  We propose an alternative variational principle whose critical point is the
algebraic plane curve associated to a matrix model (the spectral curve, i.e.
the large $N$ limit of the resolvent). More generally, we consider a
variational principle that is equivalent to the problem of finding a plane
curve with given asymptotics and given cycle integrals. This variational
principle is not given by extremization of the energy, but by the extremization
of an "entropy".
