The structure of the local time of Markov processes indexed by Levy trees

TL;DR

This paper develops a local time concept for Markov processes indexed by Levy trees, revealing new structural insights and connecting to Levy trees derived from the process’s level sets.

Contribution

It introduces a novel local time construction for Levy tree-indexed Markov processes and characterizes the structure of points where the process hits a fixed value.

Findings

Constructed local time via approximation and exit local times.

Identified the support of the local time measure.

Linked the process's level sets to a new Levy tree and its height process.

Abstract

We construct the analogue of the local time -- at a fixed point $x$ -- for Markov processes indexed by Levy trees. We start by proving that Markov processes indexed by Levy trees satisfy a special Markov property which can be thought as a spatial version of the classical Markov property. Then, we construct the analogue of the local time by an approximation procedure and we characterize the support of its Lebesgue-Stieltjes measure. We also give an equivalent construction in terms of a special family of exit local times. Finally, combining these results, we show that the points at which the Markov process takes the value $x$ encode a new Levy tree and we construct explicitly its height process. In particular, we recover a recent result of Le Gall concerning the subordinate tree of the Brownian tree where the subordination function is given by the past maximum process of Brownian motion indexed by the Brownian tree.