Kamowitz’s classical result on a compact endomorphism T of a commutative Ba- nach algebra A asserts that ∩T ∗n(Xr ) is finite where T ∗ is the adjoint of T and Xr),is the set of multiplicative linear functionals on A. This ...

Let A denote a unital Banach algebra and SA denote its unit sphere. It was proved by F. F. Bonsalland J. Duncan that when the Banach algebra is unital, the algebra numerical rangeis identical to a subset of itself. Basing ...