On November 23, 2020 (Monday) at 11:15 a.m. (local time in Bulgaria) a joint Zoom-webinar will be held of the Algebra and Logic Seminar of IMI - BAS and the Algebra Seminar of the Alfréd Rényi Institute of Mathematics, Budapest, Hungary. Two talks on: I. Anniversary: 150 Years of idempotents. II. Idempotents of 2 × 2 matrix rings over rings of formal power series. will be delivered by Vesselin Drensky. Join the Zoom meeting at https://zoom.us/j/95342234576?pwd=TTFrZmwyQ2h1QmhOc1JaWXorbzI4dz09 Meeting ID: 953 4223 4576 Passcode: 943760 Abstract. An element a in a ring A is called an idempotent if a2=a. In 2020 we celebrate an anniversary of the idempotents –150 years of their discovery. The idempotents were introduced in Ring Theory by Benjamin Peirce in 1870. Already [...]