Hangzhou Lectures on Eigenfunctions of the Laplacian
Based on lectures given at Zhejiang University in Hangzhou, China, and Johns Hopkins
University, this book introduces eigenfunctions on Riemannian manifolds. Christopher Sogge
gives a proof of the sharp Weyl formula for the distribution of eigenvalues of
Laplace-Beltrami operators, as well as an improved version of the Weyl formula, the
Duistermaat-Guillemin theorem under natural assumptions on the geodesic flow. Sogge shows
that there is quantum ergodicity of eigenfunctions if the geodesic flow is ergodic. Sogge
begins with a treatment of the Hadamard parametrix before proving the first main result,
the sharp Weyl formula. He avoids the use of Tauberian estimates and instead relies on
sup-norm estimates for eigenfunctions. The author also gives a rapid introduction to the
stationary phase and the basics of the theory of pseudodifferential operators and
microlocal analysis. These are used to prove the Duistermaat-Guillemin theorem. Turning to
the related topic of quantum ergodicity, Sogge demonstrates that if the long-term geodesic
flow is uniformly distributed, most eigenfunctions exhibit a similar behavior, in the
sense that their mass becomes equidistributed as their frequencies go to infinity.
Preface ix
1 A review: The Laplacian and the d'Alembertian 1 1.1 The Laplacian 1 1.2 Fundamental
solutions of the d'Alembertian 6
2 Geodesics and the Hadamard parametrix 16 2.1 Laplace-Beltrami operators 16 2.2 Some
elliptic regularity estimates 20 2.3 Geodesics and normal coordinates|a brief review 24
2.4 The Hadamard parametrix 31
3 The sharp Weyl formula 39 3.1 Eigenfunction expansions 39 3.2 Sup-norm estimates for
eigenfunctions and spectral clusters 48 3.3 Spectral asymptotics: The sharp Weyl formula
53 3.4 Sharpness: Spherical harmonics 55 3.5 Improved results: The torus 58 3.6 Further
improvements: Manifolds with nonpositive curvature 65
4 Stationary phase and microlocal analysis 71 4.1 The method of stationary phase 71 4.2
Pseudodifferential operators 86 4.3 Propagation of singularities and Egorov's theorem 103
4.4 The Friedrichs quantization 111
5 Improved spectral asymptotics and periodic geodesics 120 5.1 Periodic geodesics and
trace regularity 120 5.2 Trace estimates 123 5.3 The Duistermaat-Guillemin theorem 132 5.4
Geodesic loops and improved sup-norm estimates 136
6 Classical and quantum ergodicity 141 6.1 Classical ergodicity 141 6.2 Quantum
ergodicity 153
Appendix 165 A.1 The Fourier transform and the spaces S( n) and S'( n)) 165 A.2 The
spaces D'(OMEGA) and E'(OMEGA) 169 A.3 Homogeneous distributions 173 A.4 Pullbacks of
distributions 176 A.5 Convolution of distributions 179 Notes 183 Bibliography 185 Index
191 Symbol Glossary 193
208 pages, Paperback