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Jun 3, 2017 at 17:37 comment added Z. Ye @BranimirĆaćić: Sorry, I don't know much about the noncommutative geometry. Just wonder, is there any similar results formulate in the classical language or is it really necessary to go deep into the noncommutative geometry? Thank you.
May 21, 2017 at 5:44 comment added Bernd Ammann @Carlo Beenakker: However, I do not know any reference where Dirac-isospectrals pairs buidling on Heisenberg manifolds are worked out.
May 21, 2017 at 5:34 comment added Bernd Ammann @Carlo Beenakker. The examples of 4-dimensional tori follow from [8] Schiemann A. Ein Beispiel positiv definiter quadratischer Formen der Dimension 4 mit gleichen Darstellungszahlen // Arch. Math. 1990. V. 54. P. 372–375 and Conway J. H., Sloane N. J. A. Four-dimensional lattices with the same theta series // International Mathematics Research Notices. 1992. V. 4. P. 93–96. Every pair of Laplace-isospectral tori qith the trivial spin structure is also
May 13, 2017 at 17:58 history edited Carlo Beenakker CC BY-SA 3.0
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May 13, 2017 at 17:38 comment added Branimir Ćaćić (+1) That said, by a result of Connes, if one knows not only the spectrum of the Dirac operator $D$ as an operator on the separable Hilbert space $H$ of $L^2$ spinor fields, but also the relative position within the von Neumann algebra $B(H)$ of bounded operators on $H$ of the von Neumann subalgebra of $B(H)$ generated by the functional calculus of $D$ (i.e., the datum of the actual diagonalisation of $D$) and $L^\infty(M)$, viewed as multiplication operators on $B(H)$, then you can indeed pin down your Riemannian geometry.
May 13, 2017 at 17:30 history answered Carlo Beenakker CC BY-SA 3.0