# An asymptotic preserving scheme for front propagation in a kinetic reaction-transport equation

## TL;DR

This paper introduces an asymptotic preserving numerical scheme for a nonlinear kinetic reaction-transport equation, effectively handling sharp interface propagation and stiff regimes by leveraging a micro-macro decomposition aligned with the Hopf-Cole transform.

## Contribution

The proposed scheme is specifically designed for nonlinear kinetic equations, maintaining stability and accuracy in the singular limit with a maximum principle and viscosity solution approach.

## Key findings

- Successfully captures sharp interfaces in simulations
- Maintains stability across kinetic to macroscopic transition
- Efficiently handles stiff regimes with reduced computational cost

## Abstract

In this work, we propose an asymptotic preserving scheme for a non-linear kinetic reaction-transport equation, in the regime of sharp interface. With a non-linear reaction term of KPP-type, a phenomenon of front propagation has been proved in [9]. This behavior can be highlighted by considering a suitable hyperbolic limit of the kinetic equation, using a Hopf-Cole transform. It has been proved in [6, 8, 11] that the logarithm of the distribution function then converges to the viscosity solution of a constrained Hamilton-Jacobi equation. The hyperbolic scaling and the Hopf-Cole transform make the kinetic equation stiff. Thus, the numerical resolution of the problem is challenging, since the standard numerical methods usually lead to high computational costs in these regimes. The Asymptotic Preserving (AP) schemes have been typically introduced to deal with this difficulty, since they are designed to be stable along the transition to the macroscopic regime. The scheme we propose is adapted to the non-linearity of the problem, enjoys a discrete maximum principle and solves the limit equation in the sense of viscosity. It is based on a dedicated micro-macro decomposition, attached to the Hopf-Cole transform. As it is well adapted to the singular limit, our scheme is able to cope with singular behaviors in space (sharp interface), and possibly in velocity (concentration in the velocity distribution). Various numerical tests are proposed, to illustrate the properties and the efficiency of our scheme.