This paper is concerned with fractional abstract Cauchy problems with order α ∈ (1, 2). The notion of fractional solution operator is introduced, its some properties are obtained. A generation theorem for exponentially bounded fractional solution operators is given. It is proved that the homogeneous fractional Cauchy problem (F ACP0) is well-posed if and only if its coefficient operator A generates an α-order fractional solution operator. Sufficient conditions are given to guarantee the existence and uniqueness of mild solutions and strong solutions of the inhomogeneous fractional Cauchy problem (F ACP f ).
Mathematics Subject Classification (2010). Primary 34A08, Secondary 47D06.Keywords. Riemann-Liouville fractional integral, Riemann-Liouville fractional derivative, Caputo fractional derivative, fractional solution operator, fractional abstract Cauchy problem.