I Particle antiparticle creation

[Michel Raskin]

When a particle and antiparticle pair is created are they created on the same position?
If they weren't in the same position it would lead a problem on energy conservation, but they are fermions so they shouldn't be on the same position in space.

 

[Jilang]

No, they are distinguishable so that is not the the case.

 

[Nugatory]

If they weren't in the same position it would lead a problem on energy conservation

You may thinking in classical terms here.

Quantum mechanically, the "position" of a particle is a rather dubious concept unless and until you've interacted with it in a way that localizes it (informally, "measured its position"). So consider an example of an interaction that produces a pair of fermions: an energetic gamma photon interacts with a heavy nucleus and produces a positron/electron pair: all energy conservation (and similarly for momentum) requires is that when the dust settles the sum of the energies of the nucleus, electron, and positron coming out is equal to the energy of the photon and the nucleus going in. The interaction itself should be thought of as a black box: some particles went in, some other particles came out, the energy coming out is equal to energy going in.

 

[A. Neumaier]

When a particle and antiparticle pair is created are they created on the same position?
If they weren't in the same position it would lead a problem on energy conservation, but they are fermions so they shouldn't be on the same position in space.

Usually a particle and an antiparticle cannot have the same quantum number, and hence can occupy the same position.
When two photons (which are their own antiparticles) are created one cannot talk about their position and the question is moot.

In any case, the particle concept becomes meaningless at distances that are too short, and ''the same place'' becomes a nonrelativistic fiction.

 

[Michel Raskin]

Thank you A.Neumaier Nugatory andJilang for your answers they were really helpful