A posteriori existence for the Keller-Segel model via a finite volume - finite element scheme
This provides a rigorous link between numerical approximation and existence theory for the Keller-Segel model, benefiting researchers in numerical analysis and PDEs.
The paper derives conditional a posteriori error estimates for a finite volume scheme approximating the Keller-Segel system, showing linear convergence in mesh size and proving that if the numerical solution satisfies the estimate condition, a weak exact solution exists.
We derive two forms of conditional a posteriori error estimates for a finite volume scheme approximating the parabolic-elliptic Keller-Segel system. The estimates control the error in the $L^\infty(0,T, L^2(Ω))$- and $L^2(0,T;H^1(Ω))$-norm and exhibit linear convergence in the mesh size, as observed in numerical experiments. Crucially, we show that, as long as the condition of the error estimate is satisfied, a weak solution exists. This means, as long as the numerical solution has good properties, we can rigorously infer existence of an exact solution.