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# Quantum Electrodynamics - Science topic

Explore the latest questions and answers in Quantum Electrodynamics, and find Quantum Electrodynamics experts.
Questions related to Quantum Electrodynamics
Question
A body at rest has rest Energy, so it should also have rest Momentum.
Lao Tzu said, “Gravity is the root of lightness; stillness, the ruler of movement”(重为轻根，静为躁君)*. The meaning of this statement can be extended in physics to mean that "big-G determines how light or heavy an object is, and rest-m determines how easy or difficult it is to move".
According to the mass-energy equation** , E=mc^2, any object with mass m has "rest energy" , regardless of its inertial frame†. Note that E here is meant to be the energy lost when radiating the photon γ, which is absolute and unchangeable in any inertial frame. The mass-energy equation has been experimentally verified  as the correct relation.
According to special relativity , the mass of the same object is different in different inertial frames, m' = βm. Therefore, the energy of conversion of m of an object into photon γ is different in different inertial frames. This issue has been discussed in , but there is no consensus. Our view is that the "rest energy" is theoretically not Lorentz invariant, and the existence of a minimum value is a reasonable result. The most rational explanation for this is that the minimum corresponds to an absolutely static spacetime, i.e., absolute spacetime(Later we will show that absolute space-time and relative space-time are not in conflict). Analytically, this is one of the reasons why absolute spacetime should exist. The constant speed of light is another reason.
In all cases in physics, energy and momentum coexist and have a fixed relationship, not independent metrics. The energy-momentum ‡ of a photon, E=hν, P=h/λ; the energy-momentum relation of Newtonian mechanics, E=P^2/2m; and the relativistic energy-momentum relation, E^2=c^2p^2+m^2c^4. Therefore, it is assumed that if there is a body of mass m that has "rest energy", then it should also have "rest momentum". There is a "rest momentum", and the rest momentum cannot be zero. The rest energy is not intuitive, and the rest momentum should not be intuitive too. The calculation of the rest momentum is the same as the calculation of the rest energy. The nature of mass looks more like momentum; after all, energy is a sign of time, while momentum is a sign of movement. Therefore, instead of calling it the principle of equivalence of inertial mass and rest-energy, it should be called the principle of equivalence of inertial mass and rest-momentum.
When positive and negative electrons meet and annihilate , -e+e→γ+γ, radiating two photons in opposite directions. Their energy is conserved and so is their momentum. Energy is a scalar sum, while momentum is a vector sum. It seems that the "rest momentum" inside the object should be zero. However, one could argue that it is actually the momentum of the two photons that is being carried away, but in opposite directions. The momentum of the two photons should not come out of nothing, but rather there should be momentum of the two photons, also in some balanced way, and probably playing a very important role, such as the binding force.
Our questions are:
1) Since energy and momentum cannot be separated, should an object with "rest energy" necessarily have "rest momentum".
2) Elementary particles can be equated to a " energy packet ", and energy is time dependent. If an elementary particle is also equivalent to a "momentum packet", the momentum in the packet must be related to space. Does this determine the spatio-temporal nature of the elementary particles? And since momentum is related to force, is it the force that keeps the "energy packet" from dissipating?
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Notes
* Lao Tzu，Tao-Te-Ching，~500 BCE. This quote is a translation of someone else's. There are some excesses that I don't entirely agree with. Translating classical Chinese into modern Chinese is just as difficult as translating classical Chinese into English.
** There is a historical debate about the process of discovery of the mass-energy equation, and digging into the history shows that there were discoverers and revisers both before and after Einstein, see literature . Important contributions came from Poincaré, F. Hasenöhrl, Planck et al. Their derivations do not have the approximation of Einstein's mass-energy equation. And there is also a debate about the interpretation of the mass-energy equation. Notable debates can be found in the literature.
† There is a question here, i.e., is the rest mass Lorentz invariant? That is, is the rest mass the same in different inertial systems? Why?
‡ Einstein questioningly emphasized that energy and momentum seem to be inseparable, but did not explain it.
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References
 Einstein, A. (1905). "Does the inertia of a body depend upon its energy-content." Annalen der physik 18(13): 639-641.
Einstein, A. (1935). "Elementary derivation of the equivalence of mass and energy." Bulletin of the American mathematical society 41(4): 223-230.
 Rainville, S., J. K. Thompson, E. G. Myers, J. M. Brown, M. S. Dewey, E. G. Kessler, R. D. Deslattes, H. G. Börner, M. Jentschel, P. Mutti and D. E. Pritchard (2005). "A direct test of E=mc2." Nature 438(7071): 1096-1097.
 Einstein, A. (1905). "On the electrodynamics of moving bodies." Annalen der physik 17(10): 891-921.
 Is there a minimum value of m in the mass-energy equation E=mc^2? https://www.researchgate.net/post/NO7_Is_there_a_minimum_value_of_m_in_the_mass-energy_equation_Emc2；
 Planck, M. (1900). " " Verh. Deutsh. Phys. Ges 2: 237.
 Einstein, A. (1917). Physikalisehe Zeitschrift xviii: p.121
 Li, B. A. and C. N. Yang (1989). "CY Chao, Pair creation and Pair Annihilation." International Journal of Modern Physics A 4(17): 4325-4335.
 Ives, H. E. (1952). "Derivation of the mass-energy relation." JOSA 42(8): 540-543.
 Sharma, A. (0000). "The past present and future of the Mass Energy Equation DE =Dmc2." http://www.mrelativity.net/Papers/8/Sharma4.htm.
 Peierls, R., J. Warren and M. Nelkon (1987). "Mass and energy." Physics Bulletin 38(4): 127.
Dear Chian Fan ,
The next conclusion is connected to your previous comment:
So far, two people with PhDs have made veiled, arrogant criticisms... somewhat suggesting my stupidity. So far, there are four opinions. : one is a normal honestly worded opponent opinion. What's your opinion?
Regards,
Laszlo
P.S.: there is a thought that relates to your topic...
Question
God said, "Let there be light."
So, did God need to use many means when He created light? Physically we have to ask, "Should all processes of light generation obey the same equation?" "Is this equation the 'God equation'?"
Regarding the types of "light sources", we categorize them according to "how the light is emitted" (the way it is emitted):
Type 0 - naturally existing light. This philosophical assumption is important. It is important because it is impossible to determine whether it is more essential that all light is produced by matter, or that all light exists naturally and is transformed into matter. Moreover, naturally existing light can provide us with an absolute spacetime background (free light has a constant speed of light, independent of the motion of the light source and independent of the observer, which is equivalent to an absolute reference system).
Type I - Orbital Electron Transition: usually determines the characteristic spectra of the elements in the periodic table, they are the "fingerprints" of the elements; if there is human intervention, coherent optical lasers can be generated. According to the assumptions of Bohr's orbital theory, the transitions are instantaneous, there is no process, and no time is required*. Therefore, it also cannot be described using specific differential equations, but only by probabilities. However, Schrödinger believed that the wave equation could give a reasonable explanation, and that the transition was no longer an instantaneous process, but a transitional one. The wave function transitions from one stable state to another, with a "superposition of states" in between .
Type II - Accelerated motion of charged particles emitting light. There are various scenarios here, and it should be emphasized that theoretically they can produce light of any wavelength, infinitely short to infinitely long, and they are all photons. 1) Blackbody radiation : produced by the thermal motion of charged particles , is closely dependent on the temperature, and has a continuous spectrum in terms of statistical properties. This is the most ubiquitous class of light sources, ranging from stars like the Sun to the cosmic microwave background radiation , all of which have the same properties. 2) Radio: the most ubiquitous example of this is the electromagnetic waves radiated from antennas of devices such as wireless broadcasting, wireless communications, and radar. 3）Synchrotron radiation，e+e− → e+e−γ；the electromagnetic radiation emitted when charged particles travel in curved paths. 4）bremsstrahlung，for example, e+e− → qqg → 3 jets；electromagnetic radiation produced by the acceleration or especially the deceleration of a charged particle after passing through the electric and magnetic fields of a nucleus，continuous spectrum. 5）Cherenkov Radiation：light produced by charged particles when they pass through an optically transparent medium at speeds greater than the speed of light in that medium.
Type III：Partical reactions、Nuclear reactions：Any physical reaction process that produces photon (boson**) output. 1）the Gamma Decay；2）Annihilation of particles and antiparticles when they meet: this is a universal property of symmetric particles, the most typical physical reaction；3）Various concomitant light, such as during particle collisions；4）Transformational light output when light interacts with matter, such as Compton scattering.
Type IV: Various redshifts and violet shifts, changing the relative energies of light: gravitational redshift and violet shift, Doppler shift; cosmological redshift.
Type V: Virtual Photon?
Our questions are:
Among these types of light-emitting modes, type II and type IV light-emitting obey Maxwell's equation, and the type I and type III light-emitting processes are not clearly explained.
We can not know the light-emitting process, but we can be sure that the result, the final output of photons, is the same. Can we be sure that it is a different process that produces the same photons?
Is the thing that is capable of producing light, itself light? Or at least contains elements of light, e.g., an electric field E, a magnetic field H. If there aren't any elements of light in it, then how was it created? By what means was one energy, momentum, converted into another energy hν, momentum h/λ?
There is a view that "Virtual particles are indeed real particles. Quantum theory predicts that every particle spends some time as a combination of other particles in all possible ways". What then are the actual things that can fulfill this interpretation? Can it only be energy-momentum?
We believe everything needs to be described by mathematical equations (not made-up operators). If the output of a system is the same, then the process that bridges the output should also be the same. That is, the output equations for light are the same, whether it is a transition, an accelerated moving charged particle, or an annihilation process, the difference is only in the input.
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* Schrödinger said：the theory was silent about the period s of transition or 'quantum jumps' (as one then began to call them). Since intermediary states had to remain disallowed, one could not but regard the transition as instantaneous; but on the other hand, the radiating of a coherent wave train of 3 or 4 feet length, as it can be observed in an interferometer, would use up just about the average interval between two transitions, leaving the atom no time to 'be' in those stationary states, the only ones of which the theory gave a description.
** We know the most about photons, but not so much about the nature of W, Z, and g. Their mass and confined existence is a problem. We hope to be able to discuss this in a follow-up issue.
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【1】"How does light know its speed and maintain that speed?”;
【2】"How do light and particles know that they are choosing the shortest path?”
【3】"light is always propagated with a definite velocity c which is independent of the state of motion of the emitting body.";
【4】“Are annihilation and pair production mutually inverse processes?”； https://www.researchgate.net/post/NO8_Are_annihilation_and_pair_production_mutually_inverse_processes;
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Reference:
 Bohr, N. (1913). "On the constitution of atoms and molecules." The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science 26(151): 1-25.
 Schrödinger, E. (1952). "Are there quantum jumps? Part I." The British Journal for the Philosophy of science 3.10 (1952): 109-123.
 Gearhart, C. A. (2002). "Planck, the Quantum, and the Historians." Physics in perspective 4(2): 170-215.
 Jain, P. and L. Sharma (1998). "The Physics of blackbody radiation: A review." Journal of Applied Science in Southern Africa 4: 80-101. 【GR@Pushpendra K. Jain】
 Arons, A. B. and M. Peppard (1965). "Einstein's Proposal of the Photon Concept—a Translation of the Annalen der Physik Paper of 1905." American Journal of Physics 33(5): 367-374.
 PROGRAM, P. "PLANCK PROGRAM."
 韧致辐射；
 Neutrino detection by Cherenkov radiation：" Super-Kamiokande(超级神冈)." from https://www-sk.icrr.u-tokyo.ac.jp/en/sk/about/. 江门中微子实验 "The Jiangmen Underground Neutrino Observatory (JUNO)." from http://juno.ihep.cas.cn/.
 Li, B. A. and C. N. Yang (1989). "CY Chao, Pair creation and Pair Annihilation." International Journal of Modern Physics A 4(17): 4325-4335.
 Schmitz, W. (2019). Particles, Fields and Forces, Springer.
 Compton, A. H. (1923). "The Spectrum of Scattered X-Rays." Physical Review 22(5): 409-413.
 Manoukian, E. B. (2020). Transition Amplitudes and the Meaning of Virtual Particles. 100 Years of Fundamental Theoretical Physics in the Palm of Your Hand: Integrated Technical Treatment. E. B. Manoukian. Cham, Springer International Publishing: 169-175.
 Jaeger, G. (2021). "Exchange Forces in Particle Physics." Foundations of Physics 51(1): 13.
 Are virtual particles really constantly popping in and out of existence? Or are they merely a mathematical bookkeeping device for quantum mechanics? - Scientific American.
There are few things wrong with this question.
One) light is a three dimensional phenomenon in nature that cannot describe by one dimension equation.
Two) science perception of light is unknown due to origination of light testing in past to now.
three) light in science is not natural light that we observe from suns, All light that we think is light, it is artificial light or flashlight, not the natural light that it does not have constant speed, because natural sunlight with massive frequencies and wavelength cannot have constant speed. Thus, science is wrong with light and sunlight.
Am i right? thanks.
Question
Two similar charges repulse one another. if the charges are separated by 'sheet' of parallel moving photons, (the velocity of photon is normal to straight line connecting two charges, and polarization of electric field is normal to both photon motion and similar-change joining straingth line. Thus, the moving away or coming together of those similar charges are not at all effected by photons, if only velocity component of the charges facing one another is concerned. Clearly, magnetic field of photons would be parallel to straight line joining these two charges, but this would not also affect aforementioned velocity components of the charge). So, semi-classically, the moving away of the charged particles, that is their repulsion, would not be affected. also assume the media is vacuum, so no polarization of material media is occuring. Of course, all the photons are required to be palne-polarized and collimeted.
However, accroding to QFT, charged particles exchange photon (virtual?) that is manifested as attraction-repulsion between them. These exchaning photons are surely to collide with real photon stream, get deflected, and hence would no longer be captured by other charged particle. Thus the net force between the two charged particles would no longer be same.
Now my question is, is there any experiment to verify this claim of QED? Or real and virtual particles of same kind would not interact at all? Or the same charge is effective force is also explainable from lorentz force as the charged particles oscillate noremal to their connecting straight line due to electric field, and then magnetic field acts to retard?
(THIS IS A THOUGHT EXPERIMENT, so whether this situation is generatable by present technological means is immaterial. What matters is whether the setup is allowed by laws of Physics on Not. Parallel photon shower can be generated by allowing collimited photons (e.g. by Lens and Laser) to have a light-spot cross-section of a very narrow rectangle or very long slit )
Mainstream physics theories are all wrong or not understood, so reading textbooks is not the way to understand physics. The right way is to think, using logic and try to avoid received ideas, of which your textbooks are filled.
Asking questions is the right way to advance, together with logical conclusions.
JES
Question
Dear Sirs,
I did not find an answer to this question in Internet for both quasi-relativistic and relativistic case. I would be grateful if you give any article references.
As I think the answer may be yes due to the following simplest consideration. Suppose for simplicity we have a quasi relativistic particle, say electron or even W boson - carrier of weak interaction. Let us suppose we can approximately describe the particle state by Schrodinger equation for sufficiently low velocity of particle comparing to light velocity. A virtual particle has the following properties. An energy and momentum of virtual particle do not satisfy the well known relativistic energy-momentum relation E^2=m^2*c^4+p^2*c^2. It may be explained by that an energy and a momentum of the virtual particle can change their values according to the uncertainty relation for momentum and position and to the uncertainty relation for energy and time. Moreover because of the fact that the virtual particle energy value is limited by the uncertainty relation we can not observe the virtual particle in the experiment (experimental error will be more or equal to the virtual particle energy).
In the Everett's multi-worlds interpretation a wave function is not a probability, it is a real field existing at any time instant. Therefore wave function of wave packet of W boson really exists in the Universe. So real quasi relativistic W boson can be simultaneously located in many different space points, has simultaneously many different momentum and energy values. One sees that a difference between real W boson and virtual W boson is absent.
Is the above oversimplified consideration correct? Is it possible to make any conclusion for ultra relativistic virtual particle? I would be grateful to hear your advises.
A virtual particle is a particle, whose energy-momentum relation doesn’t correspond to that of a real particle.
Question
Using -e^2/(Re-Rp) potential in Shrodinger equation for hydrogen atom means that proton and electron are point particles. Why do we think, that on atomic size they are point-like? Just guess, that give exact spectrum?
Hi Preston,
I don't want to discuss your work, and let me to note, that my question is about Schrödinger equation, known don't account spin. As about relativity, it's good example when equation shows it's limits. Take Coulomb classical potential V(r)=-Z*e^2/r. (Z - nuclei charge). It can be shown, that for Z>137 Schrödinger equation has no solutions for psi(r). Physical reason is that we came to relativistic case. So now we need to use Dirac equations with V(r). Solution shows, that in this case Z-critical is more then 137. There are speculations, that here we need take into account quantum properties of nuclei and V(r) must include quantum corrections (visible as nuclei structure). I hope I described my question idea.
Question
I hope there is someone out there with a solid grasp of renormalization in quantum electrodynamics that can answer this question. It bothers me that the integrals that arise from loop Feynman diagrams involve a limit of infinite energy of virtual particles. But, according to the uncertainty principle a particle with infinite energy has a zero lifetime. It appears this consideration is not taken into account in these integrals. The position 4-vector integrals in the S matrix terms, evaluated before the 4-momentum integrals, are taken over all space and time. So how can the 4-momentum integrals take the uncertainty principle into account?
Francis,
Preston is correct. You are asking a question of mathematicians, that can only really be answered by engineers and practical people.
I have to deal with this routinely. Each group has only a partial model of any phenomena. The representations where "infinite" integrals occur, can better be simulated, allowing noise levels to determine when to truncate the summations. It is a practical solution because the mathematics just says "keep going forever". But the real world has limits. If you are trying to model something in the solar system and your equipment only capable of detecting femtometer per second squared fluctuations in the gravitational fields at 16 bits and 1 megasample per second, you can mostly ignore the rest of the universe and just keep watch on rare events or known sources.
I have to read everything on the Internet. To keep all the scientific, technical, financial, organizational, social, mathematical and other language separate and organized, I put on different hats. You are looking at the problem as a mathematician. What you need to do is look at it from an engineering standpoint. Ask yourself, "What can be measured that would allow me to calibrate my model against data from the real world?" And then ask, "Who is doing that kind of measurement, what tools do they use, what software and algorithms have they found that allow them to actually build things?" I do this every day, 12-18 hours a day. It is extremely hard to force myself to spend another few weeks learning this language, or another few weeks learning that language.
Also, if you would clarify your goals and tell people what you want to do, rather than asking about things that people have argued endlessly. This "infinite energy" has been argued much longer than when I first heard it more than 50 years ago. Frankly I am tired of hearing it.
I will say that I had to deal with this recently as I was trying for the hundredth time to set a workable mass for the graviton. You have to understand that such things serve a very human purpose to give a means of visualizing and remembering how to quickly calculate the correct scale and energies and othe properties. I would like to be able to simulate and display a model of the vacuum at Planck scale, but we simply do not have computers for that yet. We can, as a human species, handle something that is down in the picometer range, or rarely in the femtometer range. But then you are not modeling kilograms, but picograms.
If you would pick a problem in the real world, and not something in mathematics that has no basis in the world, I can tell you all the people in the world who are working on it, what they have found, and my best guess as to where it can be applied to help the human race. If you want to spend all your time on paper mathematics, I just cannot afford the time. I have gotten to the point where I am converting all the mathematical papers to symbolic math in the computer, and then "solving" mathematical papers that way. The paper notations have gotten so bizarre and arcane, it hurts my head to jump from even five or ten papers in one tiny area. But most papers can be transcribed to their equivalent computer representations and at least managed, audited and verified. It takes a human to check, but even that can be farmed out by having large groups of partially qualified people check something independently and then piece the results together. A variation on the "shot gun" method used for DNA.
I like the questions you ask. But if you are going to pick ones that people only talk about, and never actually do any work or create new things, or best help all the people in the world quit having to deal with sickness, hunger, pain, endless years of learning for simple things. Then I would be much happier to try to help.
I have layers of resolution that I have found by spending the time to learn what everyone is doing. It is not perfect, I can only estimate the sizes and importance of all the memes involved. But for everyday gravity a pico meter is fine and energies less than what we can easily produce with lasers and electronic devices. For gravitational imaging and low frequency electromagnetic imaging and communication, femtometers. For vacuum processes where matter is formed, attometers.
When I visualize all these things, I have to use human displays, even in my mind. So I visualize gravitons or particles or small glints and reflections of a light at every scale. That is because that is all I know. If I use dots, they are really particles with reflective and refractive properties - regardless of the scale. The real things might not work that way, but when I, a human, have to think about it, I use a display that any human can see.
So if you are asking "Why does it hurt when I keep banging my head on the wall?" I would suggest you stop, and find something better to do.
Have you done anything to help train a new generation to deal effectively with a simple global epidemic? What about helping the terribly young and inexperienced engineers trying to build spaceships how to model the devices and vehicles they are building, but do not really understand. More remind them that they need to take time to learn the fundamentals, besides meet a production schedule.
I like you. You are trying to ask the right questions. You are not giving up. But please pick ANY real world problem and try that. I think you have some fundamental questions to ask. But they are not how many Planck units can dance on the head of an axion, and should I continue my calculation for a billion terms or a trillion trillion terms? A wise person knows when to stop repeating things that don't work. There are priorities in the world and for the human species. If you simple ask "what is the required precision" and then truncate accordingly, you will not have to deal with infinite loops. It will always converge or termination. Every constrained optimization program or algorithm on the planet has practical ways to know when to stop.
Not sure if this helps. I want you to succeed and achieve your goals. Until you tell people what those are, they cannot work with you and help.
Richard Collins, Director, The Internet Foundation
Question
Earth has a North Pole and a South Pole. Is this a paradigm or a model that we need to understand before we can begin to understand the structural (or some other) design of the universe? If so, point to one other example of polarity. If not, why not?
Dear Brian:
I am writing to you because I have just stumbled upon your discussion in the video from which I have lifted and commented upon, as follows:
- - - "Hidden Dimensions: Exploring Hyperspace" 15 January 2015, World Science Festival
Brian Greene, Physicist, Columbia University
This is file 20180521 What string theory says about possible vibrations .txt
At this place in the video: https://youtu.be/h9MS9i-CdfY?t=3339
Brian Greene (Columbia University Physicist) says:
"The extra-dimensional shape dictates the possible vibrational patterns ... the possible notes, if you will, that the strings can play ... "
Me: The extra dimensions are the overtone series permitted by all the other kinds of matter in the systems under test, which includes their resonant frequencies at various volumes and shapes. This is what I call "Symphonic Resonance" and insight is given in my results for fragment resonances at particular Wavelengths and Temperatures, under constraints of L% and E% counts (where E% maps the m of E=mc^2). One might think of this as bulk Huygenian Entrainment. It all relates to all the overtone series that lock in at different Wavelengths and Temperatures throughout C.P. Saylor's 1935 concept of the "Zone of Match", which might better be thought of as the "Regions of Symphonic Resonances".
WNYC Journalist John Hockenberry Gets it! "So describing this sort of interactivity, if you're going back to the French Horn Model, by simply looking at what is coming out of the bell, you're going to get one small picture, but you have to understand that there is music and interaction that is directly corresponding to the piece that you're hearing in the concert hall, taking place at every point in the French Horn itself." [And at every point in the Concert Hall! --SL, 21 May 2018]
I have tried but already failed several times to publish my work, which is again under peer review for what I hope will be soon publication.
Thank you for your interesting questions, Nancy! I hope this helps. :-)
In the spirit of the Holiday Season, I am attaching a piece of art that derives from some graphical play with my data.
-Steve-
Question
Hi guys, Maybe someone can tell me about the current state of interpreting sonoluminescence as dynamical Casimir effect? Recently I came across two older theoretical papers from the 90s on this topic. One paper (actually as series) is from Julian Schwinger with the title "Casimir light", the other paper is from Claudia Eberlein "Sonoluminescence as Quantum Vacuum Radiation".
If I understand correctly, these papers say that the rapidly changing bubble wall converts virtual photons, which constitute the field of the cavity as quantum electrodynamic vacuum, into the real ones. However, it is shown that there is significant deviation between the theoretical expectation and experimental observation.
So, are there any new experiments or new theoretical calculations after the 90s on this topic? Thanks a looooot!
There's this unfortunate tendency to stick the words Casimir effect'' everywhere.
Sonoluminescence is the emission of electromagnetic waves by sound waves-it's a classical effect and doesn't depend on the ability to resolve either the photons or the phonons, whose superpositions the corresponding waves are.
The Casimir effect regards the fluctuations of the intensity of some field about its average value in the vacuum, in the presence of boundaries. This doesn't have anything to do with sonoluminescence beyond pertaining to the shot noise of the photons and/or the phonons involved in sonoluminescence, when these can be resolved, in the presence of boundaries.
Question
Let's assume that states |1> and |2> are degenerate states and the system is prepared in state |1>. Also, the matrix element of electric dipole moment is not zero between these two states (<1|mu|2>=!0). If we interact this system with vacuum field, does this system remain in its initial state? (I know from Wigner Weisskopf theory that if these two levels were not degenerate and level |1> was the excited state, the system would decay with Einstein rate.)
Hi Omid,
The spontaneous emission rate from an excited state |1> to a ground state |2> is proportional to |<1|mu|2> |^2 and w^3, where <1|mu|2> is the matrix dipole moment and w=w1-w2 is the atomic transition frequency (see Ficek, Quantum interference and coherence). It is clear that if both the states are degenerate, then w=0 since they have the same energy. Therefore, spontaneous emission does not take place between degenerate states.
When an atom decays from an excited state to a ground state, it emits a photon with frequency equal to the transition frequency. It does not make sense physically for spontaneous emission to take place between degenerate states. Please check your problem thoroughly.
Question
It is known that high energy gamma photons can decay into electron-positron pairs in a strong background field via the multi-photon Breit-Wheeler process. This real photon is first emitted by an energetic electron, therefore this is a two-step process. There exist also one-step process, where the intermediate photon is virtual, thus one electron can directly create the pair in a strong laser field. For the trident production rate I found formulas in the literature, which is implemented in EPOCH for instance, but in the code the energy of newly created particles is zero. In the case of two-step process it is clear that the total energy of pair is equal to the photon energy, but I could not find any clear expression for this initial energy in the case of trident. I think it is assumed that their initial momentum is relatively small and their recoil effect is negligible, that's why it is approximated by zero in order to reduce the computation in PIC codes. However, I could not find any paper supporting this statement. Can someone help me in this ?
Thank you for your answer! I agree, the energy of pair should be equal to the photon energy, but in the trident process the photon is virtual and it is not clear to me what is the energy of that virtual photon...
Question
The recoil force of radiation is known for spontaneous emission (for the radiation of an accelerating charge or dipole), when the photon field is empty. Is there any difference when stimulated emission is considered? Would it be enough to add an external force to the original radiative reaction-force without changing the original form of the radiative reaction?
more precisely:
" The net change regarding momentum and energy exchange with EM field
is identical to SPONTANEOUS emission, isn't it?"
Question
I'm trying to learn more about the Purcell effect and specifically how it relates to surface enhanced raman scattering (SERS).
The Purcell effect, or 'modified spontaneous emission' occurs when 'a dipolar atomic transition couples to the vacuum state of the electromagnetic field' (Le Ru and Etchegoin arXiv 2005).
This transition becomes more likely when the local electric field is made stronger, for instance due to the excitation of a surface plasmon.
I believe that the strength of the coupling between the atomic transition and the electromagnetic field depends on the strength of the local electric field. However, I don't have enough background in quantum electrodynamics to really understand why this is.
Why does the local electric field magnitude affect the emission rate (and emitted power) of an emitter?
Maybe it's due to the fact that orbitals of emitter atoms are more ionized-type when charge density increased but the atomic structure haven't been changed to the direction of neutrality enough without emission stimulations...
Question
How can I obtain the DM DM -> SM SM annihilation cross section if the DM effective operator is given? It would be really helpful if someone can show me the detail derivation.
An effective operator is obtained when the effective interaction is sandwiched between initial and final states.
To obtain scattering cross section one has to write two currents of the form Ψ̅ γμ Ψ , one from visible sector and one from dark sector, and insert a term for propagator. Then multiply with suitable interaction strengths to obtain the matrix element M, for the interaction. |M|2 is obtained as M*M. Now depending on the experiment one also sums over final spin states and average over initial spin states. Next step is to integrate spin averaged |M|2 over final state phase space. At this stage you will obtain a differential scattering cross section.
Question
There is formula relating power radiated and acceleration of charged particle. But i want to know the amount of energy is carried by the photon at a particular time by given acceleration by using relativistic quantum electrodynamics.
Quantum electrodynamics, with the "dynamics of electrons" replaced by an appropriate classical current mimicking quantum scattering of charged particles, can usefully model the soft radiation (bremsstrahlung) from such processes. This leads to results in agreement with the usual (infinite order) QED perturbation treatment of bremsstrahlung, but such a treatment in addition provides a natural and reasonable photon energy cutoff. The quantum description only involve scattering parameters of the charged particles (incoming and outgoing 4-momenta), not the intermediate dynamics. But classically the scattering parameters are sufficient to uniquely define the full dynamics --- at least for simple systems.
Question
I saw in a paper that the current in a metal is sigma (conductivity=e*mu*n) multiplied by dk/dx where k is the electrochemical energy (or fermi energy).
It seems to me that it is some kind of a generalized ohm's law (j=sigma*E) where the electric field is 1/e*dk/dx.
My questions are these:
# Is it truely a generalized ohm's law or is it comes from other more fundamental law?
# Is this law valid for semiconductors and/or outside equilibrium (steady state, external applied voltage)?
# I couldn't find anything on this equation and I'll be grateful if someone could direct me to some books referring this equation.
This is actually a very interesting question and has analogs in kinetic theory and statistical physics. I would look at the wikipedia page on the Einstein relation: https://en.wikipedia.org/wiki/Einstein_relation_(kinetic_theory)
The proof does a good job of explaining what is going on.
Essentially, to summarize: there is a detailed balance between drift and diffusion currents under equilibrium. Under non-equilibrium steady state, this can be used to derive how the current is related to potential gradients.
The more fundamental version of this is called the fluctuation dissipation theorem.
Question
As generally stated that quantum mechanics is the wider theory and it contains classical theory as a special case. We can get classical results from its quantum counter part in the limit of planck constant tends to zero. Can we get classical maxwell electrodynamics as a similar limiting case from quantum electrodynamics?.
Dear Rahul,
"Is there anyway to describe classical light-matter interaction purely as field-field interaction (theoretically). Becoz particle picture itself is problematic. Here I am referring to particle as localised object with definite momentum."
You raise a very good point here.
You do have an obvious fields vs localized EM particle interaction with the Lorentz equation F= q(E + v x B).
This equation allows establishing a precise trajectory for a single localized electron in straight line when the density of both ambient fields are equal, or on a curved trajectory if the B field is more intense than the ambient E field.
This is often given as an example in intro textbooks to explain the triple orthogonal electromagnetic relation between both fields with respect to the direction of motion of a charge.
Considering that the electron is an electromagnetic particle, it must by definition also have internal electric and magnetic fields corresponding to its mass, and that it would be these internal fields that interact with the ambient fields that can be calculated with the Lorentz equation.
Question
Just read "Inflation and the Measurement Problem". If I understand correctly, they proposed a model with interaction between Fourier modes. By tuning parameter one will obtain Harrison-Zel’dovich scale-invariant
power-spectrum as well as Gaussian Random field. What I don't understand is that I think it still need measurement to form a classical field configuration. Did I misunderstand it?
Question
In an exercise* I have to verfy that if qmu is the momentum carried by a gauge boson in QED vertex with an incoming particle and an outgoing particle both being on-shell, then q2 < 0.
*Palash B. Pal
The reason is that, beyond tree level, the global conservation laws aren't sufficient and there are integrations involved-which means that  the amplitude can't depend on q itself, anyway,  but on two of the three invariants, s, t and u. These, though, are functions of the external momenta only so the channel, still, matters. The singularities are related but not identical. And that can lead to confusion, that ought to be avoided, by stating all assumptions. No need to play games.
Question
For a Vector Boson DM, I have the following spin-independent direct detection (scattering) cross-section with nucleus (please see the attahced file), where n_n and n_p are the number of nucleons inside the nucleus and f_p, f_n are the effective nucleon-DM coupling, M_T is the mass of target nucleus and M is the DM mass.  How do I convert it to per nucleon cross-section, what will be the final expression? Thank you.
Dear Basabendu,
The answers you are seeking on DM-Nucleon scattering cross sections have been exhaustively discussed in Appendix B of arXiv:1404.0022  for tree-level scatterings in the s-channel and t-channel.. The cross sections have been derived for different types of DM candidates: real scalar, complex scalar, Majorana fermion, Dirac fermion, and Vector type DM etc. Also different cases of mediators  (like the Higgs scalar having spin zero in your formula } have been considered exhaustively. I presume your formula is a limiting case of generalised formulas given there . Also other simpliflified formulas in limiting cases are given.
All the best
Mina Ketan
Question
When electrons stabilize on atoms' orbitals, unreleasable adiabatic energy is induced in excess of the invariant energy corresponding to their rest mass. For example, an unreleasable amount of 27.2 eV is induced at the hydrogen atom rest orbital in excess of the energy corresponding to the rest mass of the electron, which is an energy not necessarily associated to a velocity, meaning that no momentum may be involved if the electron finds itself translationally immobilized, even if this energy in excess of the rest mass energy remains induced.
I did some research and found this ref. by James Montaldi 2014 (First ref. below).
In the Montaldi paper, the following topics are addressed:
Section 3.1 Zero momentum, non-zero velocity.
Section 3.2 Zero momentum, zero velocity.
Section Zero momentum, zero velocity was the one that should have covered the case, except that it assumes that ξ=0, which, unless I do not understand correctly, does not cover the case of the adiabatic energy induced in orbitals EM equilibrium states.
This makes me observe that the Hamiltonian as formulated, seems to deal only with translational momentum, and doesn't seem to be able to represent zero momentum zero velocity with energy>0, or am I missing something?
I would like input on how this case is being addressed from the electromagnetism perspective.
Adiabatic energy induction is analyzed in the second ref.
ok.
Question
Scattering of light by matter has been studied extensively in the past. Yet, the most fundamental process, the scattering of a single photon by a single atom, is largely unexplored. One prominent prediction of quantum optics is the deterministic absorption of a travelling photon by a single atom, provided the photon waveform matches spatially and temporally the time-reversed version of a spontaneously emitted photon.
Here we experimentally address this prediction and investigate the influence of the photon’s temporal profile on the scattering dynamics using a single trapped atom and heralded single photons. We don't often think of photons as being spread out in time and space and thus having a shape, but the ones in this experiment were some four meters long. Christian Kurtsiefer, Principal Investigator at CQT, and his team have learned to shape these photons with extreme precision.
According to the quantum mechanics that photon is an unstructured particle. How the concept of unstructured photon is able to describe the different shapes and four meter long of photon?
In addition to four meters long and shapes of photons, how two opposites’ charged particles such as electron and positron absorb and emit neutral and unstructured photons?
However, in CPH theory photons are combination of positive and negative virtual photons. Photon is a very weak electric dipole that is consistent with the experience and these articles are asserted. In addition, this property of photon (very weak electric dipole) can describe the absorption and emission energy by charged particles.
@ Herb Spencer
Dear sir, you are applying unacceptable method of convincing your audience in what is the truth. Simultaneously, not referring to the explicitely expressed objections, without respect to anyone to be free in understanding the world as it is seen by the observer. For instance: writing "Just keep your head stuck up the wrong paradigm" you are stating as it were certain that some paradigm (which one exactly - no word about this) is wrong. NO FURTHER DISCUSSION IN THIS WAY, PLEEEEASE!
Question
Update Oct 18: Attached is now a description enhanced by equations and graphs.
The attached text (about 1.3 pages) describes a paradox which seems to have no solution in classical physics. Two solutions in the framework of quantum mechanics are outlined.
Do you think a classical solution is possible? If so, could you please provide a sketch of your solution? If not, what do you think about the suggested QM solutions, and do you know of a better (resp. the true) solution? And finally, this might be a well known paradox; if so, could you please point me to relevant literature?
Hi Halim,
I'm looking forward to the results of this exercise! Please keep me updated. About the DC component in the radiation: Obviously, there can be no radiation with "global" DC but a crucial point of this thought experiment is that there is at most one unipolar pulse in the space between radiating antenna and absorber (distance less than lambda/2); so the radiation has kind of a temporary "local" DC component. (Of course, in this short distance the fields are a mix of radiation and reactive fields.)
The equation for the magnetic field HM is based on Maxwell's equation for curl H, and the rotational symmetry of M. Of course, it could be exactly true near M only if M were a homogeneous cylindrical sheet of current. A ring of discrete current lines would cause a different HM in the immediate neighborhood of the lines, inside M as well as outside.
Best regards
Question
I am putting this separately outlining the key aspects of it.
Radiation by an excited atom is a well established quantum phenomenon. Typically, additional energy could be supplied by multiple means such as lasers etc. Electrons jump to the higher excited states which are often unstable and so, electrons decay back to the previous configuration by emitting the excess energy as radiation.
Now consider what most books put it bluntly regarding electrodynamics of charges in motion: "An accelerated charge radiates like a dipole." My queries are:
1) Let a charged atom be in accelerated motion. Then one can account for development of fields from the notion of retarded and Lienard-Wiechert potential. However, how does this motion triggers the necessary electronic excitation required for radiation? Or, is it that radiation mechanism from an accelerated charge is not related to the electronic excitation at all?
2) Let there be an isolated charge (electrons, protons) in accelerated motion in empty space. The acceleration could be due to some initial kick (accelerator system) OR could be due to following a trajectory in curved space-time arising as a result of some gravitational potential. If the particle radiates, then by mass-energy equivalence they lose energy and finally fade out in space? True?
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.
Question
It is known that Yang-Mills theory is part of classical field theory. Therefore it seems possible to write down SU(2) electrodynamics. What do you think? Your comments are welcome.
See our new paper: Exploration of a SU(2) Electrodynamics Based on Lehnert’s Revised Quantum Electrodynamics.
The Lagrangian of Yang-Mills is definitely not the Lagrangian of electrodynamics along with some non-linear terms-that statement is, simply, wrong. It's pointless to make such wrong statements, when the correct statements are easily available, in any textbook on quantum field theory.
The equations of motion, obtained by varying the Yang-Mills action, are non-linear PDEs and describe classical vacuum configurations of the quantum theory, as is, always, the case.
If the gauge group is SU(2) then the algebra is that of quaternions-if not, it's not.
So far for the mathematics. Regarding the physics, once more, electromagnetism is a U(1) gauge theory and is unified with the weak interactions in a SU(2)_L x U(1)Y gauge theory, that's broken to U(1)em by the Brout-Englert-Higgs mechanism in a way that's described in all courses on the subject. The two U(1) groups have totally different meaning.
Gauss' law in electrodynamics is a constraint, since it doesn't contain time derivatives. There's a similar constraint among the equations of motion in any Yang-Mills theory and that constraint carries the same name-but it doesn't have anything to do with electromagnetism.
While Boozer uses the *words* color electrodynamics'', what he *means* is a gauge theory with a group other than U(1). It's misleading terminology, tthat's all. He's solving the classical equations of motion for Yang-Mills fields coupled to corresponding charges.
Question
Many mysteries and set of behaviors are based on particle and wave functions of energy. Here are few questions which might get raised for more deep down understanding and future applications of natural phenomenon in favor of man controlled technology.
0.        Energy adopted wave and particle function in one go, or its inborn or its result of evolution and what will happen if any of both get seize or get some other basic behavioral function? anyhow what any-other behavioral function can be?
01     Is there any transitional, intermediate (stable) sage between particle & wave function?
1.       What is wave function and Mass function for energy?
2.       What are the specific set of (structural & functional parameters / properties of) wave behavior and particle behavior?
3.       Do mass and particle is the same entity?
4.       Do wave and field are the same entity?
5.       Is there any particle without wave function?
6.       Can particle survive without wave fields etc?
7.       Any particle can have permanency as particle all the time?
8.       If yes then how and if NO then why?
9.       Any set of conditions in which any particle can exists in “spore formation” and shred some of its basic behaviors but still sustain as particle?
10.   Any wave/field which could have permanency as wave/field all the time?
11.   Any set of conditions in which Wave can act like a particle without transforming into particle structure?
These questions are initially for basic elementary particle, subatomic particles specifically for Electron and Photon…("Do all particles have wave function like photons ?")…. But any brainstorming is more than welcome for man-made theoretical/particle particles as well.
Thanks
In the regime of quantum mechanics, particles have wave nature as well. See for example the following link:
Question
Recently I wrote a paper discussing possibility to develop Quantum Electrodynamics in Fractal Media and Cantor Sets based on Bo Lehnert's Revised Quantum Electrodynamics. Enclosed is my paper.
I admit that my approach is very rough, but at least I found some interesting things.
This discussion is depressing! I sign out.
Question
(I already solved the problem by setting the keyboard to US English, I explain a message below)
I'm trying to use SpekCalc to simulate a X ray tube, but apprently it's not showing the bremsstrahlung radiation. I´m using a peak energy of 100keV, a theta of 16 degrees, and 5 milimeters of aluminium. But I obtain the same results whatever I have tried. I'm runing release 1.1 light for macOS, and I obtained the same results for windows.
Note: I'm using the values Nf=2 and p=1, instead of those  suggested by Poludniowski because apparently the GUI is not accepting any value minor than 1.0. I have been trying other values with similar results.
I have tried the same steps but did not face the error which you specified (see attached image).
Question
Quantum field theory comes from starting with a theory of fields, and applying the rules of quantum mechanics. A field is simply a mathematical object that is defined by its value at every point in space and time.
Renormalization, that astounding mathematical trick that enabled one to tame divergences in Feynman diagrams, led to the triumph of quantum electrodynamics. Ken Wilson made it physics, by uncovering its deep connection with scale transformations.
According to Relativity, mass and energy are convertible to each other. According to F=-dU/dx, does force (in fact bosons) and energy convert to each other? If so, by which mechanism? If no, why?
Anton @
What kind of medication are you on? The energy budget for particles in a gravity field is high-school curriculum. At least it used to be, last time I checked (after you must have passed all exams).
Question
The Nobel Prize in Physics 1965 was awarded jointly to Sin-Itiro Tomonaga, Julian Schwinger and Richard P. Feynman "for their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles".
QED rests on the idea that charged particles (e.g., electrons and positrons) interact by emitting and absorbing photons, the particles that transmit electromagnetic forces. These photons are “virtual”; that is, they cannot be seen or detected in any way because their existence violates the conservation of energy and momentum.
In quantum electrodynamics (QED) a charged particle emits exchange force particles continuously. This process has no effect on the properties of a charged particle such as its mass and charge. How is it describable?
Hossein,
Why is it that people vote down the question?  It must be that they do not understand its importance.  If we knew all there was to know about the sub-atomic then this would be a meaningless question, however we know only what "Theory" tells us and that is obviously wrong.
There needs to be a new model to the atom and we have known this ever sense Niels Bohr proposed the current model more than 100 years ago.
Even at the time Bohr knew that this was only a way to look at the atom and not the answer, yet we look at it at the truth.
The question puts into question our reasoning behind theory that has no bases in reality.  If there is objection to this line of questioning then logic has no place in science.
Where are the researchers that understand logic?
Question
A single photon state can be generated by pulsed excitation from an optical transition between two energy levels in a single quantum system such as QD. I am trying to find a way of generating indistinguishable photon pairs from say two or more sources using QFC. Any one with an idea on this can give some advice.
Thank you all
Question
By the 1950s, when Yang–Mills theory, also known as non-abelian gauge
theory, was discovered, it was already known that Quantum Electrodynamics (QED) gives an extremely accurate account of electromagnetic fields and forces. So it was natural to inquire whether non-abelian gauge theory described other forces in nature, notably the weak force and the strong or nuclear force. The massless nature of classical Yang–Mills waves was a
serious obstacle to applying Yang–Mills theory to the other forces, for the weak and nuclear forces are short range and many of the particles are massive. Hence these phenomena did not appear to be associated with long-range fields describing massless particles. In the 1960s and 1970s, physicists overcame these obstacles to the physical interpretation of non-abelian gauge theory. In the case of the weak force, this was accomplished by the Glashow–Salam– Weinberg electroweak theory. By elaborating the theory with an additional “Higgs field,” one avoided the massless nature of classical Yang–Mills waves. The solution to the problem of massless Yang–Mills fields for the strong interactions has a completely different nature. That
solution did not come from adding fields to Yang–Mills theory, but by discovering a remarkable property of the quantum Yang–Mills theory itself, called “asymptotic freedom”.Asymptotic freedom, together with other experimental and theoretical discoveries made in the 1960s and 1970s involving the symmetries and high-energy behaviour of the strong
interactions, made it possible to describe the nuclear force by a non-abelian gauge theory in which the gauge group is G = SU(3). The non-abelian gauge theory of the strong force is called Quantum Chromodynamics (QCD). But classical non-abelian gauge theory is very different from the observed world of strong interactions; for QCD to describe the strong force successfully, it must have at the quantum level the mass-gap and related color confinement
properties. Both experiment—since QCD has numerous successes in confrontation with experiment—and computer simulations carried out since the late 1970s, have given strong encouragement that QCD does have the properties of mass-gap and color confinement cited above. But they are not fully understood theoretically. In the attached link, http://dx.doi.org/10.13140/RG.2.1.1637.3205 the theoretical understanding of mass-gap and related color confinement property have been provided during mathematical calculation of the gluon emission cross section for QCD process by taking over the corresponding results from closely related aforesaid QED process under the assumption that color interactions in perturbative sector are “a copy of electromagnetic interactions.
As such, the direct mathematical calculation for QCD process has been
avoided because the presence of point-like Dirac particles inside hadrons through Bjorken scaling and the carriage of a substantial portion of proton’s momentum by neutral partons, as revealed by the ‘asymptotic freedom’ based analysis of the data on deep inelastic scattering of leptons by nucleons, do not constitute direct evidence that the aforesaid Dirac particles and neutral partons can be identified with quarks and gluons respectively for making QCD the correct physical theory.
Gluons don't become massive in the infrared limit-that statement is incorrect.  Nor is the statement about the gluon jet losing kinetic energy correct, either. The references to the two slit experiment aren't relevant.  It's useful to consult textbooks or lectures on the subject, that's now background knowledge, e.g.
The statement the emitted gluon at finite energy becomes a spatial coordinate singularity'' is meaningless and the statement that the gluon propagator doesn't have a spectrum beyond the first Gribov horizon is meaningless, also. What the Gribov ambiguity means is, simply, that it's not possible to fix the gauge uniquely, one must use coordinate patches in field space. Cf. http://projecteuclid.org/euclid.cmp/1103904019
However, when performing a tree-level computation one isn't sensitive to the Gribov ambiguity, since one is working in the coordinate patch  about the identity in field space, anyway.
Finally, the quoted text doesn't have anything to do with any comparison between a tree-level calculation and a higher loop calculation, so is completely irrelevant to the issue. It certainly doesn't produce either a mass gap or an example of color confinement. Cf. http://arxiv.org/abs/1008.1936 for how gluon jets are studied.
Question
1. When antiparticles annihilate, all the energy from matter, EM, strong, weak and Higgs fields bound to the particles converts to a pair of photons, involving only EM energy.  Across the moment of conversion, the gravitational field is unchanged.  (It may of course be changing beforehand or afterward as a result of the motion of the particles or photons and the changing quadrupole moment)
2. When a photon decays (in the presence of a suitable momentum absorber) into a particle-antiparticle pair, the reverse happens.  Again, there is no immediate change in the gravitational field.
In the case of a binary star system radiating gravitational waves, does the mass of the binary system decrease?  Or does it just exchange potential for kinetic energy as the stars revolve faster in their reduced orbit?
If the former, is the process reversible, can gravitational waves carry energy which then converts to kinetic, EM, matter (rest), strong, weak or Higgs energy?
Robert,
Yes the total system mass reduces as the gravitation waves carry energy out of the system. Surprisingly a lot of energy in the case of binary pulsars, has they are 1000's MJy sources in GW, but detectors are very inefficient.
Yes it's possible to convert the energy from GW to EM, but the processes are incredibly inefficient. For instance gravitational waves  passing through a very strong magnetic field will generate EM waves via the Li-Baker effect. The gravitational wave group at Birmingham University (UK) were looking into this for GHz GW detectors.
Question
This is not something you can find clearly stated.
If photon is a particle then it should be not applicable, but in the double slit experiment a photon interferes with itself. But if this is the case it must be propagating in all directions but it clearly doesn't.
Maxwell's equations describe the electromagnetic field at the classical level. The full description is quantum electrodynamics. The problem you are referring to is the famous wave-particle duality. The electrodynamic field is a quantum system, for some states, a particle is a better approximation, for some others, waves.
A few photons behave mostly like particles, whereas many photons (coherent states) like waves. The solutions of Maxwell's equations in the one photon case can be used to calculate probabilities of the photon hitting a certain part of the screen after the two slits.
As for propagation in all directions: that is Huygens' principle applied to the wave. But the wave is used to calculate probabilities in this case. For one photon, you cannot tell if it travelled in all directions or just one direction, only that it did hit the screen at a given point. To the amplitudes used to calculate the probability of hitting that point, all possible paths contribute.
Question
In the article "tunnel ionization of complex atoms and of atomic ions in an alternating electromagnetic field" (ADK ionization model) it is written in the introduction section that the conditions hbar*omega<<Ei and  E<<Eatom permit the use of the quasiclassical approximation, where omega and E are the frequency and amplitude of the laser field respectively and Ei & Eatom are the ionization energy and atomic field strength respectively. In the second section it is written that the quasiclassical approximation is valid when the condition n*>>1 is satisfied, where n* is the effective principal quantum number which is defined in the article as  Z/(2Ei)^(1/2) where Z is the ion charge after the ionization process.
My question is how the condition n*>>1 leads to the conditions  hbar*omega<<Ei and  E<<Eatom  and to the quasiclassical approximation?
Question
For example, a water molecule (H2O) in its vapor state has an electric dipole moment of magnitude 6.2*10^-30 C.m.
How much work must an external agent do to rotate this molecule by 180°, starting from its current position, for which theta= 0?
What do you think about the below calculations?
The work done by an external agent (by means of a torque applied to the molecule) is equal to the change in the molecule’s potential energy due to the change in orientation.
Wa= U180 - U0
=(-pE cos 180) - (-pE cos 0)
= 2pE = (2)(6.2*10^30 C.m)
= 1.24*10^-29 J
The motion of water molecules in water is an extremely complex phenomenon and some of it still a matter of research... Since hydrogen bridge bonding occurs, hydrogen atoms may even swap the oxygen atom they "belong to".  But if you would formulate a simpler model, where each H2O molecule keeps its identity, then in the liquid , any moton would be against the (thermal) motion of the surrounding. These motions generate what we know macroscopically as viscosity. [it is interesting to study the arguments of the fluctuation-dissipation-theorem in this context]
If I were to do your calculation, then I'd formulate the potential energy of the dipole in a homogeneous field which is just its electrostatic energy and closely related to your equations above. Likewise you can formulate the torque exerced by the field onto the dipole and integrate it iver rotation angle to obtain the same result.
But the motion in an external, homogeneous field (in vacuum) and the motion in the liquid are different beasts altogether: on the one hand by the sheer complexity if you consider the microscopic detail in the liquid, but also clasically, since there is friction in one case while there is none in the other; on top of that, the molecule is not a totally rigid object but has internal degrees of freedom...
Question
I know that if we solve the Maxwell equation, we will end up with the phase velocity of light being related to the permeability and the permittivity of the material. But this is not what I'm interested in - I want to go deeper than that. We know that the real speed of light is actually not changing, the decrease in speed is just apparent. Material is mostly empty, the light will still travel with c  in the spacing. The rare atoms will disturb the light in some way. So I am interested in how the atoms affect the light.
Photon absorption-emission theory
Some textbooks that I read explain it in a way kind of like this:
In a material the photons are absorbed by atom and then re-emitted a short time later, then they travel a short distance to the next atom and get absorbed&emitted again and so on. How quickly the atoms in a material can absorb and re-emit the photon and how dense the atoms decides the apparent speed of light in that material. So the light appears slower because it has a smaller “drift speed”.
Interference theory
But recently I realize an alternative explanation:
Atoms respond to the light by radiating electromagnetic wave. This “new light” interferes with the “old light” in some way that results in delayed light (advanced in phase), this can easily be shown by using simple phasor diagram. Consequently effectively the light covers a smaller phase each second, which gives the impression of a lower phase velocity. However the group velocity is changing in a complicated way.
I think that the first explanation does not explain the change in phase velocity of light. if we consider light travelling into a slab of negative refractive index non-dispersive material, let’s say the light is directed perpendicular to the slab. The phase velocity’s direction will be flipped, but group velocity’s direction in the material will not change. Only the second explanation can explain the flipped phase velocity direction. I guess that the velocity that we get in the first explanation is actually belongs to the group velocity. It makes sense to me that the front most of the photon stream determines the first information that the light delivers.
So the question is What really cause the phase velocity of light to be decreased?
"drift velocity" of photons (they aren't the same photons, they are re-emitted all the time)
phase difference between absorbed and emitted light
something else
And also, I still don't really understand detailed explanation of the absorption-emission process for small light's wavelength (for large lambda compare to the atoms spacing, the photons will be absorbed by the phonons). The dispersion relation that we know is continuous and also some material is non-dispersive, therefore the absorption process must occur in all frequency for a certain range. So definitely it doesn't involve the atomic transition, otherwise it will be quantized. My guess is that the relevant absorption process gets smooth out by the dipole moment. What makes the spectrum continuous?
Dear Hossein,
Probably, it is impossible to answer your question better than it did Richard Feynman in his course of lectures on physics: Richard P. Feynman, Robert B. Leighton, Matthew Sands. The Feynman Lectures on Physics, Addison-Wesley Publishing Company, Inc. Reading, Massachusetts, Palo Alto, London, 1963 (vol. 1, chapter 31-1).
In particular, Feynman writes that " It is approximately true that light or any electrical wave does appear to travel at the speed c/n through a material whose index of refraction is n… Our problem is to understand how the apparently slower velocity comes about”.
Therefore, I advise you to refer to this source:
Best regards, Leonid A. Skvortsov
Question
I am trying to conceptually connect the two formulations of quantum mechanics.
The phase space formulation deals with Wigner quasi-probability distributions on the phase space and the path integral formulation usually deals with a sum-over-paths in the configuration space.
I see how they both lead to non-classical physics but how do they relate? Either conceptually or formally.
The thing that motivates me is the idea that the Lagrangian, via the action, is a map from the tangent bundle of the configuration space to the reals. The Wigner function is a map from the cotangent bundle (phase space) of the configuration space to the reals. To get expectation values out both W(x,p) and eS(x,v) act as weightings in an integral (S=action, W=Wigner function). I would like to get from one to the other without using Hilbert space as an intermediary.
The paths integral leads to classical wave mechanics.  The result is not a transition probability, but a wave intensity that can be identified to a probabilty through born's interpretation.  The action is the phase difference of the wave integrated along a path, and can be thought of as a distance in some space.
Question
Quantum field theory tries to reduce the fields to particles (bosons) which interact with their sources (fermions) transferring energy and momentum, if we restrict to electrodynamics. In the case of the weak or strong nuclear interactions the gluons carry also color or flavour, that we can forget for the moment ,without entering in this question dtirectly, given its complexity.
Considering only electrodynamics then, we know that a magnetic field cannot give energy to a free electron, while the electric does. Could we understand this different physical behaviour using a Feynman diagrams or the concept of photon-electron interaction instead of the field? How could we understand the change of "magnetic photons" by "electric ones" using the Faraday or Ampere's law?
I am always a little amused by adamant statements about what QFT "is."  The topic is so formal and lacking in conceptual underpinnings that where to start of questions like the "mass gap" and so on typically involve only more ad hoc approaches.  No one can doubt the computational successes but even Feynman claimed not to understand it.
There is an old CERN report on this topic I read a long time ago by Jackon. "All known intrinsic magnetic moments (of electron, muon, proton, neutron, nuclei) are shown to be caused, to a very high precision, by circulating electric currents and not by magnetic charges. http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/09/399/9399984.pdf
Question
we know there are different systems to generate squeezing of light. But I want to know:-
1) which one is the best system and how much squeezing we can get at it's maximum and minimum value?
2) What are the different applications of squeezing of light?
There are a number of techniques known for squeezing light. The world record for squeezed light has been achieved using a zero-area Sagnac interferometer, see
Question
as we all know that skyrmion or vortex domain wall is a real-space berry phase，but In ferromagnet/heavy metal bilayers, an in-plane current gives rise to spin-orbit spin transfer torque where spin-orbit coupling has a mometun-space berry phase if we use this current to induce domain wall, what will happen?
dear Behnam Farid
Thank you very much. I'm sorry  about that there have some faults in my question .. I should change the real-space berry phase(momentum space )into topological structure . i'm thinking how the topological structure affect the  adiabat term and non-adiabat term of spin orbit torque 。even  In ferromagnet/heavy metal bilayers，these two topological structure coexist at once。
thank you again
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Everyone who is familiar with classical electrodynamics knows about Lorentz invariant quantities (E2 - B2) and (E*B)
Is there any application for these invariants in physics?
They are used as density Lagrangian for obtaining all the equations of motion of Electrodynamics.
Question
The interaction of photons with matter such as Compton and Thompson scattering are well-known at higher photon energies. What about the scattering events between photons? Those likely occur at higher energies where the photons resemble to be particles? If it is possible, the cross-section may be extremely low.
Yes!! Photon-photon scattering is possible. Indeed high-energy photons increase the probability, but the cross-section is extremely low and so a high photon flux is required. An alternative approach is to use low-energy high-intensity lasers, which modify the vacuum in a nonlinear manner leading to photon-photon scattering. I refer you to this article: Nature Photonics 4, 92 - 94 (2010) / doi:10.1038/nphoton.2009.261, with a nice summary here: Nature Photonics 4, 72 - 74 (2010) / doi:10.1038/nphoton.2009.277 .
Question
There are a number of models to analyze propagation of light in scattering media, including ballistic, diffusion, Kublai-munk, Monte-Carlo etc. The multiple scattering resembles to be dominant in highly scattering media such as biological tissues, dense clouds, ash plume, dense aerosols and dusts even colloidal solutions and suspensions, while to my knowledge there is no perfect theory to describe multiple scattering in random media or turbid media. Can you suggest how to deal with this phenomena?
In addition to the excellent book by Ishimaru, I'd recommend another one:
"Light Propagation through Biological Tissue and Other Diffusive Media: Theory, Solutions, and Software"
Author(s): Fabrizio Martelli; Samuele Del Bianco; Andrea Ismaelli; Giovanni Zaccanti
Published: 2010
DOI: 10.1117/3.824746
eISBN: 9780819481832 | Print ISBN13: 9780819476586
Question
If E-M knots can exist, they emit no light, yet they possess energy, and hence mass.  Their formation process is, I believe, still unknown, hence the possibility of large formation cross sections .  What is the possibility that a large portion of the mass of the universe is tied up in knots?
Once more: the answer to the original question is No, the knots in the electromagnetic field can't account for dark matter. And this statement holds, independently of the possibility that electromagnetic field configurations may be knotted. Electromagnetic fields, furthermore, possess energy but not mass-they have gravitational effects because the metric couples to the energy-momentum tensor in general relativity. However the mass, as defined in general relativity, of photons, the excitations of the electromagnetic field, is zero.  Finally, static configurations of finite energy don't exist in electromagnetism-so it's not true that knots wouldn't emit light, i.e. electromagnetic radiation, either. The only classical,  static, configurations would be Reissner-Nordstrom black holes (which would emit Hawking radiation, as long as their mass exceeded their charge). However black holes can be detected by studying how matter moves in and radiation is emitted from their vicinity.
Question
Can someone explain the procedure by which we can view classic electromagnetism through quantum mechanics? Are we able to look at any field as an ensemble of particles (photons), and how can we develop classic field theory assuming quantum mechanics, such as beamforming .
A somewhat formal answer might run as follows: how did we get QED in the first place? We took coordinates for which the EM field behaved as a set of uncoupled oscillators (modes) and then quantized these oscillators. The fact that we do not, usually, look at the wave function of these infinitely many oscillators, is probably more of a mathematical issue, or maybe even a historical accident. There is no intrinsic difficulty in doing so, at least if you do not give undue weight to the unfortunate fact that there are infinitely many oscillators involved.
Look at it as we may, however, we are essentially dealing with a large number of oscillators. If we then look at appropriate Gaussian packets (coherent states), we know that they follow dynamics determined exactly and uniquely by the corresponding classical dynamics. But the EM oscillators were so constructed, that their classical dynamics corresponds exactly to classical Electromagnetism. In this way, it is clear how, at least, certain states in QED will have a dynamics determined by---and in the limit of large amplitudes, close to---the behaviour determined by classical Electrodynamics.
Can I make a similar statement for all states? No: ever since Schroedinger gave us his cat'', we have known that quantum mechanics contains states which are delocalized in terms of the classical variables, and which thus do not tend to a well defined limit in the semiclassical limit. Decoherence will presumably get rid of this effect when the state comes in contact with an environment, but this is clearly another story.
Question
When we measure the speed of light, we measure a beam or pulse. Are we correct to extrapolate this speed to single photons?  Are we correct to infer that single photons have any definite speed, at all?
In QED, a definite speed is assumed.
My opinion is probably non-standard, so accept as such. IMO there is no such thing as a photon in flight. Quantization only exists at the times of emission and absorption. In between there is only the continuous development of the e/m field as described by Maxwell's equations. People will raise many objections to this and they can all be shown to be wrong.
Question
In cosmology, the rest frame for the cosmic microwave background (CMB) appears to be a preferred frame of reference. For example, galaxies tend to have an average speed of zero relative to their local CMB rest frame. If an observer is traveling at a relativistic speed relative to the local CMB rest frame, the galaxy density would not appear homogeneous in all directions. Also there would be a substantial CMB anisotropy (unequal photon pressure) which opposes motion relative to the local CMB rest frame.
Now, ignoring the anisotropic effects of the CMB, is there any reason to believe that the laws of physics would not be the same in all frames of reference? For example, if a fundamental particle has relativistic kinetic energy exceeding Planck energy (about 2×109 J), then its de Broglie wavelength viewed from the CMB rest frame would be less than Planck length. Is this possible? Is it possible that experiments conducted in such an extreme frame of reference would find noticeable differences in the laws of physics? For example, would QED and QCD operations which depended on virtual particle creation and destruction be affected?
I had a discussion on this general topic with someone not long ago.
The important point, in my view, is to distinguish between the invariance of a theory vs. the invariance of a specific solution.
Take cosmology, for instance. General relativity as a theory is fully diffeomorphism invariant. There is no preferred frame, no preferred coordinate chart. The equations remain the same. Same goes for Maxwell's theory.
However, when you solve those equations, you may introduce initial or boundary conditions that break this symmetry. Specifically, the FLRW solution in cosmology is constructed by assuming spatial isotropy and homogeneity, but no isotropy or homogeneity in the time direction.
So right there, we picked a solution with properties that identify a preferred frame by definition. And if this solution happens to describe the physical universe correctly, then the physical universe has a preferred frame, despite the fact that the underlying theory doesn't.
Personally, I don't find this particularly profound or mysterious. As a much more mundane example, here on the surface of the Earth clearly we have a preferred frame. Even though the laws of classical mechanics are invariant under an arbitrary spatial rotation, clearly its solutions as applied to terrestrial events are not invariant under rotations in anything other than the horizontal plane.
Experiments involving Planck-scale energies may very well produce exotic results, but I don't think this has much to do with the preferred frame of the FLRW metric.
Question
In his paper, Zoltan Imre Szabo argues that he can derive Lamb shift without renormalization. In short, he proposes to use De Broglie geometry to remove infinities in QEd.
So, what do you think?
This subject is, by now, of purely historical interest. The relevant, original,  work is presented in the book Quantum Electrodynamics'' edited by Schwinger, which people interested in the question, are strongly advised to read. Once more, it's not useful to confuse formalism and physics.  Different formalisms can and do describe the same physics, in the sense that they give the same answers for the same quantities and there isn't any experiment that can distinguish them.So which one uses is a matter of taste. However certain features can be easier to understand in one formalism than in another and generalizations may be easier to express in one way rather than another (stressed by Feynman in The character of physical law''). For insight in the physics Feynman's lectures on QED, http://vega.org.uk/video/subseries/8 are also strongly recommended (there's a book, QED: the strange theory of light and matter'', that's the written version). There is a well-defined method for computing the Lamb shift, for seventy years now and what it's called is irrelevant. Szabo's paper is interesting for other issues than the Lamb shift and illustrates, in this regard, another method of calculating the finite result, that's physically relevant. It is a regularization procedure, in the sense that it describes a method for dealing with finite quantities. However there are infinitely many regularization procedures: they all agree on the physical answer and differ by contributions that depend on the details of the procedure. This is well known, of course and was used by Bogoliubov, Parasiuk and Hepp in proving the consistency of perturbative quantum electrodynamics (completed by work of Zimmermann and Lowenstein-cf. Stora's review, http://hal.inria.fr/docs/00/35/49/76/PDF/Contribution_RStora.pdf).
Question
According to QED, the photon is massless. What would the magnetic field prevailing today be that is associated with its mass? Will that magnitude be a proper seed to generate large-scale structure formations of galaxies?
The photon mass is zero because it has been measured to be such, not because QED assumes that. As any experimental result, it is 0 within the accuracy of the measurements. More properly stated it is <10^–18 eV. At this level the answer to both your questions is NO
Question
While the classical, wavelike behavior of light interference and diffraction has been easily observed in undergraduate laboratories for many years, explicit observation of the quantum nature of light i.e., photons is much more difficult. For example, while well-known phenomena such as the photoelectric effect and Compton scattering strongly suggest the existence of photons, they are not definitive proof of their existence.
In particle physics, quantum field theories such as the Standard Model describe nature in terms of fields. Each field has a complementary description as the set of particles of a particular type. A force between two particles can be described either as the action of a force field generated by one particle on the other, or in terms of the exchange of virtual force carrier particles between them. The energy of a wave in a field (for example, electromagnetic waves in the electromagnetic field) is quantized, and the quantum excitation of the field can be interpreted as particles. In quantum electrodynamics (QED) a charged particle emits exchange force particles continuously. This process has no effect on the properties of a charged particle such as its mass and charge. How is it explainable? In theoretically a pure steady state spin current without charge current can induce an electric field. If a charged particle as a generator has an output known as a virtual photon, what will be its input?
Dear Mohame
Thank you very much.
I knew it very years ego. I am looking beyond of this concepts.
Question
What happens to a simple hydrogen atom, i.e. what happens to the energy binding between the electron and the proton, from the point of view of QED, when the hydrogen atom is close to a black hole?
V. Fulcoli,
Hi, I think so, although the dynamic link above does not seem to get to the correct entry - try http://en.wikipedia.org/wiki/Black_hole_firewall if that's not the same page you were linking to (the closing parenthesis is not incorporated in to the link).
Also see http://arxiv.org/abs/1207.3123 (which is I think the most recent research paper on the subject from the original proponents).
Again, much of the original discussion has been staged within the context of the entanglement of virtual particles in Harking radiation and the proposed Information Paradox. IMO, however, these issues are trivial considerations, when the principal issue is the nature of black hole formation, the accretion of external material and - most importantly, the structure of the black hole interior.
Certainly your question goes to the nature of black hole accretion - I can only guess that the binding energies between particles is released - incorporated into the black hole's mass-energy, while residual particles are expelled from the corona/event horizon. In this case, the EM charges of residual particles would be retained within the corona, likely contributing to fields that direct particles to the black hole polar jets. This is, of course speculation on my part...
Question
After investigate the data from five experiments measuring the g-factor of electron and muon, I conclude that the experimental result has a value of approximately 1.000000003 times bigger than SM prediction. Detailed discussion is on section 4.2 of my paper.
Oh man, you're a stubborn one ;-)
Here goes my last (?) attempt to convince you there's no discrepancy...
Let's do it your way: let's take ratios. But let's do it properly and use the error propagation techniques we learned many years ago, as undergrads.
To each ratio r=g_exp/g_theo, let's assign an error er=\sqrt{(er_exp/g_theo)^2+(g_exp*er_theo/g_theo^2)^2}. Take the numbers from the references I gave above and find the r and er for each species and you'll find:
12C5+: rC = 1.0000000031 (22)
16O7+: rO = 1.0000000025 (23)
28Si11+: rSi11 = 0.999999990 (26)
28Si13+: rSi13 = 1.000000000 (1)
Let's give all 4 measurements the same weight, since we have no indication that one should weigh more than the others. And let's propagate errors again properly. Then the average r is:
rav = 0.9999999989 (66).
This is (very) consistent with 1.
Cheers.
Question
For the Feynman path integral interpretation:
R. P. Feynman and A. R. Hibbs, Quantum Mechanics and Path Integrals, (McGraw-Hill, New York,1965)
You can find it here:
I have ONE only question. Given the quote of page 29:
"The phase of the contribution for a given path is the action S for that path in units of the quantum action hbar...The contribution of a path has a phase proportional to the action S:
phi[x(t)]=const exp((i/hbar) S[x(t)]) (2.15)"
*Question: What is the legitimation of such an assumption?
I think it is a great jump without reasoning, neither mathematical (why proportional and especially linear) nor physical.
I agree about the 'not wrong'. My objection is rather of aesthetical nature.
Since the same phenomenon can be explained by a variety of ways, why not to pick up the most elegant one? Let's add the criterion of aesthetical completeness in our analysis...
Question
We know that accelerating charges radiate. What if the charge was static in some reference frame and the observer was the one who accelerates with respect to that frame? Is there any relation to Unruh radiation?
Mozafar,
(1) You are partly correct in saying that the field and the charge are different entities. Well they look like being different, actually they are not. When the charge does radiate, it does not radiate away all of its field and become bare ! Part of Its field remains intact as well. Next, as an aside, even if a photon gets radiated from the accelerated charge, it remains entangled with it all along, and this entanglement is an experimentally observed fact.
(2) You cannot kick the electron without first kicking its surrounding EM field. In fact ,the same QFT as well as CFT tell us that the kicking (interaction with the electron) can occur only through the field. No direct kicking of a bare electron is possible, and there is no bare electron available either.
(3) The above applies to the freely-falling elevator frame also.
Question
New experiments confirm that the radius of the proton is smaller than expected from standard theory: http://www.newscientist.com/article/dn23105-shrinking-proton-puzzle-persists-in-new-measurement.html
Tapio,
your question suggests that QED predicts the radius of the proton. Of course, this is more a matter of QCD with only a minor influence of QED. What is predicted by QED is the connection between Pohl's experimental data and the charge distribution of the Proton.
Apart from this caveling, I have not to contribute an idea how to solve the puzzle. It's not even on my todo list (see Kimmo's contribution).
Question
I'm looking for a formal description of what exactly the "renormalization" problem is. I understand that some problems in physics can be renormalized, while some problems can't, and the renormalization problem has to do with this discrepancy. A thoroughly sufficient answer would include answers to the following questions: Formally describe what renormalization is. Answer why do we apply renormalization? How does renormalization affect the answers to the problem set? Which problem sets are we referring to? Why doesn't it work where the discrepancy exists?
It is indeed not clear that the appearance of infinities is a fundamental flaw in QED. It rather can be seen as the consequence of the fact that the infinite series of terms (Feynman digrams) is not apparently convergent. (Proof: It is not invariant to using -e instead of e for the electron charge) The arrangement of terms selected by Feynman creates infinities. It is like the series 0 = 1-1+1-1+1-1 + ... that does not satisfy the Cauchy criterium for convergent series. A rearrangement to 1+1+1+1+1+1 ...-1-1-1-1 will deliver infinity - infinity which you struggle to deal with.
This could be only overcome by using non-perturbative approaches.
Question
I have fabricated Ag nanoantenna arrays on glass. It consists of cylindrical nanoantennas at constant separation in symmetrical environment. I have observed a splitting of single particle resonance dip in transmission spectra when the periodicity of the array is increased.
What could be the reason behind the splitting (or two dips) in transmission spectra? I am attaching the image of the transmission spectra for three different periodicities.
Dear Upkar,
It could be related to the onset of the first diffraction order. You have a periodicity of 450nm and a glass substrate, so I assume a refractive index n = 1.5. Then, the first diffraction order should appear around 675nm, in good agreement with your data.
Regards!
Question
I have fabricated a periodic array of cylindrical nanoparticles and taken the transmittance spectrum. The single particle resonance dip that I am getting for the sample is getting blue shifted when the sample is coated with CdSe/ZnS quantum dots. Is it due to strong coupling of surface polaritons with the quantum dots? The absorption peak for the quantum dots are at around 613nm and florescence is at around 665nm. The dip in the transmittance spectra without quantum dot is around 650nm and with quantum dots is around 620nm.
A way to measure the polariton coupling and/or the refractive index shift is by adsorbing the particles to a gold layer generating SPR at 613 nm. At the same time you should detect the SPR excited fluorescence at 665 nm using a fluorescence camera on top of the SPR device (with reflection at the bottom). A set-up of such instrumentation was for the first time published by Wolfgang Knoll. You can find a manuscript of prof Knoll of this setup in the Handbook of Surface Plasmon Resonance chapter 9 .Thank you
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