Abstract
Let (M n,g) be a compact Riemannian manifold with Ric ≥−(n−1). It is well known that the bottom of spectrum λ 0 of its universal covering satisfies λ 0≤(n−1)2/4. We prove that equality holds iff M is hyperbolic. This follows from a sharp estimate for the Kaimanovich entropy.
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Communicated by Peter Li.
The author was partially supported by NSF Grant 0505645.
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Wang, X. Harmonic Functions, Entropy, and a Characterization of the Hyperbolic Space. J Geom Anal 18, 272–284 (2008). https://doi.org/10.1007/s12220-007-9001-z
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DOI: https://doi.org/10.1007/s12220-007-9001-z