Maximal regularity and optimal control for a non-local Cahn-Hilliard tumour growth model

Abstract: We consider a non-local tumour growth model of phase-field type, describing the evolution of tumour cells through proliferation in presence of a nutrient. The model consists of a coupled system, incorporating a non-local Cahn-Hilliard equation for the tumour phase variable and a reaction-diffusion equation for the nutrient. First, we establish novel regularity results for such a model, by applying maximal regularity theory in weighted $L^p$ spaces. This technique enables us to prove the local existence and uniqueness of a regular solution, including also chemotaxis effects. By leveraging time-regularisation properties and global boundedness estimates, we further extend the solution to a global one. These results provide the foundation for addressing an optimal distributed control problem, aimed at identifying a suitable therapy guiding the tumour towards a predefined target. Specifically, we prove the existence of an optimal therapy and, by studying the Fr\'echet-differentiability of the control-to-state operator and introducing the adjoint system, we derive first-order necessary optimality conditions.