If is an abstract logic (a.k.a. model theoretic logic), we can define the inner model by replacing first order logic with in Gödel’s definition of the inner model of constructible sets. Set theoretic properties of such inner models have been investigated recently and a spectrum of new inner models is emerging between and . The topic of this paper is the effect on of a slight modification of i.e. how sensitive is on the exact definition of ? The -extension of a logic is generally considered a “mild” extension of . We give examples of logics for which the inner model is consistently strictly smaller than the inner model , and in one case we show this follows from the existence of .

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