Fractional anisotropic Calder\'on problem with external data

TL;DR

This paper establishes that the fractional anisotropic Calderón problem in Euclidean space with external data uniquely determines the Riemannian metric up to diffeomorphism, using two different analytical approaches.

Contribution

It provides the first proof of uniqueness for the fractional anisotropic Calderón problem with external data in higher dimensions for smooth metrics.

Findings

Unique determination of Riemannian metric from exterior Dirichlet--Neumann data

Two different proof techniques demonstrating the result

Extension of Calderón problem to fractional and anisotropic settings

Abstract

In this paper, we solve the fractional anisotropic Calder\'on problem with external data in the Euclidean space, in dimensions two and higher, for smooth Riemannian metrics that agree with the Euclidean metric outside a compact set. Specifically, we prove that the knowledge of the partial exterior Dirichlet--to--Neumann map for the fractional Laplace-Beltrami operator, given on arbitrary open nonempty sets in the exterior of the domain in the Euclidean space, determines the Riemannian metric up to diffeomorphism, fixing the exterior. We provide two proofs of this result: one relies on the heat semigroup representation of the fractional Laplacian and a pseudodifferential approach, while the other is based on a variable-coefficient elliptic extension interpretation of the fractional Laplacian.