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RE: A crash course on particle physics (towards our steemSTEM meetup at CERN) - 5 - The challenges of the searches for new phenomena

in #steemstem • 7 years ago (edited)

Thanks a lot for the nice comment!

Do you have or will you have videos available of your lectures?

I am pretty sure the steemstem guys will film me and post the lectures (@suesa or @justtryme90 or @grandpere?) ;)

Also, I still don't understand how identical photons can be force carriers for both attraction and repulsion for charged particles without carrying some information about the sign of the charge of their source particle.

The electric charge (with their sign) play a role in the interaction strengths. This has therefore not much to do with the photon, but instead with the interacting particles themselves. Is it clearer? (if not, let's retry again :p )

7 years ago in #steemstem by
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     7 years ago  

    I'm looking forward to watching your video lessons.

    Strange that photons carry energy from one charged particle to another, but not any info about the sign of the charge of the particle.

    All photons carry the exact same amount of spin angular momentum, h/2π. Is the spin of all photons in the same direction, clockwise or counterclockwise? Or is the direction of spin in a photon influenced by the charge and/or spin of the source charged particle?

    I just read up a little on Quantum Field Theory on wikipedia. In QFT there are many fields to account for all the particles. Pretty strange universe.

    The gravitational field and the electromagnetic field are the only two fundamental fields in nature that have infinite range. Photons are excitations of the electromagnetic field and electrons are excitations of an underlying electron field. So I think the information of the sign of electron charge is carried by the electron field not the electromagnetic field. (Is that correct?)

    The non-relativistic Schrodinger equation wave functions are probabilities, whereas the relativistic Dirac equation wavefunctions don't have a clear probabilistic interpretation. (Is this right?) There are also problems of fitting pair production and anihilation into both equations. (Do you agree?)

    If you're too focused on the upcoming steemit meeting you're hosting, it's ok if you don't have time to respond to all these questions. I hope that everything at the meeting goes smoothly, everyone has a great time, it's not too cold there this time of year and that no unexpected interdimensional portals suddenly open. ;-)

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     7 years ago  

    Let me try to shoot answers here :)

    Strange that photons carry energy from one charged particle to another, but not any info about the sign of the charge of the particle.

    It does not: it is a virtual photon in fact. Just a way to model what is happening.

    So I think the information of the sign of electron charge is carried by the electron field not the electromagnetic field. (Is that correct?)

    Exactly.

    The non-relativistic Schrodinger equation wave functions are probabilities, whereas the relativistic Dirac equation wavefunctions don't have a clear probabilistic interpretation. (Is this right?)

    This is more the problem for the solution of the Klein-Gordon equation than the DIrac one In this last case, one can construct a probability density. But in fact, in all cases, it is sufficient to multiply it with the electric charge of the field, and we end up with a charge distribution that does not have to be positively defined.

    There are also problems of fitting pair production and anihilation into both equations. (Do you agree?)

    I don't know, what do you mean? :D