William Threlfall

William Threlfall (1888 to 1949) was a German mathematician who worked on algebraic topology and is remembered above all as the co-author, with Herbert Seifert, of the standard textbook Lehrbuch der Topologie, published in 1934. Born in Dresden to a British father who drowned in India before his son was born, he first studied chemistry at Jena, then mathematics at Gottingen, and took his doctorate at Leipzig in 1926 with a thesis on regular divisions of surfaces. He lectured at the Technische Hochschule in Dresden, where his topology course gave Seifert both the subject and a lifelong friendship, and later held chairs at Halle, Frankfurt and Heidelberg. With Seifert he also wrote a book on the calculus of variations in the large, based on Morse theory, and he published a study of group pictures in 1932. He died at the mathematics research centre at Oberwolfach in 1949.