Generating the mass gap of the sine-Gordon model

Understand

We discuss in this study the possibility of finding a finite mass gap in the broken phase of the sine-Gordon model in $d=2$ using the functional flows.

• We demonstrate that the signal of the presence of massive excitations, a finite positively-curved {\em blocked} potential around its minima, is recovered only in our treatment.
• The usual results based on the flow of the Fourier expansion of the {\em blocked} action are then shown to actually fit a singularity.