Horst Sachs (27 March 1927 – 25 April 2016) was a German

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

, an expert in

graph theory In mathematics, graph theory is the study of ''graphs'', which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of '' vertices'' (also called ''nodes'' or ''points'') which are conn ...

, a recipient of the

Euler Medal The Institute of Combinatorics and its Applications (ICA) is an international scientific organization formed in 1990 to increase the visibility and influence of the combinatorial community. In pursuit of this goal, the ICA sponsors conferences, ...

(2000). He earned the degree of

Doctor of Science Doctor of Science ( la, links=no, Scientiae Doctor), usually abbreviated Sc.D., D.Sc., S.D., or D.S., is an academic research degree awarded in a number of countries throughout the world. In some countries, "Doctor of Science" is the degree used f ...

(Dr. rer. nat.) from the Martin-Luther-Universität Halle-Wittenberg in 1958. Following his retirement in 1992, he was

professor emeritus ''Emeritus'' (; female: ''emerita'') is an adjective used to designate a retired chair, professor, pastor, bishop, pope, director, president, prime minister, rabbi, emperor, or other person who has been "permitted to retain as an honorary title ...

at the Institute of Mathematics of the

Technische Universität Ilmenau The Technische Universität Ilmenau (''Ilmenau University of Technology'', TU Ilmenau) is a German public research university located in Ilmenau, Thuringia, central Germany. Founded in 1894, it has five academic departments (faculties) with abo ...

. His encyclopedic book in spectral graph theory, ''Spectra of Graphs. Theory and Applications'' (with Dragos Cvetković and Michael Doob) has several editions and was translated in several languages.Review by P. Rowlinson (1996), ''Proceedings of the Edinburgh Mathematical Society (Series 2)'' 39: 188–189, . Two theorems in graph theory bear his name. One of them relates the coefficients of the characteristic polynomial of a graph to certain structural features of the graph. Another one is a simple relation between the characteristic polynomials of a graph and its

line graph In the mathematical discipline of graph theory, the line graph of an undirected graph is another graph that represents the adjacencies between edges of . is constructed in the following way: for each edge in , make a vertex in ; for every ...

. Sachs subgraphs are also named after Sachs.

References

1927 births 20th-century German mathematicians Graph theorists 2016 deaths Academic staff of Technische Universität Ilmenau {{Germany-mathematician-stub