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Riemannian geometry

(Spring 2020)

A mathematician's reputation rests on the number of bad proofs he has given. [Pioneer work is clumsy]
          ----------------A. S. Besicovitch, quoted in J. E. Littlewood, A Mathematician's Miscellany

Beauty is the first test: there is no permanent place in the world for ugly mathematics.
          ----------------G. H. Hardy, A Mathematician's Apology

          The above two quotations are taken from Spivak's book (Chapter 6 of Volume 1).

Notices

1. First lecture: Feb. 25, 2020.


Lectures and excercises

We refer to 2017 Spring2018 Spring, and 2019 Spring for lecture notes from previous semsters.

My former students, Yirong Hu (胡益榕), Shiyu Zhang (张世宇) and Qizhi Zhao (赵奇志) have typed up an electronic version of my lecture notes.

Lecture 1 Introduction; Riemannian metric: definition and existence. blackboard note

Lecture 2 Metric structure; Volume of a subset. blackboard note

Lecture 3 Riemannian measure; Geodesic equation. blackboard note

Lecture 4 Local existence and uniqueness of geodesics; Exponential map. blackboard note

Lecture 5 Geodesics and shortest curves. blackboard note, a correction

Lecture 6 Existence of shortest curves: from local to global blackboard note

Lecture 7 Hopf-Rinow Theorem; Injective radius; Local isometry.. blackboard note

Lecture 8 Existence of shortest geodesics in a given homotopy class. blackboard note

Lecture 9 Riemannian covering map; Laplace-Beltrami operator. blackboard note

Lecture 10 Sobolev space; Rellich compactness theorem; Poincare inequality. blackboard note

Lecture 11 Eigenvalues and eigenfunctions of Laplacian; Affine connection. blackboard note

Lecture 12 Existence and locality of affine connections; Induced connection. blackboard note

Lecture 13 Parallelism; Connections over tensor fields. blackboard note

Lecture 14 Levi-Civita connection. blackboard note

Lecture 15 First Variation; Covariant differentiation; Divergence. blackboard note

Lecture 16 Trace of Hessian is Laplacian; Ricci identity; Computation tricks. blackboard note

Lecture 17 Curvature tensor: its origin, geometric meaning and Bianchi identities. blackboard note

Lecture 18 Second Varation Formula; Riemannian curvature tensor. blackboard note

Lecture 19 Sectioinal, Ricci and Scalar curvature; Schur Theorem. blackboard note

Lecture 20 Ricci curvature and Bochner formula; Lichnerowicz estimate. blackboard note

Lecture 21 Second variation: revisited; Bonnet-Myers Theorem. blackboard note

Lecture 22 Synge Theorem; Geodesics in Rn, Sn, Hn. blackboard note

Lecture 23 Jacobi filed: examples, characterizations, and decomposition. blackboard note

Lecture 24 Conjugate points; Index form as "Hessian" of Energy. blackboard note

Lecture 25 Deep relations between index forms and conjugate points. blackboard note

Lecture 26 Index of a geodesic is finite; Cartan-Hadamard Theorem. blackboard note

Lecture 27 Uniqueness of simply-connected space forms; Convex funtions. blackboard note

Lecture 28 Rauch comparison theorem; Cut point and cut locus. blackboard note, Examples and Illustrations

Lecture 29 Hessian and Laplacian comparison theorems. blackboard note

Lecture 30 Bishop-Gromov volume comparison theorem; Cheng's maximal diameter theorem. blackboard note




Homework 1: Differential Manifolds and Riemannian metrics Due: 2020/03/17






Homework 2: Geodesics Due: 2020/03/31



Lecture Notes: Function spaces and Laplace-Beltrami operator on Riemannian manifolds

Homework 3: Function spaces and Laplace-Beltrami operator Due: 2020/04/20



Homework 4: Connections, Parallelism, and Covariant derivatives Due: 2020/04/30









Homework 5: Curvature Due: 2020/05/21


Tutorials

Tutor

Wenbo Li (李文博) patlee@mail.ustc.edu.cn

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