On exremality of affine image of topological product of some varieties

I. Sh. Jabbarov ; L. G. Ismailova

Čebyševskij sbornik, Tome 22 (2021) no. 2, pp. 490-500.

Résumé

In the theory of Diophantine Approximations one considers a question on approximation of Real Numbers by rational fractions with one and the same denominators. Among intensively studied questions of this theory a special place occupy Metric questions. Here such questions of the theory are considered which take place for almost all real numbers from given interval. For the first time similar questions have been studied by Khintchine for approximation of independent quantities. It had been investigated by him conditions at which for almost all real numbers specified accuracy of approximation is reached. Very important in the technical plan Khintchince's transference principle allows us to connect a simultaneous approximations of dependent quantities with approximations of linear forms with integral coefficients. In 1932 Mahler K. has entered classification of transcendental numbers into consideration. He showed that almost all transcendental numbers are $S$ -numbers. Moreover, Mahler had proved an existence of a constant $ \gamma> 0$ such that for almost all $ \omega $ $$ |P (\omega) |> h ^ {-n\gamma}, $$ for all polynomials $P $ of degree no more $n $ and height $h> h _ {0} (\omega, n, \gamma) $. Mahler showed that it is possible to take $$ \gamma=4 +\varepsilon. $$ In the same work Mahler made an assumption that it is possible to take $ \gamma=1 +\varepsilon $ for almost all real numbers. This hypothesis was proved by Sprindzhuk V. G by a method of essential and non-essential domains. Simultaneously, Sprindzhuk V. G. advanced some hypotheses generalising and improving Mahler's results. Further these investigations of Sprindzuk led to the development of a new direction in the theory of Diophantine Approximations – to the research of extremality of manifolds. In the present article we develop a new approach to these questions and offer a new proof for extremality of algebraic varieties. This method allows to establish extremality of affine image of topological product of some varieties. Considering one particular case, we prove that the extremality for these varieties is possible to deduct from theorems on the convergence exponent of a special integral of Terry's problem, using E.I. Kovalevskaya's lemma. Further, we derive from the getting result particular case of the Sprindzuk's hypothesis on extremality of varieties, induced by monomials of a polynomial in two variables.

Détail

Keywords: Diophantine approximation, extremal manifold, convergence exponent, special integral, Terry's problem.

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