Support of the Brown measure of a family of free multiplicative Brownian motions with non-negative initial condition

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Hauptverfasser: Hall, Brian C., Eaknipitsari, Sorawit
Format: Preprint
Veröffentlicht: 2025
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author Hall, Brian C.
Eaknipitsari, Sorawit
author_facet Hall, Brian C.
Eaknipitsari, Sorawit
contents We consider a family $b_{s,τ}$ of free multiplicative Brownian motions labeled by a real variance parameter $s$ and a complex covariance parameter $τ$. We then consider the element $xb_{s,τ}$, where $x$ is non-negative and freely independent of $b_{s,τ}$. Our goal is to identify the support of the Brown measure of $xb_{s,τ}$. In the case $τ=s$, we identify a region $Σ_s$ such that the Brown measure is vanishing outside of $\overlineΣ_s$ except possibly at the origin. For general values of $τ$, we construct a map $f_{s-τ}$ and define $D_{s,τ}$ as the complement of $f_{s-τ}(\overlineΣ_s^c)$. Then the Brown measure is zero outside $D_{s,τ}$ except possibly at the origin. The proof of these results is based on a two-stage PDE analysis, using one PDE (following the work of Driver, Hall, and Kemp) for the case $τ=s$ and a different PDE (following the work of Hall and Ho) to deform the $τ=s$ case to general values of $τ$.
format Preprint
id arxiv_https___arxiv_org_abs_2503_19682
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Support of the Brown measure of a family of free multiplicative Brownian motions with non-negative initial condition
Hall, Brian C.
Eaknipitsari, Sorawit
Probability
Mathematical Physics
Functional Analysis
We consider a family $b_{s,τ}$ of free multiplicative Brownian motions labeled by a real variance parameter $s$ and a complex covariance parameter $τ$. We then consider the element $xb_{s,τ}$, where $x$ is non-negative and freely independent of $b_{s,τ}$. Our goal is to identify the support of the Brown measure of $xb_{s,τ}$. In the case $τ=s$, we identify a region $Σ_s$ such that the Brown measure is vanishing outside of $\overlineΣ_s$ except possibly at the origin. For general values of $τ$, we construct a map $f_{s-τ}$ and define $D_{s,τ}$ as the complement of $f_{s-τ}(\overlineΣ_s^c)$. Then the Brown measure is zero outside $D_{s,τ}$ except possibly at the origin. The proof of these results is based on a two-stage PDE analysis, using one PDE (following the work of Driver, Hall, and Kemp) for the case $τ=s$ and a different PDE (following the work of Hall and Ho) to deform the $τ=s$ case to general values of $τ$.
title Support of the Brown measure of a family of free multiplicative Brownian motions with non-negative initial condition
topic Probability
Mathematical Physics
Functional Analysis
url https://arxiv.org/abs/2503.19682