Lower-Order Refinements of Greedy Approximation

Kevin Beanland, Hung Viet Chu, Thomas Schlumprecht +1

For two countable ordinals $\hat{I}\pm$ and ${\hat{I}}^2$, a basis of a Banach space $X$ is said to be $(\hat{I}\pm ,{\hat{I}}^2)$-quasi-greedy if it is 1) quasi-greedy, 2) ${\mathcal{S}}_{\hat{I}}\pm$-unconditional but not $\…