"Inverse Kinematics for Serial Kinematic Chains via Sum of Squares Optimization" by Filip Marić and Matthew Giamou and Soroush Khoubyarian and Ivan Petrović and Jonathan Kelly. Presented at the IEEE International Conference on Robotics and Automation (ICRA'20), Paris, France, May 31 - June 4, 2020.
Pre-print available: http://arxiv.org/abs/1909.09318