  We present our latest contributions in terms of mathematical modeling and
algorithm development for the global optimization of the ACOPF problem. These
contributions allow us to close the optimality gap on a number of open
instances in the PGLIB and NESTA benchmark libraries. This is achieved by
combining valid cut generation with semidefinite programming-based bound
tightening. The mathematical formulations along with the solution algorithms
are implemented in the modeling framework Gravity (www.gravityopt.com), an
open-source platform for reproducible numerical experiments.
