Schubert puzzles and integrability I: invariant trilinear forms

Allen Knutson, Paul Zinn-Justin

The puzzle rules for computing Schubert calculus on $d$-step flag manifolds, proven in [Knutson Tao 2003] for $1$-step, in [Buch Kresch Purbhoo Tamvakis 2016] for $2$-step, and con…