Who did more ring theory, Cahit Arf or Sind ibn Ali?
Sind ibn Ali He is known to have translated and modified the Zij al-Sindhind. The Zij al-Sindhind was the first astronomical table ever introduced in the Muslim World. As a mathematician Sind ibn ʿAlī was a colleague of al-Khwarizmi and worked closely with Yaqūb ibn Tāriq together they calculated the diameter of the Earth and other astronomical bodies. He also wrote a commentary on "Kitāb al-ğabr wa-l-muqābala" and helped prove the works of al-Khwarizmi. The decimal point notation to the Arabic numerals was introduced by Sind ibn Ali.
Hasan al-Utrush Abu Muḥammad al-Ḥasan ibn ‘Alī ibn al-Ḥasan ibn ‘Alī ibn ‘Umar al-Ashraf ibn ‘Alī Zayn al-‘Ābidīn (Medina, ca. 844 – Amul, January/February 917), better known as al-Ḥasan al-Uṭrūsh ("the Deaf"), was an Alid Shia missionary of the Zaydi sect who re-established Zaydid rule over the province Tabaristan in northern Iran in 914, after fourteen years of Samanid rule. He ruled Tabaristan until his death under the regnal name of al-Nāṣir li'l-Ḥaqq ("Defender of the True Faith"), and became known as al-Nāṣir al-Kabīr ("al-Nasir the Elder") to distinguish him from his descendants who bore the same surname. He is still known and recognized as Imam among the Zaydis of Yemen.