We will have the 21st online colloquium “Extreme Universe Colloquium” on December 1st (Fri) 15:30 (JST). The speaker is Prof. Nicolas Yunes (University of Illinois at Urbana-Champaign). For details, please refer to the poster. If you have not registered yet, please register at our online event website at least three days prior to the colloquium. (It is not necessary to register again if you have done it already.)