arXiv · math/0311470
A `platycosm' is a flat Riemannian 3-manifold without boundary. In this paper we prove that there is (up to scale) a unique isospectral pair of compact platycosms.
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J. P. Rossetti, J. H. Conway. 2006-02-09. Hearing the platycosms. https://arxiv.org/abs/math/0311470
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