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Christoffel functions,orthogonal polynomials,and Nevai's conjecture for Freud weights
Authors:A L Levin  D S Lubinsky
Institution:1. Department of Mathematics, The Open University of Israel, Ramat Aviv, P.O. Box 39328, 61392, Tel Aviv, Israel
2. Department of Mathematics, University of Witwatersrand, P.O. Wits 2050, Republic of South Africa
Abstract:We obtain upper and lower bounds for Christoffel functions for Freud weights by relatively new methods, including a new way to estimate discretization of potentials. We then deduce bounds for orthogonal polynomials onRopf thereby largely resolving a 1976 conjecture of P. Nevai. For example, let W:=e –Q, whereQ:RopfrarrRopf is even and continuous inRopf, Q" is continuous in (0, infin) andQ '>0 in (0, infin), while, for someA, B,

$$1< A \leqslant \frac{{(d/dx)(xQ'(x))}}{{Q'(x)}} \leqslant B,x \in (0,\infty )$$
Keywords:AMS classification" target="_blank">AMS classification  Primary 41A17  42C05  Secondary 41A10
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