Introduction 1.1. First examples 1.2. Legendrian knots 1.3. Tight vs. overtwisted 1.4. Classification of contact structures 1.5. A criterion for tightness 1.6. Relationship with foliation theory 2. Convex surfaces 2.1. Characteristic foliations 2.2. Convexity 2.3. Convex decomposition theory 3. Bypasses 3.1. Definition and examples 3.2. Finding bypasses 4. Classification of tight contact structures on lens spaces 4.1. The standard neighborhood of a Legendrian curve 4.2. Lens spaces 4.3. Solid tori 4.4. Completion of the proof of Theorems 4.2 and 4.3 5. Gluing 5.1. Basic examples with trivial state transitions 5.2. More complicated example 5.3
. Tightness and fillability ReferencesA contact manifold (M, ξ) is a (2n + 1)-dimensional manifold M equipped with a smooth maximally nonintegrable hyperplane field ξ ⊂ T M, i.e., locally ξ = ker α, where α is a 1-form which satisfies α ∧ (dα) n = 0. Since dα is a nondegenerate 2-form when restricted to ξ, contact geometry is customarily viewed as the odd-dimensional sibling of symplectic geometry. Although Date: December 31, 2003. 1 2 KO HONDAcontact geometry in dimensions ≥ 5 is still in an incipient state, contact structures in dimension 3 are much better understood, largely due to the fact that symplectic geometry in two dimensions is just the study of area. The goal of this article is to explain some of the recent developments in 3-dimensional contact geometry, with an emphasis on methods from 3-dimensional topology. Basic references include [Ae, El2, Et1, Ge]. The article [Kz] is similar in spirit to ours.Three-dimensional contact geometry lies at the interface between 3-and 4-manifold geometries, and has been an essential part of the flurry in low-dimensional geometry and topology over the last 20 years. In dimension 3, it relates to foliation theory and knot theory; in dimension 4, there are rich interactions with symplectic geometry. In both dimensions, there are relations with gauge theories such as Seiberg-Witten theory and Heegaard Floer homology. Acknowledgements. This manuscript grew out of a lecture series given at the Winter School in Contact Geometry in München in February 2003 and a minicourse given at the Geometry and Foliations 2003 conference, held at Ryokoku University in Kyoto in September 2003. I would like to thank Kai Cieliebak and Dieter Kotschick for the former, and Takashi Tsuboi for the latter, as well as for his hospitality during my visit to the University of Tokyo and the Tokyo Institute of Technology during the summer and fall of 2003. Much of the actual writing took place during this visit.