4-manifolds: 1-connected
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Any finitely presentable group may occur as the fundamental group of a smooth closed 4-manifold. On the other hand, the class of simply connected (topological or smooth) 4-manifolds still appears to be quite rich, so it appears reasonable to consider the classification of simply connected 4-manifolds in particular. | Any finitely presentable group may occur as the fundamental group of a smooth closed 4-manifold. On the other hand, the class of simply connected (topological or smooth) 4-manifolds still appears to be quite rich, so it appears reasonable to consider the classification of simply connected 4-manifolds in particular. | ||
− | It appears that the [[ | + | It appears that the [[Intersection_forms|intersection form]] is the main algebro-topological invariant of simply-connected 4-manifolds. |
Technical remark: When we mention the term ''4-manifold'' without the explicit mention of topological or smooth we shall mean the larger class of topological 4-manifolds. | Technical remark: When we mention the term ''4-manifold'' without the explicit mention of topological or smooth we shall mean the larger class of topological 4-manifolds. |
Revision as of 11:50, 8 June 2010
This page has not been refereed. The information given here might be incomplete or provisional. |
Contents |
1 Introduction
Any finitely presentable group may occur as the fundamental group of a smooth closed 4-manifold. On the other hand, the class of simply connected (topological or smooth) 4-manifolds still appears to be quite rich, so it appears reasonable to consider the classification of simply connected 4-manifolds in particular.
It appears that the intersection form is the main algebro-topological invariant of simply-connected 4-manifolds.
Technical remark: When we mention the term 4-manifold without the explicit mention of topological or smooth we shall mean the larger class of topological 4-manifolds.
2 Construction and examples, their intersection forms
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2.1 First examples
The first examples that come to one's mind are the 4-sphere , the complex projective space , the complex projective space with its opposite (non-complex) orientation , the product , various connected sums of these, and in particular .
The intersection form of the 4-sphere is the "empty form" of rank 0. The intersection forms of the others are given by
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2.2 Hypersurfaces in $\mathbb{CP}^3$
2.3 Elliptic surfaces
2.4 Branched coverings
2.5 The $E_8$ manifold
3 Invariants
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4 Classification/Characterization
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5 Further discussion
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