Stability results for backward parabolic equations with time-dependent coefficients**Dedicated to Professor Rudolf Gorenflo on the occasion of his 80th birthday.

Abstract

Let H be a Hilbert space with the norm ‖ ⋅ ‖ and A(t) (0 ⩽ t ⩽ T) be positive self-adjoint unbounded operators from D(A(t))⊂H to H. In the paper, we establish stability estimates of Hölder type and propose a regularization method for the ill-posed backward parabolic equation with time-dependent coefficients Our stability estimates improve the related results by Krein (1957 Dokl. Akad. Nauk SSSR 114 1162–5), and Agmon and Nirenberg (1963 Commun. Pure Appl. Math. 16 121–239). Our regularization method with a priori and a posteriori parameter choice yields error estimates of Hölder type. This is the only result when a regularization method for backward parabolic equations with time-dependent coefficients provides a convergence rate.