# Optimal control of reaction-diffusion systems with hysteresis

## TL;DR

This paper develops optimal control conditions for reaction-diffusion systems with hysteresis, addressing challenges posed by non-locality and rate-independent hysteresis, and establishing regularity and uniqueness results.

## Contribution

It introduces first order optimality conditions for hysteresis-including reaction-diffusion systems, with improved conditions and uniqueness results for distributed controls.

## Key findings

- Derived first order necessary optimality conditions.
- Proved regularity and uniqueness of the adjoint system.
- Analyzed the value function's regularity under control restrictions.

## Abstract

This paper is concerned with the optimal control of hysteresis-reaction-diffusion systems. We study a control problem with two sorts of controls, namely distributed control functions, or controls which act on a part of the boundary of the domain. The state equation is given by a reaction-diffusion system with the additional challenge that the reaction term includes a scalar stop operator. We choose a variational inequality to represent the hysteresis. In this paper, we prove first order necessary optimality conditions. In particular, under certain regularity assumptions, we derive results about the continuity properties of the adjoint system. For the case of distributed controls, we improve the optimality conditions and show uniqueness of the adjoint variables. We employ the optimality system to prove higher regularity of the optimal solutions of our problem. Finally, we derive regularity properties of the value function of a perturbed control problem when the set of controls is restricted. The specific feature of rate-independent hysteresis in the state equation leads to difficulties concerning the analysis of the solution operator. Non-locality in time of the Hadamard derivative of the control-to-state operator complicates the derivation of an adjoint system.