## ARAI, Toshiyasu

 Title Professor Field Mathematical Logic Research interests Proof Theory Current research In proof theory we are concerned with formal proofs in mathematics. I study mainly ordinal analysis. It is a field in proof theory, in which we associate ordinals with formal theories, thereby we are trying to unravel hidden structures in theories. Selected publications Intuitionistic fixed point theories over set theories,Arch. Math Logic 54(2015), 531-553 Lifting proof theory to the countable ordinals: Zermelo-Fraenkel set theory,Jour. Symb. Logic 79(2014), 325-354 Proof theory of weak compactness, Jour. Math. Logic 13(2013), 1350003 Proof theories of ordinals I: recursively Mahlo ordinals, Ann. Pure Appl. Logic 122(2003), 1-85 Ordinal diagrams for recursively Mahlo universes, Arch. Math. Logic 39(2000), 353-391 Memberships, activities and Awards The Mathematical Society of Japan Association for Symbolic Logic Japan Association for Philosophy of Science MSJ Autumn Prize(2003)