Numerical Reconstruction of a Discontinuous Diffusive Coefficient in Variable-Order Time-Fractional Subdiffusion

We consider a discontinuous coefficient reconstruction problem associated with a variable-order time-fractional subdiffusion equation. Both interface identification and reconstruction of piecewise constant coefficient values are considered. We show existence of a minimizer of the regularized inverse problem. Shape sensitivity analysis is performed to propose a shape gradient optimization algorithm allowing deformations. Moreover, an algorithm allowing shape and topological changes is proposed by a phase-field method with sensitivity analysis. Numerical examples are presented to demonstrate effectiveness of the two algorithms for recovering both subdiffusion interface and the two subdiffusion constants.