  As shown in [A1], the lowest constants appearing in the weak type (1,1)
inequalities satisfied by the centered Hardy-Littlewood maximal operator
associated to certain finite radial measures, grow exponentially fast with the
dimension. Here we extend this result to a wider class of radial measures and
to some values of p>1. Furthermore, we improve the previously known bounds for
p=1. Roughly speaking, whenever p\in (1, 1.03], if \mu is defined by a radial,
radially decreasing density satisfying some mild growth conditions, then the
best constants c_{p,d,\mu} in the weak type (p,p) inequalities satisfy
c_{p,d,\mu} \ge 1.005^d for all d sufficiently large. We also show that
exponential increase of the best constants occurs for certain families of
doubling measures, and for arbitrarily high values of p.
  [A1] Aldaz, J.M. Dimension dependency of the weak type (1,1) bounds for
maximal functions associated to finite radial measures. Bull. Lond. Math. Soc.
39 (2007) 203-208. Also available at the Mathematics ArXiv.
