Abraham's light momentum breaks special relativity?

[Dale]

Then there is a pool of light momentum formulations; take one that can fit your own experiment...

All of the formulations fit every possible experiment. That is what it means that the choice is arbitrary.

 

[sciencewatch]

All of the formulations fit every possible experiment. That is what it means that the choice is arbitrary.

Are you serious? or just kidding?

 

[Phrak]

"An equation is said to be Lorentz covariant if it can be written in terms of Lorentz covariant quantities (confusingly, some use the term invariant here).

good vectors are invariant. This means they don't depend on any coordinate system in use.

the elements of vectors are contravariant quantities, whereas the the bases of vectors are covariant. Together, the entire vector is invariant. The idea in play is that physics is independent of how we impose human coordanate systems on spacetime. With this point of view, vectors should not dendend on our choice of coordinate system, but be invariant or independent of them.

 

[Dale]

Are you serious? or just kidding?

100% serious, that is the whole point of the paper.

 

[sciencewatch]

... vectors should not dendend on our choice of coordinate system, ...

Not depend. A vector can be expressed in terms of both contra-variant basis vectors and co-variant basis vectors: the components on the contra-variant basis vectors are co-variant while the components on the co-variant basis vectors are contra-variant.

Usually, that a vector is said to be co-variant means the components of the vector on the contra-variant basis vectors.

In the special relativity, the basis vectors are often not used, because the Minkowski-metric tensors are defined in advance according the Lorentz time-space transformation. The distance is defined by a quadratic of the metric matrix.

In the linear space, the metric matrix is defined by the inner-products of all basis vectors. In principle, the "inner-product" definitions are arbitrary (of course, by a reversible matrix); not necessarily e1*e1=(e1)**2>0 for example.

 

[juanrga]

The Abraham's photon moment p_A=hbar*w/n*c is not Lorentz covariant, but it has been confirmed by several experiments. For example, G. B. Walker and D.G. Lahoz, Nature 253, 339 (1975); W. She, J. Yu, and R. Feng, Phys. Rev. Lett. 101, 243601 (2008).

The special relativity is flawed or the experiments were not correctly observed?

Momentum p^i is a three vector, it cannot be 4D covariant. The correct 4D covariant property is the four-momentum (or energy-momentum) p^mu

 

[yoron]

Interesting Phrak, didn't know that one. Although I did know, I think :) they should be coordinate invariant, but it's very cool to see a good explanation of how the definition looks.

 

[sciencewatch]

Momentum p^i is a three vector, it cannot be 4D covariant. The correct 4D covariant property is the four-momentum (or energy-momentum) p^mu

Please look at POST #4 .

 

[Phrak]

Not depend. A vector can be expressed in terms of both contra-variant basis vectors and co-variant basis vectors: the components on the contra-variant basis vectors are co-variant while the components on the co-variant basis vectors are contra-variant.

Usually, that a vector is said to be co-variant means the components of the vector on the contra-variant basis vectors.

Well, a covector, or one-form is not a vector. They don't transform the same, and the units are complimentary. And it really doesn't matter what is 'said to be', if it's wrong, but it is good to know what sloppy language is in common use.

 

[sciencewatch]

100% serious, that is the whole point of the paper.

Well, the options for light momentums are significantly reduced by the recent work by S. M. Barnett, Phys. Rev. Lett. 104, 070401 (2010).

 

[Dale]

I can't find it on arxiv. Perhaps you can explain why you think that, the abstract certainly doesn't seem to indicate that.

 

[sciencewatch]

I can't find it on arxiv. Perhaps you can explain why you think that, the abstract certainly doesn't seem to indicate that.

We conclude by noting that a number of further momenta
have been proposed, with the aim of resolving the
Abraham-Minkowski dilemma [2]. By demonstrating the
need for two ‘‘correct’’ momenta and associating these,
unambiguously, with the Abraham and Minkowski forms,
we may hope that we have also removed the need for
further rival forms. By S. M. Barnett, Phys. Rev. Lett. 104, 070401 (2010).

 

[yoron]

He means this one I think.

http://strathprints.strath.ac.uk/27285/1/AbMinkPhil.pdf

 

[Dale]

we have also removed the need for
further rival forms

I am not sure that is intended to imply that further forms are incorrect, but again, it is hard to tell without the full paper.

In any case, from the abstract and the quote this paper doesn't seem to claim that SR is in any way challenged by Abraham's momentum.

 

[sciencewatch]

In any case, from the abstract and the quote this paper doesn't seem to claim that SR is in any way challenged by Abraham's momentum.

This paper implicitly challenges the special relativity by claiming that Abraham's photon's momentum is correct. Because P_A=hbar*w/n*c and E_A=hbar*w, which cannot constitute Lorentz covariant 4-vector, but the wave 4-vector is Lorentz covariant and the Planck constant hbar is a Lorentz invariant.

I think the paper just wants to explain experimental results, by neglecting the self-consistence of theory.

Well, now we have the superluminant neutrino-exp which cannot be explained by SR.
Actually, the linear Sagnac experiments also challenge the principle of relativity [RuyongWang, Yi Zheng, and Aiping Yao, "Generalized Sagnac Effect", Phys. Rev. Lett. 94, 143901 (2004); R.Wang, Y. Zheng, A. Yao, and D. Langley, Phys. Lett. A 312, 7 (2003)]. But who cares?

 

[Dale]

This paper implicitly challenges the special relativity by claiming that Abraham's photon's momentum is correct.

We have already established through the review article I posted that Abrahams is correct (as well as Minkowski) and that is no contraindication to SR. This new article says the same. Evidence in favor of Abrahams is not evidence against SR, for the reasons given above.

We are going around in circles. If you have something new to say then I will be glad to discuss it, otherwise you are welcome to repeat your same invalid argument once more so as to get the last word and end the thread.

 

[sunroof]

OP is correct that Abraham–Minkowski controversy is not on technical matters. In fact, it is helpful to extend the theory of relativity,e.g.

Ravndal, F., Electromagnetism and photons in continuous media, arXiv:0810.1872

Crenshaw, M.E., Electrodynamics in a Filled Minkowski Spacetime with Application to Classical Continuum Electrodynamics, arXiv:0812.3348v2

Wang, Z.Y., Graphene, neutrino mass and oscillation, arXiv:0909.1856v2

These authors think the light speed c in vacuum can be changed to other constant velocities such as c/n in media, Fermi velocity of condensed matter physics(graphene),sonic speed and that of a neutrino. Recently, a modified Fizeau's experiment was carried out and the result was in favor of the hypothesis( Crucial experiment to resolve Abraham-Minkowski Controversy, Optik, vol122, p1994-1996,2011). An exhaustive study is necessary.

 

[sciencewatch]

We have already established through the review article I posted that Abrahams is correct (as well as Minkowski) and that is no contraindication to SR. This new article says the same.

Indeed, “Abrahams is correct” is the conclusion made by the review article you posted and the new article I posted:

1. Rev.Mod.Phys.79:1197-1216 (2007); http://arxiv.org/abs/0710.0461 : “On these grounds, all choices for the electromagnetic energy-momentum tensor are equally valid and will produce the same predicted physical results…”

2. Phys. Rev. Lett. 104, 070401 (2010); http://prl.aps.org/abstract/PRL/v104/i7/e070401 : “We show that both the Abraham and Minkowski forms of the momentum density are correct, …”

and also is the conclusion made by the recent study in a standard tensor form of relativistic electrodynamics:

3. Phys. Lett. A 375, 1703 (2011); http://arxiv.org/abs/1103.1654 : “the Abraham choice of the ‘correct’ momentum of a light pulse is only one possibility, simple and useful for the description of isotropic media, but not at all an unique one.”

However, “that is no contraindication to SR” is purely your conclusion, because I cannot find that the above papers have shown that, Abraham’s photon momentum and energy can constitute a Lorentz covariant momentum-energy 4-vector, and I cannot find that they have a statement such as Abraham’s momentum “is no contraindication to SR”, or something like that. If you find, please kindly show me.

 

[Dale]

I cannot find that they have a statement such as Abrahams momentum is no contraindication to SR

Do you find a statement in any of those that there is a contradiction with SR?

 

[sciencewatch]

Do you find a statement in any of those that there is a contradiction with SR?

No. That is why I say "This paper implicitly challenges the special relativity by claiming that Abraham's photon's momentum is correct." (see Post #45) My argument is given below:

1. The wave 4-vector is assumed to be Lorentz covariant; see: the Gordon-metric dispersion equation Eq. (A7) and the wave 4-vector definition Eq. (A8), of Phys. Lett. A 375, 1703 (2011); http://arxiv.org/abs/1103.1654

2. The Planck constant is a universal constant, namely a Lorentz invariant; see: http://physics.nist.gov/cuu/Constants/

3. The Abraham's photon energy in a medium is given by E_A=hbar*w, the same as in free space; see: U. Leonhardt, Nature 444, 823 (2006). Interestingly, in the three papers [1 Rev.Mod.Phys.79:1197-1216 (2007); http://arxiv.org/abs/0710.0461; 2 Phys. Rev. Lett. 104, 070401 (2010); http://prl.aps.org/abstract/PRL/v104/i7/e070401 ; 3 Phys. Lett. A 375, 1703 (2011); http://arxiv.org/abs/1103.1654 ], no one of them clearly mentioned what the photon’s energy in a medium is.

Based above, Abraham’s photon momentum and energy cannot constitute Lorentz covariant 4-vector. Where am I wrong? Please kindly indicate.

 

[Dale]

No. That is why I say "This paper implicitly challenges the special relativity by claiming that Abraham's photon's momentum is correct." (see Post #45)

I find it interesting that you see an implicit challenge where there is none and yet look for an explicit confirmation. That seems to indicate an anti-mainstream science bias.

My argument is given below:

1. The wave 4-vector is assumed to be Lorentz covariant; see: the Gordon-metric dispersion equation Eq. (A7) and the wave 4-vector definition Eq. (A8), of Phys. Lett. A 375, 1703 (2011); http://arxiv.org/abs/1103.1654

2. The Planck constant is a universal constant, namely a Lorentz invariant; see: http://physics.nist.gov/cuu/Constants/

3. The Abraham's photon energy in a medium is given by E_A=hbar*w, the same as in free space; see: U. Leonhardt, Nature 444, 823 (2006). Interestingly, in the three papers [1 Rev.Mod.Phys.79:1197-1216 (2007); http://arxiv.org/abs/0710.0461; 2 Phys. Rev. Lett. 104, 070401 (2010); http://prl.aps.org/abstract/PRL/v104/i7/e070401 ; 3 Phys. Lett. A 375, 1703 (2011); http://arxiv.org/abs/1103.1654 ], no one of them clearly mentioned what the photon’s energy in a medium is.

Based above, Abraham’s photon momentum and energy cannot constitute Lorentz covariant 4-vector. Where am I wrong? Please kindly indicate.

You are correct in the above. Abraham's momentum is not covariant. If you want a covariant momentum then use Minkowski.

Where you are incorrect is in thinking that challenges SR in any way.

 

[sciencewatch]

Abraham's momentum is not covariant.

Although Abraham's momentum is not compatible with the special relativity, it is supported by a recent experimental observation, Phys. Rev. Lett. 101, 243601 (2008), where a silica filament fiber "recoiled" as a laser pulse exited.

Interestingly, however, this "recoil" can be also explained as being caused by a transverse radiation force when there is an azimuthal asymmetry present in the fiber such that one side has a slightly different refractive index than the other. See: Phys. Rev. A 81, 011806(R) (2010); http://pra.aps.org/abstract/PRA/v81/i1/e011806.

 

[Dale]

it is supported by a recent experimental observation, Phys. Rev. Lett. 101, 243601 (2008), where a silica filament fiber "recoiled" as a laser pulse exited.

As is every other momentum tensor. The evidence supports Abraham, but it also supports Minkowski. The choice is arbitrary.

You seem to not understand this point despite my repeating it for four pages now.

 

[sciencewatch]

The choice is arbitrary.

The choice of light momentum formulations is arbitrary no matter whether it is compatible with the special relativity or not. --- Is that what you means for "The choice is arbitrary"?

 

[Dale]

Yes. You can choose an incompatible (with SR) momentum just as you can choose an incompatible gauge.

 

[sciencewatch]

Yes. You can choose an incompatible (with SR) momentum just as you can choose an incompatible gauge.

1. Is the light momentum a measurable physical quantity?
2. If it is, then the measured light momentum depends on the choice of light momentum formulations you take. Is that what you mean?

 

[Dale]

1. Is the light momentum a measurable physical quantity?

Yes.

2. If it is, then the measured light momentum depends on the choice of light momentum formulations you take. Is that what you mean?

Yes.

Similar things happen e.g. when you measure potential, where the measured value depends on where you set your ground, or length where the measured value depends on what simultaneity convention you adopt.

 

[sciencewatch]

Yes.

You yes that the measured light momentum depends on the choice of light momentum formulations.

In some experiments, the light momentum behaves as a visual physical phenomenon; for example, the fiber-recoiling experiment, Phys. Rev. Lett. 101, 243601 (2008); http://physics.aps.org/story/v22/st20 ; . Do you think the fiber-recoiling depends on the choice of light-momentum formulations you take?

 

[Dale]

Do you think the fiber-recoiling depends on the choice of light-momentum formulations you take?

No, fiber recoiling obviously depends on the total momentum, which is the same for Abraham and Minkowski.

How you partition that total momentum into light momentum and matter momentum is arbitrary and depends on your choice of formulations. But that partitioning won't change the result of measurements which depend on the total momentum.

 

[sciencewatch]

No, fiber recoiling obviously depends on the total momentum, which is the same for Abraham and Minkowski.

How you partition that total momentum into light momentum and matter momentum is arbitrary and depends on your choice of formulations. But that partitioning won't change the result of measurements which depend on the total momentum.

You claim that
(1) Total momentum = light momentum + matter momentum;
(2) The total momentum is the same (unique), no matter whether the light momentum is described by Abraham’s or Minkowski’s formulation (or even how to partition the total momentum into light momentum and matter momentum is arbitrary);
(3) The result of measurements or fiber recoiling only depends on the total momentum.

From your arguments it follows that:
Theoretically the Abraham’s and Minkowski’s light-momentum formulations have equal rights, and no one takes advantage.
----
My question is: Why the fiber-recoiling experiment [Phys. Rev. Lett. 101, 243601 (2008); http://physics.aps.org/story/v22/st20 ; ] cannot be explained by the Minkowski’s formulation since the Minkowski's and Abraham's formulations have equal rights?