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Shafarevich Seminar
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Rational approximation of the algebraic functions and functional analogues of the Diophantine approximations A. I. Aptekarev Keldysh Institute of Applied Mathematics of Russian Academy of Sciences, Moscow |
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Abstract: Let f be a germ (the power series expansion) of an algebraic function at infinity. We discuss the limiting properties of the convergent of a functional continued fraction with polynomial coefficients for f (alternative name is diagonal Pade approximant or best local rational approximant). If we compare this functional continued fraction for f with the usual continued fraction (with integer coefficients) for a real number, then the degree of the polynomial coefficient is analogous to the value (magnitude) of the integer coefficient. In our joint work with M. Yattselev [1], we derived strong (or Bernshtein-Szegö type) asymptotics for the denominators of the convergent of the functional continued fraction for analytic function with a finite number of branch points (which are in a generic position in the complex plane). One of the applications following from this result is a sharp estimate for a functional analog of the Thue-Siegel-Roth theorem. The bounds on the incomplete quotients for the functional continued fractions of the algebraic functions follows from thus result as well. References
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