Resumen de Robustness of Fredholm properties of parabolic evolution equations under boundary perturbations

Lahcen Maniar, Roland Schnaubelt

• We study perturbations at the boundary of linear nonautonomous parabolic boundary value problems. Our approach relies on a transformation of the given inhomogeneous boundary value problem to an evolution equation in larger, time-varying extrapolation spaces. We establish the well-posedness of this equation and Duhamel's formulas relating the evolution families solving the perturbed and the unperturbed problem. By means of these formulas, we can show that the perturbed evolution equation inherits the exponential dichotomy and Fredholm properties of the unperturbed equation if the perturbations are small in norm or compact. This result leads to a Fredholm alternative for the given perturbed boundary value problem.