Recent Progress on Ricci Solitons

Ricci solitons are natural generalizations of Einstein metrics. They are also special solutions to Hamilton's Ricci flow and play important roles in the singularity study of the Ricci flow. In this paper, we survey some of the recent progress on Ricci solitons.Comment: 32 pages; to appear in Proceedings of International Conference on Geometric Analysis (Taipei, July 2007

Geometry of Complete Gradient Shrinking Ricci Solitons

We survey some of the recent progress on complete gradient shrinking Ricci solitons, including the classifications in dimension three and asymptotic behavior of potential functions as well as volume growths of geodesic balls in higher dimensions. This article is written for the conference proceedings dedicated to Yau's 60th birthday.Comment: 16 pages; updated versio

The K\"ahler-Ricci flow on Fano manifolds

In this lecture notes, we aim at giving an introduction to the K\"ahler-Ricci flow (KRF) on Fano manifolds. It covers some of the developments of the KRF in its first twenty years (1984-2003), especially an essentially self-contained exposition of Perelman's uniform estimates on the scalar curvature, the diameter, and the Ricci potential function for the normalized K\"ahler-Ricci flow (NKRF), including the monotonicity of Perelman's \mu-entropy and \kappa-noncollapsing theorems for the Ricci flow on compact manifolds. The Notes is based on a mini-course on KRF delivered at University of Toulouse III in February 2010, a talk on Perelman's uniform estimates for NKRF at Columbia University's Geometry and Analysis Seminar in Fall 2005, and several conference talks, including "Einstein Manifolds and Beyond" at CIRM (Marseille - Luminy, fall 2007), "Program on Extremal K\"ahler Metrics and K\"ahler-Ricci Flow" at the De Giorgi Center (Pisa, spring 2008), and "Analytic Aspects of Algebraic and Complex Geometry" at CIRM (Marseille - Luminy, spring 2011).Comment: v.2: corrected a number of typos and added the proof of Theorem 2.3 on preserving positive orthogonal bisectional curvature. To appear as a book chapter in An Introduction to the K\"ahler-Ricci Flow, Lecture Notes in Mathematics, vol. 2086, Springer, 201

Existence of Gradient Kahler-Ricci Solitons

This is the original paper appeared in the book "Elliptic and Parabolic Methods in Geometry (Minneapolis, MN,1994), A K Peters, Wellesley, MA, (1996)" (p.1-16), except with a few minor modifications as described at the end of the paper (on p.14). Due to frequent requests for the article, we decided to post it on the arXiv

On Quantum de Rham Cohomology Theory

We define quantum exterior product wedge_h and quantum exterior differential d_h on Poisson manifolds (of which symplectic manifolds are an important class of examples). Quantum de Rham cohomology, which is a deformation quantization of de Rham cohomology, is defined as the cohomology of d_h. We also define quantum Dolbeault cohomology. A version of quantum integral on symplectic manifolds is considered and the correspoding quantum Stokes theorem is proved. We also derive quantum hard Lefschetz theorem. By replacing d by d_h and wedge by wedge_h in the usual definitions, we define many quantum analogues of important objects in differential geometry, e.g. quantum curvature. The quantum characteristic classes are then studied along the lines of classical Chern-Weil theory. Quantum equivariant de Rham cohomology is defined in the similar fashion.Comment: 8 pages, AMSLaTe

Matrix Li-Yau-Hamilton estimates for the heat equation on Kaehler manifolds

We proved a matrix Li-Yau-Hamilton type gradient estimates for the positive solutin of the heat equation on complete Kaehler manifolds with nonnegative bisectional curvature. As a consequence we obtain a comparison theorem for the distance function under this curvature assumption

On second variation of Perelman's Ricci shrinker entropy

In this paper we provide a detailed proof of the second variation formula, essentially due to Richard Hamilton, Tom Ilmanen and the first author, for Perelman's $\nu$-entropy. In particular, we correct an error in the stability operator stated in Theorem 6.3 of [2]. Moreover, we obtain a necessary condition for linearly stable shrinkers in terms of the least eigenvalue and its multiplicity of certain Lichnerowicz type operator associated to the second variation.Comment: 13 pages; final version; to appear in Math. An

Degenerate Chern-Weil Theory and Equivariant Cohomology

We develop a Chern-Weil theory for compact Lie group action whose generic stabilizers are finite in the framework of equivariant cohomology. This provides a method of changing an equivariant closed form within its cohomological class to a form more suitable to yield localization results. This work is motivated by our work on reproving wall crossing formulas in Seiberg-Witten theory, where the Lie group is the circle. As applications, we derive two localization formulas of Kalkman type for G = SU(2) or SO(3)-actions on compact manifolds with boundary. One of the formulas is then used to yield a very simple proof of a localization formula due to Jeffrey-Kirwan in the case of G = SU(2) or SO(3).Comment: 23 pages, AMSLaTe

Frobenius Manifold Structure on Dolbeault Cohomology and Mirror Symmetry

We construct a differential Gerstenhaber-Batalin-Vilkovisky algebra from Dolbeault complex of any close Kaehler manifold, and a Frobenius manifold structure on Dolbeault cohomology.Comment: 10 pages, AMS LaTe

DGBV Algebras and Mirror Symmetry

We describe some recent development on the theory of formal Frobenius manifolds via a construction from differential Gerstenhaber-Batalin-Vilkovisk (DGBV) algebras and formulate a version of mirror symmetry conjecture: the extended deformation problems of the complex structure and the Poisson structure are described by two DGBV algebras; mirror symmetry is interpreted in term of the invariance of the formal Frobenius manifold structures under quasi-isomorphism.Comment: 11 pages, to appear in Proceedings of ICCM9