New characterizations of the unit vector basis of $c_0$ or ${\ell }_p$

Abstract

Motivated by Altshuler's famous characterization of the unit vector basis of $c_0$ or ${\ell }_p$ among symmetric bases, we obtain similar characterizations among democratic bases and among bidemocratic bases. We also prove a separate characterization of the unit vector basis of ${\ell }_1$.