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<article article-type="research-article" dtd-version="1.3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xml:lang="ru"><front><journal-meta><journal-id journal-id-type="publisher-id">cheb</journal-id><journal-title-group><journal-title xml:lang="ru">Чебышевский сборник</journal-title><trans-title-group xml:lang="en"><trans-title>Chebyshevskii Sbornik</trans-title></trans-title-group></journal-title-group><issn pub-type="ppub">2226-8383</issn><publisher><publisher-name>Tula State Lev Tolstoy  Pedagogical University</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.22405/2226-8383-2020-21-1-357-363</article-id><article-id custom-type="elpub" pub-id-type="custom">cheb-802</article-id><article-categories><subj-group subj-group-type="heading"><subject>Research Article</subject></subj-group><subj-group subj-group-type="section-heading" xml:lang="ru"><subject>Статьи</subject></subj-group><subj-group subj-group-type="section-heading" xml:lang="en"><subject>Article</subject></subj-group></article-categories><title-group><article-title>О размере множества произведения множеств рациональных чисел</article-title><trans-title-group xml:lang="en"><trans-title>On the size of the set of the product of sets of rational numbers</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Штейников</surname><given-names>Юрий Николаевич</given-names></name><name name-style="western" xml:lang="en"><surname>Shteinikov</surname><given-names>Yuri Nikolaevich</given-names></name></name-alternatives><bio xml:lang="ru"/><email xlink:type="simple">yuriisht@gmail.com</email><xref ref-type="aff" rid="aff-1"/></contrib></contrib-group><aff-alternatives id="aff-1"><aff xml:lang="ru"><institution>Федеральный научный центр «Научно-исследовательский институт мистемных исследований РАН»</institution><country>Россия</country></aff><aff xml:lang="en"><institution>Scientific Research Institute of System Analysis</institution><country>Russian Federation</country></aff></aff-alternatives><pub-date pub-type="collection"><year>2020</year></pub-date><pub-date pub-type="epub"><day>25</day><month>04</month><year>2020</year></pub-date><volume>21</volume><issue>1</issue><fpage>357</fpage><lpage>363</lpage><permissions><copyright-statement>Copyright &amp;#x00A9; Штейников Ю.Н., 2020</copyright-statement><copyright-year>2020</copyright-year><copyright-holder xml:lang="ru">Штейников Ю.Н.</copyright-holder><copyright-holder xml:lang="en">Shteinikov Y.N.</copyright-holder><license xml:lang="ru" license-type="creative-commons-attribution" xlink:href="https://creativecommons.org/licenses/by/4.0/" xlink:type="simple"><license-p>Данная работа распространяется под лицензией Creative Commons Attribution 4.0.</license-p></license><license xml:lang="en" license-type="creative-commons-attribution" xlink:href="https://creativecommons.org/licenses/by/4.0/" xlink:type="simple"><license-p>This work is licensed under a Creative Commons Attribution 4.0 License.</license-p></license></permissions><self-uri xlink:href="https://www.chebsbornik.ru/jour/article/view/802">https://www.chebsbornik.ru/jour/article/view/802</self-uri><trans-abstract xml:lang="en"><p>For the first time  in the article [<xref ref-type="bibr" rid="cit1">1</xref>] was established non-trivial lower bounds on the size of the set of products of rational numbers, the numerators and denominators of which are limited to a certain quantity $Q$. Roughly speaking, it was shown that the size of the product deviates from the maximum by no less than $$\exp \Bigl\{(9 + o(1)) \frac{\log Q}{\sqrt{\log{\log Q}}}\Bigl\}$$ times. In the article [<xref ref-type="bibr" rid="cit7">7</xref>], the index of $ \log{\log Q} $ was improved from $ 1/2 $ to $ 1 $, and the proof of the main result on the set of fractions was fundamentally different. This proof, its argument was based on the search for a special large subset of the original set of rational numbers, the set of numerators and denominators of which were pairwise mutually prime numbers. The main tool was the consideration of random subsets. A lower estimate was obtained for the mathematical expectation of the size of this random subset. There, it was possible to obtain an upper bound for the multiplicative energy of the considered set. The lower bound for the number of products and the upper bound for the multiplicative energy of the set are close to optimal results. In this article, we propose the following scheme. In general, we follow the scheme of the proof of the article [<xref ref-type="bibr" rid="cit1">1</xref>], while modifying some steps and introducing some additional optimizations, we also improve the index from $1/2$ to $1-\varepsilon$ for an arbitrary positive $\varepsilon&gt;0$.</p></trans-abstract><kwd-group xml:lang="ru"><kwd>рациональные числа</kwd><kwd>делимость</kwd><kwd>дроби</kwd><kwd>случайное множество</kwd><kwd>энергия</kwd><kwd>число представлений</kwd><kwd>функция делителей</kwd><kwd>гладкие числа</kwd><kwd>преобразование Абеля</kwd><kwd>подмножество</kwd></kwd-group><kwd-group xml:lang="en"><kwd>rational numbers</kwd><kwd>divisibility</kwd><kwd>fractions</kwd><kwd>random set</kwd><kwd>energy</kwd><kwd>number of representations</kwd><kwd>divisor function</kwd><kwd>smooth numbers</kwd><kwd>Abel transformation</kwd><kwd>subset</kwd></kwd-group></article-meta></front><back><ref-list><title>References</title></ref-list><fn-group><fn fn-type="conflict"><p>The authors declare that there are no conflicts of interest present.</p></fn></fn-group></back></article>
