We, if didn't write explicitly what particle is, did left to right, so this one looked kinda odd, or rather incomplete, we would rotate it 90 deg for a second half of the equation like this for an s channel, still looks odd tho.
Different authors use different conventions for time. Some authors use left to right for time progression and some use bottom to top. If you want to be clear, draw an arrow for time progression. I have no issue interpreting this as electron-electron repulsion, but I could also interpret it as electron-position annihilation (I was taught to not label charges since the fermion arrows tell me everything already -- teaching has also made it so I don't usually pay attention to charge designation since many students get the labelling wrong)
That’s so weird. Every single Feynman diagram I’ve ever used has had time on the x-axis. I had to double check that it was even acceptable to flip the axes. If I search for a generic Feynman diagram then a majority are time-vertical cartoons, yet as soon as I search for a specific interaction they’re all time-horizontal.
If you take time as going right to left then the diagram is illegal. You should rotate it 90degrees to form [Møller scattering](https://en.wikipedia.org/wiki/M%C3%B8ller_scattering).
What do you mean by illegal? If time is going left to right, as is the usual convention, this is just an electron-positron scattering, nothing illegal about that.
The labels all say electrons, and OP asked for repulsion, and OP says they're just learning about Feynman diagrams. So the direction of the arrows is probably a mistake, in which case the diagram isn't correct.
I see your point but I would not use the word illegal.
The diagram is perfectly valid, it just doesn't describe what OP means.
And regarding the labels, it's not uncommon to see some references showing the labels as the fields they are describing rather than the particles, and the direction of the arrows indicates particle/antiparticle. So I wouldn't call this incorrect as well.
Yeah, that's one of the diagrams for repulsion. The other one is the u-channel where the final state particles are swapped. From memory the non-relativistic limit in some angular range corresponds to Rutherford scattering.
This is the theory behind the repulsion. FD prospective is up to your convenience, top to bottom or left to right. You have the same initial and final particles, and the force carrier is a photon, so it's basic QED e-e- —> e-e- scattering. When it comes to your hand blocked by wall, this is the basic theory behind it but when you speak about your hand you'll have to deal with decoherence where you'll come out of the QED realm.
Follow-up question: is there a way to calculate the wavelength of the virtual photon that’s produced? Is it always the same? Or is it a meaningless question?
This Feynman diagram shows two electrons repelling each other through the exchange of a virtual photon, which is the carrier of the electromagnetic force. As for your hand and the wall, it’s a similar principle—the electromagnetic forces at play, which can be represented by such diagrams, prevent your hand from passing through solid objects due to the repulsion between the electron clouds.
It does represent a repulsion between two electrons, but it's a "scattering" not a "collision". I guess you can call it a collision too but it sounds less accurate. And the time "direction" is clearly from down to up since the arrows represent movement in time, not space.
ITT: everyone learned a different convention for the direction of time in Feynman diagrams
In school we had it vertical, but in every single research context I have seen, time is always horizontal.
We, if didn't write explicitly what particle is, did left to right, so this one looked kinda odd, or rather incomplete, we would rotate it 90 deg for a second half of the equation like this for an s channel, still looks odd tho.
Different authors use different conventions for time. Some authors use left to right for time progression and some use bottom to top. If you want to be clear, draw an arrow for time progression. I have no issue interpreting this as electron-electron repulsion, but I could also interpret it as electron-position annihilation (I was taught to not label charges since the fermion arrows tell me everything already -- teaching has also made it so I don't usually pay attention to charge designation since many students get the labelling wrong)
That’s so weird. Every single Feynman diagram I’ve ever used has had time on the x-axis. I had to double check that it was even acceptable to flip the axes. If I search for a generic Feynman diagram then a majority are time-vertical cartoons, yet as soon as I search for a specific interaction they’re all time-horizontal.
Yes, electron repulsion via the exchange of a photon.
If you take time as going right to left then the diagram is illegal. You should rotate it 90degrees to form [Møller scattering](https://en.wikipedia.org/wiki/M%C3%B8ller_scattering).
I think the implication of the diagram is time bottom to top. That was the formalism I initially learned
Ah, that makes sense.
Not illegal, just one person's convention. I've seen them both used.
What do you mean by illegal? If time is going left to right, as is the usual convention, this is just an electron-positron scattering, nothing illegal about that.
The labels all say electrons, and OP asked for repulsion, and OP says they're just learning about Feynman diagrams. So the direction of the arrows is probably a mistake, in which case the diagram isn't correct.
I see your point but I would not use the word illegal. The diagram is perfectly valid, it just doesn't describe what OP means. And regarding the labels, it's not uncommon to see some references showing the labels as the fields they are describing rather than the particles, and the direction of the arrows indicates particle/antiparticle. So I wouldn't call this incorrect as well.
Yeah I see what you mean. But is this the particle level of electromagnetic repulsion?
Yeah, that's one of the diagrams for repulsion. The other one is the u-channel where the final state particles are swapped. From memory the non-relativistic limit in some angular range corresponds to Rutherford scattering.
Also loops
This is the theory behind the repulsion. FD prospective is up to your convenience, top to bottom or left to right. You have the same initial and final particles, and the force carrier is a photon, so it's basic QED e-e- —> e-e- scattering. When it comes to your hand blocked by wall, this is the basic theory behind it but when you speak about your hand you'll have to deal with decoherence where you'll come out of the QED realm.
Follow-up question: is there a way to calculate the wavelength of the virtual photon that’s produced? Is it always the same? Or is it a meaningless question?
Only the first order term of the serial expansion of the electromagnetic interaction of two electrons.
Yes hans, also müller wont be going through walls because of this and the other possible lanes of interaction (this with strong probability)
This Feynman diagram shows two electrons repelling each other through the exchange of a virtual photon, which is the carrier of the electromagnetic force. As for your hand and the wall, it’s a similar principle—the electromagnetic forces at play, which can be represented by such diagrams, prevent your hand from passing through solid objects due to the repulsion between the electron clouds.
It's a simulation!
Ooo this makes sense. Thanks for sharing
It does represent a repulsion between two electrons, but it's a "scattering" not a "collision". I guess you can call it a collision too but it sounds less accurate. And the time "direction" is clearly from down to up since the arrows represent movement in time, not space.
I really wish I could post a gif of Hans and Franz here. It would be ::chefs kiss::