Spectral characterization of a positive element in a C-star algebra
= Spectral characterization of a positive element in a C-star algebra
An element $a$ of a C-star algebra is positive if and only if it is Hermitian and $\sigma(a)\subseteq[0,\infty)$. This characterization transfers the pointwise order on continuous functions to an abstract C-star algebra through the continuous functional calculus.
= Positive elements of a C-star algebra
{synonym}