Phenomenological potentials and exchange of force carriers

[crick]

Consider a proton-neutron system.

Phenomenlogical nucleon-nucleon potentials contain exchange forces terms (Majorana, Bartlett and Heisenberg terms), which are linked to the symmetry of the state w.r.t. (for example) the exchange of isospin (i.e. charge).

On the other hand proton and neutron can interact exchanging a pion (in the Yukawa theory) and exchange their charges: if proton and neutron collide they can exchange their charges because of the exchange of a charged pion. In this sense the interaction between neutron and proton (nuclear force) can be defined as an exchange force (because of the exchange of the pion, as described here https://en.wikipedia.org/wiki/Exchange_force#Exchange_of_force_carriers_in_particle_physics).

I'm quite confused about the term "exchange", in particular in the first case: what is "exchanged" when we talk about exchange force in the case of nuclear force? Is the exchange related to the symmetry of the system (as in first case) or to the physical exchange of a particle (Yukawa meson)?

 

[LightHero]

The exchange force in the case of nuclear forces is related to the exchange of a particle, usually a pion. The Majorana, Bartlett, and Heisenberg exchange forces terms are all related to the exchange of isospin, which is an internal quantum number associated with the proton and neutron. When a proton and neutron interact, they exchange isospin, as well as exchanging a pion, which carries charge and is responsible for the charge-charge interaction between them.