“…This semigroup is extensively studied by many authors, we refer to Da Prato [3][4][5], Da Prato and Zabczyk [6][7][8], Goldys and Kocan [12], Kühnemund and van Neerven [16], Lunardi [18], Metafune et al [19], Priola [20], Rhandi [22], van Neerven [23] and van Neerven and Zabczyk [24]. The proposition below will be useful in the following and can be found, e.g., in Cerrai [2].…”