<article 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" article-type="research-article" dtd-version="1.2" xml:lang="ru"><front><journal-meta><journal-id journal-id-type="publisher-id">Journal of Experimental and Theoretical Physics</journal-id><journal-title-group><journal-title>Journal of Experimental and Theoretical Physics</journal-title></journal-title-group><issn publication-format="print">0044-4510</issn><issn publication-format="electronic">3034-641X</issn><publisher><publisher-name>Russian Academy of Science</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.31857/S0044451023120155</article-id><title-group><article-title>On the Heat Capacity of Quantum Hard Sphere Fluid</article-title><trans-title-group xml:lang="ru"><trans-title>О теплоемкости квантовой системы твердых сфер</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author"><contrib-id contrib-id-type="orcid"></contrib-id><name-alternatives><name xml:lang="en"><surname>Stishov</surname><given-names>S. M</given-names></name><name xml:lang="ru"><surname>Стишов</surname><given-names>С. М </given-names></name></name-alternatives><email>stishovsm@lebedev.ru</email><xref ref-type="aff" rid="aff-1"></xref><xref ref-type="aff" rid="aff-2"></xref></contrib></contrib-group><aff-alternatives id="aff-1"><aff><institution xml:lang="ru">Физический институт им. П. Н. Лебедева Российской академии наук</institution><institution xml:lang="en">Lebedev Physical Institute</institution></aff></aff-alternatives><aff-alternatives id="aff-2"><aff><institution xml:lang="ru"></institution><institution xml:lang="en"></institution></aff></aff-alternatives><pub-date date-type="pub" iso-8601-date="2023-12-01" publication-format="electronic"><day>01</day><month>12</month><year>2023</year></pub-date><volume>164</volume><issue>6</issue><fpage>1022</fpage><lpage>1025</lpage><abstract xml:lang="en"><p>The thermodynamic properties of the Boltzmann hard sphere system is discussed. It was found that zero point energy decreases with temperature so slowly that it turned out to be an almost a constant addition to the classical value. In result the heat capacity of the system differs little from the classical value of 3/2 k everywhere except for the narrow region of low temperatures, where heat capacity drops to zero. The predicted linear temperature contribution to the heat capacity like in ideal Fermi gas was clearly detected in the quantum hard sphere system at the lowest temperatures.</p></abstract><trans-abstract xml:lang="ru"><p>Обсуждаются термодинамические свойства больцмановской системы твердых сфер. Как оказалось, нулевая энергия системы уменьшается с температурой настолько медленно, что является почти постоянной добавкой к классической величине. В результате теплоемкость системы мало отличается от классического значения 3 / 2 k везде, кроме узкой области низких температур, где теплоемкость падает до нуля. Предсказываемый линейный температурный вклад в теплоемкость, как это имеет место в идеальном ферми-газе, обнаруживается в системе квантовых твердых сфер при самых низких температурах.</p></trans-abstract></article-meta></front><body></body><back><ref-list><ref id="B1"><label>B1</label><citation-alternatives><mixed-citation xml:lang="ru">K. J.Runge and G. V. Chester, Phys. Rev. B 38, 135 (1988).</mixed-citation><mixed-citation xml:lang="en"></mixed-citation></citation-alternatives></ref><ref id="B2"><label>B2</label><citation-alternatives><mixed-citation xml:lang="ru">J. A. Barker and D. Henderson, J.Chem.Phys. 47, 2856 (1967).</mixed-citation><mixed-citation xml:lang="en"></mixed-citation></citation-alternatives></ref><ref id="B3"><label>B3</label><citation-alternatives><mixed-citation xml:lang="ru">J.-P. Hansen, D. Levesque, and D. Schi, Phys. Rev. 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