The discussion revolves around the concept of 'off-shell' particles in the context of external fields, exploring the implications of this terminology for real, observable particles. Participants seek clarification on the meaning and significance of being 'off-shell' when energy conservation is still applicable.
Participants express uncertainty regarding the implications of 'off-shell' terminology, and there is no clear consensus on the interpretation of this concept in the context of external fields.
The discussion highlights the dependence on definitions related to 'on-shell' and 'off-shell' conditions, as well as the implications of external fields on particle behavior, which remain unresolved.
asimov42 said:could someone explain why a real, 'observable' particle is said to be 'off-shell' in an external field?
Off shell just means that the standard asymptotic (or free field) relation $p^2=m^2$ (in units where $c=1$), which defines the on shell condition, is not satisfied.asimov42 said:Or is the use of 'off shell' in this case simply to indicate that the field may influence the energy of the particle?