Cosmological constant problem

[wolram]

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

From: Dimi Chakalov <dimi@chakalov.net>
To: Thomas Thiemann <tthiemann@perimeterinstitute.ca>
Cc: <odreyer@perimeterinstitute.ca>, <fotini@perimeterinstitute.ca>,
<dgottesman@perimeterinstitute.ca>, <hburton@perimeterinstitute.ca>,
<rmyers@perimeterinstitute.ca>, <david.delphenich@uwrf.edu>,
<gleiser@dartmouth.edu>, <jb56@cus.cam.ac.uk>, <leecl@physics.ucla.edu>, <box@peter-ostermann.de>, <Dominik.Schwarz@cern.ch>, <deser@brandeis.edu>, <israel@uvphys.phys.uvic.ca>, <shapiro@astro.physics.uiuc.edu>, <saul@astro.cornell.edu>
Subject: The cosmological constant problem
Date: Tue, 27 Jan 2004 13:00:49 -0000

Dear Dr. Thiemann,

In your recent hep-th/0401172, you stated that "these new representations could solve some of the major puzzles of string theory such as the cosmological constant problem."

According to Feynman, the cosmological constant problem tell us that there could be something profound about gravity, which we still don't know,

http://members.aon.at/chakalov/Schwarz.html#1

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

Going back to an old debate of 1917, it seems to me that both Levi-Civita and Einstein were undoubtedly right [Ref. 1]. More at

http://members.aon.at/chakalov/Montesinos.html#1

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

How could Levi-Civita and Einstein be right? I'm wondering if you or any of your colleagues would agree that there is an incredible puzzle about the nature of gravity.

Regards,

Dimi Chakalov
35 Sutherland St
London SW1V 4JU
http://members.aon.at/chakalov


Reference

[Ref. 1] Angelo Loinger, Non-existence of gravitational waves. The stages of
the theoretical discovery (1917-2003),
http://arxiv.org/abs/physics/0312149

"This result has an unquestionable logical soundness, as it was finally admitted by Einstein himself. Of course, it implies the rejection of the various pseudo (false) energy tensors of the gravitational field proposed by Einstein and by other authors: a false tensor cannot have a true physical meaning!

"Einstein objected that in such a way the total energy-momentum of a closed system would always be equal to zero -- and this fact would not imply the further existence of the system under whatever form. However, from the standpoint of the coherence of the formalism, Levi-Civita -- and Lorentz [1] -- were undoubtedly right."
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non existence of gravitational waves??

 

[wolram]

NON-EXISTENCE OF GRAVITATIONAL WAVES ETC.
In these years I have published several proofs of the non-existence of the GW’s; they are exact, non-perturbative proofs [6]. I recall here only two demonstrations, which are particularly simple.
i) let us assume that at a given instant t of its motion a given point mass M begins to send forth a GW, and let us suppose that we know the kinematical characteristics of the motion between t and t + |dt|. Then, we can reproduce these characteristics in a purely gravitational motion of M in a suitable “external”, “rigid” gravitational field, within a time interval equal to |dt|, conveniently chosen. But in this case the mass M moves
along a geodesic – and therefore it cannot emit any gravitational radiation:
indeed, the geodesic motions are “free” motions; they are the analogues of the rectilinear and uniform motions of an electric charge of the customary Maxwell-Lorentz theory.
Thus we see that no “mechanism” exists for the generation of gravita
tional waves – the above restriction to motions of mass points is conceptually inessential. All the solutions of the Einsteinian field equations having an undulatory character do not describe physical waves [7].
ii) As it is well known, in GR only the concepts and the results that
are independent of the choice of the system of general co-ordinates have a physical meaning. Consider a solution of the Einstein field equations which has – in a given co-ordinate system – a wavy character. Through a finite sequence of co-ordinate transformations, endowed with convenient undulatory properties, the primary undulating character of our solution can be completely destroyed. Thus, this character is only a property of the original co-ordinate system, and therefore it has no physical meaning.(According to
a metropolitan legend, Bondi et al. – cf., e.g., H. Bondi, F.A.E. Pirani and I. Robinson, Proc.Roy.Soc., A251 (1959) 219 – would have proved the existence of a class of privileged frames insofar as the GW’s are concerned.Now, their “proof” is fully destitute of logical rigour, it is the mere expression of a desire. See at p.55 of my book quoted in [6]).
I remark further that the propagation velocity of any metric tensor de
pends on the reference system: with a suitable choice of general co-ordinates,
this velocity can take any value between zero and infinite.
APPENDIX
On the linear approximation of GR
If we restrict ourselves to the linear approximation of GR – as the experimentalists generally do –, which has Minkowski spacetime as its substrate, the physical existence of the GW’s seems, at first sight, a theoretical possibility. But the energy-momentum of such GW’s has a tensor character only under Lorentz transformations, not under general transformations. Therefore, it is always possible to find – and we remain, of course, in the ambit of the linearized version of GR – a general system of co-ordinates for which the above energy-momentum is equal to zero.
In 1944 Weyl published a remarkable article entitled “How far can one
get with a linear field theory of gravitation in flat space-time?” [8]. He remarked, in particular, that Einstein’s theory of weak gravitational fields (i.e.,

ANGELO LOINGER
the linear approximation of GR) resembles very closely Maxwell’s theory of the e.m. fields, and satisfies a principle of gauge invariance involving four arbitrary functions, but its gravitational field exerts no force on matter, i.e.
it remains “a powerless shadow”.From the standpoint of the exact GR, this is as it should be, because “the gravitational force arises only when one continues the approximation beyond the linear stage”. Clearly, Weyl alludes here a fundamental result of the EIH-method [9]. Thus, we find another argument – and a strong argument – against the physical adequacy of the linearized version of GR insofar as the question of the GW’s is concerned.
I am very grateful to Prof. A. Gsponer, who has called my attention to Weyl’s paper.
PARERGON
On the PSR 1913+16
The overwhelming majority of the astrophysicists believe that the time decrease of the revolution period of the binary radiopulsar PSR 1913+16 gives an experimental (indirect) proof of the physical reality of the gravitational radiation. As a matter of fact, the perturbative quadrupole formula gives a decrease of the revolution period which agrees very well with the observational data.
I emphasize the following points. i)In the exact theory the quadrupole formula loses any meaning because the hypothesized gravitational waves do not have a true energy; therefore, the true mechanical energy which is lost during the revolution motion ought to transform itself into the pseudo (false) energy of the hypothetical gravitational radiation: the energy account does not balance. ii) Many observational astrophysicists know that
realistic explanations of the decrease of the revolution period are quite possible: for instance, viscous losses of the pulsar companion give a decrease of the same order of magnitude of that given by the alleged emission of gravitational waves. iii) The empirical success of a given theory – or of a given computation – is not an absolute guaranty of its conceptual adequacy: for instance, the Ptolemaic theory of cycles and epicycles explained very well
the planetary orbits (with the only exception of Mercury’s).
The serious scientists should abstain from wishful thinking.

 

[wolram]

if anyone wants to follow some of the links provided in
this thread there is a huge amount of information, some
may be "historical", but to me it shows that present
theories are just a tentative step in understanding
our universe.

 

[TeV]

Originally posted by wolram
NON-EXISTENCE OF GRAVITATIONAL WAVES ETC.
But in this case the mass M moves
along a geodesic – and therefore it cannot emit any gravitational radiation:
indeed, the geodesic motions are “free” motions; they are the analogues of the rectilinear and uniform motions of an electric charge of the customary Maxwell-Lorentz theory.

Here is the catch I think.Binary pulsar "geodesic" motions of two masses aren't "free".One mass moves along geodesic lines of dynamically varied G field of another mass (that moves accelered too ).
If the theory you suggest have sense it could be compared more with EM theory of electron rotating around charged nucleus in a stable atom configuration while not emiting EM radiation.
Classical Maxwell-Lorentz theory couldn't explain this ,but Bohr and others could by establishing laws of QM ,introducing forbidden paths,and characteristic formalism in framework of QM.
Thus, looks like you are doing some sort of quantum gravity theory on MEGA macroscopic scale but still without quanta?
I can't explain orbital changes in PSR 1913+16 than in changes of the energy of the system.
Then, if that energy of movement is said to be gravitational how is being lost if not by radiation?That would be completely new turnoever by concepts of physics as we know it today..
Neverthless ,interesting subject I must say.

Regards

 

[Stingray]

Originally posted by wolram
But in this case the mass M moves
along a geodesic – and therefore it cannot emit any gravitational radiation:
indeed, the geodesic motions are “free” motions; they are the analogues of the rectilinear and uniform motions of an electric charge of the customary Maxwell-Lorentz theory.
Thus we see that no “mechanism” exists for the generation of gravita
tional waves – the above restriction to motions of mass points is conceptually inessential.

You should read up on the concept of radiation reaction/self-force. It is impossible to decouple an object's own field from its neighbor's in GR, so there is no such thing as a "rigid background" except in the test particle limit. This is also the only sense in which things move along geodesics. Objects with finite size or mass do not do this. The same thing occurs even in classical electrodynamics. The Lorentz force law is not correct in the usual sense, and finding the correct law of motion is difficult even there. There's still some argument over it actually.

ii) As it is well known, in GR only the concepts and the results that
are independent of the choice of the system of general co-ordinates have a physical meaning. Consider a solution of the Einstein field equations which has – in a given co-ordinate system – a wavy character. Through a finite sequence of co-ordinate transformations, endowed with convenient undulatory properties, the primary undulating character of our solution can be completely destroyed.

It is still possible to construct invariants that may be examined at null infinity. This is used to deal with gravity waves without coordinates. This is not a simple issue, and was not understood until relatively recently (20-30 years ago). There was originally a lot of controversy over whether grav waves were real based on your argument, but that's no longer true. Just because something doesn't look wavy doesn't mean that it necessarily isn't.

On the linear approximation of GR

Again, there is a much improved understanding of weak gravity since 1944. There are a lot of subtle issues which are ignored in textbooks. You're right that the standard treatment is not sufficient. The correct understanding was given by Jurgen Ehlers, and has no problems. It is a very beautiful framework that rigorously constructs Newtonian theory as a limit of c->infinity. There is in fact no linearization procedure at any point.

On the PSR 1913+16

Of course the 2-body problem is unsolved in exact GR, but the approximation methods used are well-motivated. You seem to have trouble because you can't show that energy is conserved in full GR. That's because nobody has shown should that it even should be conserved except in very special cases.

The Hulse-Taylor pulsar could not be well described by friction. There would be far too many coincidences involved. There are also other important orbital parameters besides the radius that are measured. These are found to be in agreement with GR as well.

Once more, look at more modern sources. There are other pulsar systems now known where things can be measured much more precisely. GR still works perfectly to within measurement error on every example.