# Generalized stability estimates in inverse transport theory

## TL;DR

This paper introduces a new stability framework in inverse transport theory using the 1-Wasserstein distance, which better accounts for measurement errors like blurring and misalignment, leading to more meaningful error estimates.

## Contribution

It proposes a novel stability estimate in inverse transport theory based on the 1-Wasserstein distance, improving robustness against measurement imperfections.

## Key findings

- Stability estimates are improved using the 1-Wasserstein metric.
- Errors due to blurring and misalignment are more accurately modeled.
- Quantitative effects of measurement errors on reconstructions are established.

## Abstract

Inverse transport theory concerns the reconstruction of the absorption and scattering coefficients in a transport equation from knowledge of the albedo operator, which models all possible boundary measurements. Uniqueness and stability results are well known and are typically obtained for errors of the albedo operator measured in the $L^1$ sense. We claim that such error estimates are not always very informative. For instance, arbitrarily small blurring and misalignment of detectors result in $O(1)$ errors of the albedo operator and hence in $O(1)$ error predictions on the reconstruction of the coefficients, which are not useful. This paper revisit such stability estimates by introducing a more forgiving metric on the measurements errors, namely the $1-$Wasserstein distances, which penalize blurring or misalignment by an amount proportional to the width of the blurring kernel or to the amount of misalignment. We obtain new stability estimates in this setting. We also consider the effect of errors, still measured in the $1-$Wasserstein distance, on the generation of the probing source. This models blurring and misalignment in the design of (laser) probes and allow us to consider a discretized sources. Under appropriate assumptions on the coefficients, we quantify the effect of such errors on the reconstructions.