Operators in tight by support Banach spaces

Summarization: Answering the question of W. T. Gowers, we give an example of a bounded operator on a subspace of Gowers unconditional space, which is not a strictly singular perturbation of a restriction of a diagonal operator. We make some observations on operators in arbitrary tight by support Banach space, showing in particular that in such a space no two isomorphic infinitely dimensional subspaces form a direct sum.Presented on: Journal of the London Mathematical Societ