Abraham's light momentum breaks special relativity?

[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?

 

[Dale]

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?

Simply because the authors of the study did not perform such an analysis does not mean that it cannot be done. Again, an experimental confirmation of Abraham is not an experimental contradiction of Minkowski.

In fact, to me it seems obvious that the fiber will be pushed regardless of the formulation. We know the momentum of the light as it exits, so by conservation of momentum we know the total momentum in the fiber is a net push. How you partition that into light and matter momentum is arbitrary.

 

[sciencewatch]

Simply because the authors of the study did not perform such an analysis does not mean that it cannot be done.

The arguments you provide:
(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.
require the Abraham’s and the Minkowski’s formulations to have equal rights, which means that, a specific experiment, which can be explained by Abraham’s formulation, also can be explained by Minkowski’s formulation. However, all reported experimental observations (http://physics.aps.org/story/v22/st20, for example) have already broken the property of equal rights that your arguments assign. I hate to but I have to say that, your arguments have some basic logical problem.

 

[sciencewatch]

Again, an experimental confirmation of Abraham is not an experimental contradiction of Minkowski.

I don't know what this sentense exactly mean. But to my best knowledge, any reported light-momentum-in-medium experiments cannot be explained by both Abraham’s and Minkowski’s formulations at the same time.

 

[Dale]

However, all reported experimental observations (http://physics.aps.org/story/v22/st20, for example) have already broken the property of equal rights that your arguments assign.

No, it didn't. I already rebutted the assertion in this story in post 61.

 

[Dale]

But to my best knowledge, any reported light-momentum-in-medium experiments cannot be explained by both Abraham’s and Minkowski’s formulations at the same time.

Then please re-read the review article I posted at the beginning of this discussion in post 3, you clearly did not understand it.

 

[sciencewatch]

Then please re-read the review article I posted at the beginning of this discussion in post 3, you clearly did not understand it.

Following your suggestion, I have re-read the review article [Rev. Mod. Phys.79:1197-1216 (2007); http://arxiv.org/abs/0710.0461 ]. The main conclusions in the article are copied below:

1(In I. INTRODUCTION). We therefore hope this paper will increase awareness that the controversy has been resolved, and that predictions regarding measurable behaviors will always be independent of the electromagnetic energy-momentum tensor chosen, provided the accompanying material tensor is also taken into account.

2(In XI. CONCLUSION). The original Abraham-Minkowski controversy, over the preferred form of the electromagnetic energy-momentum tensor in a dielectric medium, has been resolved by the recognition that division of the total energy-momentum tensor into electromagnetic and material components is arbitrary. Hence the Minkowski electromagnetic energy-momentum tensor, like the Abraham tensor, has a material counterpart, and the sum of these components yields the same total energy-momentum tensor as in the Abraham approach.

3(In XI. CONCLUSION). On these grounds, all choices for the electromagnetic energy-momentum tensor are equally valid and will produce the same predicted physical results, as has been demonstrated for a wide range of specific examples...

4(In XI. CONCLUSION)… We have discussed the realization that any electromagnetic energy-momentum tensor must always be accompanied by a counterpart material energy-momentum tensor, and that the division of the total energy-momentum tensor into these two components is entirely arbitrary.
-------
I think, the arguments you provide:
(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.

have well outlined the conclusions given in the review article.

Your arguments require both the Abraham’s and the Minkowski’s formulations to have equal rights, which means that, a specific experiment, which can be explained by Abraham’s formulation, also can be explained by Minkowski’s formulation. However, all reported experimental observations (http://physics.aps.org/story/v22/st20, for example) have already broken the property of equal rights that your arguments assign. Therefore, your arguments have a serious logical problem.

You suggest me to re-read the review article, because I “clearly did not understand it”. I guess, you mean I did not understand the following article’s statement:

“On these grounds, all choices for the electromagnetic energy-momentum tensor are equally valid and will produce the same predicted physical results, as has been demonstrated for a wide range of specific examples...”

Indeed, I did not understand what this statement exactly means. In my understanding, Abraham’s and Minkowki’s formulations are apparently not compatible, except for in free space, and the same experimental observation cannot be explained by both two formulations. If you know some experiment do can be explained by the both formulations at the same time, please kindly give specific information.

As I have indicated, your arguments have two problems:

(1) The Abraham’s momentum is not compatible with the principle of relativity;
(2) The property of equal rights assigned by your arguments is apparently broken by experimental facts [ http://physics.aps.org/story/v22/st20, Phys. Rev. Lett. 101, 243601 (2008) for example], and such arguments are not self-consistent logically.

In view of above, I would say that, it is premature to conclude “the controversy has been resolved”.

 

[rpfeifer]

Hello. I'm going to reply to this thread in a few parts. First of all, I will address the original question (Is p_A=hbar*w/n*c consistent with special relativity?), then I'll comment on the fibre experiment of She, Yu, and Feng, respond to a few other points raised in this thread, and finally I'll reply to post #66, which is about the review paper Rev. Mod. Phys.79:1197-1216 (2007), henceforth RMP79.

To begin with the original question (I will use units in which hbar=c=1, for convenience):
If k is the momentum in vacuum and p is the momentum in a medium, people often call
p=nk
the Minkowski formulation, and
p=k/n
the Abraham formulation. This is a gross oversimplification. To understand the flow of energy and momentum in a material, you cannot work with p alone. You need to use the energy-momentum tensor, made up of p (momentum), u (energy density), sigma (stress tensor) and S (Poynting vector). When dealing with electromagnetism, it is customary to further divide each of these into p_EM and p_matter, u_EM and u_matter, etc.

When you put these together in the correct way (as described in RMP79 Eq. (7)), and add together the EM and matter components, you get the total energy momentum tensor, T. Unless you're working on black holes or something, where general relativity will be required, then conservation of energy and conservation of momentum ABSOLUTELY REQUIRE that T is consistent with special relativity. However, they say nothing about individual quantities such as p_EM.

You can also put together a 4-vector (u_EM+u_matter, p_EM+p_matter)^T which also behaves correctly under special relativity. However, what about the p in p=k/n and p=nk?

You have probably figured out by now that these are just p_EM. You can make any change you like to p_EM and still be consistent with special relativity, so long as p_EM+p_matter remains the same.

Historically, a lot of people did what the original poster did, and asked questions like
"Is p_EM(Abraham)=k/n consistent with special relativity?" (Answer: NO)
"Is p_EM(Minkowski)=nk consistent with conservation of angular momentum?" (Answer: NO)
"Can p_EM(Abraham) explain this experiment?" (Answer: Yes for some, no for others)
"Can p_EM(Minkowski) explain this experiment?" (Answer: Yes for some, no for others)

The sensible question to ask is:
"Can T explain this experiment?"
Once you specify the properties of your materials, there is only one choice for T. I would like to say that again: There is only one choice for T. There is no T(Minkowski) or T(Abraham). It is uniquely fixed by conservation laws, and by special relativity.
Fortunately, the answer to the sensible question is: YES.

Hopefully things make more sense to you now.

By the way, if you're wondering where the Abraham and Minkowski formulations come into it, if T is fixed, well:
We can write down something we'll call T(EM, Minkowski) (for example). It looks like
( u_EM(Minkowski) S_EM(Minkowski) )
( p_EM(Minkowski) -σ_EM(Minkowski) )
but then T is given by T(EM,Minkowski)+T(matter,Minkowski):
( u_EM(Minkowski) S_EM(Minkowski) ) + ( u_matter(Minkowski) S_matter(Minkowski) )
( p_EM(Minkowski) -σ_EM(Minkowski) ) ( p_matter(Minkowski) -σ_matter(Minkowski) ).
Given that T is fixed, you can work out what the matter terms are. You can do exactly the same for T(EM,Abraham). Same T (it has to be, according to conservation of energy, conservation of momentum, and special relativity), and that means same behaviour.

Incidentally, you might be wondering if we can measure, say, p_EM directly and tell if it is the Abraham or Minkowski version. The short answer is: No, the mathematics of the energy-momentum tensor tells us this is impossible. Any experiment will only measure the total p, p_EM+p_matter, which is the same for Abraham and Minkowski (it has to be, as it is a part of T).

 

[rpfeifer]

Next, I will quickly comment on how this applies to the experiment of She, Yu, and Feng (Phys. Rev. Lett. 101, 243601 (2008)).

Although these authors do not publish their calculation, I suspect it went something like this:
For Minkowski, p=nk. A photon leaving a medium loses momentum, and the medium gains it, so the medium moves in the same direction as the photon.
For Abraham, p=k/n. A photon leaving a medium gains momentum, and the medium loses it, so the medium recoils.
She, Yu, and Feng observed a recoil, and concluded this meant the Abraham momentum was correct.

Let me show you why this is a problem: Read about the experiment of Ashkin and Dziedzic (Phys. Rev. Lett. 30, 139 (1973), summarised in Sec. IV.B of RMP79). As before, we say:
For Minkowski, p=nk. A photon leaving a medium loses momentum, and the medium gains it, so the medium moves in the same direction as the photon.
For Abraham, p=k/n. A photon leaving a medium gains momentum, and the medium loses it, so the medium recoils.
Ashkin and Dziedzic observed the medium moving in the same direction as the photons. Surely that means the Minkowski momentum is correct? We have reached a contradiction!

(In other words, this approach is internally inconsistent :) )

This isn't really surprising - the behaviour of the system is really described by T, and if we insist on splitting this into EM and matter parts, that's 32 separate parameters! (16 if we don't split it.) The momenta we have been using, p=nk and/or p=k/n, are only three of these 32 parameters (specifically p_EM). We've been ignoring over 90% of the physics! No wonder our results were inconsistent.

Gordon analysed the situation studied by Ashkin and Dziedzic in more detail in Phys. Rev. A 8, 14 (1973), and showed that both the Abraham and Minkowski formulations give the same result. It's quite a complicated calculation (and he uses Gaussian units, not SI, which makes things more difficult to follow for the younger generation of physicists), but the main point is this: There is NO WAY to get the correct result just from p=nk and p=k/n. I suspect She, Yu, and Feng fell into the same trap (though, unless they provide their calculation, there is no way to know for sure). A full analysis of their experiment in the Minkowski formulation would be a good exercise for a postgraduate classical field theory class.

However, we don't need to do this to know that their conclusion is wrong. Why do I say that? Because physics depends only on T, and there is only one choice for T (for a given dielectric material). I'll put a bit more historical context on this in my next post, and also respond to #66.

 

[rpfeifer]

Before I respond to #66, here are a few brief responses to some of the other posts:

Note - In my posts, to keep things clear I will only use EM to mean "Electromagnetic", never "Energy-Momentum".

Answer to #7:
Yes: In relativistic electrodynamics, there are no equations which depend explicitly on p_EM or p_matter (only on p_total, in T). Therefore, p_EM can be whatever it likes, even if it is not relativistically covariant. T is what matters; p_EM is a fiction. Sometimes it is a convenient fiction, and sometimes it is one which leads us astray. I have tried to provide some guidelines on this in Phys. Rev. A 79, 023813 (2009) (arXiv:0902.2605v2).

Comment on #14:
"Light momentum is a measuable physical quantity; theoretically there should be a correct formula to calculate, in my opinion. If both Abraham's and Minkowski's formulas are correct, then n=1 must hold."
No - momentum transfer is a measurable physical quantity. However, you have no way of ensuring that only the light transfers momentum (except by doing your experiment in vacuum, without any dielectric materials present, in which case it is indeed true that n must be exactly 1).

Answer to #30:
"For the photon, mass-energy equivalence: mass=energy/c**2=hbar*w/c**2 really has nothing open to question?"
In a medium, you have both photons and excitons (corresponding to the EM and material portions of the energy-momentum tensor).

Comment relating to #48:
In an explicitly SR formulation of EM, p_EM does not appear (except in the combination p_EM+p_matter). Thus p_EM can tell us nothing about the validity or otherwise of SR. Thus, 'Abraham’s momentum “is no contraindication to SR”'.

Comment on #57:
Some clarification is required here. You can measure "p_total while some light is passing through". This is not the same as measuring p_EM. DaleSpam may have meant the former, but many readers may have mistaken this for the latter.

 

[rpfeifer]

Response to #66:

As one of the authors of Rev. Mod. Phys.79:1197-1216 (2007), henceforth RMP79, I would like to point out that there are three very good examples of experiments which can be explained by both formulations at the same time, and which are reviewed in this very paper.
1) The experiment of Jones and Richards (later improved on by Jones and Leslie) in Proc. R. Soc. London, Ser. A 221, 480 (1954), Proc. R. Soc. London, Ser. A 360, 347 (1978), and Sec. IV.A of RMP79. In this experiment a photon reflects off a pivoting mirror suspended in a dielectric fluid. On first inspection the experiment appears to support the Minkowski formulation, but (as pointed out by Jones and Richards in the above citation, and again by Jones in Proc. R. Soc. London, Ser. A 360, 365 (1978), it is equally well explained by the Abraham formulation with appropriate accompanying material momentum tensor. This is also explained in Sec. VIII.C.1 of RMP79.
2) The experiment of Ashkin and Dziedzic (Phys. Rev. Lett. 30, 139 (1973), and Sec. IV.B of RMP79) in which a laser beam exiting a fluid causes the surface of this fluid to bulge outwards. A detailed treatment is provided by Gordon in Phys. Rev. A 8, 14 (1973) (note - he uses Gaussian units, which may cause confusion in readers accustomed to SI units).
3) The experiment of Walker, Lahoz, and Walker Can. J. Phys. 53, 2577 (1975), also Sec. IV.C of RMP79, in which angular momentum is transferred to a rotary pendulum. This experiment initially appears to support the Abraham formulation, but is also correctly described by the Minkowski formulation when the appropriate material momentum tensor is included.

In fact, the main thrust of Sec. VIII of RMP79 is that once the material properties of the dielectric are specified, the total momentum tensor is uniquely determined by
(i) consistency with special relativity, and
(ii) conservation of linear and angular momentum.
This leads to two important conclusions:
(a) No valid combination of EM and material energy-momentum tensors can break special relativity. If you are using a combination of tensors which appears to break this, then your choice of tensors is incorrect (usually, the material tensor is incorrect or missing). Note that I have never yet seen a fully relativistic formulation of the material counterpart tensors written down anywhere in the literature - even those given in RMP79 are valid only for media moving at v<<c, though the full expressions could be obtained from Eqs. (33)-(34).
(b) As the _total_ energy-momentum tensor is uniquely fixed by (i) and (ii) above, any division into components necessarily yields the same total tensor, and thus the same physical behaviours. That is, Abraham and Minkowski correspond to the same T, and thus the same physics.

In your post you stated "such arguments are not self-consistent logically", but there is nothing in your post which supports this statement (you have not presented any internal contradictions in the formulation presented in RMP79). Perhaps you meant "If Phys. Rev. Lett. 101, 243601 (2008) can only be explained by the Abraham momentum, then RMP79 is incorrect"? If so, then please carefully consider points (i), (ii), (a), and (b) above, and also post #67, as these demonstrate why _any_ experiment can be explained in terms of either the Abraham or the Minkowski formulation. If you meant something else, perhaps you can clarify?

I would just like to point out that all the examples I have provided were in RMP79, which you claim to have read. May I suggest that instead of reading superficially through the text, you work through the paper instead, making sure you understand the origin of each equation? You will probably need at the very least:
(i) A copy of Jackson's Classical Electrodynamics (1999)
(ii) Access to journals through a good university library, national library, or equivalent.
If you do this, I can more or less guarantee that all your questions will be answered.

Regards,
Robert Pfeifer
(Many thanks to DaleSpam for doing a great job, and already answering most of these questions elsewhere in the thread - it's great to see that my review paper has been read and appreciated! Hopefully by putting everything in one place like this, we can bring this thread to a close. Sciencewatch, I hope this answers your questions.)