Who did more ring theory, Cahit Arf or Sind ibn Ali?
Cahit Arf Cahit Arf (] ; 11 October 1910 – 26 December 1997) was a Turkish mathematician. He is known for the Arf invariant of a quadratic form in characteristic 2 (applied in knot theory and surgery theory) in topology, the Hasse–Arf theorem in ramification theory, Arf semigroups, and Arf rings.
Muhammad Sharif (Kalifa) Sayyid Muhammad Sharif (died 1899) was one of the three Kalifas or lieutenants of Muhammad Ahmad (1844-1885), who styled himself the Mahdi, the others being Ali wad Hilu and Abdallahi ibn Muhammad.