The killed Brox diffusion

TL;DR

This paper studies the Brox diffusion with killing, providing explicit formulas for the Green operator and the probability density function, and characterizing eigenvalues and eigenfunctions using Sturm-Liouville theory adapted for ill-posed operators.

Contribution

It introduces a novel approach to analyze Brox diffusion with killing by adapting Sturm-Liouville theory to ill-posed operators, providing explicit spectral and Green function formulas.

Findings

Explicit Green operator formula derived.

Spectral decomposition of the density function obtained.

Eigenvalues and eigenfunctions characterized via stochastic differential equations.

Abstract

We carry out an study of the Brox diffusion with killing. It turns out that when leaving fixed the environment one is able to recast some theory of diffusion and differential operators to deal with the ill-posed generator of the Brox diffusion. Our first main result is to give a close form of the Green operator associated to the generator, i.e. the inverse of the generator. We do so by setting the Lagrange identity in this context. Then, we give explicit expressions in quenched form of the probability density function of the process; such object is given in terms of the spectral decomposition using the eigenvalues and eigenfuntions of the infinitesimal generator of the diffusion. Moreover, we characterize the eigenvalues and eigenfuntions using some parsimonious stochastic differential equations. This program is carried out using the theory of Sturm-Liouville, which in fact we have adapted to deal with the ill-posed random operators.