The discussion centers on the interactions mediated by exchange particles with even and odd spins, specifically graviton (spin-2) and photon (spin-1). It is established that even spin exchange particles, such as gravitons, result in attractive forces when the charges are alike and repulsive forces when the charges are unlike. Conversely, odd spin exchange particles, like photons, lead to attractive forces when charges are unlike and repulsive forces when charges are alike. The conversation highlights the importance of understanding the role of charge signs in determining the nature of these interactions.
PREREQUISITESPhysicists, students of particle physics, and researchers interested in the fundamental forces and interactions between particles.
Where? Please give a specific reference.simplemind said:I have read
You've only given one reference. What other ones have you seen that contradict it?simplemind said:i am unsafe because there a lot of different inromations in the web
The first reference gives no details or arguments at all, so it's not very helpful.simplemind said:i am not sure if exchangeparticles with even spin always acts attractive or only if the charge is the same?
It is for unlike charges vice versa which means spin 0 repulsive and spin 1 attractiv.PeterDonis said:The first reference gives no details or arguments at all, so it's not very helpful.
The second reference does give some details and arguments (on previous pages to the one you linked to), but only for the spin-0 and spin-1 cases. Basically, those arguments boil down to this (for the simplest case where the two interacting objects start out at rest): the interaction energy is the product of the two charges (which appear as two ##J## factors in the formula) and a "propagator" ##D##, whose sign depends on the spin; for spin-0 it is negative, for spin-1 it is positive. The overall sign of the interaction energy determines whether the interaction is attractive or repulsive: negative interaction energy means attractive, positive interaction energy means repulsive. So if we consider like charges (meaning, the sign of the product of two of them is positive), then the spin-0 interaction is attractive and the spin-1 interaction is repulsive.
Can you see what the above implies for the case of unlike charges for spin-0 and spin-1?
Yes.simplemind said:It is for unlike charges vice versa which means spin 0 repulsive and spin 1 attractiv.
The only other spin for which I have seen a calculation of the propagator is spin-2, for which the propagator is negative (as in the case of gravity), so its behavior is the same as spin-0.simplemind said:Is this true for all even and odd spins?
Is the propagator negative for all even spins and positiv for all odd spins?
The abstract of that paper (I can't read the full paper since it's behind a paywall) seems to indicate that only the case of like sources, i.e., charges with the same sign, is examined. The relative sign of the charges, just by inspection, must affect the sign of the interaction energy for all spins.vanhees71 said:In the paper I quoted above it's shown that in classical field theory fields with even spin are lead always to attraction
PeterDonis said:The abstract of that paper (I can't read the full paper since it's behind a paywall) seems to indicate that only the case of like sources, i.e., charges with the same sign, is examined. The relative sign of the charges, just by inspection, must affect the sign of the interaction energy for all spins.
In even-spin cases, such as spin-2 gravity, it is often assumed that there is no such thing as "unlike charges"--that all "charges" (masses in the case of gravity) are positive, so only the like charge case is relevant. Under that assumption, the statement that "gravity is always attractive" would be correct. But I don't think it is if the possibility of unlike charges is included.
All of the results I have described are well known.simplemind said:It seems that it is not a common known result?
Yes, it is. You give the answer yourself:simplemind said:the basic question is unfortunately not answered
Yes, that's what has already been said.simplemind said:even spin of exchangeparticle (f.e. graviton) : attracitve when charges of particles are like
repulsive when charges of particles is unlike.
Yes, that's what has already been said.simplemind said:odd spin of exchangeparticle(f.e. photon) : attracitve when charges of particles are unlike
repulsive when charges of particles are like.
I have no idea why you would think this. The above entirely answers your question.simplemind said:I think i have to look somewhere else.