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Even and Old Overdetermined Strata for Degree 6 Hyperbolic Polynomials

Ezzaldine, Hayssam, Kostov, Vladimir Petrov (2008)

Serdica Mathematical Journal

2000 Mathematics Subject Classification: 12D10.In the present paper we consider degree 6 hyperbolic polynomials (HPs) in one variable (i.e. real and with all roots real). We are interested in such HPs whose number of equalities between roots of the polynomial and/or its derivatives is higher than expected. We give the complete study of the four families of such degree 6 even HPs and also of HPs which are primitives of degree 5 HPs.Research partially supported by research project 20682 for cooperation...

Even coefficient estimates for bounded univalent functions

D. V. Prokhorov (1993)

Annales Polonici Mathematici

Extremal coefficient properties of Pick functions are proved. Even coefficients of analytic univalent functions f with |f(z)| < M, |z| < 1, are bounded by the corresponding coefficients of the Pick functions for large M. This proves a conjecture of Jakubowski. Moreover, it is shown that the Pick functions are not extremal for a similar problem for odd coefficients.

Exact asymptotics of nonlinear difference equations with levels 1 and 1 +

G.K Immink (2008)

Annales de la faculté des sciences de Toulouse Mathématiques

We study a class of nonlinear difference equations admitting a 1 -Gevrey formal power series solution which, in general, is not 1 - (or Borel-) summable. Using right inverses of an associated difference operator on Banach spaces of so-called quasi-functions, we prove that this formal solution can be lifted to an analytic solution in a suitable domain of the complex plane and show that this analytic solution is an accelero-sum of the formal power series.

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