L^1-regularity of strong ILB-Lie groups

Abstract: If G is a Lie group modeled on a Fr\'echet space, let e be its neutral element and g be its Lie algebra. We show that every strong ILB-Lie group G is L^1-regular in the sense that each f in L^1([0,1],g) is the right logarithmic derivative of some absolutely continuous curve c in G with c(0)=e and the map from L^1([0,1],g) to C([0,1],G) taking f to c is smooth. More generally, the conclusion holds for a class of Fr\'echet-Lie groups considered by Hermas and Bedida. Examples are given. Notably, we obtain L^1-regularity for certain weighted diffeomorphism groups.