Unstable cohomology of ${\mathsf{GL}}_{2n}(\mathbb{Z})$ and the odd commutative graph complex

Francis Brown, Simone Hu, Erik Panzer

We study a closed differential form on the symmetric space of positive definite matrices, which is defined using the Pfaffian and is ${\mathsf{GL}}_{2n}(\mathbb{Z})$ invariant up to…