Lower-Order Refinements of Greedy Approximation

Kevin Beanland, Hung Viet Chu, Thomas Schlumprecht +1

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