This special section is dedicated to the memory of the late Professor Tohru Eguchi. Professor Eguchi passed away on 30 January 2019. His early passing before finishing his term as Editor-in-Chief of PTEP was a great loss not only for PTEP, but also much more so for researchers working in the various fields where he made a lasting mark with his many contributions. The Editorial Board of PTEP decided to pay homage to Professor Eguchi with this special section commemorating his remarkable achievements, especially in the area of mathematical methods in theoretical particle physics. The invited authors include his former collaborators, students, and associates. We hope that the present assemblage of contributing papers as a whole is useful in reviewing and grasping the current status of various research topics related to his main contributions as well as for learning about and remembering his important works, done in collaboration with many prominent researchers from different backgrounds. Some of the contributing papers also contain interesting personal reminiscences about exchanges between Professor Eguchi and the authors.

中文翻译：

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理论粒子物理学中数学方法的最新发展——纪念 Tohru Eguchi——第二部分

这个特别版块是为了纪念已故的江口彻教授。江口教授于 2019 年 1 月 30 日逝世。他在PTEP主编任期届满前的早逝，不仅是PTEP的重大损失，更是他在各个领域做出持久贡献的研究人员的巨大损失。标记他的许多贡献。PTEP编委会决定以这个特别版块向江口教授致敬，以纪念他的卓越成就，特别是在理论粒子物理学的数学方法领域。受邀作者包括他以前的合作者、学生和同事。我们希望目前的贡献论文集作为一个整体有助于回顾和掌握与他的主要贡献相关的各种研究课题的现状，以及学习和记住他与许多杰出研究人员合作完成的重要工作。不同的背景。一些投稿论文还包含了江口教授与作者之间交流的有趣的个人回忆。