Abstract
Let (M,θ) be a compact strictly pseudoconvex pseudohermitian manifold which is CR embedded into a complex space. In an earlier paper, Lin and the authors gave several sharp upper bounds for the first positive eigenvalue λ1 of the Kohn-Laplacian □b on (M,θ). In the present paper, we give a sharp upper bound for λ1, generalizing and extending some previous results. As a corollary, we obtain a Reilly-type estimate when M is embedded into the standard sphere. In another direction, using a Lichnerowicz-type estimate by Chanillo, Chiu, and Yang and an explicit formula for the Webster scalar curvature, we give a lower bound for λ1 when the pseudohermitian structure θ is volume-normalized.
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In Memory of Professor Qikeng Lu (1927–2015)
The second-named author was supported by the Austrian Science Fund FWF, Project No. I01776
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Li, S.Y., Son, D.N. The Webster Scalar Curvature and Sharp Upper and Lower Bounds for the First Positive Eigenvalue of the Kohn-Laplacian on Real Hypersurfaces. Acta. Math. Sin.-English Ser. 34, 1248–1258 (2018). https://doi.org/10.1007/s10114-018-7415-0
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DOI: https://doi.org/10.1007/s10114-018-7415-0