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キーワード:
Mathematics, Differential Geometry, Spectral Theory
要旨:
For a Riemannian covering $\pi\colon M_1\to M_0$, the bottoms of the spectra
of $M_0$ and $M_1$ coincide if the covering is amenable. The converse
implication does not always hold. Assuming completeness and a lower bound on
the Ricci curvature, we obtain a converse under a natural condition on the
spectrum of $M_0$.