Singular points of the ternary polynomials associated with 4-by-4 matrices
Mao-Ting Chien, Hiroshi Nakazato · Electronic Journal of Linear Algebra · 2012
Let T be an n × n matrix.The numerical range of T is defined as the setA homogeneous ternary polynomial associated with T is defined asThe numerical range W (T ) is the convex hull of the real affine part of the dual curve of F (t, x, y, ) = 0. We classify the numerical ranges of 4 × 4 matrices according to the singular points of the curve F (t, x, y) = 0.