Dear Dr. Mavromatos,

In your recent article "Testing models for quantum gravity" [Ref. 1], you mentioned the problem of background-dependence, the notorious problem of string theory.

I'm sure you and your colleagues at CERN are fully aware of this highly complex problem and its implications [Refs. 2-5].

May I ask you to explain, prior to the experiments on the supposed "loss of quantum coherence" [Ref. 1], your view on the background-dependence problem in quantum gravity.

Suppose, just hypothetically, that you observe loss of quantum coherence. How would you then relate such evidence to the whole bundle of problems [Refs. 2-5]? That I was never able to figure out. Hope you and your colleagues will help -- before you run the experiments.

Thank you very much in advance.

You can read this email also at

http://members.aon.at/chakalov/Mavromatos.html

Regards,

Dimiter G. Chakalov
http://members.aon.at/chakalov
--
Murphy's Law #15: Complex problems have simple, easy-to-understand wrong answers.
 
 

References

[Ref. 1] Nick Mavromatos (September 2002). Testing models for quantum gravity. CERN Courier,
http://www.cerncourier.com/main/article/42/7/18

"In the framework of local field theory, John Wheeler and Stephen Hawking have suggested that microscopic quantum space-time fluctuations of black hole type, with size of the order of the Planck length (10^35 m), characterize the quantum-gravity vacuum, giving it a "space-time foamy" nature (figure 1). Interaction of matter with such backgrounds may result in the loss of quantum coherence. This in turn could lead to significant deviations from the standard quantum-mechanical behaviour of matter particles, even at scales much lower than the characteristic quantum-gravity (Planck) energy scale of 10^19 GeV.

"This is because gravity is a non-renormalizable interaction, with a dimensionful coupling constant, and so it may manifest itself at much lower scales. An example of such a phenomenon is provided by the so-called charge-parity (CP) discrete symmetry, whose violation manifests itself at scales much lower than the characteristic scale of the underlying weak interactions responsible for the effect.
...

"For the time being, however, string theories seem to suffer from an important drawback, which probably prevents a complete understanding of quantum gravity issues within this framework. This is their background dependence - the fact that the whole formalism of strings, at least so far, is based on specific space-time backgrounds."
 

[Ref. 2] John Baez (May 5, 2000). What is a background-free theory?
http://math.ucr.edu/home/baez/background.html

"Personally I think one can dig oneself into a hole by trying to do physics without any background structure - it's a bit like trying to paint a painting without any canvas."

See also:
http://members.aon.at/chakalov/right.html#Baez_April97
 

[Ref. 3] Peter Woit (2001). String Theory: An Evaluation.
http://xxx.lanl.gov/abs/physics/0102051
 

[Ref. 4] Angelo Loinger (2001). The generation of gravitational waves.
http://xxx.lanl.gov/abs/physics/0011041

See also
http://members.aon.at/chakalov/Chiao.html
 

[Ref. 5] Mário Everaldo de Souza. Gravity cannot be quantized. Tue, 27 Aug 2002 20:43:37 GMT,
http://xxx.lanl.gov/abs/gr-qc/0208085

"And if the fermionic mass carrier exists each mass is a multiple of the fermion mass. Otherwise, mass cannot be quantized because without a fermionic mass carrier there cannot be mass currents. How can gravity be quantized without quantizing mass and without fermionic currents?

"The quantization of gravity has to exist either in curved spacetime or in flat spacetime. For example, it is expected that *if a body is excited gravitationally it should emit gravitational charge carriers into space and it is also expected that when a body is gravitationally excited the charge carriers (fermions) should change quantum states. When particles change mass in a high energ y collision there should exist such fermion currents*.

"Let us admit the existence of such mass carrier and let us call it *masson*.
...

"These two equations clearly show that the *masson* mass depends on the metric. In curved space-time we can always choose a small region where space-time is approximately flat. Hence, we can extend the meaning of  [g]  to include curved space-time. Doing this we notice that since the masson mass depends on the metric it can not be unique, that is, it has different values in different curved space-times. Since flat space time is a local approximation of curved space-time its mass has only a local meaning. Therefore, we stumbled into another obstacle in quantizing gravity.
...

"Thus, the gravitational field cannot be scalar, pseudoscalar, vectorial, pseudovectorial, and symmetric tensorial field. The only possibility left is to be an antisymmetric tensorial field which is a result that agrees well with general relativity. Misner, Thorne and Wheeler [2] have proven that the classical gravitational field is an antisymmetric tensorial field. This work shows that the same should hold quantum mechanically. But since elementary fermions are spin 1/2 particles we expect the *masson* to be also an elementary fermion. But this means that the graviton should have spin equal to 0 or 1 because bosons intermediate states between fermions. In other words if the *masson* is in a state with spin  [X]  it can only go to a state with  [X]  and this means that there should be the emission of a graviton with spin equal to 1 or 0 but as was shown above this possibility cannot happen.
...

"Therefore, the gravitational field can not be quantized and, of course, neither the masson nor the graviton exists. This leads us to say that the gravitational field is always a static field which is in line with the null results of gravitational waves."
--
[2] C.W. Misner, K.S. Thorne and J.A. Wheeler, Gravitation (W.H. Freeman and Company, San Francisco, 1973), pp 178-186.

==============
 

Subject: Re: Trying to paint a painting without any canvas
Date: Tue, 10 Sep 2002 17:47:23 +0100
From: Dimi Chakalov <dchakalov@surfeu.at>
To: Nikos Mavromatos <Nikolaos.Mavromatos@cern.ch>
CC: Nikolaos Mavromatos <nm@phpd56.ph.kcl.ac.uk>,
     Mario Everaldo de Souza <msouza@fisica.ufs.br>,
     Angelo Loinger <Angelo.Loinger@mi.infn.it>,
     Craig Hogan <hogan@u.washington.edu>,
     Giovanni Amelino-Camelia <Giovanni.Amelino-Camelia@cern.ch>,
     James Gillies <cern.courier@cern.ch>,
     David Ehrenstein <focus@aps.org>, JR Minkel <minkel@aps.org>,
     P Ball <p.ball@nature.com>,
     Steven Carlip <carlip@dirac.ucdavis.edu>,
     Stephen Adler <adler@ias.edu>,
     Carlos Barcelo <carlos.barcelo@port.ac.uk>,
     Sarben Sarkar <sarben.sarkar@kcl.ac.uk>
BCC: [snip]
 

Dear Nick,

Thank you for your kind and thoughtful reply and for explaining your viewpoint on the background dependence of quantum gravity, as I requested in my preceding email from Sat, 31 Aug 2002 14:35:11 +0300,

http://members.aon.at/chakalov/Mavromatos.html

On Fri, 6 Sep 2002 12:46:14 +0200 (MET DST), you wrote:

[snip]

> In models my colleagues and I have been involved with
> which test quantum light cone fluctuations and/or dispersion
> relations in a space-time foam background Lorentz invariance
> might be spontaneously broken and this would lead to selection
> of preferred frame. My point of view at this stage
> and in the article was simply to discuss ways of falsifying
> certain models in the sense of placing limits
> on such effects (ie by NOT seeing any effects).
>
> From your mail below you seem to think that even if such effects
> are seen one would not be able to interpret them as quantum
> gravity effects.

Please see my reply below.

> I would be very much interested in seeing how you view this
> possibility and why it should fail in the context of our specific
> models. For instance, if CPT violation is observed (hypothetically
> of course), in the sense of quantum coherence loss, this will be an
> effect calling for explanations. My point is that this effect will be
> due to a quantum gravity effect given that in flat space time CPT is
> expected to be valid.

It seems to me that your specific model is based on string theory and general relativity (as I gathered from your "Quantum Gravity and Dirichlet-Brane Phenomenology"), and hence it has a background *ab initio*.

I can not comment on your model because I was never able to understand it. I had the rare privilege to discuss the spacetime "foam" and "It from Bit" with Prof. John Wheeler in Princeton on 22 May 1989, but I'm afraid it didn't help a bit.

To understand your ideas, I respectfully asked you in my previous email for help.

I wrote: "Suppose, just hypothetically, that you observe loss of quantum coherence. How would you then relate such evidence to the whole bundle of problems [Refs. 2-5]? That I was never able to figure out. Hope you and your colleagues will help -- before you run the experiments."

In addition to [Refs. 2-5], which you can find in my previous email,

http://members.aon.at/chakalov/Mavromatos.html

please see also Steve Carlip at

http://www.physics.ucdavis.edu/Text/Carlip.html#problems

> So experiments NEED TO BE CARRIED OUT in order to guide
> us in search of such fundamental questions or (as I said in my
> article) to falsify or place bounds in certain models

I fully agree that experiments need to be carried out, but I have no idea how to interpret the results, even if you observe loss of quantum coherence. Perhaps you may wish to consult Steve Carlip by email and, during your forthcoming conference, Steve Adler

http://members.aon.at/chakalov/Adler.html#NB

and Carlos Barcelo

http://members.aon.at/chakalov/Wald.html#3

Stephen Hawking wrote in 1995: "Unless quantum gravity can make contact with observation, it will become as academic as arguments about how many angels can dance on the head of a pin."

http://members.aon.at/chakalov/Gerardus.html#Hawking

In brief, unless you solve the puzzles in [Refs. 2-5] from my previous email and crack the problems listed by Steve Carlip, I personally will remain very skeptical about your interpretation of loss of quantum coherence as "quantum gravity effects". We don't have a full-blown theory of quantum gravity, and everything we say is pretty much like "How do we know that Father Christmas has a beard? Because snow falls when he shakes it!"

BTW the story about Father Christmas' beard applies to my efforts as well. I sent today a copy from my CD ROM to Prof. Sarben Sarkar, accompanied by a letter (printed below). Should you find my CD interesting, please feel free to clone and pass it to your colleagues. I will highly appreciate all critical comments and suggestions.

Kind regards,

Dimi
=======

TO
Prof. Sarben Sarkar
Department of Physics
King's College London
Strand
London WC2R 2LS

Tuesday, 10 September 2002

Dear Professor Sarkar,

I am taking the liberty of sending you the first beta version of my CD ROM "Physics of Human Intention". You and your colleagues can find there my email to Dr. Nick Mavromatos (Mavromatos.html) and other material which, I believe, is relevant to your forthcoming conference "Branes, Gravity, Condensed Matter and Nonlinear Quantum Mechanics", September 11-14, 2002,
http://maxwel.ph.kcl.ac.uk/~dsc/workshop/wrkshp1.html

I wish I knew earlier about this very important event. Anyway, I hope you and/or some colleague of yours might find the subject of my CD ROM interesting. I mention there the research done by some of the participants of your conference.

Please convey my kind regards to Dr. Nick Mavromatos and Professor John G. Taylor.

Sincerely yours,

D. Chakalov

Encl.: 1