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ON NONUNIQUENESS FOR THE ANISOTROPIC CALDERÓN PROBLEM WITH PARTIAL DATA

Published online by Cambridge University Press:  28 January 2020

THIERRY DAUDÉ
Affiliation:
Département de Mathématiques, UMR CNRS 8088, Université de Cergy-Pontoise, 95302Cergy-Pontoise, France; thierry.daude@u-cergy.fr
NIKY KAMRAN
Affiliation:
Department of Mathematics and Statistics, McGill University, Montreal, QC, H3A 0B9, Canada; nkamran@math.mcgill.ca
FRANÇOIS NICOLEAU
Affiliation:
Laboratoire de Mathématiques Jean Leray, UMR CNRS 6629, 2 Rue de la Houssinière BP 92208, F-44322, Nantes Cedex 03, France; francois.nicoleau@univ-nantes.fr

Abstract

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We show that there is nonuniqueness for the Calderón problem with partial data for Riemannian metrics with Hölder continuous coefficients in dimension greater than or equal to three. We provide simple counterexamples in the case of cylindrical Riemannian manifolds with boundary having two ends. The coefficients of these metrics are smooth in the interior of the manifold and are only Hölder continuous of order $\unicode[STIX]{x1D70C}<1$ at the end where the measurements are made. More precisely, we construct a toroidal ring $(M,g)$ and we show that there exist in the conformal class of $g$ an infinite number of Riemannian metrics $\tilde{g}=c^{4}g$ such that their corresponding partial Dirichlet-to-Neumann maps at one end coincide. The corresponding smooth conformal factors are harmonic with respect to the metric $g$ and do not satisfy the unique continuation principle.

Information

Type
Differential Equations
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
© The Author(s) 2020