Davis-Wielandt shells of 4 by 4 matrices
Mao-Ting Chien, Hiroshi Nakazato · Linear Algebra and its Applications · 2025
In this paper, we study possible degrees of the boundary generating surfaces of the Davis-Wielandt shells of 4-by-4 upper triangular unitarily irreducible matrices. The degree can be any even number between 6 and 36 except 14,26 and 30.