2019/04/09 by Jih-Hsin Cheng, Cheng, Jih-Hsin, Andrea Malchiodi +3 · 1 citation
Mathematics · #32V20 #32V30 #35J20 #35J75 #53C17 #Analysis of PDEs (math.AP) #Differential Geometry (math.DG) #FOS: Mathematics #Geometric Analysis and Curvature Flows #Geometry and complex manifolds #Holomorphic and Operator Theory
paper · pdf · doi:10.48550/arxiv.1904.04665
openalex publication_date 2019/04/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We exhibit examples of compact three-dimensional CR manifolds of positive Webster class, \em Rossi spheres, for which the pseudo-hermitian mass as defined in \citeCMY17 is negative, and for which the infimum of the CR-Sobolev quotient is not attained. To our knowledge, this is the first geometric context on smooth closed manifolds where this phenomenon arises, in striking contrast to the Riemannian case.