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Bernstein classes

N. Roytwarf, Yosef Yomdin (1997)

Annales de l'institut Fourier

One of the classical Bernstein inequalities compares the maxima of a polynomial of a given degree on the interval [-1,1] and on the ellipse in the complex plane with the focuses -1, 1 and the semiaxes R . We prove a similar inequality for a branch of an algebraic function of a given degree on the maximal disk of its regularity, with the explicitly given constant, depending on the degree only. In particular, this improves a recent inequality of Fefferman and Narasimhan and answers one of their questions....

Bessel matrix differential equations: explicit solutions of initial and two-point boundary value problems

Enrique Navarro, Rafael Company, Lucas Jódar (1993)

Applicationes Mathematicae

In this paper we consider Bessel equations of the type t 2 X ( 2 ) ( t ) + t X ( 1 ) ( t ) + ( t 2 I - A 2 ) X ( t ) = 0 , where A is an n × n complex matrix and X(t) is an n × m matrix for t > 0. Following the ideas of the scalar case we introduce the concept of a fundamental set of solutions for the above equation expressed in terms of the data dimension. This concept allows us to give an explicit closed form solution of initial and two-point boundary value problems related to the Bessel equation.

Co-solutions of algebraic matrix equations and higher order singular regular boundary value problems

Lucas Jódar, Enrique A. Navarro (1994)

Applications of Mathematics

In this paper we obtain existence conditions and a closed form of the general solution of higher order singular regular boundary value problems. The approach is based on the concept of co-solution of algebraic matrix equations of polynomial type that permits the treatment of the problem without considering an extended first order system as it has been done in the known literature.

Cycles évanescents d’une fonction de Liouville de type f 1 λ 1 . . . f p λ p

Emmanuel Paul (1995)

Annales de l'institut Fourier

On construit un transport transverse aux fibres d’une fonction multivaluée de type f 1 λ 1 ... f p λ p ( λ i complexes), à l’origine de 2 . Ce transport est unique à isotopie près. On en déduit l’existence de voisinages réguliers dans lesquels les fibres sont toutes C difféomorphes (voire dans un cas quasi-homogène, analytiquement difféomorphes). On obtient également une généralisation de la notion de monodromie. On calcule enfin l’homologie évanescente de la fibre-type, en précisant le gradué qui lui est associé.

Diagonalization and rationalization of algebraic Laurent series

Boris Adamczewski, Jason P. Bell (2013)

Annales scientifiques de l'École Normale Supérieure

We prove a quantitative version of a result of Furstenberg [20] and Deligne [14] stating that the diagonal of a multivariate algebraic power series with coefficients in a field of positive characteristic is algebraic. As a consequence, we obtain that for every prime p the reduction modulo p of the diagonal of a multivariate algebraic power series f with integer coefficients is an algebraic power series of degree at most p A and height at most A p A , where A is an effective constant that only depends on...

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