Let 1 < p < +∞ and let v be a weight on (0, +∞) such that v(x)xρ is equivalent to a non-decreasing function on (0, +∞) for some ρ ≥ 0. Let A be the averaging operator given by
, x ∈ (0, +∞), and let Lp(v) denote the weighted Lebesgue space of all measurable functions f on (0, +∞) for which
. Then the following statements are equivalent:
(i) A is bounded on Lp(v);
(ii) A is bounded on Lp-ε(v) for some ε ∈ (0,p - 1);
(iii) A is bounded on Lp(v1+ε) for some ε > 0;
(iv) A is bounded on Lp(v(x)xε) for some ε > 0.
Moreover, if A is bounded on Lp(v), then A is bounded on Lq(v) for all q ∈ [p, +∞).
We also show that the boundedness of the averaging operator A on the space Lp(v) implies that, for all r > 0, the weight v1-p′ satisfies the reverse Hölder inequality over the interval (0, r) with respect to the measure dt, while the weight v satisfies the reverse Hölder inequality over the interval (r, +∞) with respect to the measure t-p dt.
Assume moreover that p ≤ q < +∞ and that w is a weight on (0, +∞) such that
Then the operator A is bounded on Lp(v) if and only if the operator A : Lp(v) → Lq(w) is bounded. This enables us to transfer our results on the boundedness of the operator A mentioned above to the case when the operator A acts between two weighted Lebesgue spaces Lp(v) and Lq(w).