Given p ∈ [1, ∞) and λ ∈ (0, n), we study Morrey space L p,λ (R n ) of all locally integrable complex-valued functions f on R n such that for every open Euclidean ball B ⊂ R n with radius r B there are numbers C = C(f ) (depending on f ) and c = c(f, B) (relying upon f and B) satisfying r −λ B B |f (x) − c| p dx ≤ C and derive old and new, two essentially different cases arising from either choosing c = f B = |B| −1 B
f (y) dy or replacing c by P t B (x) = t B p t B (x, y)f (y) dy-where t B is scaled to r Band p t (·, ·) is the kernel of the infinitesimal generator L of an analytic semigroup {e −tL } t≥0 on L 2 (R n ). Consequently, we are led to simultaneously characterize the old and new Morrey spaces, but also to show that for a suitable operator L, the new Morrey space is equivalent to the old one.