| Contents | 5 |
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| Preface | 9 |
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| 1 CR Manifolds | 16 |
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| 1.1 CR manifolds | 18 |
| 1.1.1 CR structures | 18 |
| 1.1.2 The Levi form | 20 |
| 1.1.3 Characteristic directions on nondegenerate CR manifolds | 23 |
| 1.1.4 CR geometry and contact Riemannian geometry | 25 |
| 1.1.5 The Heisenberg group | 26 |
| 1.1.6 Embeddable CR manifolds | 29 |
| 1.1.7 CR Lie algebras and CR Lie groups | 33 |
| 1.1.8 Twistor CR manifolds | 36 |
| 1.2 The Tanaka–Webster connection | 40 |
| 1.3 Local computations | 46 |
| 1.3.1 Christoffel symbols | 47 |
| 1.3.2 The pseudo-Hermitian torsion | 51 |
| 1.3.3 The volume form | 58 |
| 1.4 The curvature theory | 61 |
| 1.4.1 Pseudo-Hermitian Ricci and scalar curvature | 65 |
| 1.4.2 The curvature forms | 66 |
| 1.4.3 Pseudo-Hermitian sectional curvature | 73 |
| 1.5 The Chern tensor field | 75 |
| 1.6 CR structures as G-structures | 83 |
| 1.6.1 Integrability | 85 |
| 1.6.2 Nondegeneracy | 87 |
| 1.7 The tangential Cauchy–Riemann complex | 88 |
| 1.7.1 The tangential Cauchy–Riemann complex | 88 |
| 1.7.3 The Frölicher spectral sequence | 99 |
| 1.7.4 A long exact sequence | 109 |
| 1.7.5 Bott obstructions | 111 |
| 1.7.6 The Kohn–Rossi Laplacian | 114 |
| 1.8 The group of CR automorphisms | 121 |
| 2 The Fefferman Metric | 124 |
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| 2.1 The sub-Laplacian | 126 |
| 2.2 The canonical bundle | 134 |
| 2.3 The Fefferman metric | 137 |
| 2.4 A CR invariant | 150 |
| 2.5 The wave operator | 155 |
| 2.6 Curvature of Fefferman’s metric | 156 |
| 2.7 Pontryagin forms | 157 |
| 2.8 The extrinsic approach | 162 |
| 2.8.1 The Monge–Amp`ere equation | 162 |
| 2.8.2 The Fefferman metric | 165 |
| 2.8.3 Obstructions to global embeddability | 166 |
| 3 The CR Yamabe Problem | 172 |
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| 3.1 The Cayley transform | 176 |
| 3.2 Normal coordinates | 180 |
| 3.3 A Sobolev-type lemma | 191 |
| 3.4 Embedding results | 208 |
| 3.5 Regularity results | 211 |
| 3.6 Existence of extremals | 215 |
| 3.7 Uniqueness and open problems | 220 |
| 3.8 The weak maximum principle for b | 222 |
| 4 Pseudoharmonic Maps | 226 |
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| 4.1 CR and pseudoharmonic maps | 227 |
| 4.2 A geometric interpretation | 230 |
| 4.3 The variational approach | 233 |
| 4.4 Hörmander systems and harmonicity | 246 |
| 4.4.1 Hörmander systems | 248 |
| 4.4.2 Subelliptic harmonic morphisms | 251 |
| 4.4.3 The relationship to hyperbolic PDEs | 254 |
| 4.4.4 Weak harmonic maps from C(Hn) | 257 |
| 4.5 Generalizations of pseudoharmonicity | 261 |
| 4.5.1 The first variation formula | 263 |
| 4.5.2 Pseudoharmonic morphisms | 267 |
| 4.5.3 The geometric interpretation of F-pseudoharmonicity | 270 |
| 4.5.4 Weak subelliptic F-harmonic maps | 271 |
| 5 Pseudo-Einsteinian Manifolds | 290 |
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| 5.1 The local problem | 290 |
| 5.2 The divergence formula | 294 |
| 5.3 CR-pluriharmonic functions | 295 |
| 5.4 More local theory | 309 |
| 5.5 Topological obstructions | 311 |
| 5.5.1 The first Chern class of T1,0(M) | 311 |
| 5.5.2 The traceless Ricci tensor | 314 |
| 5.5.3 The Lee class | 316 |
| 5.6 The global problem | 319 |
| 5.7 The Lee conjecture | 327 |
| 5.7.1 Quotients of the Heisenberg group by properly discontinuous groups of CR automorphisms | 328 |
| 5.7.2 Regular strictly pseudoconvex CR manifolds | 333 |
| 5.7.3 The Bockstein sequence | 335 |
| 5.7.4 The tangent sphere bundle | 336 |
| 5.8 Pseudo-Hermitian holonomy | 344 |
| 5.9 Quaternionic Sasakian manifolds | 346 |
| 5.10 Homogeneous pseudo-Einsteinian manifolds | 356 |
| 6 Pseudo-Hermitian Immersions | 360 |
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| 6.1 The theorem of H. Jacobowitz | 362 |
| 6.2 The second fundamental form | 366 |
| 6.3 CR immersions into Hn+k | 371 |
| 6.4 Pseudo-Einsteinian structures | 376 |
| 6.4.1 CR-pluriharmonic functions and the Lee class | 376 |
| 6.4.2 Consequences of the embedding equations | 379 |
| 6.4.3 The first Chern class of the normal bundle | 384 |
| 7 Quasiconformal Mappings | 392 |
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| 7.1 The complex dilatation | 392 |
| 7.2 K-quasiconformal maps | 399 |
| 7.3 The tangential Beltrami equations | 400 |
| 7.3.1 Contact transformations of Hn | 403 |
| 7.3.2 The tangential Beltrami equation on H1 | 409 |
| 7.4 Symplectomorphisms | 413 |
| 7.4.1 Fefferman’s formula and boundary behavior of symplectomorphisms | 413 |
| 7.4.2 Dilatation of symplectomorphisms and the Beltrami equations | 416 |
| 7.4.3 Boundary values of solutions to the Beltrami system | 418 |
| 7.4.4 A theorem of P. Libermann | 418 |
| 7.4.5 Extensions of contact deformations | 420 |
| 8 Yang–Mills Fields on CR Manifolds | 422 |
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| 8.1 Canonical S-connections | 422 |
| 8.2 Inhomogeneous Yang–Mills equations | 425 |
| 8.3 Applications | 427 |
| 8.3.1 Trivial line bundles | 429 |
| 8.3.2 Locally trivial line bundles | 429 |
| 8.3.3 Canonical bundles | 431 |
| 8.4 Various differential operators | 433 |
| 8.5 Curvature of S-connections | 436 |
| 9 Spectral Geometry | 438 |
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| 9.1 Commutation formulas | 438 |
| 9.2 A lower bound for .1 | 442 |
| 9.2.1 A Bochner-type formula | 445 |
| 9.2.2 Two integral identities | 446 |
| 9.2.3 A. Greenleaf’s theorem | 449 |
| 9.2.4 A lower bound on the .rst eigenvalue of a Folland–Stein operator | 454 |
| 9.2.5 Z. Jiaqing and Y. Hongcang’s theorem on CR manifolds | 456 |
| A A Parametrix for | 460 |
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| References | 478 |
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| Index | 498 |