On Nevai's characterization of measures with almost everywhere positive derivative (Q1813615)

The present paper gives an alternative proof of Nevai's result [\textit{P. Nevai}, Rocky Mt. J. Math. 19, No. 1, 293-302 (1989; Zbl 0688.42021)] regarding the characterization of a finite positive measure on the unit circle with a positive differential almost everywhere by an equality involving a set of orthonormal polynomials with respect to the said measure. In the proof, another characterization of the said measure in terms of Turán-type inequalities is established.