Given a weight w in Ω ⊂ ∝ N, |Ω| < ∞ and a Young function φ, we consider the weighted modular ∫ Ω ω(f(x))w(x)dx and the resulting weighted Orlicz space L ω(w). For a Young function Ω ∉ Δ 2(∞) we present a necessary and sufficient conditions in order that L ω(w) = L ω(X Ω) up to the equivalence of norms. We find a necessary and sufficient condition for ω in order that there exists an unbounded weight w such that the above equality of spaces holds. By way of applications we simplify criteria from [5] for continuity of the composition operator from L ω into itself when ω Δ 2(∞) and obtain necessary and sufficient condition in order that the composition operator maps L ω. continuously onto L ω.
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