The $L^p$-Fisher-Rao metric and Amari-Cencov $α$-connections

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Hauptverfasser: Bauer, Martin, Brigant, Alice Le, Lu, Yuxiu, Maor, Cy
Format: Preprint
Veröffentlicht: 2023
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author Bauer, Martin
Brigant, Alice Le
Lu, Yuxiu
Maor, Cy
author_facet Bauer, Martin
Brigant, Alice Le
Lu, Yuxiu
Maor, Cy
contents We introduce a family of Finsler metrics, called the $L^p$-Fisher-Rao metrics $F_p$, for $p\in (1,\infty)$, which generalizes the classical Fisher-Rao metric $F_2$, both on the space of densities Dens$_+(M)$ and probability densities Prob$(M)$. We then study their relations to the Amari-uCencov $α$-connections $\nabla^{(α)}$ from information geometry: on Dens$_+(M)$, the geodesic equations of $F_p$ and $\nabla^{(α)}$ coincide, for $p = 2/(1-α)$. Both are pullbacks of canonical constructions on $L^p(M)$, in which geodesics are simply straight lines. In particular, this gives a new variational interpretation of $α$-geodesics as being energy minimizing curves. On Prob$(M)$, the $F_p$ and $\nabla^{(α)}$ geodesics can still be thought as pullbacks of natural operations on the unit sphere in $L^p(M)$, but in this case they no longer coincide unless $p=2$. Using this transformation, we solve the geodesic equation of the $α$-connection by showing that the geodesic are pullbacks of projections of straight lines onto the unit sphere, and they always cease to exists after finite time when they leave the positive part of the sphere. This unveils the geometric structure of solutions to the generalized Proudman-Johnson equations, and generalizes them to higher dimensions. In addition, we calculate the associate tensors of $F_p$, and study their relation to $\nabla^{(α)}$.
format Preprint
id arxiv_https___arxiv_org_abs_2306_14533
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle The $L^p$-Fisher-Rao metric and Amari-Cencov $α$-connections
Bauer, Martin
Brigant, Alice Le
Lu, Yuxiu
Maor, Cy
Differential Geometry
We introduce a family of Finsler metrics, called the $L^p$-Fisher-Rao metrics $F_p$, for $p\in (1,\infty)$, which generalizes the classical Fisher-Rao metric $F_2$, both on the space of densities Dens$_+(M)$ and probability densities Prob$(M)$. We then study their relations to the Amari-uCencov $α$-connections $\nabla^{(α)}$ from information geometry: on Dens$_+(M)$, the geodesic equations of $F_p$ and $\nabla^{(α)}$ coincide, for $p = 2/(1-α)$. Both are pullbacks of canonical constructions on $L^p(M)$, in which geodesics are simply straight lines. In particular, this gives a new variational interpretation of $α$-geodesics as being energy minimizing curves. On Prob$(M)$, the $F_p$ and $\nabla^{(α)}$ geodesics can still be thought as pullbacks of natural operations on the unit sphere in $L^p(M)$, but in this case they no longer coincide unless $p=2$. Using this transformation, we solve the geodesic equation of the $α$-connection by showing that the geodesic are pullbacks of projections of straight lines onto the unit sphere, and they always cease to exists after finite time when they leave the positive part of the sphere. This unveils the geometric structure of solutions to the generalized Proudman-Johnson equations, and generalizes them to higher dimensions. In addition, we calculate the associate tensors of $F_p$, and study their relation to $\nabla^{(α)}$.
title The $L^p$-Fisher-Rao metric and Amari-Cencov $α$-connections
topic Differential Geometry
url https://arxiv.org/abs/2306.14533