Thank you, Gert, for your answer. Best wishes

The first statement of your question about that virtual particles are the real particles is only partly correct. The virtual particle is indeed interacting as a real particle, but it does not propagate as a real particle because it is not on the mass surface. In fact, you do not have a particle in a corpuscular sense, but rather some wave front with complicated features.

You can not simply make such particle "real" because it would violate principles of conservation of energy and momentum, but you probably can create such conditions, that due to interactions with the field, the conditions of "reality" are satisfied.

Gert, it is indeed possible to "create" electron-positron pair from vacuum if you put sufficient energy to it. For example, the high energy charged particle passing through the matter usually creates a lot of such pairs. If it is possible to make such pairs with the static field is a complicated question, because in order to create particles there should be some inhomogeneity or fluctuation in that field. I am not sure that I am competent enough to discuss this possibility.

Returning to the initial question, you can consider the creation of the electron-positron pair as a decay of some virtual photon, but still you can not make such virtual photon real - it should be massive, and it is not.

I think the problem is what to call a virtual particle. As I was tough it is just a very short-lived (and short flying) particle without fixed mass, which could exist (as a particle) only because of uncertainty relation.

The laser pulse definitely can create a lot of electron-positron pairs, but i do not understand what connection does it have with virtual particles.

@Gert and Alexander. Thank you for your answers. Yes you can attach the 1930 paper if you wish, and also do you know a paper which describe theoretically how strong pulse like laser can create real particle from virtual particles? Thanks.

Indeed mass is not a conserved quantity, yet each particle has some certain mass and it can't be made "real" with different mass.

I am not arguing about possibility to create particle-antiparticle pairs from vacuum in some either static or dynamic fields. It is just a question of terminology whether to connect this process with virtual particles or not.

When one high energy proton hits the other proton there is a vast cloud of different particles. Of course you always can say that before the collision there was a cloud of virtual particles which were virtual before the collision and are made real after, but in my opinion it is a bad use of the term.

Still, I just looked up over the internet and found that that meaning is also in use, so there is no point to argue.

@Gert and Alexander. Thank you for your comments. Btw, i just found an interesting paper by Karimaki from finland, where he discusses a madelung fluid model of virtual particles, see http://arxiv.org/pdf/1206.1237v2.pdf. But alas, he does not discuss possible interaction with laser. Best wishes

@Gert, thank you very much for the papers. I will try to read them. Best wishes

@Gert. Thank you for the translation. It is really helpful. Best wishes

I believe you are refering to the Schwinger effect. I heard that the most promissing way to see this effect is in graphene where the quasi-electrons have zero mass. However, I'm not an expert on this field.

@Yonatan and Gert. Thank you for reference to Schwinger effect. Is it possible to model virtual particles as madelung fluid as proposed by Karimaki? Best wishes

Slightly tangential, but Hawking radiation is a good example of the production of real radiation from virtual particle pairs. There are several examples in superconductivity in which real photons are created from virtual pairs. One involves the Casimir effect, e.g., http://www.sciencedaily.com/releases/2011/11/111118133050.htm

Hi Victor

The hole situation is very similar to Dynamical Casimir effect where vacuum fluctuations take energy from laser

Let us estimate the laser intensity needed for particle-antiparticle generation.

Energy of mass of rest E=2mc^2 should be spend during uncertainty time t=h/E in the region comparable with Compton's wavelength l=h/(mc)

Thus, the laser intensity should be not less than

I=4E^2/(hl^3)=4(mc^2)^5/((h^4)(c^3))

For electron neutrino the minimum laser intensity is 4.2e9 W/cm^3.

The common femtosecond laser have intensity nearly

10e30 W/cm^3. So, regular lasers already generate neutrino.

Though, the minimum needed laser intensity for generation of

electron-positron pair is nearly 4e150 W/cm^3

This intensity cannot be attended in nearest future.

@Gert, John and Stanislav. Thank you for your answers. I think Stanislav is correct that the present laser technology may not be able to create real particle from virtual particles. Btw, just fyi, there is a good introduction on Schwinger effect, at: http://www.qgf.uni-jena.de/gk_quantenmedia/Texte/hebenstreit090623-p-61.pdf. best wishes

Dear all, thank you so much for all your answers. Allow me to upload here a summary of our discussion. best wishes

@Gert, you are most welcome. With regards, to your question, i am not sure i can answer that questions. But perhaps one question may be related to the mystery surrounding the Dirac sea terminology. If you know how pair production can be achieved from Dirac sea, please let me know. Furthermore, i read somewhere about Bogoliubov creation-annihilation operator, does it have anything to do with this Schwinger effect? Best wishes

Gert,

In my estimation I did not follow any papers. I just use basic principles

of quantum mechanics:

- the applied energy need to be equal or higher E=2mc^2

- the time of generation process should be equal or less time uncertainty t=h/E

- the region of energy application should be comparable to size of principle spatial uncertainty of the particle with mass of rest m. This is Compton's wavelength l=h/(mc). Otherwise it could be violation of conservation of different quantum numbers.

The static electric field DO NOT help in generation of particles, but help in SEPARATION of already generated particles

Dear Victor,

what you say about generating pairs from the vacuum with a laser field is actually possible only in theory nowadays, as the Schwinger limit (i.e. the minimum value of the electric field with which is possible to trigger the pair generation process) is still very far away and out of reach to also next generation lasers. The best I know is that scientists are forecasting the possibility to realize Hexawatt lasers (peak power of 10^18 W/cm^2) but this is still not enough. You can think about some ways to magnify this number (by foci sung the laser for example) but still is not enough, not to speak of the technological problems you can go through (how is a lens for such an intense beam built?). There were some attempts in trying to find alternative methods for enhancing the peak intensity (see for example Phys. Rev. A 86, 053836) but they are almost useless, as they allow an enhancement of maximum 1%.

So, I am afraid that we still have to wait many laser generations before being able to probe the quantum vacuum to see pair production :)

Dear Marco,

Atended intensity in femtosecond lasers is higher than you mensioned.

For example, regular fs laser has energy 2.5 mJ/pulse with pulse duration 50 fs that gives us power 5e10 W. In focus point with area 10 suared microns intensity will be 5e17 W/cm^2.

This number can be increased by 100 times due to modulator.

Though, I am absolutely agree with your conclusion about possibility of electron-positron generation due to laser irradiation

Thank you, Marco and Stanislav. Best wishes

Dear Stanislav,

yes sorry, I was having in mind output power and I instead wrote peak power. Of course with femtosecond pulses we can go beyond 10^20 W/cm^2 peak power. Nevertheless, the Schwinger limit is still (unfortunately) out of reach.

Are virtual particles really constantly popping in and out of existence?

It is not so. Higgs Boson has to be created as a Virtual Particle by violation of Uncertainty Principle; what U say is same thing:< Quantum mechanics allows, and indeed requires, temporary violations of conservation of energy,.....>

So do you think that lasers will be able to make virtual particles real?

Answer: I do not believe it will happen.

@Hardev. Thanks for your answer, but perhaps you will like this article: http://www.newscientist.com/article/dn16095-its-confirmed-matter-is-merely-vacuum-fluctuations.html#.Uz-MSvFhiSM. Best wishes

Victor: Thanks for ur suggestion. I read New Scientist Article:It's confirmed: Matter is merely vacuum fluctuations.

Pl. send me ur e-mail for sending U my Essays on God Particle.

@Hardev. Thank you for your offer, my email is [email protected]. One small note, God particle term is perhaps a misnomer, and Peter Higgs himself does not agree with that term. Best wishes

Yes, I know views of Peter Higgs. Thanks for e-mail.

@Hardev. You are welcome. Btw, according to the new scientist article that Higgs mechanism possibly only explains 1% of proton mass. So does it mean that the remaining 99% mass of proton comes from quantum vacuum? What is your opinion? Best wishes

replying to Victor C. yes, the masses of the three "valence" quarks that are always

present in the proton adds up to about 1% of its mass. The rest comes from the kinetic energy of the gluons, the masses of the virtual quark-antiquark pairs popping out of the vacuum, their kinetic energy....

@David. Thanks for your answer. I have heard that numerical calculation of proton mass is nearly impossible. Is that right? Thanks

I appreciate the Answer provided by David. My essay on God Particle: Its role in Science and Sikh Religion is already in ur mail box; please read and send ur comments.

@Hardev. Thanks for your paper, i tried to download your file, but it is broken because i use an apple ipad. Could you send me a pdf version of your file? Thank you and best wishes

Ok, I will do as U desire

@Hardev. Thank you in advance, best wishes

Dear Gert

Sorry for my excessively emotional response.

I think that discrepancy in my estimation and calculations in Fedotov's paper

can be explained by different interpretation of the basic principles of quantum mechanics.

My estimations based on assumption that the characteristic length where virtual electron -positron pare is indistinguishable is Compton's wavelength. That leads to small possible contribution of the static electric field (in compare with mass of rest) due to very small region size.

Though, in papers you mentioned is implicitly used de Brolie's wavelength as the characteristic wavelength. This leads to few orders larger characteristic regions and possibility of the electric

field to have large contribution into energy of the generated pairs.

It is absolutely ineffective to discuss who is right in this situation until the first experimental data will be obtained.

This seems oddly similar to ordinary pair production

@Peter and @Bernd, thank you for your answer. Best wishes

Various incorrect comments on this topic are predicated on a classically conditioned way of thinking and are on that account not valid in quantum mechanics (QM). Observational context is crucial in QM. Wheeler's participatory principle should be applied everywhere. Then it is meaningless to assert that virtual particles "exist, as if that was an absolute truth. How could you know? Without context, the assertion is metaphysical and therefore meaningless scientifically. The correct statement is to say that IF suitable apparatus is set up, then outcome probabilities are observed that can be interpreted mathematically in terms of virtual particle lines in Feynman diagrams"

A further point is that if we decide to use the Heisenberg picture, quantum states appear frozen relative to the observer. Do virtual particles "exist" in this case?

Classical thinking applied sloppily in QM is responsible for many of the issues of interpretation of QM.

@George. Thanks for your answer. Best wishes

Victor, "virtual particles" are definitely not "real particles", unless you believe that by calling a donut a horse you enable it to take part in a horse race. If you read Feynman's papers of 1949/50 you will find the term "virtual quantum", which later transmuted into "virtual particle". It stands there essentially for a delta-function that is obtained, when a "creation" operator is commuted with an "annihilation" operator. So your question translates to "can a delta-function become real?", which obviously does not make any sense. The confusion about virtual particles results in part from a sloppily application of classical thinking to QM (cf. George's recent contribution), but also from giving an abstract mathematical term a handy, but misleading "physical" name. Using this name in a different context can only lead to great confusion. Unfortunately, this happens every day, not only in popular science texts, of which the article in "New Scientist" is an unpleasant example.

@Walter Smilga. Thank you for your answer. You are right, that virtual particles are not real. Do you perhaps have written a paper on this issue? And furthermore, i am not specialist in QCD, but i read that quark contribution to proton mass is only 1%, and the remaining 99% comes from virtual particles. Is that right? And if yes, then what is the mechanism of virtual particles to contribute on proton mass? Thank you.

Victor, as far as I understand the experts on QCD, you simply add up the 4-momenta of the virtual (mass-less) gluons that provide the exchange of momentum between the quarks. In the rest frame of the proton the 3-momenta add up to zero, whereas the energies add up to a non-zero value that contributes with 99% to the mass of the proton.

Since you ask for a paper of mine: you will find some remarks about my understanding of virtual particles in http://dx.doi.org/10.4236/jmp.2013.45079

@Walter Smilga. Thank you, i will read your paper on reverse engineering approach on QED. Btw, did you mean the Feynman paper in the following url: http://web.ihep.su/dbserv/compas/src/feynman49b/eng.pdf? I read that he mentioned about virtual quanta. Best wishes

Dear Victor .

The existence of a quantum vacuum made ​​of an electrical storm that constantly create pairs of virtual particles and the way that quantum mechanics lies to justify Cassimir effect. However this is due to the character of quantum mechanics theorizations be a finite element theory of strings that creates the universe . This theory shows the universe made of strings with 5 dimensions and deterministic , however very intensive computations . The quantum mechanics calculations decreases but becomes statistically and creates the illusion of virtual particles . What I am describing here is posted on my page here and has a set of equations that mathematically proves this assertion . It got the equation of the Planck blackbody in form of strings are making reference to projection string in our universe . ie without constants matter , energy and speed but only the data from the quantum vacuum . magnetic permeability and electrical permittivity . This mistaken interpretation of the pairs of particle leads to Hawking radiation that does not exist. And not to be dangerous extremanete makes the LHC , since the equations of string demonstrate that with a collision of 13.07 Tev it creates a magnetic monopole . which functions as the condensation nuclei of a black hole. All this walking line 60 days after the earth create this particle will have gone the way of the planet and will be a small black hole orbiting this star .

@Jorge. Thank you for your answer. Does your theory predict how laser can stimulate particle creation? Best wishes

Victor: Yes, I mean this Feynman paper and also the other one of 1949 (The Theory of Positrons) and the one of 1950 (Mathematical Formulation of ...).

@Walter Smilga. Thanks, i will try to look for those papers. Btw, yesterday i read your other paper which mentions electron/proton mass ratio. Do you mean that Wyler arrived at the same formula? Is there other way to calculate proton mass, without using that ratio? Thanks

Dear Victor.

The theory has two ways to be seen. A purely geometrical and establishing a tissue space and constructive design of particles, for example electron and 5 made of stretched strings in oscillating fashion, two of which creates the spin axis 3 of rotation and which generates the load. Results of the mass movement of the 5 strings. If you watch my other work, which has the equation for the electron charge you clearly watched the 3 strings in the equation. The second way to see theory and her projection in our universe. where it protrudes alert the constants of space and starting from these two constants is possible to describe all the equations of physics. within this vision possible and make a detailed description of the pair of particle creation by a photon of appropriate energy. or as you are asking me how to create particles alert the intensity of the field and not by the energy of the photon. In this case a detailed and extremely laborious descrica once and a process that occurred in very specific moments. But it is possible to assure you that the best way to create this field and 6 laser beams. lasers being counter to one another in each of the 3 axes. this will maximize the creation of pairs of particles. Since it allows to excite the tissue space appropriately to marshal the strings in the format of the matter. And good to note that energy and matter are one and geometric detail. energy and matter in motion and strings and strings packaged in a geometrical structure also made of strings.

Jorge Barcellos.

@Walter Smilga. I have found the Feynman's paper on positron here http://ivanik3.narod.ru/FormProton/Pozitron/Feynman1949v76p749_1.pdf, but do you know where to find the other paper? Thanks

@Jorge. I read your 5 pages paper on blackbody radiation. Sorry, it does not explain anything.

Dear Victor .

This work demonstrates only a set of equations that show that everything has its origin in a single object .

What I'm adding you here and a bit deeper .

But the explanation of all theory and very large .

Any time I am preparing a book to describe all the details .

I'm not telling you an equation but the description of all physics and the universe in a single theory and based on a string !

What I try to show the work that you have read and first one Planck equation not reached that gave rise to quantum mechanics and mathematics logically but intuitively ! According to the so-called constants of physics are not constant , but only local numerical values ​​. and third that the very complex equation can be restricted to only 4 mathematical operations numerical values ​​of simple physics say . And finally you must be open minded to see the world from a different perspective . Once the prisms are conflicting existing ! quantum mechanics , relativity theory and particle theory has no tune.

Dear Victor.

I've been looking at their publications.

And I think I understand why you do not realize the work I have done.

Not seen or work on your string theory.

And without understanding the principles of string theories had been impossible to understand what I have done.

It is not true that the uncertainty relation requires the conservation of energy to be violated. Energy is always conserved, and anyone who works with Feynman diagrams knows that this is true when particles are created and destroyed in quantum field theory. However, because of their interactions these "virtual" particles do not obey the energy-momentum relations that you would expect from their rest-mass (they are not "on mass-shell"). The energy and momentum that we observe in particles are kinetic energy and momentum, which is not conserved because we have to take into account the potential energy (and momentum!) arising from the interaction; in other words, the free particle states are not eigenstates of the Hamiltonian. This is why they only exist for a short time.

@Anthony. Thank you for your answer. Best wishes

Victor: For Feynman's paper

"Mathematical Formulation of the Quantum Theory of Electromagnetic Interaction"

try this link

authors.library.caltech.edu/3528/1/FEYpr50.pdf‎

Victor: Just found this link, which gives you a full and comprehensive answers to the question "What is a virtual particle?" and thus, in a way, also to your question:

http://physics.stackexchange.com/a/109249

Generation with laser of second garmonik, third garmonik, and subgarmonics of parametric generators are interesting circumstantial evidences about virtual particles, but proof is difficult.

Stephen Hawking uses virtual particles making them real in black hole physics. In this way he explains why black holes are grey, as proposed by Jacob Bekenstein and expressed by Bekenstein in a thermodynamical fashion. I do not know if this helps you.

@Walter, Nico, & V. Ogluzdin, thank you for all your answers. Best wishes

Virtual phonons pop in and out of existence in material systems almost all the time. For instance, an initial state of correlated electron-hole pair with energy, E+hw, may make a transition to a another pair with energy, E, while emitting a acoustic phonon of energy hw. It is likely, with the right set of conditions (which happens quite often), for the correlated pair to reabsorb the same phonon and make a transition back to the SAME initial state.......almost as if the phonon never existed....yet it did in the intermediate state. One can treat this scattering process by modelling the phonons as virtual entities. The scattering expressions with inclusion of virtual phonons are n-ordered, depending on the number of times the virtual phonons appeared and disappeared. Of course, it can be argued that the phonons are real, as they did exist in the intermediate stage...this argument holds when there is an energy mismatch in the initial and final states.

I like ur Answer Alagu. Is there any correlation between Phonon and Photon behaviour?

Where is Univ. of South Australia located?

@Alagu, thanks for your answer. My question: does the phonon have mass, or is it only energy? Best wishes

@Hardev, have you returned from Canada? I can send you my new paper if you wish. Best wishes

@Hardev, there are similarities between phonons and photons in the way these energy-like packets get emitted and then re-absorbed by charge carriers.

UniSA is located in Adelaide.

@Christianto, phonons acquire mass only by forming composite quasi-particle such as the polaron (electron+phonon). The effective mass of the polaron thus depends on the electron-phonon coupling.....in the extreme case, the interaction gets so large that a moving polaron slows to a standstill...and can be considered to possess an infinite mass. To answer your answer, phonons on their own, don't possess mass, however it would be interesting to seek alternative views on this. In close analogy are polaritons, where photons are coupled in an exchange interaction with charge carriers. So asking whether phonons have mass is similar to asking whether photons have mass.

@Alagu. Thank you for your answer. Yes, some physicists assume than photon has non zero mass, that is why they use Proca equations. So if we assume that phonon has similarity with photon, then it seems also possible to assume that phonon has masss too, but i am not sure yet. Best wishes

Virtual particle seems to be "effective" particles such as phonon, electron hole, exciton or even soliton and photon because they have the similar behaviors just like that of the real particles. Virtual particles are not the traditional particles as the stable electrons or atoms (real particles have a very long lifetime). But in quantum theory, any objects are waves so it will be hard to say what is the difference between a virtual particle and a real particle. That the high energy field can generate real particles is just a story now I think. Why should we believe that the real particles can be generated from the "boiling" empty space?

@Lin, thank you for your answer. Best wishes

@Alagu : Could you tell some more on the electron-phonon coupling - or precisely - on the case where the polaron slows to a standstill? Can you give some references to read on that topic?

Thanks!

@Bartosz: Toyozawa (Progr. Theor. Phys. 2B, 29 (1959)) showed that in the limiting case of very strong electron-acoustic phonon coupling, there occurs a sharp increase in the effective mass of the polaron in comparison to the electronic rest mass. This means that the electronic band has vanishing width, which can only occur when the polaron is highly localized or in a self-trapped state. For the case of optical phonons, Holstein (Ann. Phys. 8, 325 & 343 (1959)) also demonstrated similar properties, in particular that the energy of the optical polaron was lower than that of free electrons. Since the theories developed in these earlier works, there has been other advancements in polaron theories incorporating excitons and low dimensional systems. Currently there is interest in the electron-phonon coupling properties of Transition metal dichalcogenides (TMDCs), with superior opto-electronic properties, some of which are as good as those of graphene.

@Alagu: I am asking about this mainly because solid-state physics phenomena seem to have their counterparts in particle physics. I do not want to go as far as connecting the electron-acoustic-phonon coupling as an analogy to the Higgs mechanism... but I do feel that there are some valid connections there.

A very recent report talks about the creation of a particle-antiparticle pair using extremely high-energy laser, in apparent confirmation of a theory suggested about 70 years back.

In any case, the "color" of the laser should be > 2 times 511 keV; this is the energy equivalent of an electron + positron pair rest mass. Intensity of the light has nothing to do, of course. Since momentum must also be preserved, the pair would have to fly off in the original direction of that gamma-ray photon, and would require a higher energy for the pair production out of vacuum, plus something else: Since photons are famously stable, such disintegration has taken place only in the presence of an inhogeneous electric field, such as that of an atom, to conserve energy and momentum of the whole process. I do not know whether a "bubly" quantum vacuum can present such inhomogeneities. Perhaps such effects can be spotted in the first seconds of supernova explosions amid the noise.

@Bartosz, Bernd, and Kurt, thank you for your answers.

@Sambhu, can you please give a link to the report that you mentioned? Because as far as i know the present laser technology cannot achieve that limit. Best wishes

No. Lasers in the gamma-ray region do not exist yet. They could vaporize the lasing medium. But perhaps...

@Kurt. Thank you for your answer. Best wishes

A high frequency laser (given in the lab. frame) laser alone cannot produce any pairs from vacuum, since you always can find a reference frame where the frequency of the laser is substantially smaller (special relativity) and thus violates the energy conservation.

@B. Najjari, thank yoj for your answer. Do you suggest that in order to create particles from virtual particles, one needs laser and also strong magnetic field? Best wishes

you need for instance a collision of primary laser and a second physical object ( Electric/Magnetic fields, 2d laser, electron, proton, ion, atom . . . ) if the energy condition holds of course.

For instance in a ollision of a laser and a proton (any charged particle) and if the laser is intense enough, even at small frequency the process of pair-creation can occur. This is because the mult-photon absorptions. Since the number of the photons are higher as the intensityof the laser is big.

Hello all,

Two references on the current understading above the SM that virtual photons, or anything virtual, should be deprecated, [1, 2]:

[1] https://www.perimeterinstitute.ca/news/new-face-feynman-diagrams

[2] http://arxiv.org/pdf/1212.5605v1.pdf

Cheers, Ed Gerck