We will discuss an equidistribution problem concerning rational planes in four-space. Due to an accidental isomorphism this problem relates in a natural manner to the simultaneous study of four CM-points on the modular surface and two points on the two-dimensional sphere. Using Duke's theorem and a joining classification we obtain joint equidistribution under suitable congruence conditions on the covolume of the planes.
This is joint work with Menny Aka and Andreas Wieser, and relies on a joint theorem with Elon Lindenstrauss.
Links:
[1] https://www.mpim-bonn.mpg.de/taxonomy/term/39
[2] https://www.mpim-bonn.mpg.de/node/3444
[3] https://www.mpim-bonn.mpg.de/node/7800