Resumen de Ideals of compact operators
We give an example of a Banach space such that is not an ideal in . We prove that if is a weak denting point in the unit ball of and if is a closed subspace of a Banach space , then the set of norm-preserving extensions of a functional is equal to the set . Using this result, we show that if is an -ideal in and is a reflexive Banach space, then is an -ideal in whenever is an ideal in . We also show that is an ideal (respectively, an -ideal) in for all Banach spaces whenever is an ideal (respectively, an -ideal) in and has the compact approximation property with conjugate operators.
