The work of T. Kawai on hyperfunction theory and microlocal analysis Part 1 - Microlocal analysis and differential equations

Takahiro Kawai talked about his first encounter with the theory of hyper-functions recently on an occasion of 70th birthday of Hikosaburo Komatsu. We start, however, the story at the time before this encounter. After Mikio Sato invented the theory of hyperfunctions together with the notion of local cohomology groups in 1957, the theory did not prevail until Komatsu gave lectures in US and Europe. Kawai's experience with the theory began when Komatsu gave an invited talk on an annual meeting of the Mathematical Society of Japan around 1967. This invited talk by Komatsu was given just after his return to Japan from his long mission abroad and really fascinated Kawai so that he left all of his belongings in the conference room. At this point, Kawai's career as mathematician might have been oriented.