Why against Stern-Gerlach experiment photons are said to be spin 1?
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From: Igor on 26 Nov 2009 09:46 On Nov 25, 1:21 pm, Jarek Duda <duda...(a)gmail.com> wrote: > On Nov 25, 6:24 pm, Igor <thoov...(a)excite.com> wrote: > > > Yeah, you're correct on that one. Apparently, after re-reading this > > paper, I see that it's based not on the conventional Standard Model, > > but on some sort of extended version of it. That's what I meant when > > I said "it would be back to the drawing board", since the conventional > > SM doesn't predict a magnetic moment for the neutrino. People are > > already anticipating new directions in which to take the SM and this > > paper is a good example. > > Current theories are usually made that we observe new phenomena and so > we add new corresponding terms to the Lagrangian ... That's true. However, we usually compartmentalize a very successful theory that has withstood test after test without being falsified by experiment. Hence the Standard Model. And we also usually relegate any modifications to such a successful theory to the fringe until such time that any of it's predictions might be verified. Let's face it. New ideas in physics aren't really worth that much until there's sufficient evidence to support them. But just keep searching. Sooner or later, someone will indeed hit upon the next big thing. > For example I have a hypothetic question: can we be sure that electron > isn't extremely weak monopole and the same with proton, but with > opposite sing? Interestingly enough, a particle that possesses both electric and magnetic charge should violate parity in a measurable way. This is because the forces it experiences will have both polar and axial vector parts. Thus, we have a concrete prediction that could be made from your hypothesis. Whether the effect is measurable under the conditions you're postulating (and they're necessary. else the effect would have been noticed already), is another issue. >So that it would sum up to zero for uncharged matter > and in the other case would be drown out by the charge... > If such monopole would be small enough, we shouldn't observe it > (yet?) ... but can we really be sure that it's not true? > There's lot's of things in physics that we can never be sure about. The problem has always been with who's willing to stick their neck out for something that might be true, but we otherwise have no clue. The main issue here is whether one wants to spend the rest of one's life jousting windmills and chasing spectors in the dark without actually getting anything accomplished. It usually helps to have at least one or two successful ideas under your belt prior to going out into the vast wasteland in search of new ideas.
From: Igor on 26 Nov 2009 09:56 On Nov 26, 4:18 am, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > 1 > the electron is not a pint particle You're right. It actually fills up a whole quart. > 2 > it means that a particle that has spin >must be subdivided to smaller orbital particles!! Even a subatomic particle apparently understands how to make more money in real estate. > 3 > the more complicated and sub built is the particle > it has more descret directions That particle must be a female. Were it a male, it would never even ask for directions. > 4 > see how particles are built That confims my response to #3.
From: Y.Porat on 26 Nov 2009 10:07 On Nov 26, 4:56 pm, Igor <thoov...(a)excite.com> wrote: > On Nov 26, 4:18 am, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > > > 1 > > the electron is not a pint particle > > You're right. It actually fills up a whole quart. > > > 2 > > it means that a particle that has spin > >must be subdivided to smaller orbital particles!! > > Even a subatomic particle apparently understands how to make more > money in real estate. > > > 3 > > the more complicated and sub built is the particle > > it has more descret directions > > That particle must be a female. Were it a male, it would never even > ask for directions. > > > 4 > > see how particles are built > > That confims my response to #3. -------------------- imbecile mathematician Bolshevik !! if you cant help at least dont disturb Y.Porat ------------------------ Y.P -----------------
From: Igor on 26 Nov 2009 10:51 On Nov 26, 10:07 am, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > On Nov 26, 4:56 pm, Igor <thoov...(a)excite.com> wrote: > > > > > > > On Nov 26, 4:18 am, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > > > > 1 > > > the electron is not a pint particle > > > You're right. It actually fills up a whole quart. > > > > 2 > > > it means that a particle that has spin > > >must be subdivided to smaller orbital particles!! > > > Even a subatomic particle apparently understands how to make more > > money in real estate. > > > > 3 > > > the more complicated and sub built is the particle > > > it has more descret directions > > > That particle must be a female. Were it a male, it would never even > > ask for directions. > > > > 4 > > > see how particles are built > > > That confims my response to #3. > > -------------------- > imbecile mathematician Bolshevik !! > if you cant help > at least dont disturb > Y.Porat You're disturbed enough for the both of us. By the way, didn't Sacha Baron Cohen make a movie about you?
From: Tom Roberts on 26 Nov 2009 12:14
Jarek Duda wrote: > I've used this example to show that waves carrying angular momentum > doesn't have to carry spin! Angular momentum is not a well-defined quantity by itself -- its value depends on the origin one selects. A pointlike object moving inertially has nonzero angular momentum relative to any point not on its trajectory. [NOTE: in this post I switch between classical and quantum models. Any mention of "representation" implies a description using Quantum Field Theory. Classical models/descriptions are mentioned explicitly.] > Ok - I'll try to explain mathematically what is the difference between > spin which is topological singularity and angular momentum carrying > twist-like traveling wave Your attempt fails. Spin need not involve a topological singularity. For example, a classical circularly-polarized EM wave carries nonzero spin, but there's no singularity involved. There are solutions to Maxwell's equations for a plane wave that is circularly polarized. At every point the E and B fields rotate in a plane perpendicular to the direction of propagation. I stress that this is at EVERY point in space, and hence there can be no topological singularity involved. The REAL distinction between spin and angular momentum is that spin is intrinsic to an object and angular momentum is not. In QFT, elementary particles are modeled with a representation of the Lorentz group having definite spin; angular momentum is modeled in configuration space by projecting the wave function onto the angular momentum eigenfunctions (the Y_lm-s). The spin representation has no dependence on position, the Y_lm-s do. The distinction is the same classically -- the earth has nonzero spin (intrinsic angular momentum), but no topological singularity. > We know that photon can be twist. > Why it's also spin? With "twist" you are attempting to make a distinction without a difference. Circularly polarized EM waves modeled classically have nonzero spin, yet they "twist" (in the sense of the fields at a given point rotate perpendicularly to the direction of propagation; you have not really defined what you mean by that word). The reason the photon has spin 1 is that its angular momentum is INTRINSIC. That is, in QFT it requires a spin-1 representation of the Lorentz group to model a photon in agreement with experimental measurements. > Another very important thing is that with topological singularity > should come some internal stress But photons have no mass, and hence no "internal stress". But they have nonzero spin. In QFT, spin has to do with which representation of the Lorentz group is used to model the particle, it has NOTHING WHATSOEVER to do with "something rotating" or "something twisting" or "something spinning". But it is an intrinsic quantity that couples to angular momentum in analogy to the spin of a classical object, hence the name. DO NOT BE FOOLED BY THE NAME. I repeat: spin does not imply any sort of topological singularity. Tom Roberts |