*(English)*Zbl 0956.42014

There is a revolution sweeping through asymptotics of orthogonal polynomials called the Riemann-Hilbert method. It has enabled researchers such as the present authors and Deift, Kriecherbauer, MacLaughlin and others to obtain very precise (and uniform) asymptotics for orthogonal polynomials for exponential weights, in situations where the classical Bernstein-SzegĂ¶ methods give limited precision. And this paper is the record of one of the first breakthroughs in this exciting development.

Let

where $g>0>t$, so that $V$ is a double-well potential. Let $0<\epsilon <1$, and for $n\ge 1$ consider a parameter $N$ satisfying

Let us consider the monic orthogonal polynomials ${P}_{n}$ with respect to the varying weight $w:=exp(-NV)$, so that

where ${h}_{n}>0$. The authors establish very precise asymptotics for ${P}_{n}$ and the associated recurrence coefficients as $n\to \infty $. Then they apply these to establish universality of the local distribution of eigenvalues in the matrix model with quartic potential.

A key point in the analysis is the Fokas-Its-Kitaev Riemann-Hilbert problem, in which the orthogonal polynomials appear explicitly. This is followed by use of an approximate solution to the Riemann-Hilbert problem, and a proof that the approximate solution gives the asymptotic formula. The paper contains an extensive review of related literature; in particular, the context of the results and their motivation is very clearly presented. This paper will be of great use to anyone interested in orthogonal polynomials and their applications.

##### MSC:

42C05 | General theory of orthogonal functions and polynomials |

33C05 | Classical hypergeometric functions, ${}_{2}{F}_{1}$ |

15A52 | Random matrices (MSC2000) |

33C45 | Orthogonal polynomials and functions of hypergeometric type |

41A60 | Asymptotic approximations, asymptotic expansions (steepest descent, etc.) |