  In this paper we propose a method to study the Functional Renormalization
Group at finite chemical potential. The method consists of mapping the FRG
equations within the Fermi surface into a differential equation defined on a
rectangle with zero boundary conditions. To solve this equation we use an
expansion of the potential in a harmonic basis. With this method we determined
the phase diagram of a simple Yukawa-type model; as expected, the bosonic
fluctuations decrease the strength of the transition.
