Polynomial numerical hulls were introduced as a tool for understanding and estimating norm of f(A) for various stroked="f" filled="f" path="m@4@5l@4@11@9@11@9@5xe" o:preferrelative="t" o:spt="75" coordsize="21600,21600" is normal, the spectrum uffices for understanding orm of f(A), but when is not normal the spectrum often does not supply the kind of information required in applications. Polynomial numerical hulls have been shown to be a useful tool in a number of applications where the underlying operator is not normal. Nonetheless, very little is known about these sets. It is also appropriate for estimating the spectrum of . It’s shown that the polynomial numerical hull of degree 1 is equal to the numerical range of .
