Proof of the Newell-Littlewood saturation conjecture

By inventing the notion of honeycombs, A. Knutson and T. Tao proved the saturation conjecture for Littlewood-Richardson coefficients. The Newell-Littlewood numbers are a generalization of the Littlewood-Richardson coefficients. By introducing honeycombs on a Möbius strip, we prove the saturation conjecture for Newell-Littlewood numbers posed by S. Gao, G. Orelowitz and A. Yong.