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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">matmess</journal-id><journal-title-group><journal-title xml:lang="ru">Математические заметки СВФУ</journal-title><trans-title-group xml:lang="en"><trans-title>Mathematical notes of NEFU</trans-title></trans-title-group></journal-title-group><issn pub-type="ppub">2411-9326</issn><issn pub-type="epub">2587-876X</issn><publisher><publisher-name>Северо-Восточный федеральный университет имени М.К. Аммосова</publisher-name></publisher></journal-meta><article-meta><article-id custom-type="elpub" pub-id-type="custom">matmess-416</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>МАТЕМАТИКА</subject></subj-group></article-categories><title-group><article-title>Сингулярные решения задачи (3 + 1)-D Проттера для волнового уравнения</article-title><trans-title-group xml:lang="en"><trans-title>SINGULAR SOLUTIONS OF THE (3+1)–D PROTTER PROBLEM FOR THE WAVE EQUATION</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>Popivanov</surname><given-names>N.</given-names></name><name name-style="western" xml:lang="en"><surname>Popivanov</surname><given-names>N.</given-names></name></name-alternatives><bio xml:lang="ru"><p>Nedyu Popivanov</p><p>Department of Mathematics and Informatics, University of Sofia, 1164 Sofia, Bulgaria </p></bio><bio xml:lang="en"><p>Nedyu Popivanov</p><p>Department of Mathematics and Informatics, University of Sofia, 1164 Sofia, Bulgaria </p></bio><email xlink:type="simple">nedyu@fmi.uni-sofia.bg</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>Popov</surname><given-names>T.</given-names></name><name name-style="western" xml:lang="en"><surname>Popov</surname><given-names>T.</given-names></name></name-alternatives><bio xml:lang="ru"><p>Todor Popov</p><p>Department of Mathematics and Informatics, University of Sofia, 1164 Sofia, Bulgaria </p></bio><bio xml:lang="en"><p>Todor Popov</p><p>Department of Mathematics and Informatics, University of Sofia, 1164 Sofia, Bulgaria </p></bio><email xlink:type="simple">topopover@fmi.uni-sofia.bg</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>Scherer</surname><given-names>R.</given-names></name><name name-style="western" xml:lang="en"><surname>Scherer</surname><given-names>R.</given-names></name></name-alternatives><bio xml:lang="ru"><p>Rudolf Scherer</p><p>Institute for Applied and Numerical Mathematics, Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe, Germany</p></bio><bio xml:lang="en"><p>Rudolf Scherer</p><p>Institute for Applied and Numerical Mathematics, Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe, Germany</p></bio><email xlink:type="simple">rudolf.scherer@kit.edu</email><xref ref-type="aff" rid="aff-2"/></contrib></contrib-group><aff-alternatives id="aff-1"><aff xml:lang="ru"><institution>University of Sofia</institution><country>Болгария</country></aff><aff xml:lang="en"><institution>University of Sofia</institution><country>Bulgaria</country></aff></aff-alternatives><aff-alternatives id="aff-2"><aff xml:lang="ru"><institution>Karlsruhe Institute of Technology (KIT)</institution><country>Германия</country></aff><aff xml:lang="en"><institution>Karlsruhe Institute of Technology (KIT)</institution><country>Germany</country></aff></aff-alternatives><pub-date pub-type="collection"><year>2015</year></pub-date><pub-date pub-type="epub"><day>07</day><month>07</month><year>2026</year></pub-date><volume>22</volume><issue>1</issue><fpage>69</fpage><lpage>77</lpage><permissions><copyright-statement>Copyright &amp;#x00A9; Popivanov N., Popov T., Scherer R., 2026</copyright-statement><copyright-year>2026</copyright-year><copyright-holder xml:lang="ru">Popivanov N., Popov T., Scherer R.</copyright-holder><copyright-holder xml:lang="en">Popivanov N., Popov T., Scherer R.</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://matmess.elpub.ru/jour/article/view/416">https://matmess.elpub.ru/jour/article/view/416</self-uri><abstract><p>Изучаются некоторые краевые задачи для неоднородного волнового уравнения с тремя пространственными и одной временной переменными. Эти задачи можно рассматривать как четырехмерный аналог плоской задачи Дарбу. В отличие от плоской задачи четырехмерная задача оказывается некорректной, поскольку однородная сопряженная к ней задача имеет бесконечно много классических решений. Таким образом, в рамках классической теории изучаемая задача не является фредгольмовой. С другой стороны, известно, что для гладкой правой части существует однозначно определенное обобщенное решение, которое может иметь сильную особенность в граничной точке. Эта особенность будет изолирована в вершине характеристического светового конуса и не будет распространяться вдоль конуса. В работе доказывается общий результат о существовании, существование сингулярних решений и для них устанавливаются априорные оценки. Прилагается обширная библиография.</p></abstract><trans-abstract xml:lang="en"><p>We study some boundary value problems for the nonhomogeneous wave equation with three space and one time variables. The problems could be viewed as R4 analogs of Darboux problems in R2. In contrast to the planar Darboux problem the fourdimensional version is ill-posed, since its homogeneous adjoint problem has infinitely many classical solutions. Thus, in the framework of the classical solvability the problem is not Fredholm. Alternatively, it is known that for smooth right-hand side functions, there is a uniquely determined generalized solution that may have strong power-type singularity at one boundary point. This singularity is isolated at the vertex of the characteristic light cone and does not propagate along the cone. In this article we give a general existence result and find a priori estimates for singular solutions. A lengthy reference list is appended.</p></trans-abstract><kwd-group xml:lang="ru"><kwd>волновое уравнение</kwd><kwd>краевая задача</kwd><kwd>обобщенное решение</kwd><kwd>сингулярное решение</kwd><kwd>распространение сингулярности</kwd><kwd>специальные функции</kwd></kwd-group><kwd-group xml:lang="en"><kwd>wave equation</kwd><kwd>boundary value problems</kwd><kwd>generalized solution</kwd><kwd>singular solutions</kwd><kwd>propagation of singularities</kwd><kwd>special functions</kwd></kwd-group><funding-group><funding-statement xml:lang="ru">The research of N. Popivanov and T. Popov was partially supported by the Bulgarian NSF Under Grant DCVP 02/1/2009 “Centre of Excellence on Supercomputer Applications” and by Sofia University Grants 94/2014 and 142/2015.</funding-statement><funding-statement xml:lang="en">The research of N. Popivanov and T. 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