Cf. Coleman's article: https://www.rand.org/content/dam/rand/pubs/research_memoranda/2006/RM2820.pdf

Having a quick look at it, I do not see any new perspective other than what is available in standard electrodynamics books.

It has been known for the last 250 years that the Coulomb force induces kinetic energy in accelerating charged particles as a function of the inverse square of the distance between them. When  two charged particles interact, this energy is vectorially directed towards the other particle if they are of opposite sign and directed away from the other particle if they have same sign.

When an electron is attracted to an ionized hydrogen atom (a proton) for example, the electron progressively accumulates kinetic energy until it is stopped when reaching the rest orbital of the hydrogen atom in a state of least action electromagnetic equilibrium, at which point, upon being stopped, it will evacuate its 13.6 eV of translational energy as a bremmsstrahlung photon, and remain captive with a stable amount of Coulomb force constantly induced adiabatically unreleasable amount of 27.2 eV of kinetic energy.

Recent textbook regrettably do not explain this clearly. You would need to locate older textbooks, preferably prior to 1950 to have a chance of finding correct descriptions.

Because there isn't any ``new perspective'' on this subject-it's understood and forms the background for other issues. There are many, equivalent, ways, of formulating this and other questions in physics, so the content matters, not the date.

Unfortunately, acceleration cannot be understood if it is not understood how the Coulomb force operates.

actio = reactio

The proton has the same kinetic energy as the electron. It is probably released at least as thermal energy. If I understand correctly, the amount of 27.2 eV of energy is the binding energy of the electron-proton-system?

Dear Hans

The kinetic energy sustaining the velocity of a particle depends on the mass of the particle. This kinetic energy is separate, or "in addition" if you prefer, to the energy making up the rest mass of the particle.

You can have two cases of kinetic energy addition with elementary particles. First, if you impart kinetic energy to a free moving electron by means of locally increasing equal density electric and magnetic fields, you will cause this electron to move in straight line at a velocity directly dependent of the amount of kinetic energy provided.

For example, if you impart in this manner 27.2 eV of kinetic energy (4.359743805 E-18 j), you will cause this electron to move at a relativistic velocity exactly equal to 2187647.561 m/s.

When the Coulomb force adiabatically induces the same amount of 27.2 eV on the mean rest orbital of a hydrogen atom, an energy which is unreleasable in the environment, this doesn't mean that the electron will necessarily move at this velocity, because local electromagnetic equilibrium may well prevent translational motion. The same amount of kinetic energy is also reciprocally induce in the proton.

In all cases however, a relativistic mass increment equal to half the imparted kinetic energy divided by the square of the speed of light will be added to the rest mass of the electron, which will be maintained as long as the electron is induced by this particular amount of kinetic energy, a relativistic mass increment that is detectable only by transverse interaction with the electron moving at this velocity, as born witness by Walter Kaufmann's experiments at the beginning of the 20th century.

As for the proton, given that its rest mass is 1.6726219 × 10-27 kg compared to 9.10938188E-31 kg for the electron, it is 1836 times more massive, it would require a much larger amount of carrying kinetic energy to cause it to move at the same velocity (2187647.561 m/s).

If interested, I put acceleration induced kinetic energy in perspective in this recently published paper:

http://www.omicsonline.com/open-access/on-adiabatic-processes-at-the-elementary-particle-level-2090-0902-1000177.php?aid=75602

1) Acceleration of atom can cause transitions of the atomic electrons to higher energy levels (excitation).

2) Let there be an isolated charge (electrons, protons) in accelerated motion in empty space. Electromagnetic radiation leads to the effective friction and deceleration of the charge in the end. 

1) True.

2) "accelerated" is a strange concept to me.

From what I understand, in physical reality, there can exist only "accelerating" charged electromagnetic elementary particles, which includes charged free moving elementary particles and charged particles stabilized in some electromagnetic equilibrium state, that is, particles in the process of increasing or decreasing their kinetic energy complement as a function of the inverse square of the distance between them (the Coulomb force).

It is well known that electrons emit radiation both in linear accelerators (linacs) and in electron storage rings (SR). Acceleration  of electrons in linacs and SRs is supported with electric field in RF cavity resonators.

Electrons in storage rings and any device that causes them to oscillate transversally with respect to their direction of motion will emit a bremmstrahlung photon each time they are forced to transversally stop and chage direction or when they are force deflected from staight line trajectory with powerfull enough magnetic fields. Totally true.

Can you frame this question at the microscopic level ? For example in terms of photons emitted by elementary particles carrying electric charges ?

Photons couple to particles carrying electric charge (such as quarks and charged leptons, W+/- bosons). So at the level of quantum field theories, one can attach an external photon line to a charged particle propagator or an external line describing a charged particle.

Bremsstrahlung is a phenomenon in which radiation is produced while a charged particle (such as an electron) is decelerated or deflected.  This radiation has a continuous spectrum but frequency shits to higher values  with the increasing change of energy of the charged particle.

A quantum mechanical treatment was first given by, Bethe and Heitler (1934) who related scattering process (of electrons with nucleus of an atom) to the frequency of the emitted photons. Currently  most books on field theory includes a treatment.

Biswajoy,

Not sure if you are addressing me, but if so, I must say that I eventually shied away completely from the Standard Model particles definitions to end up considering only the restricted subset of stable and scatterable electromagnetic elementary charged and massive particles, which are the electron, the positron, the up quark and the down quark, because all other particles in the Standard model are either unstable and almost instantly decay to end up as one of the stable set, or are not electromagnetic in nature, such as neutrinos which seem to be only translational kinetic energy and gluons and such which are mathematical metaphors meant to describe yet to be understood interactions.

My view is that all unstable partons are meaningless to describe matter in the universe because they cannot be part of atomic structures due to their so short lifespan.

To my knowledge the complete range of all possible electromagnetic frequencies can be entirely populated by bremmsstrahlung electromagnetic photons emitted somewhere in the universe one way or another without this being in conflict with the fact that we can mathematically represent the complete spectrum as being continuous.

If  I misunderstood your question, please clarify.

Andre; sorry, no I was not addressing you. Electron is the stable particle of standard model, can we ever think of electron decay?  What we observe is that our earth and the small part of the universe where we live is made up of the first generation particles such as protons and electrons. However, from theoretical considerations we know that two more generations should "exist" and now it is also experimentally verified that indeed there are three generations of quarks and leptons. So why do you think that they do not exist?

In any case looking at the total mass-energy balance sheet of the universe, it seems that visible matter is present in almost an insignificant amount; but the hope is that the rest of it can be (at least) approximately described by known theories. That is unknown things can be described in terms of the known theories. But it could be wishful thinking also, we do not really know.   

Dear Biswajoy!

There are two types of particles:

Real particles which are undoubted proven - like elctrons, positrons, protons and many other unstabel particles. Atomic nuclei are also a subset of the amount of particles.

Theoretical particles are invented by theory to explain all the real particles. This type of particles is unproven (e.g. quarks. gluons) or only indirect "proven" (e.g. neutrinos).

Maybe you can read the papers:

https://www.researchgate.net/publication/301614262_The_Reason_of_a_realistic_View_to_Particles_and_Atomic_Nuclei?ev=prf_pub

https://www.researchgate.net/publication/279963956_Theory_and_reality_on_the_experiment_of_ReinesCowan_1956?ev=prf_pub

Dark matter is also a invention by theorie. Sorry, I am not sure about the present theories in physics.

My Regards!

Hans

Research Theory and reality on the experiment of Reines/Cowan 1956

Thesis The Justification of a realistic Picture of Particles and At...

1) Returning to the original question, for example, neutrons cannot interact with atomic electrons directly, however they interact with atomic nuclei via short-range strong forces. Fast neutrons can give a kick to a nucleus and nucleus acceleration shakes atomic electron shells.  The holes in the internal electronic shells (ionization) give rise to characteristic x-ray radiation due to spontaneous transitions of electrons to the empty states.

Dear Biswajoy,

My apologies for speaking out of turn then.

Of course the electron is stable out of any doubt. And of course second and third generation quarks and leptons have been detected.

However, all these scatterable partons besides electron proton and neutron turn out to be unstable and decay within fractions of a second to leave at the end one of the stable particles, according to decay sequences very well documented.

They all can be found in the CRC Handbook of Chemistry and Physics. CRC Press, New York.

Also, none of these unstable particles can be found in atomic structures. The only scatterable elementary particles that can be detected inside protons (uud) and neutrons (udd) are stable up quarks and down quarks, which were found to be charged just like electron and positron, even if with less intense charges, and are only marginally more massive than electrons and positrons.

All unstable particles certainly do exist since we can detect them by scattering but they are not part of atoms.

From confirmed scattering facts alone, the mass-energy balance sheet of the universe seems to confirm that the stable particles set is sufficient to build the whole universe.

The idea that visible matter may be only an insignificant part of the universe is a hypothesis, not a confirmed fact.

My view is that theories are theories. A set of theories mixed with confirmed facts is different from a set of a set of confirmed facts alone being taken as a basis.

From the set of confirmed facts, all required information is already known about the building blocks of the universe. All suspected unknown things are the fruit of hypotheses not grounded on real scattering results.

For example, the magnetic inverse cube interaction law between the magnetic aspect of charged electrons has been integrated into no current theory. See paper below for this experimental proof directly obtained in 2014.

My question now is: Do current theories need to be revised to take the magnetic inverse cube interaction law into account, or do we ignore this experimentally proven fact?

I think that it is not wishful thinking to believe that the universe can be understood from the known scattering results about the stable set and the know inverse square Coulomb law and the inverse cube magnetic interaction law.

http://www.nature.com/articles/nature13403.epdf?referrer_access_token=yoC6RXrPyxwvQviChYrG0tRgN0jAjWel9jnR3ZoTv0PdPJ4geER1fKVR1YXH8GThqECstdb6e48mZm0qQo2OMX_XYURkzBSUZCrxM8VipvnG8FofxB39P4lc-1UIKEO1

@ Zhevago and all,

Am I missing out on something?

Imgaine a charged particle, atom or an electron accelerating in empty space. Then how does "Acceleration of atom can cause transitions of the atomic electrons to higher energy levels (excitation)", necessary for radiation?

Is it a well-solved problem, or is it open to research?

It is a well solved problem.

Acceleration of a complete atom induces more energy in all of its elementary components, including the electrons. If the energy in excess of the rest mass of an electron exceeds the amount allowed on one orbital to the point of reaching the level of the next orbital outward, the electron will jump to that orbital momentarily and then will jump back to its initial orbital releasing the complete amount of excess energy as an electromagnetic photon.

One more example. Let fast neutron liberates a proton from atomic nucleus, then nuclear charge suddenly changes from Z to Z-1. Mathematically, Hamiltonian of the electron-nucleus system suddenly changes and old electron states become not stationary now. You can find the probability of transitions of electrons to the new stationary states expanding the old wave functions over the new basis functions, corresponding to the new Hamiltonian. Acceleration of an ion means that the electric potential of the nucleus becomes time dependent. Any time-dependent perturbations can cause transitions between the electron states.

@ Andre and Zhevago,

So, acceleration of an atom agitates the constituent electrons? What is the underlying mechanism then? If it was in non-vacuum I could understand the energy supply from the friction, but how does kinetic energy converts to electronic energy if acceleration is in empty space?

Also, if that is the case then even a "neutral" atom should start radiating on acceleration?

Vikash

As I mentioned before, there is no way to understand acceleration and natural kinetic energy induction without understanding how the Coulomb force operates.

The Coulomb force, which is in permanent action between charged particles, induces kinetic energy in the charged particles as a function of the inverse square of the distance between them. The sum of this energy increases if the particles move towards each other and decreases when the particles move away from each other.

It is not understood what the Coulomb force is really, but we know since Coulomb that it induces kinetic energy in this manner.

As to how kinetic energy converts to electromagnetic energy, this was clarified indirectly by experiments carried out by Walter Kaufmann at the beginning of 20th century. The results of his experiments could not be interpreted until Paul Marmet discovered that the magnetic field of a moving electron increases as a function of the square of the electron velocity.

This allowed understanding the Kaufmann results and allowed understanding how kinetic energy "converts" so to speak to electromagnetic energy. I put convert between quotes because it does not really converts, it permanently remains kinetic energy, but we perceive it as behaving as electromagnetic energy.

If interested, you can find in the attached formally published paper a complete explanation of the links between Kaufmann's experiments and Marmet's discovery and how it can be logically explained how Coulomb force induced kinetic energy converts to electromagnetic status.

Note that atoms, neutral or otherwise, do not radiate upon accelerating. They radiate upon their motion being stopped or deflected.

http://www.omicsonline.com/open-access/on-de-broglies-doubleparticle-photon-hypothesis-2090-0902-1000153.php?aid=70373

Acceleration is variation of the velocity vector: w=dv/dt,.Deflection of v or stopping means acceleration, so the conclusions of André seem to me contradictory.

Acceleration is increase or decrease of kinetic energy of a charged electromagnetic particle. Or course its translational part can mathematically be represented by a velocity vector.

Actually, stopping for an electromagnetic particle means that the translational kinetic energy that causes it to move at this velocity in this particular direction has nowhere to go when the particle is stopped and has to evacuate, or else the particle would continue moving. This is what happens when an electron is captured on the mean rest orbital of an ionized hydrogen atom (a proton)

It is unusual definition of acceleration. The standard one is here 

https://en.wikipedia.org/wiki/Acceleration#Definition_and_properties

These definitions are entirely valid also. But they only mathematically describe the consequence of kinetic energy being present to sustain velocity changes of freely moving bodies.

What causes induction of kinetic energy in charged particles is the Coulomb force.

What causes the particles to move is the kinetic energy induced by the force

You can have energy induction without velocity being expressed even if the kinetic energy in a particle would be sufficient to sustain it, if the local electromagnetic equilibrium prevents motion.

For a free moving electron, it can truly be said that acceleration is a reflection of the velocity vector, but even then this vector is more fundamentally dependent on the amount of kinetic energy present. But in the case of electrons captive on atoms' orbitals, that may well be unable to translate, the adiabatic unreleasable kinetic energy corresponding to the velocity that they could have if free moving with this energy is still present, but cannot be expressed by a vector or else by a zero vector translation wise.

This is why acceleration is fundamentally primarily dependent on the kinetic energy induced in it, whether or not the velocity is expressed, which makes this definition more general.

Actually, acceleration induces more than the translational kinetic energy. The Coulomb force also induces at the same time an equal amount of kinetic energy that converts to the relativistic mass increment related to the velocity.

This is why defining acceleration as being kinetic energy dependent is a more general definition than simply defining it with respect to the velocity vector.

This is revealed when exploring Coulomb induced acceleration from the electromagnetism angle. Classical mechanics does not allow understanding this aspect.

"Radiation by an excited atom is a well established quantum phenomenon."

That is true. But it is of course not the only way to produce radiation. Synchrotron radiation is not radiation by an excited atom. The radiation by moving charges predicted from classical electrodynamics, with wavelengths in the km range or larger, is certainly not emitted by excited atoms. 

I have the solution to this problem of a freely falling charge, and it is very simple!

The true facts are:

1.       Inertial frames (and we include GR) must provide the same physical observations, even for an accelerating charge.

2.       The word “Acceleration” of a charge means that we need to have a reference frame to really say that the charge is accelerating. Without a reference frame we cannot say that something is accelerating.

3.       An accelerating charge radiates, and this radiation does not need to be treated at the quantum level.

The above three facts are true but one of them is incomplete.

Let me show that we get into an experimental contradiction using solely the above three facts. Let’s design an ideal experiment: A freely falling charge in a gravitational well. Two observers in two different inertial frames (fact 1): one co-moving with charge along the geodesic, and another along the same geodesics, but far away, say at infinity. The first observer, in free fall with the charge, will measure no acceleration (GR), since the charge appears stationary to him (fact 2). Therefore the observer records no radiation from the charge (fact 3). The second observer at infinity measures that the charge is accelerating with respect to him (fact 2), since the charge and the observer at infinity have different values of the gravitational potential. Therefore, in principle, the second observer “should” notice that the charge radiates (fact 3). But both observers are in inertial frames and therefore must observer the same physics, i.e., either there is radiation (it must be observable in both of frames) or there is not. Apparently there is a contradiction for the two inertial observers, since the one in free fall observes no radiation from the charge, while the other one at infinity observes the charge radiates. The truth that we missed here is in the incompleteness of “fact 3”: We were misguided in all discussions about a charge, that accelerates, radiates. This is not the whole story! What are Liénard–Wiechert potential, Larmor formula, and Cyclotron radiation telling us? A charge, accelerated by the influence of an external electromagnetic field, radiates. So, it is the presence of the electromagnetic field the very source of the charge’s acceleration (gravity is negligible), and it is this type of interaction that truly triggers the emission of electromagnetic radiation. Therefore, an accelerating charge under gravity, without an external electromagnetic field, will not be able to radiate. The radiation mechanism is entailed to the presence of an electromagnetic field that accelerates the charge: i.e., The interaction of a charge with an electromagnetic field, that accelerates the charge, generates the electromagnetic radiation we observe in any inertial frame.

This is analogous to the spontaneous decay of some particles in the vacuum: Why is this happening? Well, if the vacuum was without fluctuations, then no particle will spontaneous decay. But the vacuum has fluctuations that trigger the stability of a particle and make it to decay (ref., Casimir’s effect, QFT).

I hope this clarifies and answers part of the original question!

P.S. For a more detail discussion see: http://www.mathpages.com/home/kmath528/kmath528.htm

Thank you Feynman!

P.P.S.

The other Post: If a charge falls freely in the earth's gravitational field,does it radiate? - ResearchGate. Available from: https://www.researchgate.net/post/If_a_charge_falls_freely_in_the_earths_gravitational_field_does_it_radiate#view=57bac683f7b67e49060f2172 [accessed Aug 25, 2016].

What a coincidence! I found an article published on ArXiv today about the same topic. http://arxiv.org/pdf/1608.07177.pdf

Dear Sante,

A contradiction is set in your  sentence:

"...one co-moving with charge along the geodesic, and another along the same geodesics, but far away, say at infinity" - the problem is that the motion of objects along the geodesics depends under the presence of matter strongly on this matter  tensor energy-momentum, and they never can concide to each other, as you have assumed above. Thereby, this "gedanken' experiment has nothing to do with the problem under regard. This is one point. The second one is related with the electro-magnetic field quantum nature, whose is strongly relativistic and strongly supporting the Lorentz group symmetry and not satisfying the alternative general gravity theory group symmetry constraint - mainly, the geodesic motion, following exclusively   the  photon's quantum electrodynamic interaction properties.

Moreover, you wrote:

" ... Therefore, an accelerating charge under gravity, without an external electromagnetic field, will not be able to radiate. The radiation mechanism is entailed to the presence of an electromagnetic field that accelerates the charge: i.e., The interaction of a charge coupled with an electromagnetic field, that accelerates the charge, generates the electromagnetic radiation we observe in any inertial frame.  If a charge falls freely in the earth's gravitational field,does it radiate?"  -

It slightly misses with the real electromagnetic physics  -  the modern quantum electrodynamics strongly states that a charged electron disturbes the quantum vacuum backgrounds and generates the corresponding photonic electromagnetic field suitably interacting both with the surrounding charges and the electron itself (see the classical  Abraham-Lorentz radiation theory etc). Thus, one has the electric charge, one has  simultaneosly  the surrounding electromagnetic field.

Regards.

Dear Anatolij,

Details of the self-field had been omitted since we are in ideal conditions (See: http://www.mathpages.com/home/kmath528/kmath528.htm, Thank you Feynman). Instead, the following article discusses classically the famous tail of a charge along a geodesic. 

Bryce S DeWitt, Robert W Brehme : Radiation damping in a gravitational field. Annals of Physics, Volume 9.2 1960, pp. 220-259..

The argument above has been already widely discussed and we can consider it closed. I thought to provide a classical insight for those discussing charges in free fall, i.e., the primary effect. No quantum mechanics is necessary at that level. Classical radiation suffices. You are correct about the Quantum Electrodynamics and the Vacuum disturbances. But, I repeat my argument is classical and conceptual, and it does not explain further details of the radiation emission without the presence of EM field, because these effects are negligible for the original purpose. I do not know of a QED theory in GR. Superstrings are currently very promising at the level of Quantum GR detail, but why should we speculate on such infinitesimal effects, when the main effect is the most important. A freely falling charge does not emit any "observable" radiation.

Regards