  The well-known phase structure of the two-dimensional sine-Gordon model is
reconstructed by means of its renormalization group flow, the study of the
sensitivity of the dynamics on microscopic parameters. Such an analysis
resolves the apparent contradiction between the phase structure and the
triviality of the effective potential in either phases, provides a case where
usual classification of operators based on the linearization of the scaling
relation around a fixed point is not available and shows that the Maxwell-cut
generates an unusually strong universality at long distances. Possible
analogies with four-dimensional Yang-Mills theories are mentioned, too.
