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General Mathematics Seminar of the St. Petersburg Division of Steklov Institute of Mathematics, Russian Academy of Sciences
October 18, 2021 13:00, St. Petersburg, POMI, room 311 (27 Fontanka). Also it is possible to watch this talk in Zoom, see https://logic.pdmi.ras.ru/GeneralSeminar/index.html
 

Series of talks of the winners of the PDMI scientific competition 2019


On distribution of algebraic numbers

D. Zaporozhets

St. Petersburg Department of Steklov Mathematical Institute of Russian Academy of Sciences
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MP4 1,307.5 Mb

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Abstract: It follows from the group structure of rational points on the unit circle that in some sense they are uniformly distributed. The well-known “rational parametrization” $\rho:\mathbb R^1\to\mathbb S^1$ of the unit circle
$$ \rho(t)=\left(\frac{2t}{1+t^2},\frac{t^2-1}{1+t^2}\right), $$
which is nothing but the inverse stereographic projection from the upper point of the circle onto the abscissa, sets a one-to-one correspondence between the rational points on the unit circle (except the upper one) and all rational numbers. In particular, it gives one way of finding all Pythagorean triples.
The stereographic projection maps the uniform measure on the circle to the measure on the line with the Cauchy density $\frac{c}{1+t^2}$. Thus we obtain that, in some sense, the rational numbers are distributed with respect to this density (the rigorous formulation will be given).
The rational numbers are the algebraic numbers of degree 1. In this talk, we aim to generalize the above elementary observation with the Cauchy density to the algebraic numbers of arbitrary degree $n$. To this end, we will apply the theory of zeros of random polynomials.
Based on the joint paper
F. Götze, D. Koleda, D. Zaporozhets, “Joint distribution of conjugate algebraic numbers: a random polynomial approach”, Adv. Math., 359 (2020)
 
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