The Bennati-Dragulescu-Yakovenko model in the continuous setting: PDE derivation and long-time behavior

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Autori principali: Cao, Fei, Loy, Nadia
Natura: Preprint
Pubblicazione: 2025
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author Cao, Fei
Loy, Nadia
author_facet Cao, Fei
Loy, Nadia
contents In this manuscript, we develop and analyze a continuous version of the well-known Bennati-Dragulescu-Yakovenko (BDY) dollar-exchange discrete model. Starting from the conservative BDY exchange mechanism, we rely on kinetic theory for multi-agent systems in order to propose an analogue continuous dynamics, which does not belong to the class of other popular kinetic models for wealth exchange. We employ the quasi-invariant limit procedure to rigorously derive a nonlinear PDE on the half-line, which is a Fokker-Planck equation featuring the boundary value in the drift term. The PDE is supplemented with a nonlinear Robin-type boundary condition encoding conservation of total agents and wealth. We prove existence and uniqueness of the solution, which converges in relative entropy to the unique stationary state that is the Boltzmann-Gibbs (exponential) distribution. We determine the $L^1$ convergence (up to subsequences) of the solution toward this equilibrium: this requires us to make a step forward with respect to established arguments of entropy decay for Fokker-Planck equations. Thus, our results, which bridge the discrete stochastic dynamics with a continuous deterministic evolution equation, provide a novel and influential wealth exchange model in a PDE framework, which opens up many new applicative scenarios and methodological analytical challenges.
format Preprint
id arxiv_https___arxiv_org_abs_2512_06101
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Bennati-Dragulescu-Yakovenko model in the continuous setting: PDE derivation and long-time behavior
Cao, Fei
Loy, Nadia
Analysis of PDEs
35Q84, 35Q91, 82C31, 91B80
In this manuscript, we develop and analyze a continuous version of the well-known Bennati-Dragulescu-Yakovenko (BDY) dollar-exchange discrete model. Starting from the conservative BDY exchange mechanism, we rely on kinetic theory for multi-agent systems in order to propose an analogue continuous dynamics, which does not belong to the class of other popular kinetic models for wealth exchange. We employ the quasi-invariant limit procedure to rigorously derive a nonlinear PDE on the half-line, which is a Fokker-Planck equation featuring the boundary value in the drift term. The PDE is supplemented with a nonlinear Robin-type boundary condition encoding conservation of total agents and wealth. We prove existence and uniqueness of the solution, which converges in relative entropy to the unique stationary state that is the Boltzmann-Gibbs (exponential) distribution. We determine the $L^1$ convergence (up to subsequences) of the solution toward this equilibrium: this requires us to make a step forward with respect to established arguments of entropy decay for Fokker-Planck equations. Thus, our results, which bridge the discrete stochastic dynamics with a continuous deterministic evolution equation, provide a novel and influential wealth exchange model in a PDE framework, which opens up many new applicative scenarios and methodological analytical challenges.
title The Bennati-Dragulescu-Yakovenko model in the continuous setting: PDE derivation and long-time behavior
topic Analysis of PDEs
35Q84, 35Q91, 82C31, 91B80
url https://arxiv.org/abs/2512.06101