Tosio Kato aworked in the field of mathematics where he became known for "Kato's conjecture", a mathematical problem posed in 1953 which remains unsolved today.
Tosio Kato ( , Kato Toshio, August 25, 1917  October 2, 1999) was a Japanese mathematician who worked with partial differential equations, mathematical physics and functional analysis. Kato's conjecture is a mathematical problem named after mathematician Tosio Kato, of the University of California, Berkeley. Kato initially posed the problem in 1953. The problem remained unresolved for nearly a half-century, until it was jointly solved in 2001 by Pascal Auscher, Steve Hofmann, Michael Lacey, Alan McIntosh, and Philippe Tchamitchian. 
