For a convex symmetric
body B in ℝn let MB denote the centered maximal operator
for f ∈ Lloc1(ℝn). We associate with B two linear invariants σ(B) and Q(B), and
show that for p > 1 the norm of the operator MB on Lp(ℝn) is bounded by a
constant which may depend on p, σ(B) and Q(B), but not explicitly on the
dimension n. In particular, if Bq denotes the unit ball in ℝn with respect to the
lq-norm, we can prove that MBq has a bound on Lp(ℝn) which is independent of n,
provided that 1 ≤ q < ∞.
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