We construct new exceptional divisors and birational contractions
of the Grothendieck-Knudsen moduli space of stable rational curves with n
marked points, from new combinatorial structures which we call hypertrees.
This is joint work with Jenia Tevelev.
Links:
[1] https://www.mpim-bonn.mpg.de/de/taxonomy/term/39
[2] https://www.mpim-bonn.mpg.de/de/node/3444
[3] https://www.mpim-bonn.mpg.de/de/node/5312