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**From symplectic deformation to isotopy.**
*(English)*
Zbl 0928.57018

Stern, Ronald J. (ed.), Topics in symplectic \(4\)-manifolds. 1st International Press lectures presented in Irvine, CA, USA, March 28–30, 1996. Cambridge, MA: International Press. First Int. Press Lect. Ser. 1, 85-99 (1998).

Two symplectic forms on \(X\) are said to be deformation equivalent if they may be joined by a family of symplectic forms, and are called isotopic if this family may be chosen so that its elements all lie in the same cohomology class. There are no examples of cohomologous symplectic forms that are deformation equivalent but not isotopic in dimension 4, and in this note the author studies a possibility that the two notions are the same in this case. In [F. Lalonde, Math. Ann. 300, No. 2, 273-296 (1994; Zbl 0812.53032)] Lalonde and the author found an “inflation” procedure that converts a deformation into an isotopy, and they applied it to establish the uniqueness of symplectic structure on ruled surfaces. The present note extends the range of this procedure and describes various applications of it. Let \(X\) be an oriented 4-manifold which does not have simple SW-type. The author shows that any two cohomologous and deformation equivalent symplectic forms on \(X\) are isotopic.

For the entire collection see [Zbl 0906.00020].

For the entire collection see [Zbl 0906.00020].

Reviewer: Viktor Abramov (Tartu)

### MSC:

57N13 | Topology of the Euclidean \(4\)-space, \(4\)-manifolds (MSC2010) |

57R57 | Applications of global analysis to structures on manifolds |

57R55 | Differentiable structures in differential topology |

53D99 | Symplectic geometry, contact geometry |