The backward problem for time-fractional evolution equations

In this paper, we consider the backward problem for fractional in time evolution equations ∂tαu(t)=Au(t) with the Caputo derivative of order 0<α≤1, where A is a self-adjoint and bounded above operator on a Hilbert space H. First, we extend the logarithmic convexity technique to the fractional framework by analyzing the properties of the Mittag–Leffler functions. Then we prove conditional stability estimates of Hölder type for initial conditions under a weaker norm of the final data. Finally, we give several applications to show the applicability of our abstract results.