A mathematical justification of the finite time approximation of Becker-Döring equations by a Fokker-Planck dynamics

Abstract

The Becker-Döring equations are an infinite dimensional system of ordinary differntial equations describing coagulation/fragmentation processes of species of integer sizes. Formal Taylor expansions motivate that its solution should be well described by a partial differential equation for large sizes, of advection-diffusion type, called Fokker-Planck equation. We rigorously prove the link between these two descriptions for evolutions on finite times rather than in some hydrodynamic limit, motivated by the results of numerical simulations and the construction of dedicated algorithms based on splitting strategies. In fact, the Becker-Döring equations and the Fokker-Planck equation are related through some pure diffusion with unbounded diffusion coefficient. The crucial point in the analysis is to obtain decay estimates for the solution of this pure diffusion and its derivates to control remainders in the Taylor expansions. The small parameter in this analysis is the inverse of the minimal size of the species.

The initial-boundary value problem for the Lifshitz–Slyozov equation with non-smooth rates at the boundary

“…Therefore, numerical simulations are a useful way to get further insights on the asymptotic behavior; some contributions along these lines are [6,19]. A number of variants of the Lifshitz-Slyozov model have been considered in the literature as well; we refer to [10,20,22,41,42] for diffusive versions (also advocate to represent intermediate stages of aggregates growth) and to [27,34,35] for the Lifshitz-Slyozov-Wagner model.…”

The Initial-boundary value problem for the Lifshitz-Slyozov equation with non-smooth rates at the boundary

“…Therefore, numerical simulations are a useful way to get further insights on the asymptotic behavior; some contributions along these lines are [5,15]. A number of variants of the Lifshitz-Slyozov model have been considered in the literature as well; we refer to [38,9,18,37,16] for diffusive versions (also advocate to represent intermediate stages of aggregates growth) and to [22,29,30] for the Lifshitz-Slyozov-Wagner model.…”