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arXiv 0903.0086math.NT
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实数和p-adic数的同时逼近

Simultaneous Approximation to Real and p-adic Numbers

Dmitrij Zelo

摘要:

研究了用限制型整数多项式的根同时逼近一个固定的实数和p-adic数族的问题。我们用于此目的的方法是由H.达文波特和W. M.施密特在他们的研究近似实数的代数整数。这种方法基于Mahler的对偶性,要求研究具有相同因子的有理数逼近这些数的逐次幂的对偶问题。狄利克雷盒原理提供了这种近似的估计,但人们可以做得更好。在这篇论文中,我们建立了一个约束,当处理数字和它们的平方时,我们可以做得更好。我们还构造的例子表明,至少在某些情况下,这些约束是最佳的。回到原来的问题,我们得到估计的同时逼近实数和p-adic数的根的整数多项式的次数为3或4,固定系数的程度至少为3。在单个实数(且无p-adic数)的情况下,推广了D. Roy通过证明黄金分割率的平方是具有有界分母和迹的4次代数数逼近的最优指数。

英文摘要:

We study the problem of simultaneous approximation to a fixed family of real and p-adic numbers by roots of integer polynomials of restricted type. The method that we use for this purpose was developed by H. Davenport and W.M. Schmidt in their study of approximation to real numbers by algebraic integers. This method based on Mahler's Duality requires to study the dual problem of approximation to successive powers of these numbers by rational numbers with the same denominators. Dirichlet's Box Principle provides estimates for such approximations but one can do better. In this thesis we establish constraints on how much better one can do when dealing with the numbers and their squares. We also construct examples showing that at least in some instances these constraints are optimal. Going back to the original problem, we obtain estimates for simultaneous approximation to real and p-adic numbers by roots of integer polynomials of degree 3 or 4 with fixed coefficients in degree at least 3. In the case of a single real number (and no p-adic numbers), we extend work of D. Roy by showing that the square of the golden ratio is the optimal exponent of approximation by algebraic numbers of degree 4 with bounded denominator and trace.

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