Diffusions under a local strong Hörmander condition. Part II: tube estimates

Vlad Bally 1, 2 Lucia Caramellino 3 Paolo Pigato 4, 5
1 MATHRISK - Mathematical Risk Handling
UPEM - Université Paris-Est Marne-la-Vallée, ENPC - École des Ponts ParisTech, Inria de Paris
INRIA Lorraine, CRISAM - Inria Sophia Antipolis - Méditerranée , UHP - Université Henri Poincaré - Nancy 1, Université Nancy 2, INPL - Institut National Polytechnique de Lorraine, CNRS - Centre National de la Recherche Scientifique : UMR7502
Abstract : We study lower and upper bounds for the probability that a diffusion process in R^n remains in a tube around a skeleton path up to a fixed time. We assume that the diffusion coefficients σ_1 ,. .. , σ_d may degenerate but they satisfy a strong Hörmander condition involving the first order Lie brackets around the skeleton of interest. The tube is written in terms of a norm which accounts for the non-isotropic structure of the problem: in a small time δ, the diffusion process propagates with speed √ δ in the direction of the diffusion vector fields σ_j and with speed δ = √ δ × √ δ in the direction of [σ_i , σ_j ]. The proof consists in a concatenation technique which strongly uses the lower and upper bounds for the density proved in the part I.
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Submitted on : Friday, December 2, 2016 - 10:17:00 AM
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  • HAL Id : hal-01407420, version 1
  • ARXIV : 1607.04544


Vlad Bally, Lucia Caramellino, Paolo Pigato. Diffusions under a local strong Hörmander condition. Part II: tube estimates. 2016. ⟨hal-01407420⟩



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