Rudolf Halin (February 3, 1934 – November 14, 2014) was a German graph theorist, known for defining the ends of infinite graphs,[1] for Halin's grid theorem,[2][3] for extending Menger's theorem to infinite graphs,[4] and for his early research on treewidth and tree decomposition.
[5] He is also the namesake of Halin graphs, a class of planar graphs constructed from trees by adding a cycle through the leaves of the given tree; earlier researchers had studied the subclass of cubic Halin graphs but Halin was the first to study this class of graphs in full generality.
[7] He earned his doctorate from the University of Cologne in 1962, under the supervision of Klaus Wagner and Karl Dörge, after which he joined the faculty of the University of Hamburg.
[7] In February 1994, a colloquium was held at the University of Hamburg in honor of Halin's 60th birthday.
[9] In 2017, a special issue of the journal Abhandlungen aus dem Mathematischen Seminar der Universität Hamburg was published in his memory.