# Mathematics Colloquia and Seminars

### Tournaments and slide rules for $\omega$ and $\psi$ class products on $\overline{M}_{0,n}$
We present two combinatorial algorithms on trivalent trees that give rise to new geometric interpretations of the multidegrees of certain projective embeddings of the moduli space $\overline{M}_{0,n}$ of stable n-marked genus 0 curves. The first algorithm is in terms of lazy tournaments and gives a simple proof of the fact that the total degree of this moduli space under the iterated Kapranov embedding is $(2n-1)!!$. The second formula is via slide labelings and allows us to express products of omega and psi classes as positive multiplicity-free sums of boundary strata.