### Abstract

In the Joint work with M. Bertola (math-ph/0605043), we have studied properties of a special type of algebraic curves, which we called admissible Boutrox curves. We have shown that these curves can be used to compute the asymptotics of semi-classical orthogonal polynomials via the `Riemann-Hilbert method'. In this talk I will explain what these admissible Boutroux curves are and how they are related to the `Riemann-Hilbert method'.