The Calderon problem in transversally anisotropic geometries

TL;DR

This paper advances the understanding of the Calderon problem in anisotropic geometries by establishing uniqueness results for boundary measurements in more general settings, including non-simple transversal manifolds, using advanced mathematical techniques.

Contribution

It extends previous results by proving uniqueness of boundary measurements in transversally anisotropic geometries without the simplicity condition, employing complex geometrical optics and boundary control methods.

Findings

Boundary measurements determine a mixed Fourier/attenuated geodesic transform of unknown coefficients.

Uniqueness results hold when the geodesic ray transform on the transversal manifold is injective.

Boundary measurements in an infinite cylinder uniquely determine the transversal metric.

Abstract

We consider the anisotropic Calderon problem of recovering a conductivity matrix or a Riemannian metric from electrical boundary measurements in three and higher dimensions. In the earlier work \cite{DKSaU}, it was shown that a metric in a fixed conformal class is uniquely determined by boundary measurements under two conditions: (1) the metric is conformally transversally anisotropic (CTA), and (2) the transversal manifold is simple. In this paper we will consider geometries satisfying (1) but not (2). The first main result states that the boundary measurements uniquely determine a mixed Fourier transform / attenuated geodesic ray transform (or integral against a more general semiclassical limit measure) of an unknown coefficient. In particular, one obtains uniqueness results whenever the geodesic ray transform on the transversal manifold is injective. The second result shows that the boundary measurements in an infinite cylinder uniquely determine the transversal metric. The first result is proved by using complex geometrical optics solutions involving Gaussian beam quasimodes, and the second result follows from a connection between the Calderon problem and Gel'fand's inverse problem for the wave equation and the boundary control method.