A Generalized Mean Value Inequality for Subharmonic Functions and Applications

If u ≥ 0 is subharmonic on a domain Ω in Rn and p > 0, then it is well-known that there is a constant C(n, p) ≥ 1 such that u(x)p ≤C(n, p)M V (up,B(x,r)) for each ball B(x,r) ⊂ Ω. We recently showed that a similar result holds more generally for functions of the form ψ◦ u where ψ : R+ → R+ may be any surjective, concave function whose inverse ψ−1 satisfies the ∆2-condition. Now we point out that this result can be extended slightly further. We also apply this extended result to the weighted boundary behavior and nonintegrability questions of subharmonic and superharmonic functions.