# Controllability and optimal control of the transport equation with a localized vector field

## TL;DR

This paper investigates the controllability of a transport PDE related to crowd models, establishing conditions under which the system can be controlled via a localized Lipschitz vector field and analyzing minimal time requirements.

## Contribution

It provides new controllability results for a transport PDE with localized control, including necessary crossing conditions and minimal time estimates.

## Key findings

- Controllability depends on the uncontrolled dynamics crossing the control set.
- Minimal time is related to the mass in the control region.
- Control is achievable with Lipschitz vector fields under certain conditions.

## Abstract

We study controllability of a Partial Differential Equation of transport type, that arises in crowd models. We are interested in controlling such system with a control being a Lipschitz vector field on a fixed control set $\omega$. We prove that, for each initial and final configuration, one can steer one to another with such class of controls only if the uncontrolled dynamics allows to cross the control set $\omega$. We also prove a minimal time result for such systems. We show that the minimal time to steer one initial configuration to another is related to the condition of having enough mass in $\omega$ to feed the desired final configuration.