Elements of noncommutative geometry in inverse problems on manifolds

We deal with two dynamical systems associated with a Riemannian manifold with boundary. The first one is a system governed by the scalar wave equation, and the second is governed by the Maxwell equations. Both systems are controlled from the boundary. The inverse problem is to recover the manifold from measurements on the boundary (inverse data). We show that the inverse data determine C*-algebras, whose (topologized) spectra are identical to the manifold. For this reason, to recover the manifold one can determine a proper algebra from the inverse data, find its spectrum, and provide the spectrum with a Riemannian structure. The paper develops an algebraic version of the boundary control method, which is an approach to inverse problems based on their relations to control theory. (C) 2014 Elsevier B.V. All rights reserved.