Quote by arroy_0205
1. I read that the picture of gauge bosons as mediators of interaction originates in and is valid in perturbation theory. But how do we know that picture is correct? We do perturbation theory only because we do not know how to study a system in a fully nonperturbative way. If someday we discover a nonperturbative way of doing all such calculations what will happen to this picture?

In order to do that you need some theory (= a collection of mathematical expressions and rules how to use them). Then you can start to test perturbative and nonperturbative approaches. For QCD we have both (applicable in different regimes) and it seems that it works quite well.
As long as we start to write down a Lagrangian which contains gauge bosons we will never find sonmething else and the final theory will always contain gauge bosons; the question whether we do perturbative or nonperturbative calculations is only a technical one.
So the picture with gauge bosons will not break down when we do nonperturbative calculations using gauge bosons; it will break down when we write down something which does not contain gauge bosons ;)