J Austral Math Soc Ser A 45 pp78--82, 1988.
(Received 3 December 1986)
Let N be a nilpotent simply connected Lie group, and A be a commutative connected d-dimensional Lie group of automorphisms of N which correspond to semisimple endomorphisms of the Lie algebra of N with positive eigenvalues. From the split extension S = N × A @ N × a, a being the Lie algebra of A. We consider a family of "rectangles" Br is S, parametrized by r > 0, such that the measure of Br behaves asymptotically as a fixed power of r. One can construct the Hardy-Littlewood maximal function operator f ® Mf relative to left translates of teh family {Br}. We prove that M is of weak type (1, 1). This complements a result of J.-O. Strömberg concerning maximal functions defined relative to hyperbolic balls in a symmetric space.
1980 AMS Subject Classification: primary 43A80, 22E30; secondary 42B25
Last Modified: Wed Feb 19 10:27:49 2003