The principal investigator will continue her study of the Laplace-Beltrami operator on compact Riemannian manifolds. She will try to determine the extent to which the spectrum of the Laplacian determines the geometry of the manifold. One goal of the research is to study examples of isospectral manifolds and identify geometric invariants which are not determined by the spectra. In addition she will try to identify other natural operators whose spectra might distinguish the metrics. Two manifolds or surfaces are said to be isospectral if the corresponding eigenvalues of the Laplacians on the manifolds are equal. If one thought of the two surfaces as surfaces of drums this would mean that the two drums would sound the same when struck. The principal investigator will study situations in which the two surfaces "sound the same" but have different shapes.