Electromagnetism

Electromagnetism

  • Suhas Dinesh added an answer:
    8
    Why are Electric and Magnetic Fields perpendicular to each other in an Electromagnetic Wave?

    Why are Electric and Magnetic Fields perpendicular to each other in an Electromagnetic Wave?

    Suhas Dinesh

    The mathematical analysis in the link attached proves how E,H and k (propagation constant) are all perpendicular to each other and how EM radiation propagates at the speed of light.

    http://farside.ph.utexas.edu/teaching/em/lectures/node48.html

  • I. Radinschi added an answer:
    2
    What are gravitinos?

    In supergravity theories combining general relativity and supersymmetry, the gravitino is the gauge fermion supersymmetric partner of the hypothesized graviton. It has been suggested as a candidate for dark matter.The gravitino is the fermion mediating supergravity interactions, just as the photon is mediating electromagnetism, and the graviton is presumably mediating gravitation. Whenever supersymmetry is broken in supergravity theories, it acquires a mass which is determined by the scale at which supersymmetry is broken.

    I. Radinschi

    Maybe you can take a look here, seems to be interesting (if you are not aware of it) : https://www.mpi-hd.mpg.de/lin/events/launch09/talks/LAUNCH09_Buchmuller.pdf. And, also http://www.weizmann.ac.il/particle/perez/Courses/Ad_Top_Par_Phys_09/chapter8.pdf.

    Interesting question!

  • L. Neslušan added an answer:
    56
    May there be gravity from the electromagnetism?

    In some old and modern articles and books there is discussed an idea that gravity law can result from the fact that atraction force between oppsite signes charges is slightly greater than the repulsion between the same sign charges. - yet a  deep physical question arises - why?  One can find in literature the follwing controversial answer - because in reality there exist only ... attraction forces, and the repulsion forces are the resulting oppositely  directed attraction forces caused  by other far distant surrounding  charges, whose existence is owing to the assumed matter neutrality. 

    The idea of ​​the electrical nature of gravitation expressed M. Faraday, John. Maxwell H. Lorentz, O. Heaviside and others. German physicists W. Weber and F. Zolner in 1882 proposed the concept of gravity, based on the difference between the forces of attraction and repulsion of electrical charges, which make up all of the body (the book of F. Zolner
    «Erkliirung der universellen Gravitation», Leipzig, 1882). However, the physical reasons for the difference they have not specified. Much later, a possible cause of the excess power of attraction over the forces of repulsion expressed  by Sir A.  Eddington in his book "Fundamental Theory" (Cambridge, 1946, pp.103). He was guided by the principle of Mach: "Even in the simplest case, we obviously have to deal with possible action
    just two particles, it is impossible to lose sight of the rest of the universe. " Electric field lines of the two charges of opposite sign extend from one charge to the next, and so this system is closed and is independent from the rest of the universe. The situation is different in the charge of one sign - here the lines of force go into space, ending up somewhere on the other sites. So naturally expected that the objects of the universe have some influence on the
    interaction, reducing its strength."
    The Lorentz article "Reflections on gravity" (Proc. Amst. Acad. 11, 1900, p. 559), and then Adamuti (I.А. Adamuti. Gen. Re1at. and Gravitation. Proc. 1 Ехр. Gravitation Symp.
    Bucharest, 1980, p. 202)  develop the electrodynamic theory of gravity. It  like the mentioned model of Lesage, assumes some penetrating  electromagnetic radiation influence on the body from all sides and partially absorbed by them, when this actioin  is not compensated by pressure on the body of this radiation, which is partially screened by one side of the second body. Since the solid angle subtended by the body 2 by the body 1, is inversely proportional to the square of the distance r, the number of them is blocked by the particle radiation proportional to 11^-1 and as the number of absorbed particles is proportional to the  mass, the gravitational force is proportional to the mass of bodies. Consequently, the theory provides the law of gravitation. Speed ​​of gravitation, of course, is equal to the speed of light. However, the theory gives rise to having a large resistance to movement of bodies with  oncoming flux, which is contrary to the experience: no slowing movement of the Earth and other celestial bodies in orbit  rotation is observed.
    Lyttleton and Bondi suggested a   hypothesis  of electrical nature of gravitation, based on the assumption that the proton charge slightly (by 10^-18) is greater than the charge of the electron. (R. А. Lyttleton, Н. Bondi. Gravity and Electricuty. Proc. Roy. Soc,
    1959, А252, p. 313)  They managed to obtain the  Newton's law, explaining  the observed expansion of the universe, the  Blacket law on the magnetic moment of the heavenly bodies and a number of other facts. However, the hypothesis refutes the  direct measurements of the charge of the electron and the proton,  which had proved  that their difference is less than 10^-21.   Despite this, the hypothesis of different tse charges of elementary particles put forward again and again  (N.E. Zaev. "Electromagnetic mass and gravity nature". Journal of the Russian Physical-Mathematical Society, 1992, N2 1-12, p. 32).  The idea of ​​the electromagnetic nature of gravity has been developing  also by A.D. Sakharov, considering the latest results of the quantum fluctuations of fields. (A.D. Sakharov. "Vacuum quantum fluctuations in the curved spacetime and gravity theory". - Doklady AN SSSR, 1967, v. 177, p. 70).  However, the quantum theory of gravity has not been completed and its evaluation is premature. According to A. Barut, gravity is not connected with the static and dynamic effects of electromagnetic and gravitational interactions caused by the electromagnetic radiation produced by the distortion of the structure of elementary charge in the presence of a massive body (А. О. Barut. Gravity and Electromagnetism. - Proc. 2  Marcel Grossmann Meet. Gen. Relativity, Trieste, 1979. Part А. Amsterdam, 1982, p 163).    However, specific evaluations, allowing to  confirm or reject the hypothesis are  not presented.

    L. Neslušan

    @ John Macken and everybody who is interested in the "theory of almost everything" based on Maxwell exlectromagnetism.

    I am sorry for a delay in my response - since the regular scientific papers are sometimes long and difficult to read (because of a lot of new things), I wrote a compactified, (relatively) short article (15 pages, but in large font) to clarify my results concerning a unification of gravity with the electric force.

    John, yes, I agree that there is a certain correspondence between the corresponding forces (both electrostatic and gravitational) as derived by you and me. Anyway, I think that the "potential" of the Maxwell electromagnetism is much larger than outlined in your paper (you referred to it last time) or in my short contributions in this forum.

    I try, again, to indicate this potential is a relatively brief paper linked to this message (it can also be downloaded from https://www.astro.sk/~ne/GUHbrief2.pdf).

    There are many fundamental questions, which should be answered by every theory, which attempts to be regarded as more advanced than the currently accepted theories. For example:

    1. Why there is inertia related to mass, but no inertia related to electric charge?

    2. Why is the size of the charge of all electrically charged elementary particles the same?

    3. Why is the orientation of gravitational force the same as the electric force between two charges of opposite polarities?

    4. What is the model of atom (at least the simplest hydrogen atom) created on the basis of the theory?

    5. What is the origin (explanation) of uncertainity principle?

    Etc., etc., etc. More answers, better theory.

  • Vladimir Onoochin added an answer:
    17
    What is the true order of calculation of the EM fields of the classical charge?

    It is known that the Lienard-Wiechert potentials cannot be derived from the wave equation if a radius R of the classical charge is initially assumed to be equal to zero. In original works of both authors, the radius of the charge is assumed to be finite and after calculation of the potentials, R -> 0 (according to Schott, 'the point laws of Lienard and Wiechert).

    But the EM fields are calculated from the potentials under assumption that the charge 'is treated as if concentrated at a point'. In the other words, R = 0.
    So my question is: what is a reason that we must assume R = 0 but not R -> 0 after calculation of the fields?

    I am concerned in it because the procedure with R -> 0 gives the solution of the wave equation corresponding to so called 'longitudinal EM waves (E_{||} ~ 1/distance).

    I add that the existence of such a solution (E_{||} ~ 1/distance) formally doesn't contradict to the Maxwell equation div E = 4\pi\rho because this equation forbids the existence of irrotational component E_{irr} ~ 1/distance. One can see it by solving the Maxwell equations in the gauge which Maxwell itself used, in the Coulomb gauge. The irrotational component isn't identical to the longitudinal component.

    The proof of the absence of E_{||} ~ 1/distance follows from Lienard's expression for the EM field (the book of Schott, Sec. 13).

    Vladimir Onoochin

    To Anatolij

    I have read carefully enough.
    You wrote: '"Its exact form (exact!) is easily given by means of well known formula'.
    Please, write such a formula allowing to make transformation of the present time variables in one frame to the retarded variables in the other frame.

    And how about my second question?

  • Ashar J Malik added an answer:
    1
    Can anyone explain the algorithm for the calculation of change in energy by Ewald sum method?

    I am having problem with ewald sum energy calculation part.

    I have written the code and validated it with NIST data for total coulomb potential, it is matching well. But when i am trying to calculate  change in coulomb potential (new configuration - old configuration), i am confused with this part.

    Ashar J Malik

    Hi, 

    It is not clear from what you have written - to completely grasp what the problem is. Could you please add some more information?

    What is the system you are studying - values will depend on that.

    When you say you wrote some code - does that mean you wrote it yourself - or put together libraries? What language are you using?

    What exactly is confusing you? Are the values not what you are expecting?

    If you add the above information you will be better able to get a coherent answer.

    Best,
    /A 

  • Sara Liyuba Vesely added an answer:
    1
    How does thermal noise of an electromagnetic mode appear on a square law detector?

    I have a signal which is thermally occupied. The signal is filtered with an cavity, therefore the noise spectrum is simply a Lorentzian function. I was wondering what would be the resulting noise floor on a square law detector (V ~ P2). Will the signal to noise ratio just be the square of signal power / integrated noise spectrum? I am asking this since I think there should be a beating between different frequency components of the noise. Shouldn't that increase the noise floor? If so, how can it be derived? Can anyone provide literature on that?

    Sara Liyuba Vesely

    In my opinion, to observe noise beats the “frequency components” of the noise should be phase-locked. However, it is usually assumed that noise phases are random.

    On the other side a frequency modulation can arise because of parametric amplification of an unwanted signal, which can be called noise as well. Both problems have been faced from a classical viewpoint at radio frequencies, for instance:

    http://www.pa.msu.edu/~edmunds/Parametric_Amplifier/parametric_amplifier_some_notes_on_history.pdf

  • Vladislav Gavryusev added an answer:
    3
    How can get the complex susceptibility parameters for electromagnetically induced transparency?

    I am going to calculate the complex susceptibility of three-level silicon atom which doped in a silica substrate under electromagnetically induced transparency conditions. I have extracted corresponding relations from “Quantum Optics” by Marlan O.Scully and M.Suhail zubairy (page 227- relations: 7.3.14 and 7.3.15 which I attached here). Base on this reference and considering ωab=305.9 THz (λab=980 nm) and ωac=νµ=193.4 THz (λac=1550 nm), How I can calculate or take into account the other parameters consist of Dipole Momentum, off-diagonal decay rates for ρab and ρac (denoted by γ1 and γ2) and Rabi frequency (Ωµ)?

    Best,

    Bijan Goudarzi

    Vladislav Gavryusev

    Well, you should calculate or estimate these parameters independently. You can calculate the dipole momentum from the Fermi Rule or a better approach for your system (still within quantum mechanics). Knowing your laser intensity and the dipole matrix element for the involved transitions, you can calculate the corresponding Rabi frequencies. Concerning the decay rates, they can be composed of different contributions, like state lifetime, laser dephasing, collisional dephasing, temperature effects (like doppler broadening).
    You can get more insight in this paper:

    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: Coherent preparation by laser light of quantum states of atoms and molecules can lead to quantum interference in the amplitudes of optical transitions. In this way the optical properties of a medium can be dramatically modified, leading to electromagnetically induced transparency and related effects, which have placed gas-phase systems at the center of recent advances in the development of media with radically new optical properties. This article reviews these advances and the new possibilities they offer for nonlinear optics and quantum information science. As a basis for the theory of electromagnetically induced transparency the authors consider the atomic dynamics and the optical response of the medium to a continuous-wave laser. They then discuss pulse propagation and the adiabatic evolution of field-coupled states and show how coherently prepared media can be used to improve frequency conversion in nonlinear optical mixing experiments. The extension of these concepts to very weak optical fields in the few-photon limit is then examined. The review concludes with a discussion of future prospects and potential new applications.
      Full-text · Article · Jul 2005 · Review of Modern Physics
  • Qian Xu added an answer:
    1
    How can draw the electric field amplitude and phase at a given distance from antenna (radiation field) in CST ?

    Hi everyone ;
    I wish to draw the distribution of electric field amplitude and phase at a given distance from my patch antenna in cartesian coordinates.someone has already done!?

    Thank you

  • B. Sh. Singer added an answer:
    4
    What is the significance of dipole moment vector?

    in calculation of atomic charge, what is the significance of dipole moment vector?

    B. Sh. Singer

    If you have a 3D volume, which is electrically neutral, then the electromagnetic field at a large distance from this volume is determined by the dipole moment of the volume.  The large distance means "the distance, which is much larger than the diameter (or the size) of the volume"

  • Vedvyas Jayprakash Dwivedi added an answer:
    3
    What is mean Electromagnetically Induced Transparency in Metamaterials?

    What is mean Electromagnetically Induced Transparency in Metamaterials?

    Vedvyas Jayprakash Dwivedi

    Agreed with Vladimir.

    I read these articles and are very clear and correct

  • Lukáš Richtera added an answer:
    1
    How does sunlight affect the structure of silver nano particles?

    i m working on silver and i want to know this reason

    Lukáš Richtera

    Here is one article on RG:

    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: Photoinduced shape conversion of silver nanoparticles was realized using sunlight. The silver seeds were transformed to silver nanoprisms under sunlight when the concentration of citrate was low (<= 5.0 X10� -4 M). Nevertheless, sunlight converted the obtained silver nanoprisms to silver nanodecahe-drons when the concentration of citrate in reaction system was increased. It was found that the ultravi-olet light from sunlight played a vital role in the shape conversion from nanoprism to nanodecahedron. Lighting power density did not influence the shape conversion except for reaction rate. Besides, the silver nanodecahedrons were synthesized in the mixed solution of AgNO3 and citrate in absence of silver seeds through irradiation by simulated sunlight. The mechanism on the sunlight induced synthesis of silver nanoparticles was discussed. Anisotropic silver nanoparticles including nanoprisms and nanodecahe-drons were obtained through controlling the citrate concentration and irradiation time by sunlight from green light source.
      Full-text · Article · Jan 2015 · The Chemical Engineering Journal
  • Daniel Baldomir added an answer:
    3
    Is exchange bias effect possible in ferrimagnetic (instead of ferromagnetic) and Antiferromagnetic heterostructures in nano range?

    Is it possible to have significant exchange bias effect in ferrimagnetic and antiferromagnetic multilayer nanostructures or core shell nanostructures.

    Please give some supporting references if possible................

    Daniel Baldomir

    The exchange bias in one interface between ferrimagnetic-antiferromagnetic orders is possible and it was studied in the literature. See the references:

    [1] P.J. van der Zaag, R.M. Wolf, A.R. Ball, C. Bordel, L.F.
    Feiner, R. Jungblut, J. Magn. Magn. Mater. 148 (1995)
    346.
    [2] W.C. Cain, M.H. Kryder, J. Appl. Phys. 67 (1990)
    5722

  • P.J. Cregg added an answer:
    4
    Which frequency is the permittivity we obtain through the equation above related to?

    as we all konw, we can get the permittivity via the equation that 

    C=εS/(4πkd) = Q/U

    where, C is the Capacity od the dielectric, S & d represent the area & thickness, k is boltzmann constant, Q & U are the charge quantity and the voltage

    but since the permittivity is related to the frequency, the relative permittivity shows different values under different frequency

    i want to ask, which frequency is the perimittivity we obtain through the equation above related to ?

    P.J. Cregg

    First off should Capacitance  C not be simply

    C=epsilon Area/ distance ?

    Why does Boltzmann's constant make an appearance?

    Is complex permittivity perhaps what you need to consider?

  • Daniel Baldomir added an answer:
    11
    Why the permittivity of free space has non zero value while the sucseptibility is zero?

    The electrical permittivity of free space has constant value of the order of 10-12 F/m while the susceptibility has the exact zero value...The basic physical explanation is sought rather than mathematical..

    Daniel Baldomir

         This is a very interesting question related with what electromagnetic vacuum means in Physics. First of all, vacuum is a very different concept than emptiness as it is well known and in fact corresponds to the fundamental state or to the minimal energy that the system can get.
        Suppose a cavity surrounded for perfect conductors with one electromagnetic field inside, this electromagnetic vacuum is with a high energy. Or two neutral plates separated only 10 nm in vacuum, they attract (Casimir effect) with around one atmosphere between them, forgetting details as the form of these metallic plates.
         But if we reduce the distance and look on the charges we can see virtual photons (pairs of electron-positron) which gives an electric polarization. Therefore in such a case the susceptibility is non zero and obviously the permeability and permittivity too. Thus is seems reasonable that the vacuum has not zero for these quantities as well as it happens in QED.
     

  • Hugo Alberto Fernández added an answer:
    99+
    Does a uniformly accelerated charge radiate?
    In classical electromagnetism, any accelerated charge should radiate. The back reaction on the charge due to radiation is given by radiation reaction which depends on time derivative of acceleration. However for uniformly accelerated charge there is radiation but no radiation reaction. I would appreciate any comment on this apparent paradox.
    Hugo Alberto Fernández

    The phenomenon of emission (continuous or photonic) is a causal process, so it is "absolute". There is no way that emitted radiation can be canceled if we accept the principle of causality. The phenomenon exists for all observers, inertial or non-inertial (including the comoving observer), although under certain conditions can't be actually observed. The comoving position and a low acceleration are the worst conditions to detect radiation.
    On the other hand, radiation cannot be produced by the observer movement, whatever it is. A single charge only emits if it has acceleration with reference to an inertial frame.

    The recently cited article has not relevance because the event horizon's argument has no physical consistency (it has been discussed in this thread), producing absurd results. Besides, if we accept such event horizon, the radiation emission is observer dependent, against the Causality Principle.

  • Marek Wojciech Gutowski added an answer:
    8
    How can I calculate force between permanent magnet and electromagnet?

    I need to calculate force between Permanent magnet (NdFeb) and electromagnet for different voltages(5-24). They are 5 mm apart in the device.

    Currently I had measure the Magnetic field  for Permanent magnet in terms of Magnetic Fled Vs Distance  (197 mT at 5 mm) and for electromagnet in terms on Magnetic Field Vs Voltage (134 mT for 12V at contact). 

    Any suggestions will be highly appreciated.

    Thanks in advance.

    Marek Wojciech Gutowski

    Please have a look at the recent paper:

    Parametric resonance induced chaos in magnetic damped driven pendulum by Giorgi Khomeriki, http://arxiv.org/abs/1511.04593

    The calculations presented there are simplified but nevertheless quite useful for the situation described, similar to yours.

  • Thorsten Beuth added an answer:
    5
    Under which conditions are Mie Scattering Amplitudes imaginary?

    Hi,

    I am using Maetzlers Mie Scattering Script from 2002 to calculate Phase Matrix entries. But under no conditions I am able to produce imaginary scattering amplitudes S1 and S2 which is kind of strange to me because in the phase matrix they produce the side entries. I know that some side entries vanish for spheres - or do they all actually?

    So my question is basically: What are the conditions of imaginary scattering amplitudes.


    Thank you and best regards

    Thorsten Beuth

    Thorsten Beuth

    Dear Denis, thank you for the papers, they are very interesting. Unfortunatly they are not specifically what I was looking for. I found the "error" in Maetzlers script by comparing the formulars directly with his written code. At some point he took the absolute value of the scattering amplitudes which denied plausible results concerning the Mueller scattering matrix for the Stokes vector (plausible at least for my purpose) .

    Never trust a code that you have not written on your own :-)

    -----> SOLUTION <-----

    So just if someone else is looking for it: Mie2_tetascan and Mie_tetascan do not give back scattering amplitudes (as written in the technical manual) for calculating the phase scattering matrix. You have to manipulate the next two lines after "a(:,j)=Mie_S12(m,x,u);" to get the imaginary parts of the solution as well.

  • Marcin Nabiałek added an answer:
    4
    How to calculate the mangetic permeability from hysteresis loop (polarization versus magnetic flux) ?

    I would like to ask about the mangetic permeability, I have measured the hysteresis loop, its polarization (T) versus magnetic flux density (mT). do we need to convert first polarization to magnetization or we can calculate from the formula mu = J/ H / mu° +1 ...

    Marcin Nabiałek

    The first magnetization curve tangent to the curve, so as to under it. Yes designate the initial permeability. The maximum permeability is tangent to the curve but as if over her. Touches on his knee Ewing, at the approach to ferromagnetic saturation.

  • Manuel Morales added an answer:
    99+
    What should be rated higher: experiment or theory?
    Faraday laws of Electromagnetism were followed by Maxwell Equations, which explained Faraday results and predicted Electromagnetic Waves, beyond FARADAY results.
    Manuel Morales

    My findings show that the current scientific method is based on omitted-variable bias which can only lead to obtaining false-positive data.

    I have invited the public in exposing this fundamental defect in order to help science to self-correct and advance as is necessary when a new discovery supersedes previous knowledge (see links).

    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: Albert Einstein held the belief that quantum mechanics was an incomplete theory and that there were local hidden variables that would give us a complete sense of reality. As the findings show, he was correct about there being hidden variables. However, he was incorrect as to where to find them. The basketball examples serve to illustrate the findings of the Tempt Destiny experiment and the mechanics involved. The "Flawed Scientific Method" illustrations were designed to go with the public invitation to help science self-correct. In essence, this one page document illustrates for the public the mechanics of the discovery of Einstein's nonlocal hidden variables which in turn revealed how the scientific method is fundamentally flawed and how to fix it.
      Full-text · Dataset · Nov 2015

    + 1 more attachment

  • Johneph Sukham added an answer:
    9
    What courses should be taught in a masters program for "Metamaterials"?
    The research center for Nanophotonics and Metamaterials, Saint-Petersburg University ITMO, launches new master program in the field of metamaterials. The course list is available on our website. What have we forgotten or what do you think should be excluded from the course list?
    Johneph Sukham

    Solid State physics and Photonics

  • Hossein Javadi added an answer:
    19
    Is there a relationship between speed and spontaneous symmetry breaking in particle physics?

    Symmetries are not hard to find. Plates in the china shop look the same when rotated; serving platters are identical to their mirror reflection. But much of the world is messy and asymmetric, and discovering how certain symmetries are violated, or broken, can reveal deeper physics.

    Nambu developed a mathematical mechanism for spontaneous symmetry breaking in particle physics. Spontaneous symmetry breaking occurs in systems that under certain conditions are symmetric, but whose lowest energy state is not. A classic example is a hot chunk of magnetic material, in which the atomic-scale “bar magnets” point in random directions, making its interior symmetric under rotation. But as the material cools, these elements align in a single direction, and the metal becomes magnetized. The rotational symmetry is broken in this lowest energy configuration, hiding the symmetry that still exists in the equations of electromagnetism.

    Something similar happens in a superconductor. At high temperature, the electrons in the material are free to roam around randomly, but below a critical temperature their lowest energy state is one in which they pair up. Nambu modeled this behavior in the context of quantum field theory. He was able to explain the expulsion of magnetic fields by superconductors in a new and elegant way involving the breaking of symmetry in the field equations when electrons pair up.

    https://physics.aps.org/story/v22/st13

    Spontaneous symmetry breaking (SSB), which is the main subject of my talk, is a phenomenon where a symmetry in the basic laws of physics appears to be broken. In fact, it is a very familiar one in our daily life, although the name SSB is not. For example, consider an elastic straight rod standing vertically. It has a rotational symmetry; it looks the same from any horizontal direction. But if one applies increasing pressure to squeeze it, it will bend in some direction, and the symmetry is lost. The bending can occur in principle in any direction since all directions are equivalent. But you do not see it unless you repeat the experiment many times. This is SSB. A part of Nobel Lecture by Yoichiro Nambu (2008)

    http://journals.aps.org/rmp/abstract/10.1103/RevModPhys.81.1015#fulltext

    In a particle accelerator, beams of subatomic particles are boosted to nearly the speed of light and then brought into collision with either a stationary target or another beam of accelerated particles coming head-on.

    http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=4629896

    So, this question arise that what is the relationship between speed and Spontaneous symmetry breaking?

    Hossein Javadi

    Dear Vassili
    "... the maximal attainable speeds are different for different kinds of particles."
    Exatly, it deppends to structure of particles.
    In pair production, a photon that moves with speed c, converts to electron and positron that move with speed v<c, and other bosons also occur. Before pair
    production, there is a photon only. After pair production, there is an electron, a positron and virtual photon (boson) that carries electromagnetic force. In fact; Spontaneous Symmetry Breaking has occurred at speed v<c.
    Theoretically, after big bang:
    Grand Unification Epoch, from 106^-43 seconds to 10^-36 seconds:
    The force of gravity separates from the other fundamental forces (which remain unified), and the earliest elementary particles (and antiparticles) begin to be created.
    Inflationary Epoch, from 10^-36 seconds to 10^-32 seconds.

    https://www.researchgate.net/publication/279446746_Graviton_and_cosmology_equations_before_the_Big_Bang?ev=prf_pub

    What is the role of is speed in creation of particle and Spontaneous Symmetry Broken?

    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: For long time seemed the Friedmann equation is able to explain universe, but in recent years, the cosmological constant was of interest to cosmologists. However, these two equations are unable to explain before the Big Bang. Thus this paper, from a new approach, turns out to merge the fundamental principles of quantum physics, relativity and classical mechanics through a new definition of rest state of particles like photon, and attempts to present the reasons and the possibilities of the existence of the superluminal speeds. So according to this new view some complex concepts and unanswered questions is explained in this paper.
      Full-text · Article · Jul 2015
  • Antoine J.H. Acke added an answer:
    5
    What's the relationship between gravitoelectromagnetism and electromagnetism ?

    I worked out this formula B=Bg/4π√(εG)

    Where B is the magnetic flux density at the surface of the Earth or a body, Bg is the gravitomagnetic field of the Earth or a body,  ε is the permittvity of free space and G is the gravitatonal constant.

    I realised that when I substitute the Bg of the Earth, B concided with the experimentally measured magnetic flux density of the Earth's surface.

    Could this be the relation ?

    Antoine J.H. Acke

    Gravitoelectromagnetism (Heaviside, Jefimenko, ...) and Electromagnetism (Maxwell) describe the gravitational and the electromagnetic phenomena in an analogue way. In GEM the gravitational field plays the  role that  the electromagnetic field plays in EM: it intermediates in the interactions between whether or not moving masses just as the electromagnetic field intermediates in the interactions between whether or not moving charges.  The gravitational field is generated by masses, the electromagnetic by charges.  Both are described by an analogue  set of equations.

    GEM as well as EM  perfectly can be explained in the frame of classical  physics starting from the hypothesis that every material object manifests itself in space by the emission -  at a rate proportional to its rest mass -  of mass and energy less entities that run away with the speed of light and that carry information about the position, the velocity and the electric status of their emitter.  Because these entities are grains of information, we call them "informatons".

    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: The theory of informatons unifies gravito-electromagnetism (GEM) with electromagnetism (EM) by the hypothesis that "information" is the substance of GEM- and of EM-fields. The constituent element of that substance is called an "informaton". The theory starts from the idea that any material object manifests itself in space by the emission - at a rate proportional to its rest mass - of informatons: granular mass and energy less entities rushing away with the speed of light and carrying information about the position, the velocity and the electrical status of their emitter. The GEM- and the EM-field at a point are charactarized as the macroscopic manifestations of the presence of a cloud of informatons near that point, and the quantities "field" and "induction" are identified with respectively the density of the flow and the density of the cloud of information at that point. The laws of GEM and Maxwell's laws are mathematically deduced from the kinematics of the informatons. The gravitational and the electromagnetic interactions are explained as the effect of the tendency of an object to accelerate in order to become blind for flows of information generated by other objects; and gravitons and photons are identified as informatons carrying a quantum of energy, what allows us to understand the dual nature of light.
      Full-text · Article · Jan 2015
  • Jeffrey Tuhtan added an answer:
    6
    How are the Biot-Savart law and pressure Poisson equations related?

    Formulations for both are found in many books on fluid mechanics and turbulent flows. However, I am looking for a way to understand the two approaches from a common point of view and would like to find a derivation which goes from one to the other, if possible.

    Jeffrey Tuhtan

    Alex, thank you for the reference, amazing work! Looking through the paper, it seems like Eqn. 16 describes the pressure difference as a function of the chordwise vorticity. Does seem like a reasonable place to start looking for connections between the near body pressure and vorticity?

  • Georg R. Pesch added an answer:
    4
    How can I simulate a magnetic field generated by a single solenoid with COMSOL?

    It might sound simple but I'm having trouble with simulation of a solenoid's magnetic field. most of what I know about electromagnetism is from what we had in Physics II which is not much. But being a chemical engineer it is not very likely not to know COMSOL. So here I am asking for help from those who can explain to me how to simulate the magnetic field of single solenoid with COMSOL. Please have in mind my knowledge of the case is limited and any suggestions and resources are more than welcome.

    Georg R. Pesch

    You might want to look at the AC/DC User Manual of Comsol:

    http://hpc.mtech.edu/comsol/pdf/ACDC_Module/ACDCModuleUsersGuide.pdf

    Page 178 and following deal with coils!

  • Myroslav I. Kozak added an answer:
    4
    Is there any good method that can be used to detect the polarization of the field near focus?
    If the polarization is changed dramatically near the focus, can we image the polarization in an experiment?
    Myroslav I. Kozak

    Enter linearly polarized light. Register the usual method through the compensator and polarizer. Be sure to let us know that as a result.

  • Marek Wojciech Gutowski added an answer:
    2
    Any advice on conductivity tensor and lattice symmetry?

    In book it says" If a field in x direction induce any current in y direction,by exploiting the symmetry,one can predict  a same current will arise in -y direction,only consistent possibility is zero current so the conductivity tensor is diagonal  in cubic symmetry lattice"

    What hell he is talking? why field in x direction can induce current in y direction?And if so,why will be same current induced in -y direction? why those stuff related to symmetry? I have no clue about this

    Marek Wojciech Gutowski

    Crystals are not isotropic media, like majority of liquids.  Thus the electric current density in them satisfies the relation j=\sigma E, where j is vector of current density, E is electric field vector, and \sigma is generally the 3x3 tensor of conductivity. \sigma in cubic crystals is not only diagonal, its all three diagonal elements are equal to each other.  This need not to be the case in other symmetries, for example in tetragonal crystals \sigma_xx=\sigma_yy but \sigma_zz usually has different value.  In still lower symmetry you may expect more non-zero elements of \sigma. If you don't see why in crystals the vectors j and E don't have to be parallel, think about a bunch of parallel insulated wires, not aligned with power source contacts attached to their ends.

  • V.G. Irisov added an answer:
    2
    How do I linearize the force generated by two opposite electromagnets for the levitation of ferromagnetic object?

    I want to model my levitation system in simulink, for that I need linearization of force for levitation generated by two electromagnets.

    V.G. Irisov

    You may consider non-stationary setup: magnetic field between two ems has a point where the second derivative over the distance is zero. This is the area there the field is the most linear. Changing the strength of em currents you can shift this area up and down. Doing this periodically with high enough frequency you may get quasi-linear mean magnetic field in a larger area. Just an idea, may not work. 

  • Igor Goliney added an answer:
    3
    Is the mechanical analogy of a child's swing to an electric oscillator valid when passing through resonance?

    When introducing the behavior of RLC series circuits around series resonance, it is often compared to a child's swing. In fact both can be made to reach a large amplitude at resonance. However, can the swing's frequency range from lower to higher values than the resonance one? In case it can, how is the passage to higher frequencies expected to occur?

    Furthermore, could the tippe top's characteristic feature of turning upside down when spun fast enough be explained by the same mechanism?

    http://io9.com/5689842/why-the-humble-tippe-top-baffled-physicists-and-statesmen

    Igor Goliney

    A swing is an example of a parametric resonance. A child must bend her knees twice per period of oscillations. Read about it deeper.

    A pendulum is better analogy to the electric oscillations.  Small oscillations of the pendulum are isochronic, which means their frequency does not depend on amplitude. For the arbitrary oscillations the frequency does depend on amplitude. There is an analytic solution of for the pendulum which describes anything in it including the mode of rotation. 

    The  top is a problem of  axial solid body rotation in the gravitational field with one point fixed. It has the analytic solution. I don'k know if anybody bothered to consider what happens if that one fixed point is lost and it turns upside down. 

  • Myroslav I. Kozak added an answer:
    9
    Computing the E field resulting from a short dipole above a stratified media?

    Is there any software (preferably MATLAB) for computing the E field resulting from a short dipole above a stratified media? I found something for a line source, but not a dipole.

    Myroslav I. Kozak

    I'm counting at ovo, therefore am never wrong.

  • Gifuni Angelo added an answer:
    3
    Why is absorption cross section a far field phenomenon, as we calculate it over desired volume of a nano-structure ?

    Why absorption cross section is far field phenomenon, as we calculate it over desired volume of a nano-structure ?

    Gifuni Angelo

     Waseem Raja,

    You talk of nanostructure and of far field phenomenon; but, you do not specify the frequencies of interest.

    You can see if the attached file and/or the references that you find there can help you.

    Best Regards

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