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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">matatecs</journal-id><journal-title-group><journal-title xml:lang="ru">Математика и теоретические компьютерные науки</journal-title><trans-title-group xml:lang="en"><trans-title>Mathematics and Theoretical Computer Science</trans-title></trans-title-group></journal-title-group><issn pub-type="epub">2949-3919</issn><publisher><publisher-name>Казанский (Приволжский) федеральный университет</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.26907/2949-3919.2026.1.67-91</article-id><article-id custom-type="elpub" pub-id-type="custom">matatecs-105</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></article-categories><title-group><article-title>Многообразие SP(M3). II. Дуальность</article-title><trans-title-group xml:lang="en"><trans-title>The quasivariety SP (M3). II. Duality</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>Изъюрова</surname><given-names>А. Е.</given-names></name><name name-style="western" xml:lang="en"><surname>Izyurova</surname><given-names>A. E.</given-names></name></name-alternatives><bio xml:lang="ru"><p>Александра Евгеньевна Изъюрова</p><p>Ул. Пирогова, д. 1, Новосибирск, 630090</p></bio><bio xml:lang="en"><p>Aleksandra Evgenyevna Izyurova</p><p>1 Pirogov str., Novosibirsk 630090</p></bio><email xlink:type="simple">a.izyurova@g.nsu.ru</email><xref ref-type="aff" rid="aff-1"/></contrib><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Швидефски</surname><given-names>М. В.</given-names></name><name name-style="western" xml:lang="en"><surname>Schwidefsky</surname><given-names>M. V.</given-names></name></name-alternatives><bio xml:lang="ru"><p>Марина Владимировна Швидефски</p><p>Ул. Пирогова, д. 1, Новосибирск, 630090; пр. Акад. Коптюга, д. 4, г. Новосибирск, 630090</p></bio><bio xml:lang="en"><p>Marina Vladimirovna Schwidefsky</p><p>1 Pirogov str., Novosibirsk 630090; 4 Acad. Koptyug Ave., Novosibirsk 630090</p></bio><email xlink:type="simple">m.schwidefsky@g.nsu.ru</email><xref ref-type="aff" rid="aff-2"/></contrib></contrib-group><aff-alternatives id="aff-1"><aff xml:lang="ru"><institution>Новосибирский национальный исследовательский государственный университет</institution><country>Россия</country></aff><aff xml:lang="en"><institution>Novosibirsk State University</institution><country>Russian Federation</country></aff></aff-alternatives><aff-alternatives id="aff-2"><aff xml:lang="ru"><institution>Новосибирский национальный исследовательский государственный университет; Институт математики им. С.Л. Соболева СО РАН</institution><country>Россия</country></aff><aff xml:lang="en"><institution>Novosibirsk State University; Sobolev Institute of Mathematics SB RAS</institution><country>Russian Federation</country></aff></aff-alternatives><pub-date pub-type="collection"><year>2026</year></pub-date><pub-date pub-type="epub"><day>22</day><month>06</month><year>2026</year></pub-date><volume>4</volume><issue>1</issue><fpage>67</fpage><lpage>91</lpage><permissions><copyright-statement>Copyright &amp;#x00A9; Изъюрова А.Е., Швидефски М.В., 2026</copyright-statement><copyright-year>2026</copyright-year><copyright-holder xml:lang="ru">Изъюрова А.Е., Швидефски М.В.</copyright-holder><copyright-holder xml:lang="en">Izyurova A.E., Schwidefsky M.V.</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://matatecs.elpub.ru/jour/article/view/105">https://matatecs.elpub.ru/jour/article/view/105</self-uri><abstract><p>Диамантом называется пятиэлементная решетка M3, которая является наименьшей недистрибутивной модулярной решеткой. Мы устанавливаем дуальную эквивалентность категории, объектами которой являются биалгебраические решетки, принадлежащие многообразию, порожденному M3, а морфизмами – полные гомоморфизмы решеток, и категории, объектами которой являются так называемые M3-пространства, упорядоченные пространства с отношением эквивалентности, а морфизмами – так называемые M3-морфизмы. Аналогичный результат был установлен ранее В. Дзёбяком и вторым автором для пентагона N5, наименьшей немодулярной решетки с пятью элементами. Так называемые N5-пространства и M3-пространства имеют различную структуру. Однако, N5-морфизмы и M3-морфизмы соответственно возникают благодаря использованию классического понятия – понятия минимального покрытия элемента решетки.</p></abstract><trans-abstract xml:lang="en"><p>The diamond M3 is a five-element lattice which is the smallest nondistributive modular lattice. We establish the dual equivalence of the category with objects being bi-algebraic lattices belonging to the variety generated by M3 and with morphisms being complete lattice homomorphisms and the category with objects, called by us M3-spaces, being ordered spaces endowed with an equivalence relation and with so-called M3-morphisms. A similar result for the pentagon N5, a five-element lattice which is the smallest non-modular lattice, was established earlier by W. Dziobiak and the second author. The so-called N5-spaces there and M3-spaces here are completely different. However, morphisms between N5-spaces and between M3-spaces, respectively, are an application of an old concept – the minimal join cover refinement property for join covers of an element in a lattice.</p></trans-abstract><kwd-group xml:lang="ru"><kwd>решетка</kwd><kwd>многообразие</kwd><kwd>диамант</kwd><kwd>дуальность</kwd></kwd-group><kwd-group xml:lang="en"><kwd>lattice</kwd><kwd>variety</kwd><kwd>diamond</kwd><kwd>duality</kwd></kwd-group><funding-group><funding-statement xml:lang="ru">Работа поддержана Российским научным фондом, проект № 24-21-00075, https://rscf.ru/project/24-21-00075/</funding-statement><funding-statement xml:lang="en">The work is supported by the Russian Science Foundation (project № 24-21-00075), https://rscf.ru/project/24-21-00075/</funding-statement></funding-group></article-meta></front><back><ref-list><title>References</title><ref id="cit1"><label>1</label><citation-alternatives><mixed-citation xml:lang="ru">W. Dziobiak, M.V. 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