# Metrics, quantization and registration in varifold spaces

## TL;DR

This paper advances the theory and algorithms for shape analysis using varifold spaces, enabling registration of diverse geometric objects through new metrics, models, and numerical methods with proven convergence properties.

## Contribution

It introduces a generalized framework for diffeomorphic registration of varifolds, including new metrics, a mathematical model, and quantization techniques with convergence guarantees.

## Key findings

- Development of kernel metrics on varifold spaces
- A mathematical model for diffeomorphic registration under group actions
- Numerical pipelines demonstrating initial results in 1D and 2D

## Abstract

This paper is concerned with the theory and applications of varifolds to the representation, approximation and diffeomorphic registration of shapes. One of its purpose is to synthesize and extend several prior works which, so far, have made use of this framework mainly in the context of submanifold comparison and matching. In this work, we instead consider deformation models acting on general varifold spaces, which allows to formulate and tackle diffeomorphic registration problems for a much wider class of geometric objects and lead to a more versatile algorithmic pipeline. We study in detail the construction of kernel metrics on varifold spaces and the resulting topological properties of those metrics, then propose a mathematical model for diffeomorphic registration of varifolds under a specific group action which we formulate in the framework of optimal control theory. A second important part of the paper focuses on the discrete aspects. Specifically, we address the problem of optimal finite approximations (quantization) for those metrics and show a $\Gamma$-convergence property for the corresponding registration functionals. Finally, we develop numerical pipelines for quantization and registration before showing a few preliminary results for one and two-dimensional varifolds.