Enlarge Greedy Sums in Greedy-Type Properties by Different Factors

Abstract

It was previously known that the almost greedy (AG) property essentially remains the same when we enlarge greedy sums in the classical definition by a factor $λ\geqslant 1$. The present paper shows that if instead, we enlarge greedy sums in a reformulation of the AG property, we obtain a weaker one. However, the new property is essentially independent of the enlarging factor $λ$ once $λ> 1$. In contrast, we observe a continuum of partially greedy-like properties by varying $λ\in [1,\infty)$. Last but not least, under a threshold for $λ$, we characterize the isometric version of the weakened AG property. Specifically, the characterization holds if and only if $λ\in [1, 2]$.