Fredagskollokvium: Quartic spectrahedra

Matrices and especially symmetric matrices are among the most useful and used mathematical “inventions”.  In optimization models  linear spaces of symmetric matrices are used since the semidefinite ones form a convex set.    I shall show what these 3-dimensional convex sets may look  like for 3x3 and  4x4 matrices.  Their boundary are called cubic and quartic spectrahedra, respectively.