Gravitational interaction within the Einstein's is not related directly with rotations and in fact appears related with traslations of space-time through the enery-momentum tensor. There are extensions as the Einstein-Cartan model which introduced the torsion tensor associted to antisymmetric parts of the affine connection of the called Riemann-Cartan space-time.

"traslations of space-time through the enery-momentum tensor"

any translation/momentum in a mass becomes  a fraction of angular momentum around the axis passing through the center of the mass.

    Dear Stefano,

Translations and rotations are very different geometrical transformations. Their associated symmetries are also very different: the symmetry associated to time translation of a system allows us define energy, with respect to space the linear momentum and with space-time rotations gives the conservation of the angular momentum as Noether currents. Notice that the angular momentum has 6 conserved laws while the space-time translations only have 4.

It is true that if you take a big radius and an small angle the tangent gives you an infinitesimal "translation", but this is not the answer to the general question that you have put: Is the Gravitational interaction intimately connected with angular momenta? The answer is no because the Einsteins equations do not take into account this physical magnitude explicitly, although there are other theories that have tried to enlarge it on this aspect as the one of Cartan. The problem is that it seems that experiments do not accompanied them.

Dear Daniel,

Einsteins equations do not take into account this physical magnitude explicitly, although there are other theories that have tried to enlarge it on this aspect as the one of Cartan

I know that Einstein does not consider angular momenta... and probably affirmed that the average of those angular momenta is 0.

I think though that a good part of physics was lost not considering it negligible..probably the intimate connection with quantum physics...

Hope the Cartan's attempt was complete in order to faslify such hypothesys.

Dear estefano,

Do you know any effect in gravitation related with rotations conservation or angular momenta? In other words, do you think that the metric of the space-time has to include information of the inner gravitational rotations different than a theoretical speculation?

Dear Stefano,

I have to answer your question with a big YES given my own analysis that resulted in the theory of physics in 5 dimensions. There is no short way to summarize the theory, but one key point is that in order to exist in our universe, the hypothesis is that all particles and resulting bodies (matter) have a closed path in space with an inherent angular momentum.

In the case of the electron, the inherent angular momentum is equal to Planck’s constant and always has this value. For electrons in various atoms, this constant angular momentum gives the radii of the electrons basically in agreement with current classical theory, under which I include the Hartree theory and Schrödinger’s theory.  

So the angular momentum is a function of the existence of the particle and has nothing to do with attractive forces. So the suggestion is that we have a chicken and egg scenario here, where classical physics designates attractive forces (electrostatic & gravity) as the cause for particles and other bodies to orbit central masses, whereas the alternative is that all matter has to have a closed path in space and belong to a local space for other reasons than an attractive force.

The paths of particles and other bodies in space retain significant objectivity with this theory. For example a particle moving in space with a velocity of the speed of light, may be considered to be following a “coil” like path, where the velocity along the coil is the speed of light c, a view of the cross-section of the coil showing the body orbiting in a circle with an orbital velocity v4 on a radius r of the coil, and the velocity v5 measured along the axis at the center of the coil will be less than c. So the spin of particles has an objective view. There are many other geometric options that fit the theory too.

The full text of the book on “physics in 5 Dimensions” is available from my RG profile or a simpler introduction can be found at the website www.physics-in-5-dimensions.com. For a quick view of the results of this theory, the resulting key expressions help and can be found at http://www.physics-in-5-dimensions.com/keysubjects/AlanDennisClark-KS-5th-dimension-expressions.pdf, where the expressions of current physics in 4-dimensions can be compared with the same expressions in 5-dimensions.

In any event, whether you follow my hypotheses or not, your question about gravity and angular momentum warrants close attention.

Alan Clark

Dear Stefano

If we consider that gravitation results from the presence of matter (mass) altering the characteristics of the local space then we must regard that vacuum space is real and not merely ‘empty vacuum’.  We nowadays readily accept that vacuum space is ‘active’ with virtual particle pairs. Furthermore if we accept that 3D space and time are linked as space-time then it is not unreasonable to consider that fermions of matter are topological quirks of space-time (maybe even quarks and leptons).

Relating two or more spatial dimensions with what we observe as time defines spin and permits angular momentum.  An active vacuum composed of interacting bound fermions inevitably would connect spin and gravitation.  Consider the electron-positron lattice model of the vacuum by M. Simhony where spin moments responsible for stabilising that lattice interact with spin moments of guest particles to present as gravitation between guest particles not bound in the lattice.

Guy

Dear Daniel,

"Do you know any effect in gravitation related with rotations conservation or angular momenta? "

In analogy to the Aharonov-Bohm effect in electromagnetism, the quantum mechanical phase (spin) is a function of the gravitational potential.

Force-Free Gravitational Redshift: Proposed Gravitational Aharonov-Bohm experiment arXiv:1109.4887v3 [quant-ph] 7 Jun 2012...ANTON ZELINGER

If you see it in reverse, the gravitational potential has to be influenced by  quantum mechanical phases... since the force is the gradient of the gravitational potential there should be a dependence of it by the spins...

This paper is related to the Cartan's theory of torsion, is from 2007.

http://arxiv.org/abs/arXiv:gr-qc/0608121

Dear Alan,

your book is a new committment for me to read ....congratulations

"So the angular momentum is a function of the existence of the particle and has nothing to do with attractive forces"..

I would  say it has a much deeper origin maybe in the vacuum interactions, but it has implication in ENTROPY and GRAVITATION..

 A spherical mass has a  virtually infinite number of axes passing through its center of mass. The system posesses angular momenta, bends the space time fabric or creates a special additional dimension warping the space around.

The contribution of any partcle spin (an enormous number) adds up by the Huygens Steiner theorem to the momenta relevant to the relevant axis passing through the center of mass.

It should be 3D+ charge + spin. For sure the GRT has to be extended to SPINORS.

I think for a theory of such an extension  accounting for so many features, only the topological advancements of PERELMAN can make a difference, explaining how, thanks  to a virtually infinite angular momenta referred to a virtually infinite axes, referred to the same center of mass,  provokes a 3D space transform into a superior dimensional space...

Dear Guy,

I agree...

"we must regard that vacuum space is real and not merely ‘empty vacuum’. "

I don't think about space-time as empty vacuum.

For me it is the QUANTUM SPACE TIME an active medium  which allows everything to occur, thanks to its peculiar properties. I've an holistic view..the "reductionism" is a loser  by definition.

The virtual particles view is a reductionist POV. It does not really account for coherence of spins in collective quantum physics, since the virutal particles account only for the "force" of the fileds. The Ahranov Bohm effect by many physicists has not been accepted or understood properly regardless of its many experimental demonstrations.

It is the base of the new physics based on PHASE not FORCE, information, not energy, Quanglement not finite speed transmission of energy....

Dear Stefano,

The Aharonov-Bohm effect produced a shift of the interference effect for electrons moving between slits. This is obviously measurable and substitutes the classical Lorentz equation of motion for electrons in this case.

My question was if you could find something as this effect that it could be measurable or better, that it was already measured. As I told you there are models as one of Cartan that introduce theoretically the torsion but without effect for several reasons:

1. If you go to measure the effect of gravitation on spins, even they have very small energy, it is quite big with respect to the gravitational torsion. Higher than the experimental error.

2. I do not know the form to distinguish the rotations due to the gravitatinal torsion to the ones due to usual mechanics, e.g. in a galaxy which is rotating or in a black hole.

Dear Daniel,

I don't mean gravitational torsion .

I simply suggest that there should be a very complicated transformation of angular momenta or action or h, into space-time bending, better than what occurs for momenta....

Atomic clocks sniff the "action"....being also the energy density contained inside a 4 dimensional surface (SPACE-TIME), they change their clock rates on that base...

The Aharonov-Bohm effect produced a shift of the interference effect for electrons moving between slits.

The effect , affects the phase of particles. The vector potential changes it. All the coherence in matter is based on that...collective quantum physics see MARIAN APOSTOL for it.

My question was if you could find something as this effect that it could be measurable or better, that it was already measured

"A method to measure the resonance transitions between the gravitationally bound quantum states of neutrons in the GRANIT spectrometer" ..

Dear Stefano

Obviously when I explained the interference of the electrons I was speaking about their constant phase under a potential vector without the presence of the field. That is to say, we have a change of constant phase in one place where classical electrodynamics didn't could take into account because the Lorentz force was zero. This was one effect that David Bohm was trying to find for a long time because he believed in the hidden variables of Quantum Mechanics and nowadays was generalized with the Berry's phase.

In all that I know there are no experiments possible for inner rotations or change of phases in classical gravitation.(Einstein, Cartan or others), but another thing is if we think in the possibility of Quantum Gravitation.

In such a case I understand now your comment:

A method to measure the resonance transitions between the gravitationally bound quantum states of neutrons in the GRANIT spectrometer" .

Where cold neutrons with a broad wavelength distribution were delivered from a liquid-deuterium for measuring the transitions between bound gravitational states. In all that I know the laboratory of ILL of Grenoble has claimed to do it for first time. But Quantum Gravitation is still very far of being a realistic theory. For example, see:

http://www.scientificamerican.com/article/physicists-eye-quantum-gravity-interface/

Dear Daniel

"In all that I know there are no experiments possible for inner rotations or change of phases in classical gravitation.(Einstein, Cartan or others), but another thing is if we think in the possibility of Quantum Gravitation.

In such a case I understand now your comment.."

I think there is no such thing as "quantum gravitation"...better maybe Quantum Space time theory... gravitation in itself cannot be quantized, if it is a side effect of an HYPER MEDIUM, the quantisation will be performed on the HYPER MEDIUM...like the successful attempt of Sakharov in the 60's at explaining relations beteween the h and G constants throgh quantisation of the fabric of the ST...

    Dear Stefano,

    I think that we are both in agreement, the only difference are words. For Quantum Gravitation obviously the space time at Planck scale needs to be changed of the usual continuous space-time defined with a metric.

Dear Daniel,

meanwhile in order to approach to a quantum understanding of things, I'm fighting to get rid of the Einstein Equivalence Principle...there is no actual equivalence between an accelerating frame of reference and a gravitational field... the UCR falsifies the principle in which it is supposed to be contained..

Article A Falsification of the extension of the Equivalence Principle

In the Gravitational model of strong interaction, the particles spins (rotating mass currents) produce the gravitational torsion force as rotating charge currents produce the magnetic force. See https://en.wikiversity.org/wiki/Gravitational_model_of_strong_interaction , https://en.wikiversity.org/wiki/Strong_gravitation , https://en.wikiversity.org/wiki/Gravitational_torsion_field .

The gravitational torsion force of nucleons in nucleus is balanced by strong gravitation. If you are interesting in such effect of gravitational action on particles, as phase shift, see https://en.wikiversity.org/wiki/Covariant_theory_of_gravitation#The_principle_of_least_action .

In general the quantum gravitation may be deduced from the Lorentz-invariant theory of gravitation , see https://en.wikiversity.org/wiki/Lorentz-invariant_theory_of_gravitation ,

after quantisation procedure just as for the quantum electrodynamics. You need also use the Strong gravitational constant in the equations, see https://en.wikiversity.org/wiki/Strong_gravitational_constant .

Thanks Sergey,

that is interesting...but the torsion is not the thing I'm referring to..

My concern is deeper....it is the proper angulare momentum or spin which is the ACTION and is h/2,  half the minimun possible action h..

Summing up such contributions vectorially I would reach an enormous value of the ACTION. But these contribution due to intrinsic disorder (ENTROPY) which is in GRAVITATION (PENROSE) sort of cancel out but not completely.....

I only guess what you mean when you summing up to find action and may be gravitational force of the action. In my opinion the Dirac constant is a measure of angular momentum of particles such as nucleons and electrons. The angular momentum is the main source of gravitational torsion field (in general relativity it is gravitomagnetic field) of particles.

Sergey,

of big bodies, dragging the lorentz frames around LENSE THIRRING...

I tell you about the same in other words. 

It is not LENSE THIRRING I'm talking about, LENSE THIRRING, frame dragging  is a secondary effect 

Dear Stefano,

I think that your idea of trying to overcome the principle of equivalence is interesting if you want to obtain another theory of gravitation different than the Einstein's one which fails to be compatible with quantization. The problem is that I think that this is the fantastic point that joints geometry and physics in gravitation in clever form. But I do not know ....

Dear Daniel,

Serious doubts rise about the equivalence even "local" for accelerations and gravitational fields. The equivalence certainly holds between gravitaitonal field and centrifuge field which is a consequence of an angular momentum...

The rotating disk example is a good example of replications of effects of gravitation (force and time dilation) along the rink of a disk..

That is why angular momenta are so important.

The least action principle is based on minimisation of the action which has the dimension of angular momentum. So the minimisation is performed on angular momenta.... The universe tends to minimise the angular momenta....

There  should be a reason why the universe doesn't want things spinning....

ONe of the conundrums of GRT is the free falling isolated charged partcile in a gravitational field..(no other electric field is present during the fall)

According to SEP it should not radiate...but instead it seems it should radiate...

Dear Stefano,

I do not know if have understood you properly, if the rotations are important due to the acceleration that they produce, in any case the acceleration and then principle of equivalence seems the important thing. On the other hand it is what allows to deduce the change of Riemann to Euclid (geometry part) and general relativity to Newton's gravitation. This is a well established procedure for obtaining the Einstein's equations of gravitation. Unfortunately you are right that this is beautiful but is difficult to put in agreement with quantum theories.

I don't understand your remark that the Universe try to avoid rotations because they are in every place that you look around in the sky.

Dear Daniel,

the equivalence if necessary is not with the "linear acceleration" which is accounted for in GRT.  We can establish an equivalence, but it is not between lenear acceleration which gives the motion and a gravitational field,  but a with a centripetal acceleration "field" and gravitational acceleration field...

The idea of Einstein of the acceleration was to find something which was absolute...Linear acceleration can be measured without looking outside in my laboratory (doppler shift of EM waves between two oscillators along the direction of motion), so it is absolute, but nobody can affirm that even if it is absolute it has to be necessarily used for the theory.

Centripetal acceleration, centrifugal force is absolute too...

The basic idea of Curved Space-time stays alive...but it is much better connected with quantum mechanics...

Dear Stefano,

Let me to see if we are in the same discussion or not. Is the equivalence principle the one which assume that the gravitational mass is equal to the inertial mass?

Dear Stefano,

We can link inertia and momentum to straight-line de Broglie rays of a particle and phase waves of the body in vibrations of the components of the vacuum medium. These waves do not enjoy rotation and will radiate energy unless formed into a closed wave. They will bend with the gravitational curvature of the medium or by the influence of another force - eg the Coulomb force holding atomic electron/s in the closed orbital of a shell with an integer number of wavelengths that you identify with centripetal acceleration and centrifugal force.

Dear Daniel,

"Let me to see if we are in the same discussion or not. Is the equivalence principle the one which assume that the gravitational mass is equal to the inertial mass?"

It is more complicated. What you are referring is the WEP which is valid  but for  big masses is falsified (orbit of mercury) by the correction of GRT.

The Extension of WEP proposed by Einstein is the equivalence of accelerating frame with a gravitational field, later encoded in EEP. THis is not true at all if at finite distance and my brief paper shows its falsification.

The UFF is a version of WEP, Universality of Free FAll (Galileo Galilei) and is verified at medium and short distances.

At infinitesimal distance the EEP  is likely to be true, unless it comes out that in the case of free fall, a  charge radiates...

Anyway Daniel, even the equivalence with a centrifuge field can't exaclty hold with gravitation since a charge if posed on a rotating disk, even if this disk is very very wide,  radiates a little, which doesn't seem to be true for a charge stationary in a gravitational field.

Dear Stefano,

Are you sure that an accelerated charge into a gravitational field is not radiating? Do you know measurements of this?

A static charge in a gravitational field as far as I know does not radiate, since would violate the NOETHER'S theorem.

A free falling charge in a gravitational field is more likely to radiate, since its radiation would alter its speed won't violate NOETHER's... Such experiments are difficult to perform since the radiation if any would be of very low frequency in the gravitationa field of earth..

Dear Stefano,

I do not know what is the role of the Nother's theorems here where no symmetries of the action and their conservation associated laws.

In any case, I agree that an static electric charge doesn't radiate because it is without motion. I understand that it is the same that you can give a force on a wall but no change of energy is obtained, but it seems that the pure equivalent principle in this case needs explanation: motion is needed to assume.

In motion the electron is with acceleration g that you can substitute in Larmor (relativistic or not depending of the value of the initial velocity) equation for obtaining the radiation. Frankly I do not see what is the problem with the electric charge within a gravitational field or the equivalent principle of GR that you have mentioned in a previous message.

Dear Daniel,

I do not know what is the role of the Nother's theorems here where no symmetries of the action and their conservation associated laws.

Just energy conservation theorem.

In  the Larmor's case the charge should be accelerated by a electric field. So it radiates because its variable interaction with the electric field, producing an EM wave.

In constant  acceleration without the help of a EM field, a free charge does not radiate.

While it seems that in a gravitational field it does...one of the reason is that the field is never constant.

The nonexistence of infinite homogeneous gravitational fields assures us that observation of radiation (observer at large distance from the source) takes place outside the homogeneous part of the gravitational field.

Frankly I do not see what is the problem with the electric charge within a gravitational field or the equivalent principle of GR that you have mentioned in a previous message.

The problem is that in constant acceleration a charge doesn't radiate in free fall a charge could radiate.

Thomas Fulton, Fritz Rohrlich, Annals of Physics: 9, 499-517 (1960)

OR

http://www.hep.princeton.edu/~mcdonald/accel/unruhrad.pdf

The existence of Unruh radiation provides an interesting comment on the “perpetual prob-lem” of whether a uniformly accelerated charge emits electromagnetic radiation [13].

Thus, on p. 573 of the article by Ginzburg [13] we read: “neither

a homogeneous gravitational field nor a uniformly accelerated reference frame can actually

“generate” free particles, expecially photons”

THe real thing is:

did somebody ever find an homogeneous gravitational field??

Dear Stefano,

I understand your difficulty. If the electric charge accelerates under a gravitational field it is due to its mass, in principle, and the acceleration produce the electromagnetic radiation which can be calculated by Larmor. On the other hand if the charge moves in a geodesic no force is on it (and it seems that this is only gravitational). The problem is that the energy-momentum contains both the gravitational and the electromagnetic interactions. My question is if you have an electric charge falling at a constant acceleration (i.e.g) what is the actual geodesic?  

Dear Daniel,

"On the other hand if the charge moves in a geodesic no force is on it (and it seems that this is only gravitational). "

This is the problem, I don't think though that the geodesic motion can treat a free fall, even if most of relativist would assume it.

Geodesic motion should only be a circular orbit...but I have to demostrate it

     Dear Stefano,

     Good luck. Go ahead!

Dear Daniel,

thanks a lot..

SInce I saw you in a thread with Eric Lord discussing of Poynting vectors and EM energy, I would like to ask you a question.

 Einstein declared that he didn't put the contribution of radiant energy in his equations because such contribution was negligible compared to the energy momentum  contribution in general. It is reasonable.

 But Einsein was smart enough to have a better reason.... I dared say that he didn't consider such contribution because he thought It would have been difficult to treat...

Light is not "attracted" by a gravitational field like a massive object..unlike what supposed in his 1911 paper.  It is massless (integer spin),  follows null geodesics... it follows the curved space-time but it does not affect the structure of the space-time itself. I suppose that only massive objects (tied energy to fermions) can affect the curvature of the space-time...light cannot...

I suppose that the space-time reacts as a Whole with integer spin particles..so light when follows the curve is like having to do with a infinite mass and rigid thing which drives it but it is not influenced by it...

I ask for your opinion....

Dear Stefano,

The first experiment associated to General Relativity (GR)was made by Eddington at 29 May of 1929, employing the eclipse of Sun for measuring the bent of the light rays close to the Sun. It is known that the measurements were in agreement with GR producing a bent of them.

As you know, the idea is that the geodesic close to the Sun have a curvature of the space-time and therefore the light or other signal must go through them following a Riemann geometry instead an Euclidean, i.e, the minimum distance between points is curve and no a straight line.

This is independent of electrodynamics and only is due that the photons carry an energy which must follow the above geodesics. I don't know if you find any comparison with the discussion that you said, but I don't see it. Poynting vector is completely out of this benting if you forget that the energy of a photon is momentum by c.

Dear Daniel,

I know that poynting vector responds to another theory and should be found a new theory in order for it to play a role in gravitation. Maybe returning to Quaternions and express the curvature of ST with Quaternions too,

I suppose anyway that photons should be  untouched in their EnergyMomentum (direction is the same as the space-time) no  interaction with masses at all if the are not absorbed (quantum interaction). According to my opinion that a planet can be influenced by a very strong beam passing close,  which does not interact directly (quantum) with it,  does not convince me.

I asked your opinion also because somebody else affirm   for that photons do enter in the computation of the energy-stress tensor of GRT.

Stefano

   Dear Stefano,

   My opinion is that the gravitational energy of photons is absolutely negligible respect to the source of the gravitational field which curves the space-time where they move.

Dear Daniel,

you have the same opinion as Einstein's, and I agree with it basically. But negligible does not mean NULL.

I know in physics the two aspects sometimes go together because experimental physics makes no sense to go under the possibility of instruments. Sometimes though  by clarifying such things it  would bring to interesting insights.

 I presume you know the Mossbauer effect.

In his nobel lecture Rudolf Mossbauer affirmed that the motion of the cristal absorbing the recoil of one gamma photon was "negligibly small" because the kinetic energy of one nucleous emitting the gamma photon was not comparable with the mass of the Crystal....here there are many things to reason about but I just stick to one only...

Well in such case the negligibly small means that it will be  impossible to be appreciated by instruments but has to exist.....

This for example would mean that at every recoil the Crystal would have to move a bit...but at which expenses....if the nuclear resonance absorption is reversible??? There is the risk to build a perpetual motion...

I presume that the Crystal doesn't move at all...and the nuclear domain responding to such momentum (10^19 atoms??) at almost 0 k, is  intimately connected with the background quantum vacuum, which responds as an infinite wall...

For gravitational lensing I would presume it is the same phenomenon, but since we are talking about integer spin particles, there is no need to reach the zero k..

I think we are taliking about your field so you will be able to spot mistakes in what I'm presuming....

Dear Stefano,

Sorry I hadn't enough time to answer you. The idea is that the light photons have a mean mass of 10^(-37) kg while the Sun is around 10^(30). That is to say 67 orders of magnitude of difference, do you think that it is reasonable to their gravitational interaction? I think that it is logic to neglect it, if you do not find another place to make it more important.

Mossbauer is another very different story and very interesting if you want to know the red ship of the electromagnetic spectrum within a gravitational field. In such a case the absorption of a photon by an iron 57 atom can be seen and to measure the frequency change due to its Zeeman energy of the splitting levels. This is a reasonable measurement of course.

Dear Daniel,

Zeeman energy or Zero point energy???

Stefano

Dear Stefano,

It is the Zeeman energy associated to the nuclear magnetic dipole (due to the nuclear spin) on the magnetic field B (external, electronic orbital and electronic spin).

Dear Daniel,

can you have a look at what I wrote in a couple of pages, it is not complicated by I ask an opinion of a Physicist like you...the infringments of the conservation laws by the SEP should be demonstrated there.

Stefano

   Dear Stefano,

   where are the two pages written by you?

Dear Daniel,

I didn't know KALMAN-THIRRING theory and FEYNMAN's extension.

The angular momenta play a role, not just as a frame dragging effect of big bodies..

Spinning bodies distort space and may modify the gravitational attraction...

Stefano

Article On the motion of rotating bodies in field gravity theory and...

Dear Stefano,

This TFG model is very interesting for trying to unify gravitation with the other three fundamental interactions, but unfortunately, in all that I know it is with great problems for the moment. In fact it is a quite all idea starting with Poincare (1906) before the GR and almost at the same time than the SR. Let me to summarize only some points.

The main problems of TFG are the physically grounded choice of Lagrangian and choice of gravitational energy-momentum tensor (EMT) which cannot be fixed with Lagrangian. Still, there is a well known unresolved

problem with quantum-field divergences (non renormalized theory). Another difficulty is connected with the absence of experiments on quantum gravity as you surely know, due to smallness of expected effects, which makes it much harder to proceed and test the theory. Note, in this connection, the recently suggested experiment for measurment of the frequency dependence of gravitational bending of light by planets (Baryshev, Raikov (1995); Baryshev,

Gubanov, Raikov (1996)), which could detect a quantum effects even in weak gravity field. An important possibility of non-zero rest mass of the graviton has been considered by Visser(1998). A possibility of existance a scalar component of gravitational field was discussed recently by Damour(1999).

Baryshev Yu.V., Gubanov A.G., Raikov A.A. , Gravitation, 1996,v.2, iss.1, p.72.(1996)

Visser M. (1998), gr-qc/9705051

Damour T. (1999),gr-qc/9904057.

Dear Daniel,

today Harihar Behera showed this very interesting paper very close to the angular momenta/gravitation arguments...

Stefano

    Dear Stefano,

    Thank you very much for this paper, it seems quite original and interesting. I'll read it .

Dear Daniel,

what do you think about these pages of Fock's gravitation??

https://archive.org/stream/TheTheoryOfSpaceTimeGravitation/Fock-TheTheoryOfSpaceTimeGravitation#page/n243/mode/2up...

Is it correct according to your opinion the way he mathematically compares an accelerated reference frame and a gravitational field??

Stefano

  Dear Stefano,

  Thank you very much for the book which unfortunately I haven't time to read it slowly, but the idea avoiding the equivalence principle is for me wrong. He tries to compare in the flat space-time both theories and it can be that in such conditions they are equivalent but they are not in general, I think.

  I recognize that I needed to enter in more details for proving this statement but unfortunately I haven't time at present.

Dear Daniel,

the EP is not avoidable the dynamic equivalence as shown in the Eotvos experiment in undenyable. EP  is intrinsic in the Newtonian dynamics (NEP) or WEP. 

The limit in the big framework of the EP is the  Mercury Perhielion precession values in which a contribution of the curved space has to appear, predicted only by GRT . The resulting acceleration is a correction of the Newtonian one.

The extension performed by Einstein E-WEP regarding the equivalence of accelerated frames and gravitational fields is questionable at  finite distance, and for finite bodies... The intertial reference frame, the equivalence of Galilean and free falling is yet another matter that comes from the WEP. Nowadays such extension EEP or SEP,   is recognised  valid at infinitesimal level only. The EP being verified by GRT.

The absence of weight is certainly present in the Newtonian theory. It cannot make a difference in predicting differently some phenomena from Newtonian to GRT..

The things that make a real difference according to my opinion can  be only:

a)  Stress energy tensor which accounts for the presence of a hypermedium whose transmission speed is limited (metric theory) and accounts for phenomena on the warped space-time like time dilation and length contraction.

b) the boundary conditions of the metric as locally Minkowskian (postulate, at sub atomic dimensions the gravitational field gets more negligible compared to the other interactions..)

c) the boundary conditions at infinity, Minkowskian,  far from the masses (reasonable as influence of gravitating body gets negligible, getting farther and farther)

That the E-WEP is an euristic tool ok. That the structure of a gravitational field can be approximated by linear accelerated frames is doubtful. A  reasonable equivalence can be with a centrifugal field...

Dear Stefano.

The question for me is if we have gravitation only as an acceleration field or not. If that is true then,i.e. it is only a field of accelerations, it is clear that GRT must explain it locally and the WEP must be followed. Although it is true that the gravitational field has a spherical global symmetry making difficult to find real observers which match their vectorial accelerations. Therefore two given observers moving in such one is falling in Italy and the another in New Zeland has difficult to find a global system of EP which applies simultaneously to both.

Another problem is if GR is the only theory to take into account of gravitation. For me it is clear that this is not true because gravitation is treated in very different form of the rest of physical interactions and , at least, we needed to know the cause of such behaviour. But this is, perhaps, only in other scales of energy that we are speaking on.

Dear Daniel,

a) We are sitting on a planet,

b) we are inside a huge spinning weel, so huge that we are not able to see anything but flatness and the speed of the wheel is such that the acceleration is g.

 if I'm not able to measure the convexity of the concavity of the surface I'm sitting on because it is very huge, it would be really difficult to distinguish the situation from within.

how would I spot the difference? The pound and rebka experiment would come out fine, time dilation would be actual, not "fake" like in accelerated situations.

    Dear Stefano.

    I have explained badly using the example of the Earth I only wanted to say that gravitation is with spherical symmetry. It is obvious that the space-time curvature produced by the mass of the Earth is very small indeed.

If one were to recognise that gravity is caused by push forces due to energy density gradients in the binding energy of an all pervasive 'vacuum medium' and inertia by passage through that medium of the gradients imposed by guest matter particles then the equivalence principle is not mysterious. Distinctions between free fall and many-body interactions become recognisable and one can distinguish between weak and strong EP

Dear Daniel,

"I only wanted to say that gravitation is with spherical symmetry"

yes, so it is the centrifugal field a good equivalent...

In the case of equally accelerating bodies they cannot have any actual time dilation, so the "equivalence" is just fictitious. The principle of equivalence in the way Einstein applied it for non infinitesimal situations can be considered only an euristic tool..

Dear Guy,

"inertia by passage through that medium of the gradients imposed by guest matter particles "

Yes, I find here the Higgs mechanism which provides also the inertia throught the De Broglie relation of fermions (PENROSE).

"Distinctions between free fall and many-body interactions become recognisable and one can distinguish between weak and strong EP"

The WEP works also for material finite dimensional bodies and it gives birth to the UFF universality of free fall. They are testing it in orbiting Labs at atomic level.

The SEP is quite stringent, it is WEP+ LPI + LLI..valid in a sufficiently small volume.

LPI or UCR (universality of clock rates) is  relevant to the possibility to measure time. If I don't have some matter I cannot perform such measurement.

According to SEP clocks which free fall should not present any time dilation.

This can't be true for two reasons:

1)  the doppler effect of the first order in a free falling system is present for sure between two masses along the radial direction.  The classical doppler is  always an energy variation of the photons exchanged.

Since in a ff system  no frequency shift is detected,  the only way to allow for energy variation without being detected is the relative frequency shift of the absorber/emitter atoms (time dilation).

2) a master clock watching from Earth the free falling objects, is able to detect, exchanging photons, different frequency shifts due only to GRT effects, not classical doppler which can be cancelled (GP-A experiment, vessot and Levine). How can it be that if I use the  free falling clock as the master one, no time-shift is detected with the other free falling clock?? The clock on Earth has time dilation with A,  DeltaTA and B DeltaTB where Delta TA-DeltaTB>0. According to SEP  if I compare A and B directly for A or B I don't spot any difference... this is not very convincing...

These are heavy incongruences which can be investigated only by using  more sophisticated techniques. Nowadays some are doing experiments with Quanglement (Anton Zelinger), also with oscillators and quantum entagled photons.

In order to definitely clarify on the subject would be enough to make a quanglement connection between distant clocks at different heights in free fall. Without exchanging energy the tick of one twin oscillator will be transferred instantly to the other one for comparison, after sincronisation. Only this way it will be definitely detected

a) if the space-time affects physically the oscillator (which is quite obvious)

b) the free fall cannot satisfy the SEP at finite distances since not only tidal effects are present. Free falling frame cannot be approximated to a galilean insertial frame in real experiments.

I just found this old paper of 1989 which considered the Jacobi action in order to account for the phenomena predicted by GRT.

Neutron stars are quite massive and they rotate at very high speed. They posess a tremendous angular momentum. There are the so called millisecond pulsars  pulsar with a rotational period in the range of about 1-10 milliseconds which have to have a rotational speed. The top seems to be a neutron star rotating at 1.1 khz.

Such angular momentum I doubt is accounted in the stress-energy momentum tensor  to warp space time the effect of rotation is only considered as an additional kinetic energy just  comparable with the direct effect of barionic matter, in addition to a short range frame dragging effect.

EDDINGTON: space-time and gravitation.

"After mass and energy there is one physical quantity which plays a very

fundamental part in modern physics, known as Action.

In the relativity theory in particular this seems in many

respects to be the most fundamental thing of all. The reason is not dif-

cult to see. If we wish to speak of the continuous matter present at

any particular point of space and time, we must use the term density.

Density multiplied by volume in space gives us mass or, what appears to

be the same thing, energy. But from our space-time point of view, a far

more important thing is density multiplied by a four-dimensional volume of space and time; this is action. The multiplication by three dimensions gives mass or energy; and the fourth multiplication gives mass or energy multiplied by time. Action is thus mass multiplied by time, or energy multiplied by time, and is more fundamental than either.

Action is the curvature of the world. It is scarcely possible to visualise

this statement, because our notion of curvature is derived from surfaces

of two dimensions in a three-dimensional space, and this gives too limited

an idea of the possibilities of a four-dimensional surface in space of ve or

more dimensions.