Thanks, this makes sense. I was somehow confused, but your comment answers exactly my question.dextercioby said:connected or disconnected it doesn't matter, since there are only 2 spacetime points.
The dressed propagator is a mathematical concept used in quantum field theory to describe the propagation of a particle in an interacting system. It takes into account the effects of interactions between particles, which can modify the properties of the propagating particle.
The dressed propagator can be calculated using Feynman diagrams, which represent the interactions between particles. These diagrams involve integrating over all possible paths that a particle can take, taking into account the interactions at each point along the path.
The dressed propagator has the following properties:
The dressed propagator is an important concept in quantum field theory, as it allows us to calculate physical observables such as particle scattering amplitudes. It also helps us understand the effects of interactions between particles, which are crucial in many physical processes.
The bare propagator is the propagator that describes a free particle, without taking into account any interactions. The dressed propagator, on the other hand, includes the effects of interactions between particles. This results in a more complex and frequency-dependent propagator, which is necessary for accurately describing physical systems.