Ideal Structure of the Algebra of Bounded Operators Acting on a Banach Space

We construct a Banach space Z such that the lattice of closed two-sided ideals of the Banach algebra B(Z) of bounded operators on Z is as follows: {0} ⊂ K (Z) ⊂ E (Z) ⊂ ⊂ M1 M2 ⊂ ⊂ We then determine which kinds of approximate identities (bounded/left/right), if any, each of the four non-trivial closed ideals of B(Z) contains, and we show that the maximal ideal M1 is generated as a left ideal by two operators, but not by a single operator, thus answering a question left open in our collaboration with Dales, Kochanek and Koszmider (Studia Math. 2013). In contrast, the other maximal ideal M2 is not nitely generated as a left ideal. The Banach space Z is the direct sum of Argyros and Haydon's Banach space XAH which has very few operators and a certain subspace Y of XAH. The key property of Y is that every bounded operator from Y into XAH is the sum of a scalar multiple of the inclusion map and a compact operator.