2011/04/23 by Helton, J. William, Spitkovsky, Ilya M.
#Algebraic Geometry (math.AG) #FOS: Mathematics #Functional Analysis (math.FA)
paper · doi:10.48550/arxiv.1104.4587
Which convex subsets of the complex plane are the numerical range W(A of some matrix A? This paper gives a precise characterization of these sets. In addition to this we show that for any A there exists a symmetric matrix B of the same size such that W(A)=W(B).