### Abstract

This paper develops a method to rigorously show the validity of continuum description for the deterministic dynamics of many interacting particles with random initial data. We consider a hard sphere flow where particles are removed after the first collision. A fixed number of particles is drawn randomly according to an initial density f_{0}(u; v) depending on d-dimensional position u and velocity v. In the Boltzmann Grad scaling, we derive the validity of a Boltzmann

equation without gain term for arbitrary long times, when we assume finiteness of moments up to order two and initial data that are L^{∞} in space. We characterize the many particle flow by collision trees which encode possible collisions. The convergence of the many-particle dynamics to the Boltzmann dynamics is achieved via the convergence of associated probability measures on collision

trees. These probability measures satisfy nonlinear Kolmogorov equations, which are shown to be well-posed by semigroup methods.

Original language | English |
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Pages (from-to) | 4345–4379 |

Number of pages | 35 |

Journal | SIAM Journal on Mathematical Analysis (SIMA) |

Volume | 44 |

Issue number | 6 |

Early online date | 18 Dec 2012 |

DOIs | |

Publication status | Published - 2012 |

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### Cite this

*SIAM Journal on Mathematical Analysis (SIMA)*,

*44*(6), 4345–4379. https://doi.org/10.1137/120865598