For an arbitrary continuous, increasing function ω : [0, ∞) ↦ C of finite exponential type, we characterize Laplace-Stieltjes transforms of Banach-space-valued functions that are O(ω) , and use this to establish a Hille-Yosida type theorem for strongly continuous semigroups that are O(ω) . Corollaries include characterizing generators of strongly continuous semigroups that are \documentclass[12pt]{minimal}
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$$O\left( {\exp \left( {dt^{\tfrac{1}{d}} } \right)} \right)$$
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