetime, I am pro their divorce.

See my essay http://fqxi.org/community/forum/topic/1413

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Yuri Danoyan replied on Sep. 6, 2012 @ 00:28 GMT
Giovanni

Again want to go back to the issue of the divorce of space and time and again to ask you to read my essay.

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Frank Ullmann wrote on Aug. 28, 2012 @ 23:02 GMT
Hi Giovanni,

When I started studying physics I would have thought that critique of Einstein's theory is something like a sacrilege. But things change. I really enjoyed reading your essay.

Kind regards, Frank

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Frank Ullmann replied on Aug. 29, 2012 @ 00:55 GMT
It is late. I did not mean the theory itself but its geometric aspect.

Frank

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Darth Sidious wrote on Aug. 29, 2012 @ 06:14 GMT
It is simpler to admit the non-existence of a quantum gravity theory rather than admitting the non-existence of a spacetime....

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Joy Christian replied on Aug. 29, 2012 @ 06:37 GMT
It is simpler still to admit the wackyness of the foundations of quantum theory itself rather than going after spacetime, especially since GR has been experimentally better confirmed (by several orders of magnitude) than the crown jewel of quantum theory (namely QED).

Nevertheless, Good luck, Giovanni, for the essay competition.

Joy

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Pentcho Valev replied on Aug. 29, 2012 @ 06:48 GMT
The simplest thing is to admit that the speed of light does depend on the speed of the light source - the "recourse to contracting lengths, local time, or Lorentz transformations" was a costly mistake:

http://www.amazon.com/Relativity-Its-Roots-Banesh-Ho
ffmann/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

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Darth Sidious replied on Aug. 29, 2012 @ 13:36 GMT
I totally agree with Joy Christian

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Peter Jackson wrote on Aug. 29, 2012 @ 07:26 GMT
Giovanni

Simpler than the winner of the last 3 world simpleton championships (in the famous words of Blackadder) "observers in relative motion do not share the same time." Precisely as you propose. (Pentcho this is the subtle point you missed). If what is termed a 'space time event' can grow and shrink on transformation, (change of kinetic state) then so must the length between peaks of a wave.

I loved your incisive essay Giovanni. I too considered "detection at a given detector" and analyse it's massive (lol) consequences. I can't agree all agree with the clear truth of your suggestion; "...over the last century we gradually came to appreciate that there would be no spacetime without particles."

I've been working on a re-interpretation of 'spacetime' with others including John Minkowski, which wirks well, and we believe the simplest of simpletons could comprehend if only they could drop the assumptions around the earlier interpretations. You beautifully show these assumptions as questionable and point in the same direction.

I hope you may be able to read and comment on my essay (beneath the kinetic theatre).

Congratulations on a fine and important essay.

Peter

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Yuri Danoyan replied on Oct. 12, 2012 @ 21:23 GMT
I totally agree admit a quantum gravity problem as a pseudoproblem

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Georgina Parry replied on Oct. 24, 2012 @ 21:20 GMT

I disagree with the quoted statement."observers in relative motion do not share the same time." The observers must occupy (and thus share) the same and only 'foundational' time but observe different times (so not sharing the same) due to the way in which data is received and processed into their individual experiences. That might sound pedantic or unnecessarily complicating matters but I think it is very important to make the distinction between the foundational reality and the emergent reality. It is necessary to overcome the temporal paradoxes and unite QM and GR.

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Peter Jackson replied on Oct. 25, 2012 @ 11:37 GMT
Georgina

Considering the statement in context I think Giovani meant what I mean and make clear in my essay, which is I am sure also what you mean; This is that there are TWO cases, where current science considers only the fundamental absolute case.

So we are here considering OBSERVERS or OBSERVED rate of passage of time as the second case, which then varies between all observers in...

view entire post

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Author Giovanni Amelino-Camelia wrote on Aug. 29, 2012 @ 07:34 GMT
dear Frank and Peter

many thanks for the encouragement!

dear Peter and Yuri

I'll have to catch up on reading the other essays. It was hard enough to finish my essay on time for the deadline (August is a holiday period in Italy...and my kids correctly make every effort to remind me of that...)

ciao Joy

how is everything?

as you know a few moons ago I would have given an assessment very similar to yours

but gradually I developed the intuition that the most serious difficulties are at the interface between quantum theory and relativistic spacetime inferences

and I am intrigued by the challenge of reassessing all this while weakening our insistence on the robustness of spacetime inferences

it is interesting that both you and Darth (thanks Darth) look at things from the perspective of which challenge is simpler: quantum mechanics (/quantum gravity) or spacetime...I would go after all opportunities of finding new insight experimentally without imposing much prejudice on which avenues look more promising

dear Pentcho

as you can see from my essay I am not allowing myself much room for assessments such as "true postulates" and surely not for "true consequences of true postulates"

In relation to your question I am only allowing myself to take notice of the fact that the predictions of relativistic theories have been very successful. Those predictions concern the readouts of our detectors and clocks, when arranged appropriately. The spacetime inferences based on those readouts have been so far very successful, but it is an experimental question whether or not those spacetime inferences will be allowed in all experimental setups. Most notably I fear that we could miss on some discoveries if instead of handling the availability of spacetime inferences as an experimental issue we adopted an unquestioning attitude toward spacetime

best regards

Giovanni

Joy Christian replied on Aug. 29, 2012 @ 07:57 GMT
Ciao Giovanni,

It is good to know your kids are making you keep your priorities straight.

Well, I agree with you that "the most serious difficulties are at the interface between quantum theory and relativistic spacetime inferences", but the question of the century is: What must give?

You are right, of course, to "go after all opportunities of finding new insight experimentally without imposing much prejudice on which avenues look more promising." The latter would be like looking for the keys where light is, not where they are lost.

All the best,

Joy

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Author Giovanni Amelino-Camelia wrote on Aug. 29, 2012 @ 10:05 GMT
dear Pentcho

I don't think other aspects of your post really apply to my approach...

but "protective stupidity" could perhaps be adapted...I am concerned about the implications of our instinctive desire to let Nature conform to our expectations about it...

cheers

Giovanni

Pentcho Valev replied on Aug. 29, 2012 @ 10:40 GMT
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

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Pentcho Valev replied on Aug. 29, 2012 @ 14:27 GMT
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

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Avtar Singh wrote on Aug. 29, 2012 @ 15:00 GMT
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.

Best Regards

Avtar Singh

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Israel Perez wrote on Aug. 29, 2012 @ 17:34 GMT
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...

view entire post

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Author Giovanni Amelino-Camelia wrote on Aug. 30, 2012 @ 11:14 GMT
dear Pentcho

I am indeed more than willing

to "question the truth of Einstein's 1905 postulates"

actually I do not assign any truth to any postulates (my understanding is that "truth" is of interest for professions different from mine....)

I am the type of physicist more intrigued by the challenge of finding the boundaries of theories, rather than elaborating more and more instances of success of any given theory

and I take as working assumption that all theories have a limited realm of applicability, so for each of them I expect we will eventually find its "boundary of applicability"

best regards

Giovanni

Pentcho Valev replied on Aug. 30, 2012 @ 12:34 GMT
Dear Giovanni,

You are "more than willing to question the truth of Einstein's 1905 postulates" and at the same time your understanding is that "truth" is of interest for professions different from yours? Sounds contradictory. I think "truth" is quite relevant to your profession. Of the two statements:

A. The speed of light varies with the speed of the light source.

B. The...

view entire post

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Author Giovanni Amelino-Camelia wrote on Aug. 30, 2012 @ 11:16 GMT
dear Avtar and Israel Omar

as mentioned in a previous post I find myself having to catch up on other essays in the competition

I am not surprised Israel Omar would see as desireable more details on my thesis for the redundancy of spacetime inferences. It is that part of the paper which I ended up making more compromizes with in order to match the length limit set for the competition.

On the other hand it can be a simple exercise: think of any measurement procedure for "spacetime observables" you might like; analyze it carefully, decomposing it in all of its most primitive/elementary ingredients; then notice the role for some timed particle detections and the role played by spacetime inferences.

The way I found for handling this while satisfying the length limitations for the competition was to offer comments on the two extreme casess: our most rudimentary (but ultra-abundant) acquaintances with spacetime are through our resident devices, some particle detectors, and our most advanced acquaintances with spacetime, the ones of our most powerful microscopes (the LHC and other particle accelerators) also evidently involve inferences based on readouts of some particle detectors

best regards

Giovanni

Israel Perez replied on Aug. 31, 2012 @ 17:41 GMT
Hi Giovanni

Good luck in the contest

Best regards

Israel

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Lawrence B Crowell wrote on Sep. 1, 2012 @ 02:52 GMT
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

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Author Giovanni Amelino-Camelia wrote on Sep. 1, 2012 @ 20:39 GMT
dear Pentcho

perhaps my previous post would have been clearer if I discussed the differences between "experimental facts" and "true postulates" (the former are of interest to me, the latter require a sort of training I never had...)

in any case I feel this issue of "true postulates" might be taking me far from my essay: my essay is exclusively about experimental facts (with of course no mention of "true postulates"), highlighting how experimental facts presently available provide support for our spacetime inferences and how some scenarios and preliminary results may suggest that at some point we might have to give up the luxury of such spacetime inferences

best regards

Giovanni

Pentcho Valev replied on Sep. 1, 2012 @ 21:59 GMT
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."...

view entire post

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Pentcho Valev replied on Sep. 2, 2012 @ 04:27 GMT
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

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Author Giovanni Amelino-Camelia wrote on Sep. 1, 2012 @ 20:40 GMT
dear Lawrence

I have also posted on the page linked to your essay: there are indeed some connections between our essays, in spite of the differences of approach and goals

and now that I have studied your essay I can observer that there are closer connections between parts of your essay and some of my works, see e.g.

http://arxiv.org/abs/arXiv:1206.3805

http://arxiv.org/abs/arXiv:1107.1724

http://arxiv.org/abs/arXiv:1101.0931

best regards

Giovanni

Lawrence B Crowell replied on Sep. 2, 2012 @ 02:11 GMT
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. ...

view entire post

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DANIEL WAGNER FONTELES ALVES wrote on Sep. 2, 2012 @ 18:44 GMT
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...

view entire post

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Paul Reed wrote on Sep. 4, 2012 @ 16:28 GMT
Giovanna

I would agree with your questioning of spacetime as a valid model of physical reality (and indeed with the basis of QM but that is a different story), but on more fundamental grounds. Neither space nor time physically exist!

Something exists, not space. Space is a way of conceptualising the physical presence of something (ie dimension, size, shape). In effect we are conceiving of a matrix of spatial points and then defining the relative occupancy of any given something being considered. Another way of putting this is that nothing cannot physically exist, only something can.

Time cannot be an attribute of physical reality, because it (or any sequence thereof) can only occur in one physically existent state at a time. In other words, time (or more precisely timing) is an extrinsic measuring system which differentiates the rate at which physical change occurs (ie from one reality to another).

Paul

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Anonymous wrote on Sep. 4, 2012 @ 17:15 GMT
Dear Giovanni Amelino-Camelia

Your well-written paper, I think, supports the Leibniz view of space i.e. "Space is determined from the things it contains" and that space-time is a web of relations among things. I wander what will happen if this relation may not be uniquely determined and depends upon the things. If this is the case, the fabric of cosmos arena may consist of various emergent space-time patches of different sizes and properties, like black Holes and tunneling space. Maybe dark matter and dark energy reside in such spaces we do not have access so far (like the previous aforesaid two spaces). In some cases the emergent of a certain space-time patch entails the existence of another, e.g. (i) the elementary particles world entails the existence of the tunneling space, (ii)The grin of Cheshire cat and the feline itself abide obviously in different spaces, but the one space entails the other.

There are so to speak two intertwined conjugate spaces and maybe we can infer the laws and the properties of one from the other.

In a picture of the universe like this, what will be the role of the vacuum? And if "we do not have the luxury of referring to some objective space-time structure "as you mentioned in your paper, do we have it for the vacuum?

Best regards

Basileios Grispos

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Saibal Mitra wrote on Sep. 4, 2012 @ 17:43 GMT
I saw Giovanni in this documentary yesterday. He was riding his motorbike :) .

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Author Giovanni Amelino-Camelia wrote on Sep. 6, 2012 @ 00:15 GMT
dear Saibal

I had not seen the documentary until this evening, since I am at a workshop in Budapest

I was just told I could see it on youtube, so now I know what you meant

I see,,,the BBC used a lot of the motorbike footage,,,I can imagine worse things they could have done,,,the director and the crue were really very nice and I am just glad they left out of the documentary some of the stupidest things I said,,,

and my motorbike allows me to bring us back to my essay, which after all is the topic of this thread: bulky motorbike, safely in the classical regime, space-time inferences very robustly reliable

cheers

Giovanni

Author Giovanni Amelino-Camelia wrote on Sep. 6, 2012 @ 00:17 GMT
dear Daniel

I enjoyed it very much.

Of course we are pursuing different objectives, but there is a common drive toward seeking the building blocks of space-time notions in your essay and mine.

I am trying to take a certain leap in the (conceptually) unknown: doing physics without space, time, motion,,,,only particle detections and relationships among detectors,,,,this is after all what we really do operatively and I am intrigued by the possibility that if we stick to this minimalistic description, if we get read of the extra luggage of space-time inferences, perhaps we might travel more comfortably toward addressing some of the foundational issues we are facing

and by the way to me a clock is a box Alice gives to Bob: when the box is materially connected, in appropriate ways, to Bob's ``particle-detector box"

the combination of the two boxes produces readouts which assign a certain number, "time", to each particle detection,,,,,it seems to me this is what is actually done by the objects we call clocks,,,

if we found a steady source of particles in nature, let me call them particles of type A, it could be all in one box: detector distinguishes two types of particles and uses number of particles detected of type A as time whereas it handles number of particles detected of type B as its actual detections, so it times the detections by producing readouts of pairs of numbers, correlations n_A,n_B (had value of the counter B equal to n_B in correspondence of the value of the counter A equal to n_A)

best wishes for the competition

Giovanni

Anton Lorenz Vrba wrote on Sep. 6, 2012 @ 06:43 GMT
Hi Giovanni

Good to note that space-time is questioned by forward thinking professionals who realise something has to give such that QM and gravity can find a common underlying structure.

You write: " v=sqrt[(E-U)/m].  Since in quantum tunneling E − U < 0 this recipe for the speed (and therefore the corresponding derivation of the travel time) becomes meaningless."

Why meaningless, trust the mathematics; accept imaginary velocities. This you can do by adopting a hyper-space where each axis is complex.

Exactly such a complex hyper-space I propose in my essay, your comment to this idea would be interesting.

Regards

Anton @ (  ../topic/1458  )

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Lawrence B Crowell wrote on Sep. 6, 2012 @ 23:06 GMT
I read your arXiv:1206.3805 paper a couple of time. I don’t have time to write at length right now. However, this structure seems to be very similar to twisters. In fact I have today been thinking quite a bit about how one could construct T-theory with q-deformations. I will try to write more about the connection with T-theory after I have tried to bend metal on the idea.

I gave your paper a high score. It deserves it and I think it should be ranked higher on the list than it has been.

Cheers LC

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Lawrence B. Crowell replied on Sep. 8, 2012 @ 01:55 GMT
The connection to twistor theory is I think not hard to see. The boost operator P_μ that acts on [x_i, x_0] = ilx_i such that

P_μ > [x_i, x_0] = il P_μ > x_i

The coordinates (x_j, x_0) we write in spinor form

x_j = σ_j^{aa’}ω_{aa’}

x_0 = σ_0^{aa’}ω_{aa’},

where ω_{aa’} = ξ_a ω_{a’} + ξ_{a’}ω_a. This commutator has the form

[x_i, x_0] = σ_j^{aa’}σ_0^{bb’}[ω_{aa’}, ω_{bb’}]

= iC^{cc’}_{aa’bb’} σ_j^{aa’} σ_0^{bb’} ω_{aa’}

= i|C| σ_j^{aa’}ω_{aa’}

where the magnitude of the structure matrix is |C| = l. In general this may be written for

x_j = σ_j^{aa’}ω_{aa’}

x_0 = σ_0^{aa’}ω_{aa’} + iq_{aa’}π^{aa’},

where the commutator [ω_{aa’}, π^{bb’}] = iδ_a^bδ_{a’}^{b’} and the general form of the commutator is then

[x_i, x_0] = i|C| σ_j^{aa’}ω_{aa’} + iσ_j^{aa’}q_{bb’}[ω_{aa’}, π^{bb’’}

[x_i, x_0] = ilσ_j^{aa’}ω_{aa’} - σ_j^{aa’}q_{aa’}.

The boost operation B = 1 + a^l_jP^j on the commutator [x_i, x_0] is then equivalent to the commutation between spinors [ω_a, ω’_b] for ω’_b = ω_b + iq_{bb’}π^{b’},

[ω_a, ω’_b] = [ω_a, ω_b] + iq_{bb’}[ω_a , π^{b’}]

= C^c_{ab} ω_c + iq_{ab}.

This could be explored more deeply. Ed Witten demonstrated the "twistor revolution" in string theory. If twistors are connected to κ-Minkowski spacetime there might then be a link between string theory and LQG and other "edgelink" type of quantum gravity theories. This would be potentially interesting, for this might serve to correct the difficulties with each of these.

Cheers LC

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Constantinos Ragazas wrote on Sep. 9, 2012 @ 04:26 GMT
Greetings Giovanni,

I would like to suggest the problem with Spacetime is that physical events are considered to be 'instantaneous' at time t. This fundamental assumption is in conflict with the Second Law of Thermodynamics which can be shown to state “every physical event needs some positive duration of time to occur” (see my Chapter, “The Thermodynamics in Planck's Law” ). Thus, the Second Law establishes 'physical time' to be 'duration' Δt and not 'instantiation' t . Each moment of a particle moving along a smooth worldline is a 'physical event' requiring a positive duration of time to occur. Spacetime violates this requirement of the Second Law. This, in my opinion, explains why Cosmology is in conflict with Thermodynamics.

Constantinos

“The Metaphysics of Physics”

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Author Giovanni Amelino-Camelia wrote on Sep. 9, 2012 @ 06:54 GMT
dear Anton

I have nothing against adopting, if the formalism provides room for it, some formal notion of velocity that takes imaginary values, but you see from my essay that I am "detectors first",,,,readouts are real numbers,,,,surely you can combine TWO real numbers to get an imaginary one, but would that help? and what is the second number I should measure?

In any case this is surely connected to the properties of the "Feynman-path time" (also imaginary) which I mention in parts of the essay

best wishes for the competition

Giovanni

Author Giovanni Amelino-Camelia wrote on Sep. 9, 2012 @ 06:56 GMT
dear Lawrence

thanks for your interest in the essay

and your choice of expressing appreciation specifically for arXiv:1206.3805 tells me a lot....that is not the easiest paper to read among my papers...

and most intriguing are your observations about twistors: I had been thinking about a connection between twistors and relative locality but only at a somewhat "intuitive" level, still looking for a formalization. It seems you have a case for one possible formalization of the connection.

It would be nice if you managed to bring this to full fruition. I may be thinking about it (and we could be in touch for that) gradually as the end of this fall will approach (I have a couple of ongoing projects to finalize and two students presenting their PhD thesis over the next few weeks)

cheers

Giovanni

Lawrence B. Crowell replied on Sep. 10, 2012 @ 01:42 GMT
I will think about this more as well. There may be a more general isomorphism of some type.

I find myself wondering if twistores might be some type of connection to between loopy and stringy approaches to quantum gravity.

Cheers LC

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Member Benjamin F. Dribus wrote on Sep. 9, 2012 @ 09:27 GMT
Dear Giovanni,

1. I agree wholeheartedly that modeling classical spacetime as a manifold over the continuum is at the very best redundant. Some would argue that it "does no harm" and that it "makes no difference" what the structure is at arbitrarily small scales, but something that bothers me about this view, in...

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Pentcho Valev wrote on Sep. 12, 2012 @ 12:09 GMT
Giovanni,

If the absurd "energy-dependent but observer-independent" speed of light is a failure, why don't you try, for a change, "energy-independent but observer-dependent" speed of light? I am not sure about the energy independence but "observer-dependent speed of light" sounds quite reasonable. I have tried to show this in my essay:

http://fqxi.org/community/forum/topic/1398

Pentcho Valev

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Author Giovanni Amelino-Camelia wrote on Sep. 12, 2012 @ 13:30 GMT
dear Pentcho

consistently with the rest of my posts, let me just confirm that for me any proposal which is consistent with available experimental data and can be fit within a logically-consistent mathematical framework is good-enough for testing. So I am fine with speculations about "energy-independent but observer-dependent" speed of light. I do not "BELIEVE" something is right or wrong. What can happen occasionally is that I (or someone else) rigorously SHOW that some proposal is either in conflict with available experimental data or lacks internal logical consistency. But as long as no such proof against the proposal is given I will not build any prejudice/belief against a proposal. One might have to go to a next level of assessment ("plausibility", "intuition", "conservativeness") when tough decisions must be made about which proposals deserve top priority, considering the limitations of our resources, but that is whole other challenge.

best wishes for the competition

Giovanni

Author Giovanni Amelino-Camelia wrote on Sep. 12, 2012 @ 13:43 GMT
dear Ben

In the meantime let me start by giving a concise answer concerning my "interpretation" of quantum mechanics. For me quantum mechanics is just like any other theory in physics: it is a formalism predicting certain correlations among the readouts of detectors (and clocks) built following certain craftmanship procedures. Its predictions are successful so I am "happy" with quantum mechanics. The part which is successful of quantum mechanics, the part which I use, the part which produces succesful predictions, is the same in all of its "alternative" reformulations. So its alterantive reformulations are not of interest to me within the confines of quantum mechanics itelf.

There is however an area of speculation about the applicability of quantum mchanics (or some modification of it) to a class of measurement procedures we have never managed to perform, the class we colloquially label "quantum gravity observables". In that realm we have at present no experimental basis. It is then legitimate to speculate that quantum mechanics might have to adjust at least a bit. And then the alternative formulations of quantum mechanics can become of interest also to someone like me (equivalent reformulations of the starting point may well not be equally efficacious in getting us to the finish line)

best wishes for the competition

Giovanni

Member Benjamin F. Dribus replied on Sep. 17, 2012 @ 01:50 GMT
Dear Giovanni,

I appreciate the response! I think we agree on how quantum theory should be viewed in general. As you suggest, however, different interpretations might generalize in different ways. For example, in Feynman's original sum over histories formulation (the 1948 paper), he sums over "particle trajectories" on a fixed background. If you believe GR, though, you know that the "spacetime" itself should respond in different ways to different trajectories, so each trajectory has its own spacetime, and suddenly you are summing over universes, but the underlying concept of a sum over histories comes through unscathed. The alternative formulation of a probability density function on spacetime, which works fine for a fixed background, doesn't generalize as easily to the background-independent scenario. Take care,

Ben

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Peter Jackson wrote on Sep. 17, 2012 @ 15:55 GMT
Giovanni

Can you advise if light passes through the visor material of your helmet at the constant speed c/n irrespective of the speed at which you are driving?

If so, have you considered that, as your visor is equivalent to a lens medium, CSL may then be simply explained by light changing speed on arrival at your visor or lens. Wavelength and thus frequency also change (inversely) because c (as c/n) is conserved in both the rest and co-moving (bike) frame.

The boundary condition between frames is the equivalent to dynamic fluid coupling at the surface fine structure of all dielectric media, including the diffuse ISM.

You did indicate you'd try to read my essay, I hope you may soon get there and comment. It considers this 'discrete field' model and boundary mechanism in detail, also with a little theatre. I have been unable to falsify it, found the implications broader than they may at first appear.

Many thanks in advance. PS, I confirm I still think yours is worth a far higher placing and intend to help it achieve that.

Best wishes

Peter

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Yuri Danoyan wrote on Sep. 18, 2012 @ 02:34 GMT
For better clarification my approach

I sending to you Frank Wilczek’s 3 keen articles

http://ctpweb.lns.mit.edu/physics_today/phystoday/Ab
s_limits388.pdf

http://ctpweb.lns.mit.edu/physics_today/physt
oday/Abs_limits393.pdf

http://ctpweb.lns.mit.edu/physics_toda
y/phystoday/Abs_limits400.pdf

All the best

Yuri Danoyan

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John Merryman wrote on Sep. 20, 2012 @ 03:44 GMT
Giovanni,

e problem as I see it, is that we perceive time as a sequence from past to future and physics re-enforces this by treating it as a measurement issue, ie. clocks, detectors, days, etc, but the physical reality is the changing configurations turn future into past. It is not the earth traveling a narrative dimension from yesterday to tomorrow, but tomorrow becoming yesterday because the earth rotates. In this way, time is an effect of action. Like temperature it emerges from that basic thermodynamic activity. Clock rates vary, as levels of activity vary. More activity, faster clock rate. If time were a dimension from past to future, one would think a faster clock rate would travel into the future more quickly, but the opposite is true. As it ages/burns quicker, it moves into the past faster. The twin in the faster frame is dead when her twin in the slower frame returns.

Duration is not some dimension that transcends the present, but is the state of the present between detections.

Since the lightcone of any event is incomplete prior to the event, the future is probabilistic, even if the laws determining its outcome are deterministic.

It is the collapse of probabilities which yields actualities, so the cat is not both dead and alive, because there is no external timeline moving the present from past to future, but the actual occurrence of events turning future into past.

Cause and effect is not sequence, but energy exchange. Yesterday didn't cause today, any more than one rung on a ladder causes the next. It is the sun radiating on this rotating planet that creates this sequencing called days. Time is an effect, not a cause.

Knowledge is created inductively, as future becomes past, but is used deductively, as the past is used to predict the future.

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John Merryman replied on Sep. 20, 2012 @ 03:46 GMT

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Hoang cao Hai wrote on Sep. 22, 2012 @ 17:46 GMT
Dear Giovanni Amelino-Camelia

Separate Space and Time is a reasonable opinion.

Because each space has a different lifetime, and they are two completely different issues, as well as can be completely independent of each other.

Kind Regards.Hải.Caohoàng

of THE INCORRECT ASSUMPTIONS AND A CORRECT THEORY

August 23, 2012 - 11:51 GMT on this essay contest.

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Pentcho Valev wrote on Sep. 24, 2012 @ 17:53 GMT
Giovanni,

You will get maximum rating from me. Something tells me you share Magueijo's and Smolin's conviction that "the root of all the evil is special relativity":

Joao Magueijo, Faster Than the Speed of Light, p. 250: "Lee [Smolin] and I discussed these paradoxes at great length for many months, starting in January 2001. We would meet in cafés in South Kensington or Holland Park to mull over the problem. THE ROOT OF ALL THE EVIL WAS CLEARLY SPECIAL RELATIVITY. All these paradoxes resulted from well known effects such as length contraction, time dilation, or E=mc^2, all basic predictions of special relativity. And all denied the possibility of establishing a well-defined border, common to all observers, capable of containing new quantum gravitational effects."

Pentcho Valev

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Jonathan Kerr wrote on Sep. 24, 2012 @ 22:57 GMT
Hello Giovanni,

I found your essay one of the best I've read, and you argue very well for weaknesses in the spacetime interpretation at a small scale in some areas. But you talk as if all is well with spacetime elsewhere and generally, as intuition says it should be. Of course SR is right, but a close look and you'll see that all is not well generally with the spacetime interpretation. You...

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Georgina Parry replied on Sep. 25, 2012 @ 00:23 GMT
Dear Giovanni Amelino-Camelia,

your introduction immediately caught my attention and compelled me to read to the end of your very fine essay. Though I disagree with the answers to those initial questions we are both saying that space-time is not required 'throughout'.I am not saying these following things to be critical of your writing but to highlight another option that is available. It...

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Pentcho Valev replied on Sep. 25, 2012 @ 09:32 GMT
Jonathan,

You wrote: "Of course SR is right... (...) If we don't look at the clues in front of us, however unexpected, I'm not sure how we're going to reach a point where we understand time. There are also missing pieces of the puzzle, and we need to allow for their existence. Because it leads to block time, spacetime is in contradiction with the standard view of quantum theory about whether the future currently exists. That is a deep contradiction. And there are some places where the implications of spacetime jar with our picture that deeply, and conflict directly with what we observe. So although it is convenient to use, it looks like it might be flawed. (...) Of course SR is right..."

If spacetime is flawed, SR cannot be right. Logic forbids a situation in which the premises (Einstein's 1905 postulates) are true and the consequence (Minkowski spacetime) flawed. So let us "look at the clues in front of us, however unexpected", Jonathan.

Pentcho Valev

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Anonymous replied on Sep. 25, 2012 @ 14:56 GMT
Pentcho, briefly,

you and I have already discussed this question at length on my page, and I have shown you to be wrong, in a way that even you eventually didn't argue back about. The reason we call it "the spacetime interpretation" is because it's an interpretation. It's untested - unlike SR, which is extremely well confirmed by experiment. People often imply that spacetime is an unavoidable consequence of SR, but no-one will actually say that it is, because it isn't.

Jonathan

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Don Limuti wrote on Sep. 25, 2012 @ 03:56 GMT
Dear Giovanni,

First I must agree with you about reconsidering space-time. i think of Space-time as a very convenient lie. We build this lie with the relationships between individual particles and then fall in love with the mathematical beauty of the field and call the field real.

And space-time is very, very convenient field, it is almost as if it were genetic. Breaking away is going to be difficult, many worthwhile things are.

You may be interested in my essay in that it joins quantum mechanics and special relativity via boundary conditions. Some earlier posts indicated you had an interest in this. http://www.fqxi.org/community/forum/topic/1403

Thanks for your though provoking essay.

Don L

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Yuri Danoyan wrote on Sep. 25, 2012 @ 10:57 GMT
See my discussion with George Ellis

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Yuri Danoyan wrote on Sep. 26, 2012 @ 13:06 GMT
Giovanni wrote:

"In quantum-gravity research there is a long-standing effort

of understanding how spacetime should be described when both

Planck’s constant ~ and Newton’s constant GN are nonnegligible.

We cannot claim much success addressing this issue."

Giovanni,

what mean "nonnegligible"?

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Author Giovanni Amelino-Camelia wrote on Sep. 26, 2012 @ 16:11 GMT
Dear Yuri

I use "nonnegligible" in relation to the different regimes of physics which we are able to explore with different types (and different senstitivity levels for) our experimental setups. If we measure a "spacetime observable" (e.g. distance) pertaining to macroscopic bodies separated by macroscopic distances we can neglect quantum mechanics (because its effects in such setups are negligibly small) but we often then must take into account gravitation. If we measure a "spacetime observable" pertaining to a pair of microscopic particles (e.g. electrons) with energies of say a few GeVs, then their mutual gravitational influence is negligibly small, but their quantum-mechanical properties are tangible. If one day we will manage to measure spacetime observables pertaining pairs of microscopic particles of Planckian wavelength and separated by Planckian distances then we expect that both their mutual gravitational influence and their quantum-mechanical properties will be tangible (non-negligible, affecting tangibly the relevant measurement results).

I hope this clarifies.

best regards

Giovanni

Yuri Danoyan replied on Sep. 26, 2012 @ 16:35 GMT

My opinion:Planck constant is major constant of Nature.

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Yuri Danoyan replied on Oct. 12, 2012 @ 21:09 GMT
I don't understand why used word "nonnegligible"?

Why double "no"?

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Author Giovanni Amelino-Camelia wrote on Sep. 26, 2012 @ 16:35 GMT
dear Jonathan and Pentcho

I have made a note of reading frequently the pages of the blog for Jonathan's essay, so I can follow your discussion of these matters.

dear Georgina and Don

In relation to some of Georgina's comments let me stress that the essay I here proposed focuses on my latest speculation. Searching inspires with "f a Amelino-Camelia" you will see that I have in the past investigated (and I am still investigating) also other speculative scenarios, and some of them are not mutually exclusive. But in this essay I thought it would be in the interest of clarity (also considering the word count allowed) if I focused on my speculations "against spacetime" without elaborating for example on what might (or might not) be the implications for the boundaries of the regime of applicability of the (Einsteinian) relativistic theory currently adopted.

best regards

Giovanni

Janko Kokosar wrote on Sep. 29, 2012 @ 09:20 GMT
Dear Giovanni

I agree a lot of thing with you. I agree that space-time is emergent.

I wrote my own appendix to explanation of emergence of space-time.

Mass can only run inside of elementary particles, and they are rest. Thus, in principle time does not run in empty space. Thus empty space-time does not exist, or if all matter was removed from our universe, space-time would disappear. (If relativistic mass is used in derivation of special relativity, this is still clearer.)

Do you maybe read Markopoulou? Where your theory is distinct from her?

It is interesting your viewpoint about unclear definition of run of clocks. Do you have any reference of this viewpoint, which can be found also on Internet. I am interested in more precisely described mechanism of those differences? Otherwise this seems unlikely to me, because time is the essence of mechanisms of special and general relativity ...

I am not sure also about your generalization of uncertainty principle on time and energy. I wrote about this in my essay where I suggest a different approach.

Thus I suggest my model but we agree that space-time is emergent. I suggest also that space-time is emergent, do you agree to this?

Best regards Janko Kokosar

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Janko Kokosar replied on Sep. 30, 2012 @ 12:56 GMT
correction of the last sentence:

I suggest also that interior of black hole does not exist, do you agree to this?

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Anonymous wrote on Sep. 29, 2012 @ 18:27 GMT
Hi Giovanni,

I just want to say how much I enjoyed reading your essay. I've been fascinated by your notion of relative locality ever since I wrote about it for New Scientist last year, and it's great to now read about its deep implications in your paper here. Between your group's work and others' work on holography, it's hard to imagine that spacetime can survive as an observer-independent feature of the world.

That is similarly the theme of my essay here. If you have a spare moment to look at it, I'd be extremely interested to hear your thoughts. My argument, in brief, is that given the relativity of the location of information in spacetime, and given the fact that there seems to be no way to patch together different obsevers' spacetimes into a single spacetime without violating the laws of physics, we may have to give up the assumption that there exists a single universe containing multiple observers.

In any case, thanks for your wonderful essay and I look forward to following your work in the future!

All best,

Amanda

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Member Gheorghe-Sorin Sorin Paraoanu wrote on Sep. 30, 2012 @ 19:16 GMT
Dear Giovanni,

This is a very well-written piece, in the tradition of "against" in the philosophy of physics (with Paul Feyerabend's "Against Method" and John Bell's "Against measurement").

I also feel that some of the points you make are not singular and might reflect the views of many other physicists as well. I would enjoy to hear more about your thoughts about the problem of time of tunneling. I agree that it supports the view that time in spacetime is not an absolute quantity but it is instead detector-dependent, but then what's next? Can one construct a theory based on this observation? I realy am looking forward for Ref. [2], for which the current essay is a nice teaser :-).

Best of luck with the contest.

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qsa wrote on Oct. 1, 2012 @ 00:05 GMT
Hi Giovanni,

In my theory everything is emergent all from a mathematical structure that describes random numbers and imperative relations between them. Interpreting the random numbers as line lengths, the relations between these lines generate all of the laws of physics. You get a beautiful unified picture of space (its points are the crossing of the lines-dynamic-),...

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attachments: 4_newqsa.pdf

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Victoria wrote on Oct. 2, 2012 @ 16:44 GMT
Dear Giovanni,

More than a hundred years, physicists curve space (ideal self), and now you want to make the human race at the homeless and deprived of his memory.

All best,

Victoria

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Author Giovanni Amelino-Camelia wrote on Oct. 2, 2012 @ 23:27 GMT
Dear Janko

I like that you noticed that there are some shared elements between Fotini's (Markopoulou) perspective and mine. Fotini is indeed among the physicists whose feedback I have most relied upon over the years, so surely there are some reciprocal influences that intertwine with the inevitable differences of perspective

concerning the interior of a black hole...well...to get an answer of the only type I am interested in I would need to find a very passionate, innovative and trustworthy graduate student...

there may be one daring to take the journey inside the black hole

and I am willing to imagine that there can be one creative enough to find a way to send infos (tunneling?) back outside the black hole to me

but how could I trust her/his report of the measurement results?

so I should be the one to go on the journey inside the black hole, but I am not going

cheers

Giovanni

Author Giovanni Amelino-Camelia wrote on Oct. 2, 2012 @ 23:28 GMT
dear Victoria

thanks

I very much like your connection:

spacetimeless homeless

cheers

Giovanni

Author Giovanni Amelino-Camelia wrote on Oct. 2, 2012 @ 23:34 GMT
Dear Amanda

I am glad you liked my essay

yours was one of the first essays I looked at because of the title (well I now like your title...but at first I was simply curious about the title because "solipsism" was not in my English vocabulary, which as you might remember has severe limitations)

I really enoyed your essay and I am routing for you

there are very many essays competing but it is nonetheless surprising to me that quite a few of them are against or partly-against spacetime

it seems however that quantum mechanics is "most popular" (which in a sense means least popular...considered most likely to be superseded soon...)

cheers

Giovanni

Author Giovanni Amelino-Camelia wrote on Oct. 2, 2012 @ 23:40 GMT
dear Gheorghe

I am of course very glad you liked my essay

And I agree that views against or partly-against spacetime are starting to be not uncommon. I get a sense of that also from the choice of subject of some of the essays in this competition

and concerning "what next?"...well....formulating a theory without a "time of spacetime" but only very many (not necessarily mutually consistent in the standard sense) possibilities for a "time of a specific clock" looks like a formidable challenge....but a challenge that I consider interesting conceptually even if in the end Nature turned out not make use of it...

and I confess that I have not so far managed to imagine how to do it...the farthest I have gone along roughly this direction is my work on the "relative-locality framework" but that only goes no more than half way: in relative locality one can still refer to a "time of spacetime" and a "space of spacetime" with the only limitation that inferences about the spacetime location of networks of distant events are less robust, with anomalies governed by the minute Planck length but qualitatively striking

cheers

Giovanni

Janko Kokosar wrote on Oct. 3, 2012 @ 09:38 GMT
Dear Giovanni,

Quantum mechanics says: if something cannot be measured, this does not exist. Your answer to me show on this property (nonexistence) for interior of a black hole. Admittedly, it is not absolutely clear, if your examples really means nonexistence of measurement.

The second is my argument in my essay that this interior is a similar "almost impossible thing" as tahions.

The third argument is what you hinted in your essay.

The fourth argument is that this is not contradictory supposition.

etc..

It is also interesting your use of imaginary numbers in physics. My article gives a simple argument for nonexistence of space-time, but besides, it here is also one example for use of imaginary numbers. Imaginary distance between two events in space-time of Minkowski means that signaling between these two events is not possible. Your imaginary speed at tunneling can give a similar pedagogical conclusion ...

One essay with this idea of emergent space-time is also of Dribus. I suspect it we are not the only one here.

I am very sure that space-time is emergent. It is not problem to me to bet with someone. Do you also? :)

P.S.

Do you know Italian form of name Janko. The answer is hidden in this post. :)

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Sergey G Fedosin wrote on Oct. 4, 2012 @ 06:02 GMT
If you do not understand why your rating dropped down. As I found ratings in the contest are calculated in the next way. Suppose your rating is
$R_1$
and
$N_1$
was the quantity of people which gave you ratings. Then you have
$S_1=R_1 N_1$
of points. After it anyone give you
$dS$
of points so you have
$S_2=S_1+ dS$
of points and
$N_2=N_1+1$
is the common quantity of the people which gave you ratings. At the same time you will have
$S_2=R_2 N_2$
of points. From here, if you want to be R2 > R1 there must be:
$S_2/ N_2>S_1/ N_1$
or
$(S_1+ dS) / (N_1+1) >S_1/ N_1$
or
$dS >S_1/ N_1 =R_1$
In other words if you want to increase rating of anyone you must give him more points
$dS$
then the participant`s rating
$R_1$
was at the moment you rated him. From here it is seen that in the contest are special rules for ratings. And from here there are misunderstanding of some participants what is happened with their ratings. Moreover since community ratings are hided some participants do not sure how increase ratings of others and gives them maximum 10 points. But in the case the scale from 1 to 10 of points do not work, and some essays are overestimated and some essays are drop down. In my opinion it is a bad problem with this Contest rating process. I hope the FQXI community will change the rating process.

Sergey Fedosin

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Frank Ullmann wrote on Oct. 4, 2012 @ 18:18 GMT
Dear Giovanni,

As I said in my first post I have read your essay with great interest.

After reading your essay again I thought that you might like to read something that was once intended to be my diploma thesis (in a quiet longer and more complicated version). : About the length of world lines … (my essay)

My abstract could be like this:

There is a way to test if the metric (based on the notion of distance, given by the Minkowski norm) tying space and time to space-time really exists.

By using an assumption that is (WLOG) weaker then the assumption that has been used to derive Minkowski norm, we can see that reversed triangle inequality (one of the three conditions that have to be met for space and time to be a four-dimensional metric space) is violated. Thus space and time can not be seen as a four-dimensional metric space.

Kind regards,

Frank

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Frank Martin DiMeglio wrote on Oct. 5, 2012 @ 04:02 GMT
Giovanni, General Relativity is lacking: instantaneity, fundamental inertial and gravitational equivalency and balancing, gravity cannot be shielded, fundamental F=ma, fundamentally balanced and equivalent attraction and repulsion, invisible and visible space in fundamental equilibrium and balance, fundamentally stabilized and balanced distance in/of space in and with time.

(Physics happens in AND with time.) Physics cannot fundamentally step outside of time.

It is amazing that GR falls is so highly regarded given that it clearly falls far short of demonstrating the above. The above fundamentally and generally exposes the deficiencies and failings of GR.

The Equivalence Principle does not fundamentally and truly demonstrate inertial and gravitational equivalency and balancing OR F=ma.

You ignored my prior post and essay. My essay proves everything in the first paragraph, and it fundamentally and generally reveals the limits of physical understanding and description.

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Jin He wrote on Oct. 5, 2012 @ 11:45 GMT
You mainstreamsians controle science for over 50 years. You mainstream and Hawking failed. The bad science is because of the Top-Down controle of the people like you. Why do you need money and fame from FQXI where the authors are mostly jobless, are mostly independent researchers, are mostly viXra.org authers? Do you need money and fame by controling jobless???

I want to rate you 0!

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Jin He wrote on Oct. 5, 2012 @ 11:58 GMT
You mainstreamsians controle science for over 50 years. You mainstream and Hawking failed. The bad science is because of the Top-Down controle of the people like you. Why do you need money and fame from FQXI where the authors are mostly jobless, are mostly independent researchers, are mostly viXra.org authers? Do you need money and fame by controling jobless???

I want to rate you 0!

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Matthew Peter Jackson wrote on Oct. 5, 2012 @ 19:43 GMT
Giovanni

Jin He's comment is badly targeted here, but he does have a point. There is far too much complacency and arrogance among your colleagues. Please never lower your own approach to their standards. Open minds and fresh ides rule.

Good essay, and good score. I'd love your views on our logical Copenhagen.

Matt

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Author Giovanni Amelino-Camelia wrote on Oct. 5, 2012 @ 20:43 GMT
Hi everyone

the last few days were remarkably busy for me. A combination of strange italian-style rules make the first week of october at Sapienza University the time when most students must finalize their undegraduate, master or PhD theses. The fact I like to follow and work with students has the little downside of creating this challenge for me every first week of october.

I postpone commenting on other recent posts until I have had time to recover, over the weekend. But I felt compelled to offer some comments immediately in relation to Matt's post

I would say that Jim He's post is prototypical of why the "report post as inappropriate" button exists. But I will not reports it as inappropriate for at least two reasons:

1. I want it to be visible that someone on the planet thinks I am mainstream. That was one label I was missing, probably for good reasons. But it is cool to have that label at least once.

2. Jim opted to be simply unpolite/rude, but implicit in his rude comments is a point that one could legitimately raise (I think the point is actually wrong, but I still think it could be legitimately raised)

Concerning arrogance: I do find that some of my colleagues are pretty arrogant (and maybe others feel that I am arrogant), but it seems to me that FQXi tends to attract an anomalously large proportion of non-arrogant scientists. And this is partly related to the spirit of FQXi which essentially allows Jim to express his thoughts in the way he expressed them. In this I see a paradox.

regards

Giovanni

Jonathan Kerr replied on Oct. 25, 2012 @ 10:37 GMT
I suppose there was a touch of calling you 'mainstream' in my post to you, if so I'm sorry! I found your essay to be one of the very best anyway.

Best wishes, Jonathan

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Thomas Howard Ray replied on Oct. 25, 2012 @ 17:51 GMT
Dear Giovanni,

I don't think that spacetime is redundant (at least not in a fully relativistic theory) for reasons explained in my essay , so I have been silent on the interesting and bold questions raised in your well written and well argued piece. I did chuckle, though, at the irony of protesting "mainstreamian" participation in the contest. It isn't the first time I have heard the message that "you insiders don't need the money or recogniition, so why don't you leave the competition to the amateurs and the unknowns?"

Jin, it isn't all about money and recognition. By definition, the mainstream dominates every professional field. FQXi's noble and inclusive mission is to allow minority and amateur ideas to openly compete on the main stage of cutting edge physics -- and I, for one, think that it's doing an outstanding job. Only "mainstreamian" participation makes that goal even possible. I wish more of the mainstream would come out and play.

Tom

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Jayakar Johnson Joseph wrote on Oct. 24, 2012 @ 14:43 GMT
Dear Giovanni Amelino-Camelia,

As time emerges with the dynamics of the peripheral end of an eigen-rotational string-segment in Coherently-cyclic cluster-matter paradigm of universe, space-time is expressional as discrete closed loops in holarchy, in that discrete cyclic-times is descriptive. Thus the implication of this scenario of space-time abstraction in quantum tunnelling differs, in that string-matter continuum is expressional.

With best wishes

Jayakar

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Amrit Srecko Sorli wrote on Oct. 29, 2012 @ 19:11 GMT
Common understanding in physics is that with clocks we measure time as a 4th dimension of space-time in which material change run. This understanding is contradictory to the experimental measurement of time where we measure with clocks a numerical order of material changes which run in a 3D space. Measurement of numerical order of material changes with clocks confirms time is exclusively a mathematical quantity dependent on the run of material changes. Material changes, i.e. motion run in a 3D space and time is their numerical order. Mass of elementary particles has origin in a diminished energy density of a 3D space.

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Davide wrote on Dec. 26, 2012 @ 17:39 GMT
hallo there, I came across this paper during these Christmas holydays, through FB.

I've got a point or two about the issue, which I'd like to discuss - at best, perhaps, with the author himself, Giovanni.

( BTW: I'm italian, so if he should come across this comment he may, of course, reply in italian )

Not knowing if a comment, written 2 months from the last one published,...

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