Haruo Hosoya

Haruo Hosoya (Japanese: 細矢 治夫, Hepburn: Hosoya Haruo, born 1936) is a Japanese chemist and emeritus professor of Ochanomizu University, Tokyo, Japan. He is the namesake of the Hosoya index used in computational chemistry.

Haruo Hosoya was born in Kamakura, Japan to a family of an office worker. During 1955-1959 he studied at the University of Tokyo. In 1964 he wrote his Ph.D. thesis, "Study on the Structure of Reactive Intermediates and Reaction Mechanism". After postdoc work abroad (Ann Arbor, Michigan, with prof. John Platt), in 1969 he became associate professor at the Ochanomizu University, where he worked for 33 years until his retirement in 2002. After retirement he keeps working in computational chemistry.

In 1971, Hosoya defined topological index (a graph invariant) as the total number of matchings of a graph plus 1. The Hosoya index is often used in computer (mathematical) chemistry investigations for organic compounds.

In 2002-2003 the Internet Electronic Journal of Molecular Design dedicated a series of issues to commemorate the 65th birthday of professor Hosoya.

Hosoya's article "The Topological Index Z Before and After 1971" describes the history of the notion and the associated inside stories and details other Hosoya's achievements.