Symmetrizing Bregman Divergence on the Cone of Positive Definite Matrices: Which Mean to Use and Why

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Hauptverfasser: Sial, Tushar, Halder, Abhishek
Format: Preprint
Veröffentlicht: 2026
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author Sial, Tushar
Halder, Abhishek
author_facet Sial, Tushar
Halder, Abhishek
contents This work uncovers variational principles behind symmetrizing the Bregman divergences induced by generic mirror maps over the cone of positive definite matrices. We show that computing the canonical means for this symmetrization can be posed as minimizing the desired symmetrized divergences over a set of mean functionals defined axiomatically to satisfy certain properties. For the forward symmetrization, we prove that the arithmetic mean over the primal space is canonical for any mirror map over the positive definite cone. For the reverse symmetrization, we show that the canonical mean is the arithmetic mean over the dual space, pulled back to the primal space. Applying this result to three common mirror maps used in practice, we show that the canonical means for reverse symmetrization, in those cases, turn out to be the arithmetic, log-Euclidean and harmonic means. Our results improve understanding of existing symmetrization practices in the literature, and can be seen as a navigational chart to help decide which mean to use when.
format Preprint
id arxiv_https___arxiv_org_abs_2603_28917
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Symmetrizing Bregman Divergence on the Cone of Positive Definite Matrices: Which Mean to Use and Why
Sial, Tushar
Halder, Abhishek
Optimization and Control
Machine Learning
Systems and Control
This work uncovers variational principles behind symmetrizing the Bregman divergences induced by generic mirror maps over the cone of positive definite matrices. We show that computing the canonical means for this symmetrization can be posed as minimizing the desired symmetrized divergences over a set of mean functionals defined axiomatically to satisfy certain properties. For the forward symmetrization, we prove that the arithmetic mean over the primal space is canonical for any mirror map over the positive definite cone. For the reverse symmetrization, we show that the canonical mean is the arithmetic mean over the dual space, pulled back to the primal space. Applying this result to three common mirror maps used in practice, we show that the canonical means for reverse symmetrization, in those cases, turn out to be the arithmetic, log-Euclidean and harmonic means. Our results improve understanding of existing symmetrization practices in the literature, and can be seen as a navigational chart to help decide which mean to use when.
title Symmetrizing Bregman Divergence on the Cone of Positive Definite Matrices: Which Mean to Use and Why
topic Optimization and Control
Machine Learning
Systems and Control
url https://arxiv.org/abs/2603.28917