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 2d comment What is the symmetry which is responsible for preservation/conservation of electrical charges? @JohnMcVirgo: How about Feynman lectures, chapter 28 (feynmanlectures.caltech.edu/II_28.html)? How about Landau-Lifshitz textbook about the same matter? Apr 26 comment What is the symmetry which is responsible for preservation/conservation of electrical charges? @JohnMcVirgo: For a physical system, you say? We speak of equations and sometimes these equations have non physical solutions. Their Lagrangian exists and the Noether theorem gives formal formulas for conserving quantities as if the solutions were physical. What would you say in case of non physical solutions? What is conserved? Apr 24 comment What is the symmetry which is responsible for preservation/conservation of electrical charges? If something is obtained from Noether's theorem, it does not mean it cannot be obtained differently. In case of the total charge, it is necessary for equations to have physical solutions and it is implied so while integrating the charge density. Apr 24 comment What is the symmetry which is responsible for preservation/conservation of electrical charges? @JohnMcVirgo: the charge conservation of an interacting system of charges follows from the equations. And one can obtain the total charge as a sum of constituents from the equations. Consider the total field of the system at a long distance which gets into the equations of motion of a distant probe charge. The leading term is determined with the total charge. Note, the sum of masses is also constant - by definition of masses, but we do not obtain it from equations because we must deal with the total energy involving the interaction energy too. Mar 24 comment Fourier transform of the Coulomb potential Yes, it is. Nobody arrived at a different result so far ;-) Jan 16 awarded Yearling Jan 7 comment Showing that $\lambda$ is the probability per unit time that one particle will decay in 1 second @rob: It is the definition of probability - it concerns one single particle. For ensembles one writes numbers of decayed or "alive" particles (see eq.(A) of OP, for example). Jan 7 revised Are parts of objects part of that object's mass? added 138 characters in body Jan 7 answered Are parts of objects part of that object's mass? Jan 7 answered Showing that $\lambda$ is the probability per unit time that one particle will decay in 1 second Jan 4 comment Why doesn't a Gaussian beam converge to a point? @CuriousOne: You again pretend that I say something contradicting to or not supported with experiments. In reality I am referring to a typical QM calculation with no hypotheses at all. Jan 4 comment Why doesn't a Gaussian beam converge to a point? @CuriousOne: And you may want to read my statements about pointlikeness and smearing in QM here: aiscience.org/journal/paperInfo/pj?paperId=2156 Jan 4 comment Why doesn't a Gaussian beam converge to a point? @CuriousOne: You said that a point-like bare electron exists in QED, but it anyway gets a structure from "the induced distribution of virtual photons and electrons"... and I just seconded it underlying that photons also belong to the particle zoo. Jan 4 comment Why doesn't a Gaussian beam converge to a point? @CuriousOne: Ha! Now, according to you, I am against QM. Funny you are. What I was responding to was your "bit of intellectual nonsense" where I included photons on equal footing with your Higgs. Jan 4 comment Why doesn't a Gaussian beam converge to a point? @CuriousOne: Don't think of my (mis)understanding; better think of the geometric optics, which is relevant to the question. Jan 4 comment Why doesn't a Gaussian beam converge to a point? @CuriousOne: I disagree with you about it, but let's stop our discussion. Jan 4 comment Why doesn't a Gaussian beam converge to a point? @CuriousOne: Quantum (photon) caries away some energy-momentum and angular momentum, so what the difference are you talking about? In QM all particles (excitations) are treated on equal footing. Jan 4 comment Why doesn't a Gaussian beam converge to a point? @CuriousOne: "Quanta" means "particles". Whatever. Jan 3 comment Why doesn't a Gaussian beam converge to a point? @CuriousOne: And below 1 MeV we still have plenty of particles - photons - in scattering processes. Nov 30 comment Interpretation of QED gauge freedom @RobinEkman; I understand your worry, but if you know what the magnetic field is "inside", there is no reason to think that the electron is unaware about this magnetic field. Because you too are a "source" of the electron. Do not forget - the boundary conditions are solutions (simplified, though) to the complete set of all equations.