A Proof of the Dittert Conjecture in Dimension 4 via an Exact Constrained Sum-of-Squares Certificate

Jinhui Li, Beibei Xiong, Zhengfeng Yang

The Dittert conjecture states that the Dittert functional on nonnegative $n\times n$ matrices whose entries sum to $n$ is uniquely maximized by the uniform matrix. We prove the con…